Stanford Research Systems DS345 Users Guide

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MODEL DS345

Synthesized Function Generator

1290-D Reamwood Avenue

Sunnyvale, California 94089

Phone: (408) 744-9040 • Fax: (408) 744-9049

email: info@thinkSRS.com • www.thinkSRS.com

Revision 1.8 (03/2005)

DS345 Synthesized Function Generator

Table of Contents

Condensed Information

SRS Symbols iii Safety and Use iv Specifications v Abridged Command List ix

Getting Started

Introduction 1-1 CW Function Generation 1-1 Frequency Sweep 1-2 Tone Bursts 1-3

Operation

Introduction to DDS 2-1

DS345 Features 2-5

Front Panel Features 2-5 Rear Panel Features 2-7

Function Setting 2-9

Setting the Function 2-10 Frequency 2-10 Amplitude 2-11 DC Offset 2-12 Phase 2-12

Sweeps and Modulation 2-13

Modulation Parameters 2-13 Modulation On/Off 2-13 Modulation Type 2-13 Modulation Rate 2-14 Amplitude Modulation 2-15 External AM 2-15 Internal AM 2-15 Frequency Modulation 2-16 Phase Modulation 2-17 Burst Modulation 2-18 Burst Count 2-18 Starting Point 2-18 Frequency Sweeps 2-19 Sweep Type 2-19 Sweep Frequencies 2-19 Sweep Markers 2-20 Sweep Outputs 2-21 Trigger Generator 2-22 Arbitrary Modulation Patterns 2-23 Pulse Generation 2-24

Instrument Setup 2-25

Default Settings 2-25 Store and Recall 2-25

GPIB and RS232 Setup 2-26 Self-Test and Autocal 2-27

Arbitrary Waveform Editing 2-29

Edit Menu 2-29 Point Format Editing 2-30 Point Format Example 2-31 Vector Format Editing 2-32 Vector Format Example 2-33

Programming

Programming the DS345 3-1 Communications 3-1

GPIB Communication 3-1 RS-232 Communication 3-1 Data Window 3-1

Command Syntax 3-1

Detailed Command List 3-3

Function Output Commands 3-3 Modulation Control 3-4 Arb Waveform and Modulation 3-6 Setup Control Commands 3-9 Status Reporting Commands 3-9 Test and Calibration Commands 3-10 Status Byte Definitions 3-12

Programming Examples 3-15

Arbitrary AM Modulation 3-16 Arbitrary FM Modulation 3-17 Arbitrary PM Modulation 3-18 Point Mode Arb Waveform 3-19 Vector Mode Arb Waveform 3-20

Test and Calibration

Troubleshooting 4-1

Operation Error Messages 4-1 Self-Test Error Messages 4-3 Autocal Error Messages 4-4

Performance Tests 5-1 Necessary Equipment 5-1

Functional Tests 5-2

Front Panel Test 5-2 Self Tests 5-2 Sine Wave 5-2 Square Wave 5-2 Amplitude Flatness 5-3 Output Level 5-3

DS345 Synthesized Function Generator

Performance Tests 5-5

Frequency Accuracy 5-5 Amplitude Accuracy 5-5 DC Offset Accuracy 5-7 Subharmonics 5-7 Spurious Signals 5-8 Harmonic Distortion 5-8 Phase Noise 5-9 Square Wave Rise Time 5-10 Square Wave Symmetry 5-10 AM Envelope Distortion 5-10

Test Scorecard 5-11

Calibration 6-1

Introduction 6-1 Calibration Enable 6-1 Calbytes 6-1

Necessary Equipment 6-3

Adjustments 6-3

Clock Adjustment 6-3 DAC Reference Voltage 6-4 Output Amplifier Bandwidth 6-4 Bessel Filter Adjustment 6-4 Harmonic Distortion 6-5

Calibration 6-6

5.00 V Reference 6-6 Clock Calibration 6-6 Attenuator Calibration 6-6 Carrier Null Calibration 6-7 Sinewave Amplitude 6-8 Square Wave Amplitude 6-8 Square Wave Symmetry 6-9

Arbitrary Waveform Software

Introduction 7-1 Installing AWC 7-1 Getting Started with AWC 7-1 Hardware Requirements 7-3

Menus 7-3

File Menu 7-3 Edit Menu 7-3 Waveform Menu 7-4 Send Data Menu 7-5 Set DS345 Menu 7-5 Trigger Menu 7-6 Zoom Menu 7-6 Help Menu 7-7

Data File Format 7-7

For More Info 7-7

DS345 Circuitry

Circuit Description 8-1 Bottom PC Board 8-1

Power Supplies 8-1 Microprocessor System 8-1 Display and Keyboard 8-1 Ribbon Cable, Trigger and Sync 8-2 GPIB and RS232 Interfaces 8-2 Output Amplifier 8-3 Output Attenuator 8-3

Top PC Board 8-4

Ribbon Cable, ADC, DACs 8-4 Clocks 8-4 DDS ASIC and Memory 8-5 Amplitude and Sweep DACs 8-5 DDS Waveform DAC 8-6 DDS Output Filters and Doubler 8-6 Sync and Gain Adjust 8-6

Component Parts List 9-1

Bottom PC Board and Front Panel 9-1 Top PC Board 9-10 Optional PC Board 9-21 Miscellaneous Parts 9-22

Schematic Circuit Diagrams Sheet No. Bottom PC Board

Power Supplies 1/7 Microprocessor System 2/7 Display and Keyboard 3/7 Ribbon Cable, Trigger and Sync 4/7 GPIB and RS232 Interfaces 5/7 Output Amplifier 6/7 Output Attenuator 7/7

Top PC Board

Ribbon Cable, ADC, DACs 1/7 Clocks 2/7 DDS ASIC and Memory 3/7 Amplitude and Sweep DACs 4/7 DDS Waveform DAC 5/7 DDS Output Filters and Doubler 6/7 Sync and Gain Adjust 7/7

Front Panel

Keypad 1/2 LED Display 2/2

Bottom PCB Component Placement Top PCB Component Placement

DS345 Synthesized Function Generator

iii

DS345 Synthesized Function Generator

Safety and Preparation for Use

WARNING: Dangerous voltages, capable of causing death, are present in this instrument. Use extreme caution whenever the instrument covers are removed.

This instrument may be damaged if operated with the LINE VOLTAGE SELECTOR set for the wrong ac line voltage or if the wrong fuse is installed.

LINE VOLTAGE SELECTION

The DS345 operates from a 100V, 120V, 220V, or 240V nominal ac power source having a line frequency of 50 or 60 Hz. Before connecting the power cord to a power source, verify that the LINE VOLTAGE SELECTOR card, located in the rear panel fuse holder, is set so that the correct ac input voltage value is visible.

Conversion to other ac input voltages requires a change in the fuse holder voltage card position and fuse value. Disconnect the power cord, open the fuse holder cover door and rotate the fuse-pull lever to remove the fuse. Remove the small printed circuit board and select the operating voltage by orienting the board so that the desired voltage is visible when it is pushed firmly back into its slot. Rotate the fuse-pull lever back into its normal position and insert the correct fuse into the fuse holder.

LINE FUSE

Verify that the correct line fuse is installed before connecting the line cord. For 100V/120V, use a 1 Amp fuse and for 220V/240V, use a 1/2 Amp fuse.

LINE CORD

The DS345 has a detachable, three-wire power cord for connection to the power source and to a protective ground. The exposed metal parts of the instrument are connected to the outlet ground to protect against electrical shock. Always use an outlet which has a properly connected protective ground.

Specifications

SPECIFICATIONS

FREQUENCY RANGE

Waveform Sine 30.2 MHz 1 µHz Square 30.2 MHz 1 µHz Ramp 100 KHz 1 µHz Triangle 100 KHz 1 µHz Noise 10 MHz (Gaussian Weighting) Arbitrary 10 MHz 40 MHz sample rate

OUTPUT

Source Impedance 50 Ω Output may float up to ±40V (AC + DC) relative to earth ground.

AMPLITUDE

Range into 50Ω load (limited such that |V

Maximum Freq Resolution

| + |Vdc| ≤ 5 V)

ac peak

rms

dBm (50Ω)

Function Max. Min. Max. Min. Max. Min.

Sine Square Triangle Ramp Noise Arbitrary

10V 10V 10V 10V 10V 10V

10 mV 10 mV 10 mV 10 mV 10 mV 10 mV

3.54V 5V

2.89V

2.09V n.a.

3.54 mV 5 mV

2.89 mV

2.09 mV n.a.

+23.98 +26.99 +22.22 +22.22 +19.41 n.a.

-36.02

-33.0

-37.78

-40.59 n.a.

Resolution 3 digits (DC offset = 0V)

Accuracy (with 0V DC Offset)

Sine: 1µHz 100 kHz 20 MHz 30.2 MHz 10Vpp

±0.2 dB ±0.2dB ±0.3dB

5Vpp

±0.4 dB ±0.4dB ±0.5dB

0.01Vpp

Square: 1µHz 100 kHz 20 MHz 30.2 MHz 10Vpp

±3 % ±6% ±15%

5Vpp

±5% ±8% ±18%

0.01Vpp

Specifications

Triangle, Ramp, Arbitrary: ±3% > 5Vpp ±5% < 5Vpp

DC OFFSET

Range: ±5V (limited such that |V Resolution: 3 digits (VAC = 0) Accuracy: 1.5% of setting + 0.2 mV (DC only) ±0.8 mV to ±80 mV depending on AC and DC settings

WAVEFORMS

Sinewave Spectral Purity

Spurious: < -50 dBc (non-harmonic) Phase Noise: < -55 dBc in a 30 KHz band centered on the carrier, exclusive of

discrete spurious signals Subharmonic: < -50 dBc Harmonic Distortion: Harmonically related signals will be less than:

Level Frequency Range

| + |Vdc| ≤ 5 V)

ac peak

< -55 dBc < -45 dBc < -35 dBc < -25 dBc

DC to 100 KHz .1 to 1 MHz 1 to 10 MHz 10 to 30 MHz

Square Wave

Rise/Fall Time: < 15 nS (10 to 90%), at full output Asymmetry: < 1% of period + 4nS Overshoot: < 5% of peak to peak amplitude at full output

Ramps, Triangle and Arbitrary

Rise/Fall Time 35 nS (10 MHz Bessel Filter) Linearity ±0.5% of full scale output Settling Time < 1 µs to settle within 0.1% of final value at full output

Arbitrary Function

Sample Rate: 40 MHz/N, N = 1 to 2

-1. Memory Length: 8 to 16,300 points Resolution: 12 bits (0.025% of full scale)

PHASE

Range: ±7199.999° with respect to arbitrary starting phase Resolution: 0.001°

AMPLITUDE MODULATION

Source: Internal (sine, square, triangle, or ramp) or External Depth: 0 to 100% AM or DSBSC Rate: 0.001 Hz to 10 kHz internal, 20 kHz max external Distortion: < -35dB at 1kHz, 80% depth

Specifications

DSB Carrier: < -35db typical at 1 kHz modulation rate (DSBSC) Ext Input: ±5V for 100% modulation, 100 kW impedance.

FREQUENCY MODULATION

Source: Internal (sine, square, triangle, ramp) Rate: 0.001 Hz to 10 kHz Span: 1 µHz to 30.2 MHz (100 kHz for triangle or ramp)

PHASE MODULATION

Source: Internal (sine, square, triangle, ramp) Rate: 0.001 Hz to 10 kHz Span: ±7199.999°

FREQUENCY SWEEP

Type: Linear or Log, phase continuous Waveform: up, down, up-down, single sweep Time: 0.001s to 1000s Span: 1 µHz to 30.2 MHz (100 kHz for triangle,ramp) Markers: Two markers may be set at any sweep point (TTL output) Sweep Output: 0 - 10 V linear ramp signal, syncronized to sweep

BURST MODULATION

Waveform: any waveform except NOISE may be BURST Frequency: Sine, square to 1 MHz; triangle, ramp to 100 kHz; arbitrary to 40 MHz

sample rate

Count: 1 to 30,000 cycles/burst (1µs to 500s burst time limits)

TRIGGER GENERATOR

Source: Single, Internal, External, Line Rate: 0.001 Hz to 10 kHz internal (2 digit resolution) External: Positive or Negative edge, TTL input Output: TTL output

TIMEBASE

Accuracy ±5 ppm (20 to 30° C) Aging 5 ppm/year Input 10 MHz/N ± 2 ppm. N = 1 to 8. 1V pk-pk minimum input level. Output 10 MHz, >1 Vpp sine into 50 Ω

Optional Timebase Type: Ovenized AT-cut oscillator Stability: < 0.01ppm, 20 - 60°C Aging: < 0.001ppm/day Short Term: < 5 x 10

-11

1s Allan Variance

vii

Specifications

GENERAL

Interfaces RS232-C (300 to 19200 Baud, DCE) and IEEE-488.2 with free DOS

Based Arbitrary Waveform Software

All instrument functions are controllable over the interfaces.

Weight 10 lbs Dimensions 8.5" x 3.5" x 13" (WHL) Power 50 VA, 100/120/220/240 Vac 50/60 Hz

viii

Abridged Command List

Syntax

Variables i,j are integers. Variable x is a real number in integer, real, or exponential notation.

Commands which may be queried have a ? in parentheses (?) after the mnemonic. The ( ) are not sent. Commands that may only be queried have a '?' after the mnemonic. Commands which may not be queried have no '?'. Optional parameters are enclosed by {}.

Function Output Control Commands

AECL Sets the output amplitude/offset to ECL levels (1Vpp, -1.3V offset). AMPL(?) x Sets the output amplitude to x. x is a value plus units indicator. The units can be VP

(Vpp), VR (Vrms), or DB (dBm). Example: AMPL 1.00VR sets 1.00 Vrms.

ATTL Sets the output amplitude/offset to TTL levels (5 Vpp, 2.5 V offset). FREQ(?) x Sets the output frequency to x Hz. FSMP(?) x Sets the arbitrary waveform sampling frequency to x Hz. FUNC(?) i Sets the output function. 0 = sine, 1 = square, 2 = triangle, 3 = ramp, 4 = noise,

5= arbitrary.

INVT(?)i Set output inversion on (i=1) or off (i=0). OFFS(?)x Sets the output offset to x volts. PCLR Sets the current waveform phase to zero. PHSE(?) x Sets the waveform output phase to x degrees.

Modulation control commands

*TRG Triggers bursts/single sweeps if in single trigger mode. BCNT(?) i Sets the burst count to i. DPTH(?) i Sets the AM modulation depth to i %. If i is negative sets DSBSC with i % modulation. FDEV(?) x Sets the FM span to x Hz. MDWF(?) i Sets the modulation waveform. 0 = single sweep, 1 = ramp, 2 = triangle, 3 = sine,

4 = square, 5 = arbitrary, 6 = none.

MENA(?) i Turns modulation on (i=1) or off (i=0). MKSP Sets the sweep markers to the extremes to the sweep span. MRKF(?) i ,x Sets marker frequency i to x Hz. 0 = mrk start freq, 1 = stop freq, 2 = center freq,

3 = span.

MTYP(?) i Sets the modulation type. 0 = lin sweep, 1 = log sweep, 2 = AM, 3 = FM, 4 = PM,

5 = Burst.

PDEV(?) x Sets the phase modulation span to x degrees. RATE(?) x Sets the modulation rate to x Hz. SPAN(?) x Sets the sweep span to x Hz. SPCF(?) x Sets the sweep center frequency to x Hz. SPFR(?) x Sets the sweep stop frequency to x Hz. SPMK Sets the sweep span to the sweep marker positions. STFR(?) x Sets the sweep start frequency to x Hz. TRAT(?) x Sets the internal trigger rate to x Hz. TSRC(?) i Sets the trigger source. 0 = single, 1 = internal, 2 = + Ext, 3 = - Ext, 4 = line.

Arbitrary Waveform and Modulation commands

AMRT(?) i Sets the arbitrary modulation rate divider to i. AMOD? i Allows downloading a i point arbitrary modulation waveform if the modulation type is

AM, FM, or PM. After execution of this query the DS345 will return the ASCII value 1. The binary waveform data may now be downloaded.

Abridged Command List

LDWF? i,j Allows downloading a j point arbitrary waveform of format i. i = 0 = point format, i= 1 =

vector format. After execution of this query the DS345 will return the ascii value 1. The binary waveform data may now be downloaded.

Setup Control Commands

*IDN? Returns the device identification . *RCL i Recalls stored setting i. *RST Clears instrument to default settings. *SAV i Stores the current settings in storage location i.

Status Reporting Commands

*CLS Clears all status registers. *ESE(?) j Sets/reads the standard status byte enable register. *ESR? {j} Reads the standard status register, or just bit j of register. *PSC(?) j Sets the power on status clear bit. This allows SRQ's on power up if desired. *SRE(?) j Sets/reads the serial poll enable register. *STB? {j} Reads the serial poll register, or just bit n of register. STAT? {j} Reads the DDS status register, or just bit n of register. DENA(?) j Sets/reads the DDS status enable register.

Hardware Test and Calibration Control

*CAL? Starts autocal and returns status when done. *TST? Starts self-test and returns status when done.

Status Byte Definitions

Serial Poll Status Byte

bit name usage 0 Sweep Done set when no sweeps in

progress

1 Mod Enable set when modulation is

enabled

2 User SRQ set when the user issues a

front panel SRQ

3 DDS set when an unmasked bit in

DDS status byte is set

4 MAV set when GPIB output queue is

non-empty

5 ESB set when an unmasked bit in

std event status byte is set 6 RQS SRQ bit 7 No Command set when there are no

unexecuted commands in input

queue

Standard Event Status Byte

bit name usage 0 unused 1 unused 2 Query Error set on output queue overflow 3 unused 4 Execution Err set on error in command

execution 5 Command Err set on command syntax error 6 URQ set on any front panel key

press 7 PON set on power on

DDS Status Byte

bit name usage 0 Trig'd set on burst/sweep trigger 1 Trig Error set on trigger error 2 Ext Clock set when locked to an external

clock 3 Clk Error set when an external clock

error occurs 4 Warmup set when the DS345 is warmed

up 5 Test Error set when self test fails 6 Cal Error set when autocal fails 7 mem err set on power up memory error

Getting Started

Introduction

This section is designed to familiarize you with the operation of the DS345 Synthesized Function Generator. The DS345 is a powerful, flexible generator capable of producing both continuous and modulated waveforms of exceptional purity and resolution. The DS345 is also relatively simple to use, the following examples take the user step by step through some typical uses.

Data Entry

Setting the DS345's operating parameters is done by first pressing the key with the desired parameter's name on it (FREQ, for example, to set the frequency). Some parameters are labelled above the keys in light gray. To display these values first press the SHIFT key and then the labelled key. [SHIFT][SWP CF] for example, displays the sweep center frequency. Values are changed through the numeric keypad or the MODIFY keys. To enter a value simply type the new value using the keypad and complete the entry by hitting one of the UNITS keys. If the entry does not have units, any of the UNITS keys may be pressed. If an error is made, pressing the CLR key returns the previous value. The current parameter value may also be increased or decreased with the MODIFY keys. Pressing the UP ARROW key will increase the value by the current step size, while pressing the DOWN ARROW key will decrease the value by the current step size. If the entered value is outside of the allowable limits for the parameter the DS345 will beep and display an error message.

Step Size

Each parameter has an associated step size which may be an exact power of 10 (1 Hz, 10 Hz or 100 Hz for example), or may be an arbitrary value. If the step size is an exact power of 10, that digit of the display will flash. Pressing [STEP SIZE] displays the step size for the current parameter (the STEP LED will be lit). Pressing [STEP SIZE] again returns the display to the previously displayed parameter. The step size may be changed by typing a new value while the STEP LED is lit. Pressing the MODIFY UP ARROW key while the step size is displayed increases the step size to the next larger decade, while pressing the MODIFY DOWN ARROW key will decrease the step size to the next smaller decade.

CW Function Generation

Our first example demonstrates generating CW waveforms and the DS345's data entry functions. Connect the front panel FUNCTION output to an oscilloscope, terminating the output into 50 ohms. Turn the DS345 on and wait until the message "TEST PASS" is displayed.

Press [SHIFT][DEFAULTS].

Press [AMPL]. Then press [5][Vpp].

Press [FUNCTION DOWN ARROW] twice.

Press [FREQ] and then [1][0][kHz].

This recalls the DS345's default settings. Displays the amplitude and sets it to 5 Vpp. The

scope should show a 5 Vpp 1 kHz sine wave. The function should change to a square wave and

then a triangle wave. Displays the frequency and sets it to 10 kHz. The

scope should now display a 10 kHz triangle wave.

1-1

Getting Started

5) Press [MODIFY UP ARROW].

6) Press [STEP SIZE].

7) Press [1][2][3][Hz]. Then press [STEP SIZE].

8) Press [MODIFY DOWN ARROW].

9) Press [STEP SIZE] then [MODIFY UP ARROW]

10) Press [STEP SIZE].

11) Press [MODIFY UP ARROW].

The frequency will increment to 10.1 kHz. The flashing digit indicates a step size of 100 Hz.

Observe that the step size is indeed 100 Hz. The STEP LED should be on.

We've changed the step size to 123 Hz and displayed the output frequency again.

The frequency is decreased by 123 Hz to 9977 Hz.

The step size is displayed and is increased from 123 Hz to the next larger decade–1 kHz.

The frequency is displayed again. The flashing digit indicates that the step size is 1 kHz.

The frequency is incremented to 10.977 kHz.

Frequency Sweep

The next example sets up a linear frequency sweep with markers. The DS345 can sweep the output frequency of any function over any range of allowable output frequencies. There are no restrictions on minimum or maximum sweep span. The sweep time may range from 1 ms to 1000 s. The DS345 also has two independent rear-panel markers that may be used indicate specific frequencies in the sweep. The MARKER output goes high at the start marker position and low at the stop marker position.

An oscilloscope that can display three channels is required. Attach the FUNCTION output BNC to the oscilloscope, terminating the output into 50 ohms. Set the scope to 2V/div. Attach the SWEEP rear-panel BNC to the scope and set it to 2V/div. The scope should be set to trigger on the falling edge of this signal. Attach the MARKER rear-panel BNC to the scope's third channel. This signal will have TTL levels.

1) Press [SHIFT][DEFAULTS].

2) Press [AMPL] then [5][Vpp].

3) Press [SWEEP MODE UP ARROW] twice.

4) Press [RATE] then [1][0][0][Hz].

5) Press [START FREQ] then [1][0][0][kHz].

This recalls the DS345's default settings. Set the amplitude to 5Vpp. Set the modulation type to linear sweep. Set the sweep rate to 100 Hz. The sweep will take

10 ms (1/100Hz). Set the scope time base to 1ms/div.

Set the sweep start frequency to 100 kHz.

1-2

Getting Started

6) Press [SHIFT][STOP F] then [1][MHz].

7) Press [SWEEP ON/OFF].

8) Press [SHIFT][MRK STOP] then [9][0][0][kHz].

9) Press [SHIFT][MRK START] then [2][0][0][kHz].

10) Press [SHIFT][SPAN=MRK].

Set the stop frequency to 1 MHz. This starts the sweep. The MOD/SWP LED will

light, indicating that the DS345 is sweeping. The scope should show the SWEEP output as a 0V to 10 V sawtooth wave. The sweep starts at 100kHz when the sawtooth is at 0 V and moves to 1MHz when the sawtooth is at 10 V. The FUNCTION output is the swept sine wave. The markers are not yet active.

Display the stop marker position and set the stop marker to 900 kHz. The marker should now be high from the start of the sweep to 900kHz (9V on the sweep sawtooth), then the marker should go low.

Set the start marker to 200 kHz. The marker is now low from the beginning of the sweep until the 200 kHz start marker (2V on the sawtooth). The marker stays high until the 900 kHz stop marker. The markers allows designating any two frequencies in the sweep.

This sets the sweep span to the marker positions. The sweep now goes from 200 kHz to 900 kHz. This function allows zooming in on any feature in the sweep without entering the frequencies.

Tone Bursts

This example demonstrates the DS345's tone burst capability. The DS345 can produce a burst of 1 to 30,000 cycles of any of its output functions. The bursts may be triggered by the internal rate generator, the line frequency, a front panel button, or an external rising or falling edge. The TRIGGER output goes high when the burst is triggered and low when the burst is over.

Connect the DS345's FUNCTION output to an oscilloscope, terminating the output into 50 ohms. Set the sensitivity to 2V/div. Connect the rear-panel TRIGGER output to the scope and set 2V/div. Trigger the scope on the rising edge of the TRIGGER output. Set the scope timebase to 0.5ms/div.

1) Press [SHIFT][DEFAULTS].

2) Press [AMPL] then [5][Vpp].

3) Press [FREQ] then [1][0][kHz].

This recalls the DS345's default settings. Set the amplitude to 5Vpp. Set the output frequency to 10 kHz. This will be

the frequency of the tone.

1-3

Getting Started

4) Press [SWEEP MODE DOWN ARROW] three times.

5) Press [SHIFT][BRST CNT]. Then [1][0][Hz].

6) Press [SHIFT][TRIG SOURCE] Then press [MODIFY UP ARROW].

7) Press [SHIFT][TRIG RATE] then [4][0][0][Hz].

8) Press [SWEEP ON/OFF].

9) Press [SHIFT][BRST CNT].

10) Press [MODIFY DOWN ARROW] twice.

Set the modulation type to BURST.

Set the number of pulses in the burst to 10. Any of the units keys may be used to terminate the entry.

Display the burst trigger source. Then change the source from single trigger to the internal trigger rate generator.

Set the internal trigger rate generator to 400 Hz. Enable the burst. The MOD/SWP LED will light.

The scope should show two bursts of 10 cycles of a sine wave.

Display the burst count again. There should now be 8 pulses in each burst.

1-4

Introduction to Direct Digital Synthesis

Accumulator

48 bits

External Control

DAC

Frequency

Filter

Direct Digital Synthesis

Introduction

Traditional Generators Frequency synthesized function generators typically use a phase-locked loop

Arbitrary Waveforms Arbitrary function generators bypass the need for wave-shaping circuitry.

Direct Digital Synthesis (DDS) is a method of generating very pure waveforms with extraordinary frequency resolution, low frequency switching time, crystal clock-like phase noise, and flexible modulation. As an introduction to DDS let's review how traditional function generators work.

(PLL) to lock an oscillator to a stable reference. Wave-shaping circuits are used to produce the desired function. It is difficult to make a very high resolution PLL so the frequency resolution is usually limited to about 1:106 (some sophisticated fractional-N PLLs do have much higher resolution). Due to the action of the PLL loop filter, these synthesizers typically have poor phase jitter and frequency switching response. In addition, a separate wave-shaping circuit is needed for each type of waveform desired, and these often produce large amounts of waveform distortion.

Usually, a PLL is used to create a variable frequency clock that increments an address counter. The counter addresses memory locations in waveform RAM, and the RAM output is converted by a high speed digital-to-analog converter (DAC) to produce an analog waveform. The waveform RAM can be filled with any pattern to produce "arbitrary" functions as well as the usual sine, triangle, etc. The sampling theorem states that, as long as the sampling rate is greater than twice the frequency of the waveform being produced, with an appropriate filter the desired waveform can be perfectly reproduced. Since the frequency of the waveform is adjusted by changing the clock rate, the output filter frequency must also be variable. Arbitrary generators with a PLL suffer the same phase jitter, transient response, and resolution problems as synthesizers.

DDS DDS also works by generating addresses to a waveform RAM to produce

data for a DAC. However, unlike earlier techniques, the clock is a fixed frequency reference. Instead of using a counter to generate addresses, an adder is used. On each clock cycle, the contents of a Phase Increment Register are added to the contents of the Phase Accumulator. The Phase Accumulator output is the address to the waveform RAM (see diagram below). By changing the Phase Increment the number of clock cycles needed to step

DDS ASIC

Figure 1: Block diagram of SRS DDS ASIC

Fixed Frequency Reference

Phase

Increment

48 Bits

Modulation CPU

Phase

Modulation RAM

Waveform

RAM

16k points

Fixed

2-1

Introduction

through the entire waveform RAM changes, thus changing the output frequency.

Frequency changes now can be accomplished phase continuously in only one clock cycle. And the fixed clock eliminates phase jitter and requires only a simple fixed frequency anti-aliasing filter at the output.

The DS345 uses a custom Application Specific Integrated Circuit (ASIC) to implement the address generation in a single component. The frequency resolution is equal to the resolution with which the Phase Increment can be set. In the DS345, the phase registers are 48 bits long, resulting in an impressive 1:1014 frequency resolution. The ASIC also contains a modulation control CPU that operates on the Phase Accumulator, Phase Increment, and external circuitry to allow digital synthesis and control of waveform modulation. The Modulation CPU uses data stored in the Modulation RAM to produce amplitude, frequency, phase, and burst modulation, as well as frequency sweeps. All modulation parameters, such as rate, frequency deviation, and modulation index, are digitally programmed.

DDS gives the DS345 greater flexibility and power than conventional synthesizers or arbitrary waveform generators without the drawbacks inherent in PLL designs.

DS345 Description

12 bit DAC

10 MHz Bessel Filter

Output Amp

Attenuators

Function Output

Square Wave Comparator

Sync Output

AM Input

Modulation RAM

40MHz Clock

DDS345 ASIC

Amplitude DAC

Waveform RAM

Amplitude Control

Cauer Filter

Figure 2: DS345 Block Diagram

A block diagram of the DS345 is shown in Figure 2. The heart of the DS345 is a 40 MHz crystal clock. This clock is internally provided, but may be phase locked to an external reference. The 40 MHz clock controls the DDS345 ASIC, waveform RAM, and high-speed 12bit DAC. Sampling theory limits the frequency of the waveform output from the DAC to about 40% of 40 MHz, or 15 MHz. The 48 bit length of the DDS345's PIR's sets the frequency resolution to about 146 nHz. These parameters and the DAC's 12 bit resolution define the performance limits of the DS345.

2-2

Introduction

The reconstruction filter is key to accurately reproducing a waveform in a sampled data system. The DS345 contains two separate filters. For sine w

ave generation the output of the DAC goes through a 9th order Cauer filter,

while ramps, triangles, and arbitrary waveforms pass instead through a 10

MHz 7

order Bessel filter. The Cauer filter has a cutoff frequency of 16.5 MHz and a stopband attenuation of 85dB, and also includes a peaking circuit to correct for the sine(x)/x amplitude response characteristic of a sampled system. This filter eliminates any alias frequencies from the waveform output and allows generation of extremely pure sine waves. The output of the Cauer filter is then frequency doubled by an analog multiplier. This multiplies the DAC's 0 - 15 MHz output frequency range to the final 0 - 30 MHz range. However, the Cauer filter has very poor time response and is only useful for CW waveforms. Therefore, the Bessel filter was chosen for its ideal time response, eliminating rings and overshoots from stepped waveform outputs. This filter limits the frequency of arbitrary waveforms to 10 MHz and rise times to 35 ns.

The output of the filters pass to an analog multiplier that controls the amplitude of the waveform. This multiplier controls the waveform amplitude with an AM signal that may come from either the ASIC or the external AM input. This allows both internally and externally controlled amplitude modulation. The amplitude control is followed with a wide bandwidth power amplifier that outputs 10 V peak-to-peak into a 50 ohm load with a rise time of less than 15 ns. The output of the power amplifier passes through a series of three step attenuators (6, 12, and 24 dB) that set the DS345's final output amplitude. The post amplifier attenuators allow internal signal levels to remain as large as possible, minimizing output noise and signal degradation.

Square waves and waveform sync signals are generated by discriminating the function waveform with a high-speed comparator. The output of the comparator passes to the SYNC OUTPUT and, in the case of square waves, to the amplitude control multiplier input. Generating square waves by discriminating the sine wave signal produces a square wave output with rise and fall times much faster than allowed by either of the signal filters.

2-3

Introduction

2-4

OUTPUTS

FUNCTION

SYNC

REM SRQ ACT ERR

EXT ERR

ARB

NOISE

BURST

AM (INT)

LOG SWP

LIN SWP

TRIG'D SINGLE

ARB

MOD/SWP SHIFT

Hz dBm

DEG Vrms

% Vpp

FREQ AMPL OFFS PHASE TRIG STEP SPAN RATE MRK STRT f STOP f

ON/STBY

SRS

STANFORD RESEARCH SYSTEMS MODEL DS345 30MHz SYNTHESIZED FUNCTION GENERATOR

TIMEBASE

STATUS

Ω

40V max.

TTL

ECL

TTL

REL=0

TRIG SWP CF

BRST CNT

STOP f

MRK START

GPIB

TRIG SOURCE

MRK STOP

SRQ

TRIG RATE

ARB EDIT

MRK CF

RS232

MRK=SPAN

DEFAULTS

MRK SPAN

DATA

SPAN=MRK

CALIBRATE

LOCAL

AMPL

FREQ

OFFST

PHASE

RATE

SWEEP

ON/OFF

SPAN

(DEPTH)

START

FREQ

SHIFT STO RCL CLR

DEG

MHz dBm

kHz

Vrms

Vpp

STEP SIZE

+/-

FUNCTION

MODULATION

FUNCTION SWEEP/MODULATE MODIFYENTRY

1) Power Switch

The power switch turns the DS345 on and off. In the STBY position power is maintained to the DS345's internal oscillator, minimizing warmup time.

2) MODIFY Keys

The modify keys permit the operator to increase or decrease the displayed parameter value. The step size may be determined by pressing the STEP SIZE key (the STEP LED will light). Every displayed parameter has an associated step size, pressing the MODIFY UP arrow key adds the step size to the current value, while pressing the MODIFY DOWN arrow key subtracts the step size from the current value. If the step size is set to an exact power of 10 (1, 10, or 100, for example) the corresponding digit of the display will flash. To change the step size, display the step size and then either enter a new value with the ENTRY keys or the MODIFY keys. Pressing the MODIFY UP arrow while the step LED is lit will increase the step size to the next larger decade, while pressing the MODIFY DOWN arrow will decrease the step size to the next smaller decade. The MODIFY UP/DOWN arrows also select between different menu selections (ie., trigger source). Sometimes the parameter display will have more than one parameter displayed at a time, and the [SHIFT][LEFT] and [SHIFT][RIGHT] keys will select between these values.

3) ENTRY Keys

The numeric keypad allows for direct entry of the DS345's parameters. To change a parameter value simply type the new value using the keypad. The value is entered by terminating the entry with one of the UNITS keys. A typing error may be corrected by using the CLR key. The +/- key may be selected at any time during number entry.

4) Units Keys

The UNITS keys are used to terminate numeric entries. Simply press the key with the desired units to enter the typed value. Some parameters don't have

2-5

Front Panel Features

DS345 FEATURES

any associated units and

any

of the units keys may be used to enter the value. When the amplitude is displayed, pressing a units key without entering a new value will displayed the amplitude in the new units. This allows the am

plitude display to be switched between Vpp, Vrms, and dBm without entering

a new value.

5) Shift Key

The shift key is used to select the functions printed in gray above the keys. Press [SHIFT] and then [key] to select the desired function (for example [SHIFT][SWP CF] to display the sweep center frequency). When the SHIFT key is pressed the SHIFT LED will light. This indicates that the keyboard is in shift mode. Pressing [SHIFT] a second time will deactivate shift mode.

6) Modulation Keys

These keys control the DS345's modulation capabilities. The MODULATION TYPE up/down arrow keys select the modulation type. The MODULATION WAVEFORM up/down arrow keys select the waveform of the modulating function. The [SWEEP ON/OFF] key turns the modulation on and off. When the modulation is turned on the MOD/SWP LED will light. If the modulation parameters are not permitted for the selected output function, an error message will be displayed and modulation will not be turned on. Some modulation parameters are not relevant to all modulation types (start frequency is not relevant to AM, for example), and the message "NOT APPLIC" will be displayed if they are selected.

7) Function Keys

These keys choose the main function output. The FUNCTION up/down arrow keys select between the output functions. If the output frequency is set beyond of the range allowed for a waveform (> 100 kHz for triangle and ramp) a message will be displayed and the frequency will be set to the maximum allowed for that function.

8) Main Function BNC

This output has an impedance of 50Ω. If it is terminated into an impedance other than 50Ω the output amplitude will be incorrect and may exhibit increased distortion. The shield of this output may be floated up to ±40V relative to earth ground.

9) Sync Output BNC

This output is a TTL square wave synchronized to the main function output and has a 50Ω output impedance. The shield of this output may be floated up to ±40V relative to earth ground.

10) Status LEDs

These six LEDs indicate the DS345's status. The LED functions are: name

function

REM

The DS345 is in GPIB remote state. The STEP SIZE key returns local control.

SRQ

The DS345 has requested service on the GPIB interface.

ACT

Flashes on RS232/GPIB activity.

ERR

Flashes on an error in the execution of a remote command.

EXT CLOCK

The DS345 has detected a signal at its TIMEBASE input and is trying to phase lock to it.

CLOCK ERR

The DS345 is unable to lock to the signal at the TIMEBASE input. This is usually because the signal is too far (>2ppm) from the nominal values of 10, 5, 3.33, 2.5 or 1.25 MHz.

11) Parameter Display

This 12 digit display shows the value of the currently displayed parameter. The LEDs below the display indicate which parameter is being viewed. Error messages may also appear on the display. When an error message is displayed you can return to the normal operation by pressing any key.

2-6

12) Units LEDs

These LEDs indicate the units of the displayed value. If no LED is lit the number displayed has no units.

Rear Panel Features

FUSE: 3/4A (100/120VAC) or 3/8A (220/240VAC)

TRIGGER AM(EXT) TIMEBASE

TRIGGER MODULATION 10MHz

SWEEP MARKER BLANK/LIFT

TTL 0-5V 10MHz

TTL 0-5V 1V

TTLTTL0-10V

INPUTS

OUTPUTS

WARNING: No user serviceable parts inside. Refer to operation manual for safety notice. For use by qualified laboratory personnel only.

IEEE-488 STD PORT (GPIB) RS232 (DCE, 8d, 0p, 2s bits)

1) Power Entry Module

This contains the DS345's fuse and line voltage selector. Use a 3/4 amp fuse for 100/120 volt operation, and a 3/8 amp fuse for 220/240 volt operation. To set the line voltage selector for the correct line voltage first remove the fuse. Then, remove the line voltage selector card and rotate the card so that the correct line voltage is displayed when the card is reinserted. Replace the fuse.

2) External Inputs Trigger Input

The trigger input is a TTL compatible input used to trigger modulation sweeps and bursts. This input has a 10 kΩ input impedance. The shield of this input is tied to that of the function output and may be floated up to ±40V relative to earth ground.

AM Input

The AM input controls the amplitude of the function output. This input has a 100 kΩ input impedance and a ±5V range, where +5V sets the output to 100% of the front panel setting, 0V sets the output to 0, and -5V sets the output to -100% of the setting. The 0 to 5V range is used for normal AM operation, while the ±5V range is used for DSBSC modulation. This input is always active and should

only

be be connected if AM is desired. The shield of this input is tied to the shield of the function output and may be floated up to ±40V relative to earth ground.

DS345 FEATURES

2-7

DS345 FEATURES

Timebase Input

This 1kΩ impedance input allows the DS345 to lock to an external timebase. The external source should be greater than 1V pk-to-pk and should be within ±2 ppm of 10 MHz or any subharmonic down to 1.25 MHz.

The shield of

this input is connected to earth ground.

3) Auxiliary Outputs 10 MHz Output

This output produces a >1V pk-pk 10 MHz sinewave from the DS345's internal oscillator. It expects a 50Ω termination.

The shield of this output is

connected to earth ground.

Modulation Out

This output generates a 0 - 5V representation of the current modulation function. The shield of this output is tied to that of the function output and may be floated up to ±40V relative to earth ground.

Trigger Output

This TTL compatible output goes high when a triggered sweep or burst begins, and goes low when it ends. This may be used to synchronize an external device to the sweep/burst. The shield of this output is tied to that of the function output and may be floated up to ±40V relative to earth ground.

Sweep Output

This output generates a 0 - 10 V ramp that is synchronous with the DS345's frequency sweep. The shield of this output is tied to that of the function output and may be floated up to ±40V relative to earth ground.

Marker Output

This TTL compatible output goes high when the DS345's frequency sweep passes the start marker frequency, and goes low when the sweep passes the stop marker frequency. The shield of this output is tied to that of the function output and may be floated up to ±40V relative to earth ground.

Blank/Lift Out

This TTL compatible output is low during the upsweep of a frequency sweep, and is high during the sweep retrace. The shield of this output is tied to that of the function output and may be floated up to ±40V relative to earth ground.

4) GPIB Connector

If the DS345 has the optional GPIB/RS232 interface this connector is used for IEEE-488.1 and .2 compatible communications.

The shield of this con-

nector is connected to earth ground.

5) RS232 Connector

If the DS345 has the optional GPIB/RS232 interface this connector is used for RS232 communication. The DS345 is a DCE and accepts 8 bits, no parity, 2 stop bits and 300 and 19.2k Baud.

The shield of this connector is

connected to earth ground.

2-8

DS345 OPERATION

SYNC

FUNCTION

40V max

Ω

TTL

NOISE

TRIG'D

FREQ

AMPL

TTL

ECL OFFST REL=O PHASE

ARB

Introduction The following sections describe the operation of the DS345. The first section

describes the basics of setting the function, frequency, amplitude, and offset. The second section explains sweeps and modulation. The third section explains storing and recalling setups, running self-test and autocalibration, and setting the computer interfaces. The fourth and last section describes front panel editing of arbitrary waveforms.

Power-On When the power is first applied to the DS345 the unit will display its serial

number and ROM version for about three seconds. The DS345 will then initiate a series of self-tests of the circuitry and stored data. The test should take about three seconds and end with the message "TEST PASS". If the self test fails the DS345 will display an error message indicating the nature of the problem (see the TROUBLESHOOTING section for more details, page 4-

1). The DS345 will attempt to operate normally after a self-test failure, (pressing any key will erase the error message).

SETTING THE FUNCTION

OUTPUTS The FUNCTION and SYNC BNCs are the DS345's main outputs. Both of

these outputs are fully floating, and their shields may be floated relative to earth ground by up to ±40V. Both outputs also have a 50Ω output impedance. If the outputs are terminated into high impedance instead of 50Ω the signal levels will be twice those programmed (the FUNCTION output may also show an increase in waveform distortion). The programmed waveform comes from the FUNCTION output, while the SYNC output generates a TTL compatible (2.5 V into 50Ω) signal that is synchronous with the function out-

put. The SYNC signal is suppressed if the function is set to NOISE or BURST modulation. If the function is set to ARB the SYNC signal is a 25ns negative going pulse at the start of each waveform.

2-9

Function Setting

FUNCTION SELECTION

The DS345's output function is selected using the FUNCTION UP/DOWN arrow keys. Simply press the keys until the desired function LED is lit. If the programmed frequency is outside of the range allowed for the selected function, an error message will be displayed and the frequency will be set to the maximum allowed for that function. If modulation is enabled and the modulation type or parameters are incompatible with the new function, an error message will be displayed and the modulation will be turned off (the parameters will not be altered).

Ramps

Ramp functions usually ramp up in voltage, however, downward ramps may be programmed with the output invert function (see AMPLITUDE section).

Arbitrary Functions

Arbitrary functions may be created on a computer and downloaded to the DS345 via the computer interfaces, or they may be created using the DS345's front panel editing functions. Arbitrary waveforms normally repeat continuously, single triggering and burst triggering of arbitrary waveforms is accomplished using the DS345's BURST modulation function. (See the ARBITRARY WAVEFORM EDITING section for more detail.)

FREQUENCY

To display the DS345's output frequency press [FREQ]. The frequency is always displayed in units of Hz. The DS345 has 1 µHz frequency resolution at all fre

quencies, for all functions. The maximum frequency depends on the

Function

Frequency Range

Sine

1 µHz → 30.200000000000 MHz

Square

1 µHz → 30.200000000000 MHz

Triangle

1 µHz → 100,000.000000 Hz

Ramp

1 µHz → 100,000.000000 Hz

Noise

10 MHz White Noise (fixed)

Arbitrary

0.002329Hz → 40.0 MHz sampling

function selected as listed below: Frequency is usually displayed by the DS345 with 1 mHz resolution. However, if the frequency is below 1 MHz and the microhertz digits are not zero the DS345 will display the frequency with 1 µHz resolution. At frequencies greater than 1 MHz the digits below 1 mHz cannot be displayed, but the frequency still has 1 µHz resolution and may be set via the computer interfaces or by using the MODIFY keys with a step size less than 1 mHz.

If the function is set to NOISE the character of the noise is fixed with a band limit of 10 MHz. The frequency is not adjustable and the FREQ display will read "noise" instead of a numerical value.

If the function is set to ARB the frequency displayed is the

sampling fre-

quency

of the arbitrary waveform. This number is independent of the usual frequency; it is the dwell time that the DS345 spends on each point in an arbitrary waveform. This sampling frequency must be an integer submultiple

of the the 40 MHz clock frequency. That is, 40 MHz/N where N = 1,2,3... 234-1 (40 MHz, 20 MHz, 13.3333 MHz, 10 MHz, ...). The DS345 will spend

2-10

Function Setting

Fsample

on each point. When a new sampling frequency value is entered the DS345 will round the value to the nearest integer submultiple of 40 MHz. Note that the frequency for the standard functions is

never

rounded.

Setting the Frequency

To set the frequency of any function simply type a new value on the keypad and complete the entry with the appropriate units (Hz, kHz, or MHz). The MODIFY keys may be used to increase or decrease the frequency by the current step size. Press [STEP SIZE] key to display and change the step size.

AMPLITUDE

Pressing [AMPL] displays the amplitude of the output function. The amplitude may be set and displayed in units of Vpp, V

rms

, and dBm. The current units are indicated by the LEDs at the right of the display. The amplitude range is limited by the DC offset setting since |V

ac peak

| + |Vdc| ≤ 5 V. If the DC offset

is zero the amplitude range for each of the functions is shown below:

note

: The rms and dBm values for NOISE are based on the total power in the

output bandwidth (about 10 MHz) at a given peak to peak setting.

rms

dBm (50Ω)

Function

Max.

Min.

Max.

Min.

Max.

Min.

Sine

10V

10 mV

3.54V

3.54 mV

+23.98

-36.02

Square

10V

10 mV

5 mV

+26.99

-33.0

Triangle

10V

10 mV

2.89V

2.89 mV

+22.22

-37.78

Ramp

10V

10 mV

2.89V

2.89 mV

+22.22

-37.78

Noise

10V

10 mV

2.09V

2.09 mV

+19.41

-40.59

Arbitrary

10V

10 mV

n.a.

Arbitrary function amplitude may

only

be set in units of Vpp. The output sig-

nal will briefly go to zero as the output attenuators are switched. The units of the amplitude display may be switched between Vpp, V

rms

, and dBm without changing the actual amplitude by pressing the corresponding units

key. When the DS345 is switched from one function to another the peak-to-peak amplitude is held constant. If the DC offset is zero, the amplitude may be set with three digits of resolution. If the DC offset is not zero the larger of the amplitude and the offset determines the resolution of both parameters. The amplitude display is automatically adjusted such that all of the digits that may be changed are displayed.

Output Inversion

For ramp and arbitrary functions the DS345's output may be inverted. This is useful for turning positive ramps into negative ramps, or inverting arbitrary waveforms. Pressing [AMPL] two times displays the invert enable option. Use the UP/DOWN MODIFY keys to enable or disable the inversion.

D.C. Only

The output of the DS345 may be set to a DC level by entering an amplitude of 0V. When the amplitude is set to zero the A.C. waveform will be off and the DS345 may be used as a DC voltage source. If the amplitude is zero the display will read "no AC" when the units are set to dBm.

TTL Settings

Pressing [SHIFT][TTL] sets the output amplitude and offset to TTL values.

2-11

Function Setting

TTL levels are 5 V

with a 2.5V offset (the output will swing between 0 and

+5V).

ECL Settings

Pressing [SHIFT][ECL] sets the output amplitude and offset to ECL values. ECL levels are 1 Vpp with a -1.3V offset (the output will swing between -1.8V and -0.8V).

DC OFFSET

The DC offset may range between ±5V, but is restricted such that |V

ac peak

| + |Vdc| ≤ 5 V. When [OFFST] is pressed a new value may be entered using any amplitude unit key, the Vpp indicator LED will be lit . When the offset is changed the output signal will

briefly go to zero as the output attenuators are switched. If the amplitude is zero, the offset may be set with three digits of resolution. If the amplitude is not zero the larger of the amplitude and offset determines the resolution of both parameters. The offset display is automatically adjusted such that all of the digits that may be changed are displayed.

PHASE

Press [PHASE] to display and modify the phase of the FUNCTION output. Phase is always measured with respect to the internal timebase,

not

the

SYNC output. The phase may be changed with the keypad and the DEG

unit key, or using the MODIFY keys. The range of the phase setting is ±7199.999° and may be set with 0.001° resolution. If the function is set to NOISE, ARB, or modulation is enabled in SWEEP, FM, or PM modes the phase cannot be changed and the message "no Phase" will be displayed. In BURST modulation mode the PHASE function will set the waveform phase at the start of the burst. This is quite useful for starting the burst at a particular point in the waveform.

Zero Phase

The current phase may be assigned the value zero by pressing [SHIFT] [REL=0]. Subsequent changes to phase will be relative to this value.

2-12

SWEEPS AND MODULATION

LIN SWP SINGLE MOD/SWP

SWEEP ON/OFF

BURST

RATE

BRST CNT

SWP CF

SPAN

(DEPTH)

STOP f START

FREQ

ARB TRIG

AM (INT)

LOG SWP

Introduction

This section of the manual describes the DS345's modulation capabilities. The DS345 has extremely powerful and flexible built-in modulation functions. It is capable of AM (both simple and double sideband suppressed carrier (DSBSC)), FM, PM, tone bursts, and frequency sweeps. The modulation waveform may be a sine, square, ramp, or triangle wave. Frequency can be swept up or down at a linear or logarithmic rate. A built-in trigger generator allows triggering of single sweeps and bursts. For additional flexibility the DS345 can also modulate the output waveform with an arbitrary pattern of amplitude, frequency, or phase values.

SWEEP/MODULATE

MODULATION ON/OFF The SWEEP ON/OFF key enables the DS345's modulation functions. Press-

MODULATION TYPE The type of modulation is selected using the MODULATION TYPE [UP/

MODULATION WAVEFORM The waveform of the modulating function is selected with MODULATION

ing the key toggles the modulation status. When modulation is on the [MOD/SWP] LED will light. When modulation is enabled the modulation type and modulation parameters are checked for consistency with the selected output function. If the selected modulation is illegal (for example, FM frequency out of range for the function) the DS345 will display an error message and not enable the modulation. The erroneous value must be changed before the modulation is turned on.

DOWN] arrow keys. Most of the output functions can be modulated by any type of modulation. However, NOISE can only be modulated by the external AM input, and ARB waveforms can only be modulated by AM and BURST modulations. If an invalid choice is selected the message "funct error" is displayed.

WAVEFORM UP/DOWN arrow keys. If no LEDs are lit the selected modulation type has no associated waveform (BURST, for example, has no modulation waveform). Not all modulation types may use all modulation waveforms. The allowable combinations are listed on the following page. Note that ARB modulation waveforms can only be downloaded via the computer interfaces.

2-13

Modulation and Sweeps

If no waveform has been downloaded when this modulation is enabled the message "arb corrupt" will be displayed (see the ARBITRARY MODULATION section).

Single

Ramp

Triangle

Sine

Square

Arb

None

Type

Linear Swp

Yes

Log Swp

Yes

Burst

Yes

Table 1: Allowed modulation waveforms for each modulation type

MODULATION RATE

Pressing [RATE] displays and sets the modulation rate. Use the keypad and unit indicators of Hz, kHz, or MHz (or the MODIFY up/down keys) to set the modulation rate.

The modulation rate is the frequency of the modulation waveform. For example, if the modulation type is AM, the waveform a sine wave, and the rate 1 kHz the modulating waveform will be a 1 kHz sine wave. For sweeps the modulation rate is the inverse of the sweep time (ie., a 10ms sweep would be entered as 100 Hz). Burst modulation has no associated modulation rate and the message "not applic" is displayed if [RATE] is pushed.

The modulation rate has a range of 0.001 Hz to 10 kHz for AM, FM, and PM. The range for sweeps is 0.001 Hz to 1 kHz (1000s to 0.001s sweep time). The modulation rate may be set with two digits of resolution. If the modulation waveform is set to ARB (AM ARB, FM ARB, or PM ARB) the modulation rate has a different meaning. See the ARBITRARY MODULATION section for more details.

2-14

AMPLITUDE MODULATION

Introduction

The DS345 has the ability to amplitude modulate its function output with both the internal modulation generator and an external analog voltage. The internal modulation generator may modulate the output with a sine, square (pulse modulation), triangle, ramp, or arbitrary modulation pattern. The external modulation may be either simple AM or Double Sideband Suppressed Carrier (DSBSC) modulation.

External AM Source

The rear-panel AM INPUT is active at

all

times (even in concert with any other modulation type). The AM INPUT has an input voltage range of ±5V. A +5V input produces an output that is 100% of the programmed value, a 0V input turns the output will off (0%), and at -5V input produces an output that is -100% of the programmed output (a 180° phase change). Applying voltages from 0 to 5V will result in simple AM. If the voltages are balanced around zero (from -5V to +5V) DSBSC modulation will result (for good carrier suppression the modulating signal must have an average value of zero). The AM INPUT has a bandwidth of about 20 kHz.

INTERNAL AM

The internal modulation generator can modulate any of the DS345's output functions except NOISE. The modulating waveform may be a sine, square, triangle, ramp, or arbitrary pattern. The rear-panel MODULATION OUTPUT outputs a signal corresponding to the amplitude control voltage. 100% of the output amplitude will produce an output of +5V, zero output will produce 0V, and -100% output will produce -5V out.

Modulation Depth

Press [DEPTH] to display and set to the AM modulation depth. The value may be set using the keypad and % units key, or the MODIFY keys. This value has a range of ±100% with 1% resolution. Positive values (0 to100%) will set simple AM with a modulation percentage equal to the DEPTH. Zero percent depth corresponds to no modulation, while 100% depth corresponds to modulating the output from full off to full on. Negative values (-1% to

-100%

)

will set DSBSC modulation with a modulation percentage equal to the depth.

Modulation Rate

Press [RATE] to display and to set the frequency of the modulating function. The frequency may be set with two digits of resolution from 0.001 Hz to 10 kHz

Modulation and Sweeps

2-15

Modulation and Sweeps

FREQUENCY MODULATION

Introduction

The DS345 is capable of frequency modulating any of its output functions, except NOISE and ARB, using its internal modulation generator. The modulation waveform may be a sine, square (FSK), triangle, ramp, or an arbitrary pattern. The rear-panel MODULATION OUTPUT outputs a signal with 0V corresponding to the smallest frequency output and +5V corresponding to the largest frequency output.

Frequency Span

During FM the DS345 outputs a signal whose frequency range is centered about the programmed frequency. SPAN sets the amount that the frequency varies from the center frequency. The minimum frequency output will be the center frequency - SPAN/2, while the maximum frequency will be the center frequency + SPAN/2. The value SPAN/2 is commonly called the

deviation

(that is, SPAN = Deviation x 2). The SPAN is displayed and set by pressing [SPAN]. The SPAN may be set with 1 µHz resolution, and has a limited

range such that the output frequency is always greater than zero and less than or equal to the maximum allowed for the function selected (30.2 MHz for sine and square, 100 kHz for triangle and ramp).

Modulation Rate

Pressing [RATE] displays and sets the frequency of the modulating function. The frequency may be set with two digits of resolution from 0.001 Hz to 10 kHz.

2-16

PHASE MODULATION

Introduction

The DS345 is capable of phase modulating any of its output functions, except NOISE and ARB, using its internal modulation generator. The modulation waveform may be a sine, square (PSK), triangle, ramp, or arbitrary pattern (see ARBITRARY MODULATION section for information about ARB patterns). The rear-panel MODULATION OUTPUT outputs a signal with 0V corresponding to the largest negative phase deviation and +5V corresponding to the largest positive phase deviation.

Phase Span

During PM the DS345 outputs a signal whose frequency is centered about the programmed frequency. SPAN sets the amount that the phase varies relative to zero phase. The minimum phase shift output will be -SPAN/2, while the maximum phase shift output will be +SPAN/2. The value SPAN/2 is commonly called the

deviation

(that is, SPAN = Deviation x 2). The SPAN is dis-

played and set by pressing [SPAN]. The value of the SPAN may be set with

0.001° resolution with a range of 0° to 7199.999°.

Modulation Rate

Press [RATE] to display and set the frequency of the modulating function. The frequency may be set with two digits of resolution in the 0.001 Hz to 10 kHz range.

Modulation and Sweeps

2-17

Modulation and Sweeps

BURST MODULATION

Introduction

The DS345 generates tone bursts of any of its periodic output functions. The frequency of the output function is limited to 1 MHz for sine and square waves, 100 kHz for triangles and ramps, and no limits for ARBs. When a trigger signal is received the DS345 initiates a burst starting at a specific point (phase) in the output waveform, outputs the exact number of programmed waveform cycles, and then stops. The rear-panel TRIGGER OUTPUT generates a TTL compatible signal that goes high when the burst is triggered and low when the burst is complete. This signal may be used to synchronize external equipment to the burst. The SYNC output is not active during tone bursts.

Burst Count

The number of complete cycles in a burst is set by pressing [SHIFT][BRST CNT]. The number may be set from 1 to 30000 cycles. The maximum time for a complete burst is 500s, the time for a burst is easily computed from the following formulas:

Burst

for sine, square, triangle, ramp

Burst Time =

Burst Count× # Waveform Points

Sampling Frequency

for ARB

Waveform Starting Point The point in the waveform at which the burst starts (the phase) may be ad-

Time =

justed for sine, square, triangle, and ramp waves. For ARBs the burst always starts on the first waveform point. Changing the PHASE changes the point at which the burst starts. 0.000 degrees phase corresponds to the positive zero crossing of the function, and values up to 359.999 degrees increment through the waveform. PHASE values larger than 360 degrees are set to modulo 360 degrees.

Burst Count

Frequency

Triggering a Burst Burst modulation is a triggered function, and therefore a signal needs to ini-

tiate the burst. The trigger generator can initiate a burst from the front panel [TRIG] key, the internal rate generator, the external trigger input, or the power line frequency. Setting the trigger generator is detailed in the TRIGGER GENERATOR section (2-22). The TRIG'D LED flashes green each time a burst is triggered. If the DS345 is triggered before the previous burst is complete the TRIG'D LED flashes red, indicating a trigger error. At high trigger rates a combination of triggers (green) and trigger errors (red) can make the TRIG'D LED appear orange. Once a burst is triggered the DS345 will ignore all other triggers until the burst is complete.

2-18

FREQUENCY SWEEPS

Introduction

The DS345 can frequency sweep its function output for sine, square, triangle, and ramp waves. The sweeps may be up or down in frequency, and may be linear or log in nature. The frequency changes during the sweep are phase continuous and the sweep time may be set between 0.001 and 1000 seconds. The DS345 has an analog SWEEP output that may be used to drive an x-y recorder or oscilloscope, a TTL BLANK/LIFT output that can lift a chart recorder pen during the sweep retrace, and a TTL MARKER output that may be set to make transitions at two programmable frequencies during the sweep.

Sweep Type

Pressing the MODULATION TYPE UP/DOWN ARROW keys sets the sweep to either a linear or log sweep. The output frequency in a linear sweep changes linearly during the sweep time. The output frequency in a log sweep changes exponentially during the sweep time, spending an equal amount of time in each decade of frequency. For example, in a sweep from 1 kHz to 100 kHz, the sweep will spend half the time in the 1 kHz to 10 kHz range and half the time in the 10 kHz to 100 kHz range). It should be noted that these are digital sweeps, and that the sweep is actually composed of 1500 to 3000 discrete frequency points, depending on the sweep rate.

Sweep Waveform

The DS345's sweep waveform may be set to single, triangle, or ramp using the MODULATION WAVEFORM UP/DOWN arrow keys. With the SINGLE setting the DS345's output frequency will be the sweep start frequency until a trigger is received. The output will then sweep to the stop frequency, reset to the start frequency and wait for another trigger (see the TRIGGER GENERATOR section for setting the trigger source). If the waveform is set to a RAMP the DS345 will sweep from the start to the stop frequency, jump back to the start frequency, and repeat continuously. If the waveform is a TRIANGLE the DS345 will sweep from the start to the stop frequency, sweep back from the stop frequency to the start frequency, and repeat continuously.

Sweep RATE/Time

The duration of the sweep is set by [RATE], and the value is entered or modified with the keypad. The sweep rate may be set over the range of 0.001 Hz to1 kHz. The sweep rate is the inverse of the sweep time, a 0.001 Hz rate is equal to a 1000s sweep time, and a1 kHz rate is equal to a 1 ms sweep time. For a TRIANGLE sweep the sweep time is the total time to sweep up and down.

SWEEP FREQUENCIES

The DS345 may sweep over any portion of its frequency range:1 µHz to

30.2 MHz for sine and square waves, and 1 µHz to 100 kHz for triangle and ramp waves. There are no restrictions on minimum or maximum sweep span.

The DS345's sweep range may be set by entering either the start and stop frequencies, or the center frequency and span. The relationships between the frequencies are:

Center Frequency

= (Stop Frequency + Start Frequency) / 2

Span

= Stop Frequency - Start Frequency

Start Frequency

= Center Frequency - Span/2

Stop Frequency

= Center Frequency + Span/2

Modulation and Sweeps

2-19

Modulation and Sweeps

Start and Stop Frequencies

To enter the sweep start frequency press [START FREQ]. Set the stop frequency by pressing [SHIFT][STOP F]. The start and stop frequencies may have any values that are allowed for the displayed waveform. If the stop frequency is greater than the start frequency the DS345 will sweep up, while if the start frequency is larger the DS345 will sweep down.

Center Frequency and Span

To set the sweep center frequency press [SHIFT][SWP CF]. The center frequency may be set to any value allowed for the displayed waveform. Set the sweep span by pressing [SPAN]. The span value is restricted to sweep frequencies greater than zero and less than or equal to the maximum allowed frequency. If the span is positive the DS345 will sweep up, if it is negative the DS345 will sweep down. The MODIFY keys may be used to change the span: pressing [MODIFY UP] will double the span, while pressing [MODIFY DOWN] divides the span in half. The MODIFY keys affect the span in octaves–the size of the step is the value displayed by the step size. When the center frequency is changed the span is held constant, while changing the span holds the center frequency constant. If the center frequency or span is changed such that the sweep frequencies are out of the allowed range an error will be displayed on the front panel.

SWEEP MARKERS

The DS345 has two sweep markers that may be used to indicate any two frequencies in the sweep. The MARKER output is a TTL compatible signal that goes high when the sweep frequency crosses the start marker frequency and low when the sweep frequency crosses the stop marker frequency. In a triangle sweep the markers are only active on the up sweep. The marker positions may be set by entering the marker start and stop frequencies, or the center frequency and span.

Marker Start and Stop

The marker start and stop frequencies are independent of each other and are set by pressing [SHIFT][MRK START] and [SHIFT][MRK STOP] respectively. The frequencies can be set to any value from 1 µHz to 30.2 MHz. If the

mark-

er start frequency is lower than the marker stop frequency the MARKER output will initially be low, go high when the sweep crosses the start marker position, and go low again when the sweep crosses the stop marker position. If the marker start frequency is greater than the marker stop frequency the MARKER output will be initially high, go low when the sweep crosses the stop marker position, and go high again when the sweep crosses the start marker position. If either of the marker positions are outside of the sweep range the marker output will behave as if the sweep had crossed its position. These cases are shown in the diagram below:

Case 1: Marker Start Freq < Marker Stop Freq

Case 2: Marker Start Freq > Marker Stop Freq

Case 3: Marker Start Freq < Sweep Start Freq

Figure 1: Marker Output for different relationships between the marker start and stop frequencies.

Mrk Start

Mrk Stop

Sweep Start Frequency

Mrk Start

Mrk Stop

Mrk Start

Sweep Stop Frequency

Mrk Stop

2-20

Modulation and Sweeps

Marker Center and Span

The markers may also be set by the center frequency and span (width) of the marked region. Pressing [SHIFT][MRK CF] and [SHIFT][MRK SPAN] respectively sets the center frequency and span. The center frequency may have any value from 1 µHz to 30.2 MHz range. The span may be any value such

that the marker frequencies are greater than zero and less than or equal to

30.2 MHz. If the span is positive the marker start position will be below the stop position, while if the span is negative the marker start position will be greater than the stop position. If the MODIFY keys are used to change the span- pressing [MODIFY UP] will double the span, and pressing [MODIFY DOWN] will divide the span in half. When the center frequency is changed the span is held constant, while changing the span holds the center frequency constant. If the center frequency or span is changed such that the marker frequencies are out of the allowed range an error will be displayed.

Marker to Span

Pressing [SHIFT][MRK=SPAN] sets the positions of the markers to the extremes of the sweep span. The marker start frequency will be set to the sweep start frequency, and the marker stop frequency will be set to the sweep stop frequency. This function is useful for finding the markers when setting up a sweep.

Span to Marker

Press [SHIFT][SPAN=MRK] to set the sweep span to the marker positions. Now the sweep start frequency will be set to the marker start frequency, and the sweep stop frequency will be set to the marker stop frequency. This function can be used to "zoom in" on a marked section of the sweep. If this function sets the sweep frequencies to a value not allowed for the selected waveform, an error will be generated and the sweep disabled.

SWEEP OUTPUT

The rear-panel SWEEP output is a 0–10 V analog output that ramps linearly during a sweep. The output voltage is 0V at the sweep start frequency, and 10V at the sweep stop frequency (during TRIANGLE sweeps the SWEEP output will go from 0V to 10V to 0V). This output may be used to drive a chart recorder or x-y oscilloscope.

BLANK/LIFT OUTPUT

This is a TTL compatible output that is low during the upsweep of a sweep and high during the during the downsweep or sweep reset. This output may be used to blank the retrace of an x-y oscilloscope, or lift the pen on a chart recorder.

10V

Sweep Output

Blank/Lift Output

10V

Sweep Output

Blank/Lift Output

TRIANGLE Sweep

Figure 2: Auxilliary output waveforms during different types of sweeps.

RAMP and SINGLE Sweep

2-21

Modulation and Sweeps

TRIGGER GENERATOR

Introduction

The DS345 has an internal trigger generator that triggers BURSTS and SINGLE sweeps from a wide variety of sources. Once a BURST/SWEEP is triggered the DS345 will ignore all triggers until the BURST/SWEEP is complete. Therefore, a BURST/SWEEP cannot be affected by accidentally triggering too rapidly.

Trigger Source

Press [SHIFT][TRIG SOURCE] to display the trigger source. Use the MODIFY keys to change the source. The choices are:

Source

Function

SINGLE

The front-panel TRIG key starts the BURST/SWEEP.

RATE

The internal rate generator starts the BURST/SWEEP.

POS IN

The rising edge of the TRIGGER input starts the BURST/ SWEEP

NEG IN

The falling edge of the TRIGGER input starts the BURST/ SWEEP.

LINE

The power line frequency starts the BURST/SWEEP.

Trigger Rate

The frequency of the internal trigger rate generator is set by pressing [SHIFT][TRIG RATE]. The rate may be set to any value in the range 0.001 Hz to 10 kHz with two digits of resolution.

TRIG'D LED

The TRIG'D LED indicates the DS345's trigger status. Each time a trigger is

accepted the TRIG'D LED flashes green. If the DS345 is triggered again before the previous BURST/SWEEP is complete, the TRIG'D LED will flash red, indicating a trigger error. At higher trigger rates a combination of triggers (green) and trigger errors (red) can make the TRIG'D LED appear orange.

Trigger Input

The rear-panel TRIGGER input is a TTL compatible input. An edge at this input will trigger a BURST/SWEEP if the trigger source is set to POS IN or NEG IN.

Trigger Output

The rear-panel TRIGGER output is a TTL compatible output that goes high when the DS345 triggers a BURST/SWEEP, and goes low again when the BURST/SWEEP is complete. This output is operational for all trigger sources.

2-22

ARBITRARY MODULATION PATTERNS

Introduction

In addition to the usual sine, square, triangle, and ramp waveforms the DS345's AM, FM, and PM functions can modulate the output waveform with an arbitrary modulation pattern. The arbitrary modulation pattern can only be set using a computer interface and the AMOD? query command. The computer downloads a list of amplitude percentages, frequencies, or phase shifts to the DS345. The DS345 then modulates the waveform using these values. To use arbitrary modulation, the modulation type must be set to AM, FM, or PM, and an arbitrary pattern must then be sent to the DS345. If no pattern has been loaded the DS345 will display the message "arb corrupt". [SWEEP ON/OFF] enables the arbitrary modulation. Switching to a different modulation type or waveform after a pattern has been downloaded to the DS345 will erase the donwloaded pattern.

Modulation Rate

Pressing [RATE] sets the modulation rate. The value displayed when the modulation waveform is set to ARB is different than the usual modulation rate. The value displayed is the value of the

modulation rate divider

(MRD)

, which can be set between 1 and 223-1 (8,388,607). This value sets

the

time

the DS345 spends at each point in the arbitrary modulation wave-

form. The time at each point is given by:

Type of Arb Modulation

Time

150ns * MRD

1 µs * MRD

250ns * MRD

Waveform List

The ARB waveform is created by downloading a list of values via the computer interface. For ARB AM the values are percentages of the programmed amplitude. The waveform may have up to 10,000 AM points. For ARB FM the values are the frequencies to be output, and must be a valid frequency for the selected function. The waveform may have up to 1500 FM points. For ARB PM the values are phase

shifts

(relative to the current phase) in the

range ±180°. The waveform may contain up to 4000 PM points.

Downloading

The waveform list may be downloaded to the DS345 via the RS232 or the GPIB interface. The data format is discussed in the PROGRAMMING section under the AMOD? command. The PROGRAM EXAMPLES section (pgs. 3-5) provides examples of generating and downloading waveform data.

Modulation and Sweeps

2-23

Modulation and Sweeps

DS345 AS A PULSE GENERATOR

Introduction

The DS345 can be easily used as a pulse generator. Pulse widths down to 500 ns with rise/fall times of 30 ns and repetition rates up to 10 kHz internally and 500 kHz externally triggered are possible. You can even do bursts of groups of pulses (each pulse has to be the same width and separated by 1 pulse width).

Procedure

tart with a square wave as the main waveform, selecting the square wave frequency (1 MHz max. for this purpose) so that half of a period is the width of the pulse you want. Then choose burst modulation, with a burst count of 1 and turn on sweep mode. Use the phase control to adjust the phase of the square wave within the burst so that only a positive going or negative going half cycle is visible (generally a phase shift of 180 degrees for a positive pulse). Note that by varying the phase you can also delay a pulse by up to one half a period of the frequency with respect to an external trigger. Finally, use the offset control to adjust the baseline of the pulse to be 0 Volts. You will have to start with a square wave amplitude of at most one half of the maximum DS345 peak to peak amplitude. This gives a maximum pulse amplitude of 10 Volts into high impedance or 5 Volts into 50 Ohms.

After setting this up, changing the burst rate will change the pulse repetition rate, and changing the square wave frequency will change the pulse width. To do groups of pulses, simply increase the burst count to the number of pulses you want in the burst. Use the trigger input connector and set the trigger control to external (positive or negative) for externally triggered bursts. If the source of the trigger has a 10 MHz clock input, connecting this to the DS345 clock output will reduce pulse to pulse jitter.

Arbitrary Waveform

he other way to create pulses is using arbitrary waveforms, which can be done from the front panel using vector entry mode, or through the AWC software. This technique is a little more complicated and does not allow the same ease of changing pulse width or repetition rates, but pulse widths down to 50 ns and externally triggered repetition rates up to 2 MHz are possible.See other sections of this manual for instructions for arbitrary waveform generation and AWC software.

2-24

INSTRUMENT SETUP

Setting

Default Value

Frequency

1.0 kHz

Arb Sampling Frequency

40.0 MHz

Amplitude

0.01 Vpp

Offset

0.0 V

Inversion

Off

Phase

0.0°

Modulation Enable

Off

Modulation Rate

1.0 kHz

Modulation Type

Modulation Waveform

Sine

Sweep Parameters

1.0 Hz start frequency and start marker ,

100.0 kHz stop frequency and stop marker

AM Parameters

50% depth, sine wave

FM Parameters

1.0 kHz span, sine wave

PM Parameters

45.0° span, sine wave

Burst Parameters

1 cycle

Trigger Source

SINGLE

Trigger Rate

1.0 kHz

Interface

RS232

Baud Rate

9600

GPIB Address

Power on Status Clear

Storing Setups

To store the DS345's current setup press [STO] followed by a location number in the range of 0 to 9. Pressing any of the UNITS key to enter the location number, the message "Store Done" indicates that all of the settings have been stored.

Recalling Stored Settings

To recall a stored setting press [RCL] followed by the location number (0 - 9). Pressing any UNITS key enters the location number, and the message "recall done" indicates that the complete settings have been recalled. If nothing is stored in the selected location or the settings have become corrupted, the DS345 will display "rcl error".

2-25

Introduction

Default Settings Pressing [SHIFT][DEFAULTS] recalls the DS345's default settings and clears

This section details the DS345's default settings, storing and recalling settings, setting the computer interfaces, and running self-test and autocal.

any stored arbitrary waveforms. The DS345's default settings are listed below:

DS345 Setup

GPIB Setup

To set the DS345's GPIB interface press [SHIFT][GPIB]. Use the MODIFY up/down keys to enable the GPIB interface. Pressing [SHIFT][GPIB] again displays the GPIB address. Enter the desired address using the keypad or MODIFY keys. The range of valid addresses is 0 to 30.

NOTE:

If the DS345 does not have the optional GPIB/RS232 interfaces the message "no interface" will be displayed when the GPIB menu is accessed. The GPIB and RS232 interfaces are exclusive, only one may be active at a given time (the RS232 interface is automatically disabled when GPIB is enabled).

RS232 Setup

To set the DS345's RS232 interface press [SHIFT][RS232]. Use the MODIFY up/down keys to enable the RS232 interface. Pressing [SHIFT][RS232] again displays the RS232 baud rate selection. Baud rates of 300, 600, 1200, 2400, 4800, 9600, or 19200 are set with the MODIFY keys.

NOTE:

If no interface option is present the message "no interface" will be displayed when the RS232 menu is accessed. The GPIB and RS232 interfaces are exclusive, only one may be active at a given time (the GPIB interface is automatically disabled when RS232 is enabled).

User Service Requests

While GPIB is enabled the user may issue a service request (SRQ) by pressing [SHIFT][SRQ] followed by any of the UNITS keys. The message "srq sent" will be displayed, and the SRQ LED will light. The SRQ LED will go off after the host computer does a serial poll of the DS345. The user service request is in addition to the usual service requests based on status conditions (see PROGRAMMING section for details).

Communications Data

Press [SHIFT][DATA] to display the last 256 characters of data that the DS345 has received. This display is a scrollable 4 character window into the DS345's input data queue. The data is displayed in ASCII hex format, with each input character represented by 2 hexadecimal digits. The most recently received character has a decimal point indicator. Pressing [MODIFY DOWN ARROW] scrolls the display earlier in the queue, and [MODIFY UP ARROW] scrolls later in the queue. The display cannot be moved later than the last character received.

2-26

AUTO-TEST AND CALIBRATION

Introduction

The DS345 has built-in test and calibration routines that allow the user to quickly and easily test and calibrate virtually the entire instrument. [SHIFT] [CALIBRATE] cycles the DS345 through the calibration menu. Self-test and autocal are started by pressing any UNITS keys while the menu line is displayed.

SELF-TEST

The DS345's always executes a self-test on power-up, self-tests can also be initiated from the test menu. These tests check most of the analog and digital signal generation circuitry in the DS345. Pressing any UNITS key when the SELF-TEST menu item is displayed starts the self-tests. The tests take about three seconds to execute, and should end with the display "test pass". If the self-test encounters a problem it will immediately stop and display a warning message. See the

TROUBLESHOOTING

section for a list and explanation of the error messages. If the DS345 fails any test it still may be operated, simply press any key to erase the error message.

note:

the error "Gain FS Err" can occur if a signal is applied to the external

AM input during self-test. Disconnect any signals at this input during self-test. The DS345 tests its CPU and data memory, ROM program memory, calibra-

tion constant integrity, ASIC waveform memory, modulation program memory, 12-bit waveform DAC, analog-to-digital converter, output amplifier, offset and amplitude control circuits, frequency doubler, and square wave comparator.

Items

not

tested are the connections from the PC boards to the BNC connectors, the output attenuators, the 40 MHz clock and phase locking circuitry, the computer interfaces, and the SYNC output driver.

AUTOCAL

The DS345's autocal routine calibrates the majority of the signal generation path, including the DC offsets of the output amplifier, the signal path offsets, the offset and gain of the amplitude controls, and the gain of the output amplifier. These calibrations correct for any aging and temperature dependencies of the DS345's circuits. Pressing any UNITS key when the AUTOCAL menu item is displayed starts the calibration. Autocal is disabled during the first two minutes after power on to allow the DS345 to warm up (an error will be displayed if autocal is started before this time).

Autocal takes about two minutes to execute and should end with the message "cal done".

note:

Be sure to have disconnected any signals from the External AM input during Autocal. If AUTOCAL encounters a problem it will immediately stop and display an error message. See the

TROUBLESHOOT-

ING

section (pg. 4-1) for a list and explanation of the error messages. If the DS345 fails its AUTOCAL it still may be operated, simply press any key to erase the error message. However, the error may be indicating a hardware problem that probably should be addressed.

The items

not

calibrated by the autocal procedure are the frequency dependent amplitude corrections, the doubler carrier null, the attenuator ratios, and the clock frequency. These values are stable and should not need adjustment except during an annual recalibration.

note:

Disconnect any signals from the External AM input during Autocal

DS345 Setup

2-27

DS345 Setup

The items

not

calibrated are the frequency dependent amplitude corrections, the doubler carrier null, the attenuator ratios, and the clock frequency. These values are stable and should not need adjustment except during the yearly recalibration.

2-28

ARBITRARY WAVEFORM EDITING

Introduction

Sampling Rate When the function is set to ARB the displayed frequency is the arbitrary

This section describes the DS345's arbitrary waveform capabilities, and how to edit those waveforms from the front panel. The DS345 can store arbitrary waveforms in two formats: point and vector. In point format the DS345 stores only a list of amplitude values to load into the waveform RAM. This list can be up to 16,300 points long, with each memory point representing a point in the output waveform. In vector format the data stored is a list of vertices– x,y pairs of values (up to 6144 pairs). Each data pair specifies an address in waveform RAM (the x value), and the amplitude at that point (the y value). The waveform RAM locations between successive vertices are automatically filled in by connecting the vertices with straight lines.

Note: Front panel editing can be very tedious. Large or complex waveforms are easily created using the Arbitrary Waveform Composer Software.

waveform sampling frequency. This number is not related to the normal waveform frequency, but is the time that the DS345 dwells at each point in the arbitrary waveform. This sampling frequency must be an integer submultiple of the the 40 MHz clock frequency. That is, 40 MHz/N where N = 1,2,3...

-1 (for example 40 MHz, 20 MHz, 13.3333 MHz, 10 MHz,...). The DS345

2 will spend 1/Fsample on each point (40 MHz = 25 ns, 20 MHz = 50 ns, etc.). When a new sampling frequency value is entered the DS345 will round the value to the nearest integer submultiple of 40 MHz. The time needed to repeat a complete waveform is simply: # points in waveform/Fsample.

SYNC Output During arbitrary waveform generation the front-panel SYNC output generates

a negative going (5V to 0V) 25ns pulse at the start of the arbitrary waveform.

EDIT MENU Pressing [SHIFT][ARB EDIT] repeatedly cycles through the three lines of the

EDIT menu.

Storage Format The first menu line allows selecting the ARB waveform storage mode. Simply

select POINT or VECTOR using the MODIFY up/down keys. The arbitrary waveform must be cleared before the storage mode can be changed (see below).

Clearing Current Waveform The third line of the EDIT menu allows the current ARB waveform to be

cleared. Pressing any of the UNITS keys with this line displayed clears the current waveform.

EDITING The second line of the EDIT menu allows editing of actual waveform data.

The editing process is interactive, the waveform RAM is updated any time an editing operation takes place. Displaying the FUNCTION output on an oscilloscope allows the user to see the waveform change as the data is modified.

2-29

Arbitrary Waveform Editing

Data Display

The format of the data display is shown below for both point and vector format. The data line has two values in both formats. The left value is the point/ vertex number, indicating which point/vertex is being edited. The right hand value is the data for that point. Only one value is active (flashing) at any time. The active value is selected by pressing [SHIFT][RIGHT ARROW] or [SHIFT][LEFT ARROW]. The active value may be changed with the keypad or MODIFY up/down keys. In vector format the x/y indicator denotes that the data value is either the x value (h) or y value (y) for the given vertex. The display is switched between x and y by pressing [STEP SIZE].

Point Format:

00123 1234

Point #

Point Value

Vector Format:

0123 h 1234

x/y indicator

POINT EDITING

The following section describes editing point format arbitrary waveforms.

Point Number

The point number may be set to any value between 0 and the total number of points in the current waveform. The point number is set by either the keypad or the MODIFY up/down keys. The maximum point number is 16,299 (there must more than 8 and less than 16,300 points in a waveform). If the point number is set to a value greater than the maximum (where there is no data), an "edit error" will result. Also, if the waveform has fewer than 8 points the remaining points will automatically be filled with zeroes to bring the number of output points to 8.

Point Value

Each point may have an amplitude value ranging between -2048 and +2047 (12 bit DAC). If a point has no value (before a value has been entered, for example) the data will be displayed as five dashes (-----).

Adding a point to the end of the waveform

To add a point to the end of a waveform set the point number to the last point + 1. The value will be displayed as ----- prior to entering a value. Enter a new value for the point value.

Deleting a Point

To delete a point, enter the point number to be removed. Then, with the point number active (flashing), press [CLR]. The remaining points will automatically be renumbered as necessary.

Duplicating a Point

To duplicate a point, enter the point number to be copied. While the point number is active (flashing) press any UNITS key. The point will be duplicated and the point number incremented to display the new point.

Inserting a Point

To insert a point in the middle of a waveform, duplicate the point currently at the insertion point. It is easy to modify this new point to the desired value.

Vertex #

data Value

2-30

Arbitrary Waveform Editing

POINT EDIT EXAMPLE

The following is a step-by-step example for creating a point format waveform. We will create an 8 point waveform with the values 0,400,800,1200,0,0,0,0. Along the way we will make some mistakes that we will fix using the editing facilities. To watch the waveform grow, display the FUNCTION output on an oscilloscope. Trigger the scope on the SYNC output.

1) Press [FUNCTION DOWN ARROW] until ARB LED is lit.

2) Press [SHIFT][ARB EDIT] three times to display Arb clear line, then press any [UNITS] key.

3) Press [SHIFT][ARB EDIT] and use MODIFY keys to set "Entry" to POINT.

4) Press [SHIFT][ARB EDIT].

5) Press [SHIFT][RIGHT ARROW]. Then [0] [UNITS].

6) Press [SHIFT][LEFT ARROW]. Then any [UNITS] key.

7) Press [SHIFT][RIGHT ARROW], then [4][0][0] [UNITS].

8) Press [SHIFT][LEFT ARROW], [MODIFY UP ARROW].

9) Press [SHIFT][RIGHT ARROW], then [8][0][0] [UNITS].

10) Press [SHIFT][LEFT ARROW]. Then press [UNITS] twice.

11) Press [MODIFY DOWN ARROW], [SHIFT] [RIGHT ARROW], and [1][2][0][0][UNITS].

12) Press [SHIFT][LEFT ARROW], [MODIFY UP ARROW].

13) Press [CLR].

14) DONE!

Set output function to ARB.

Set point entry mode if necessary.

Clear arb function. The message "arb cleared" will be displayed.

Display edit line. It should read "00000 ------". Point number 0 (the first point) has no data.

Activate point value field and set y value for point zero to 0.

Activate point number. Duplicate point by pressing UNITS key. Point # 1 now has y = 0.

Activate y value. Set point # 1 y value to 400.

Set display to point #2. Y value currently is ------. We will add a point to the end of the waveform

Activate point #2 y value and set to 800.

Activate point number. Duplicate point number 2 twice. Display shows point number 4 (last point made). Points 2,3, and 4 now have y value 800.

Decrement point number to point #3. Activate y value and set to 1200. Oops! Point #4 is extra!

Activate point number and increment to point #4.

Delete point #4. y value becomes ------ (no data). We only entered 4 data points. The DS345 will

automatically fill in the 4 trailing zero values when it loads the waveform RAM. The DS345 only adds enough zeroes to make the total number of points equal to 8, and none if there are 8 or more points.

2-31

Arbitrary Waveform Editing

VECTOR EDITING

Described below are the methods for editing vector format arbitrary waveforms. Each stored data value (vertex) contains an x value (address in waveform RAM) and y value (amplitude). The vertices in the data list are connected by straight lines when the DS345 loads the waveform RAM. For a given vertex, the display is switched between x and y values by pressing [STEP SIZE].

Vertex Number

The vertex number can be set to any value between 0 and the number of vertices in the current waveform. The absolute maximum vertex number is 6143 (there can only be 6144 vertices in a waveform). The vertex number may be set using either the keypad or the MODIFY up/down keys. If the vertex number is set past the end of the waveform (where there is no data) an "edit error" will result.

x Value

The vertex x value is the location of the vertex in waveform RAM. This value may range from 0 to 16299. Each vertex must have a x value equal to or greater than that of the previous vertex, and if two or more vertices have the same x value only the first is loaded (the rest are ignored). If the first vertex of the waveform does not have an x value of 0 (the start of memory) the DS345 will automatically add a vertex at 0,0. If the x value has no data (before a value has been entered, for example) the data will be displayed as five dashes (-----).

y Value

Each vertex may have an amplitude value ranging between -2048 and +2047 (12 bit DAC). If a vertex has no value (before a value has been entered) the data will be displayed as five dashes (-----).

Adding a vertex at the end of the waveform

To add a vertex at the end of the waveform set the vertex number to the last vertex + 1 (vertex 4, for example, if 0,1,2,3 are filled). The value will be displayed as ----- (indicating no data yet). Enter a new value for either x or y. If x is entered first y will be set to 0, while if y is entered first x will be set to the value of the previous vertex (0 for the first vertex).

Deleting a Vertex

To delete a vertex, enter the vertex number of the vertex to be removed. Then, with the vertex number active (flashing) press [CLR]. The remaining vertices will be renumbered if necessary.

Duplicating a Vertex

To duplicate a vertex, enter the vertex number of the vertex to be copied. Then, with the vertex number active (flashing) press any UNITS key. The vertex will be duplicated (both x and y) and the vertex number incremented to display the new vertex.

Inserting a Vertex

To insert a vertex in the middle of a waveform, duplicate the vertex currently at the insertion point. Then, modify the new vertex to the desired value.

2-32

Arbitrary Waveform Editing

VECTOR EDIT EXAMPLE

The following is a step-by-step example of creating a vector format waveform. We will create a "heartbeat" waveform with 9 vertices. The vertices will be (0,0), (50,200), (150,0), (175,-300), (225,2000), (275,-50), (425,225), (500,0), (800,0). In the example [UNITS] refers to

any

UNITS key. To watch the waveform grow, display the FUNCTION output on an oscilloscope. Trigger the scope on the SYNC output. The waveform should look like the diagram below when done.

(0,0)

(50,200)

(150,0)

(175,-300)

(225,2000)

(275,-50)

(425,225)

(500,0)

(800,0)

Heartbeat Arbitrary Waveform

1) Press [FUNCTION DOWN ARROW] until ARB LED is lit.

2) Press [SHIFT][ARB EDIT] three times to display Arb clear line, then press any [UNITS] key.

3) Press [SHIFT][ARB EDIT] and use MODIFY keys to set "Entry" to VECTOR.

4) Press [SHIFT][ARB EDIT] once.

5) Press [SHIFT][RIGHT ARROW] then [5][0] [UNITS].

6) Press [STEP SIZE] then [2][0][0][UNITS].

7) Press [SHIFT][LEFT ARROW] then [MODIFY UP ARROW].

8) Press [SHIFT][RIGHT ARROW], [0][UNITS], [STEP SIZE], and [1][5][0][UNITS].

9) Press [SHIFT][LEFT ARROW], [MODIFY UP ARROW], [SHIFT][RIGHT ARROW], [1][7][5] [UNITS].

10) Press [STEP SIZE], then [-][3][0][0][UNITS].

Set output function to ARB.

Set vector entry mode if necessary.

Clear arb function. The message "arb cleared" will be displayed.

Display edit line. It should read "00000 ------". Vertex number 0 (the first vertex) has no data.

Activate x value and set to 50. We will let the DS345 add the 0,0 vertex automatically.

Switch to y value and set to 200. Select vertex number and increment to vertex #1.

Select y value and set to 0, then select x value and set to 150.

Select vertex # and increment to 2, then select x value and set to 175.

Select y value and set to -300.

2-33

Arbitrary Waveform Editing

11) Press [SHIFT][LEFT ARROW], [MODIFY UP ARROW], [SHIFT][RIGHT ARROW], [2][0][0][0] [UNITS].

12) Press [STEP SIZE], then [2][2][5][UNITS].

13) Press [SHIFT][LEFT ARROW], [MODIFY UP ARROW], [SHIFT][RIGHT ARROW], [2][7][5] [UNITS].

14) Press [STEP SIZE], then [-][5][0][UNITS].

15) Press [SHIFT][LEFT ARROW], [MODIFY UP ARROW], [SHIFT][RIGHT ARROW], [2][2][5] [UNITS].

16) Press [STEP SIZE], then [4][2][5][UNITS].

17) Press [SHIFT][LEFT ARROW], [MODIFY UP ARROW], [SHIFT][RIGHT ARROW], [5][0][0] [UNITS].

18) Press [SHIFT][LEFT ARROW] then [UNITS].

19) Press [SHIFT][RIGHT ARROW], [STEP SIZE], and [8][0][0][UNITS].

20) DONE!

Select vertex # and increment to 3, then select y value and set to 2000.

Select x value and set to 225. Select vertex # and increment to 4, then select x

value and set to 275.

Select y value and set to -50. Select vertex # and increment to 5, then select y

value and set to 225.

Select x value and set to 425. Select vertex # and increment to 6, then select x

value and set to 500. The y value is automatically set to 0.

Select vertex number and duplicate vertex. Vertex 7 created with value (500,0).

Select the x value of vertex #7 and set to 800.

The scope should now show a heartbeat waveform.

2-34

PROGRAMMING THE DS345

The DS345 Function Generator may be remotely programmed via the RS232 or GPIB (IEEE-488) interfaces. Any computer supporting one of these interfaces may be used to program the DS345. Only one interface is active at a time. The active interface may be set by entering either the GPIB or RS232 menu and turning the interface ON. The interfaces are exclusive, so while one is on the other will always be off (not responsive). All front and rear panel features (except power) may be controlled.

GPIB Communications The DS345 supports the IEEE-488.1 (1978) interface standard. It also sup-

ports the required common commands of the IEEE-488.2 (1987) standard. Before attempting to communicate with the DS345 over the GPIB interface, the DS345's device address must be set. The address is set in the second line of the GPIB menu (type [SHIFT][GPIB] twice) and can be set between 0 and 30.

RS232 Communications The DS345 is configured as a DCE ( transmit on pin 3, receive on pin 2) and

supports CTS/DTR hardware handshaking. The CTS signal (pin 5) is an output indicating that the DS345 is ready, while the DTR signal (pin 20) is an input that is used to control the DS345's transmitting. If desired, the handshake pins may be ignored and a simple 3 wire interface (pins 2,3 and 7) may be used. The RS232 interface baud rate may be set in the second line of the RS232 menu (type [SHIFT][RS232] twice). The interface is fixed at 8 data bits, no parity, and 2 stop bits.

Front Panel LEDs To assist in programming, the DS345 has 3 front panel status LEDs. The

ACT LED flashes whenever a character is received or sent over either interface. The ERR LED flashes when an error has been detected, such as an illegal command, or an out of range parameter. The REM LED is lit whenever the DS345 is in a remote state (front panel locked out).

Data Window To help find program errors, the DS345 has an input data window which dis-

plays the data received over either the GPIB or RS232 interfaces. This window is the DATA menu and displays the received data in hexadecimal format. Scroll back and forth through the last 256 characters received using the MODIFY up/down arrow keys. A decimal point indicates the most recently received character.

Command Syntax Communication with the DS345 uses ASCII characters. Commands may be

in either UPPER or lower case and may contain any number of embedded space characters. A command to the DS345 consists of a four character command mnemonic, arguments if necessary, and a command terminator. The terminator may be either a carriage return <cr> or linefeed <lf> on RS232, or a linefeed <lf> or EOI on GPIB. No command processing occurs until a command terminator is received. All commands function identically on GPIB and RS232. Command mnemonics beginning with an asterisk "*" are IEEE-488.2 (1987) defined common commands. These commands also function identically on RS232. Commands may require one or more parameters. Multiple parameters are separated by commas ",".

Multiple commands may be sent on one command line by separating them by semicolons ";". The difference between sending several commands on the same line and sending several independent commands is that when a command line is parsed and executed the entire line is executed before any other device action proceeds.

3-1

Programming Commands

There is no need to wait between commands. The DS345 has a 256 character input buffer and processes commands in the order received. If the buffer fills up the DS345 will hold off handshaking on the GPIB and attempt to hold off handshaking on RS232. If the buffer overflows the buffer will be cleared and an error reported. Similarly, the DS345 has a 256 character output buffer to store output until the host computer is ready to receive it. If the output buffer fills up it is cleared and an error reported. The GPIB output buffer may be cleared by using the Device Clear universal command.

The present value of a particular parameter may be determined by querying the DS345 for its value. A query is formed by appending a question mark "?" to the command mnemonic and omitting the desired parameter from the command. If multiple queries are sent on one command line (separated by semicolons, of course) the answers will be returned in a single response line with the individual responses separated by semicolons. The default response terminator that the DS345 sends with any answer to a query is carriage return-linefeed <cr><lf> on RS232, and linefeed plus EOI on GPIB. All commands return integer results except as noted in individual command descriptions.

Examples of Command Formats MRKF1, 1000.0 <lf>

Sets the stop marker to 1000 Hz (2 parameters).

MRKF? 1 <lf>

Queries the stop marker frequency (query of 2 parameter command ).

*IDN? <lf>

Queries the device identification (query, no parameters).

*TRG <lf>

Triggers a sweep (no parameters).

FUNC 1 ;FUNC? <lf>

Sets function to square wave(1) then queries the function.

Programming Errors

The DS345 reports two types of errors that may occur during command execution: command errors and execution errors. For example, unrecognized commands, illegal queries, lack of terminators, and non-numeric arguments are examples of command errors. Execution errors are errors that occur during the execution of syntactically correct commands. For example, out of range parameters and commands that are illegal for a particular mode of operation are classified as execution errors

No Command Bit

The NO COMMAND bit in the serial poll register indicates that there no commands waiting to be executed in the input queue. This bit is reset when a complete command is received in the input queue and is set when all of the commands in the queue have been executed. This bit is useful in determining when all of the commands sent to the DS345 have been executed. This is convenient because some commands, such as setting the function, modulation, or autocalibration, take a long time to execute and there is no other way of determining when they are done. The NO COMMAND bit may be read while commands are being executed by doing a GPIB serial poll. There is no way to read this bit over RS232. Note that using the *STB? query to read this bit will always return the value 0 because it will always return an answer while a command is executing- the *STB? command itself!

3-2

Programming Commands

DETAILED COMMAND LIST

The four letter mnemonic in each command sequence specifies the command. The rest of the sequence consists of parameters. Multiple parameters are separated by commas. Parameters shown in {} are optional or may be queried while those not in {} are required. Commands that may be queried have a question mark ? in parentheses (?) after the mnemonic. Commands that may ONLY be queried have a ? after the mnemonic. Commands that MAY NOT be queried have no ?. Do not send ( ) or { } as part of the command.

All variables may be expressed in integer, floating point or exponential formats ( ie., the number five can be either 5, 5.0, or .5E1). The variables i and j usually take integer values, while the variable x takes real number values.

Function Output Control Commands

AECL

The AECL command sets the output to the ECL levels of 1 V peak-to-peak with a -1.3 V offset. That is, from -1.8V to -0.8V.

AMPL (?) x

The AMPL command sets the output amplitude to x. The value x must consist of the numerical value and a units indicator. The units may be VP (Vpp), VR (Vrms), or DB (dBm). For example, the command AMPL 1.00DB will set the output to 1.0 dBm. For arbitrary waveforms the amplitude may

only

be set in terms of peak-to-peak value. Note that the peak AC voltage (Vpp/2) plus the DC offset voltage must be less than 5 Volts. Setting the amplitude to 0 Volts will produce a DC only (no AC function) output controlled by the OFFS command.

The AMPL? query will return the amplitude in the currently displayed units. For example, if the display is 3.0 Vrms the AMPL? query will return 3.0VR. If a units indicator is sent with the AMPL? query (such as, AMPL? VP) the displayed units will be changed to match the units indicator and the amplitude returned in those units.

ATTL

The ATTL command sets the TTL output levels of 5 V peak-to-peak with a

2.5 V offset. That is, from 0V to 5V.

FREQ (?) x

The FREQ command sets the output frequency to x Hertz. The FREQ? query returns the current output frequency. The frequency is set and re-

turned with 1µHz resolution. If the current waveform is NOISE an error will be generated and the frequency will not be changed. This command does

not

set the sampling frequency for arbitrary waveforms- see the FSMP com-

mand.

FSMP (?) x

The FSMP command sets the arbitrary waveform sampling frequency to x. This frequency determines the rate at which each arbitrary waveform point is output. That is, each point in the waveform is played for a time equal to 1/ FSMP. The allowed values are 40 MHz/N where N is an integer between 1

and 234-1. If x is not an exact divisor of 40 MHz the value will be rounded to the nearest exact frequency.. The FSMP? query returns the current arbitrary waveform sampling frequency.

FUNC (?) i

The FUNC command sets the output function type to i. The correspondence of i and function type is shown in the table below. If the currently selected frequency is incompatible with the selected function an error will be generat-

3-3

Programming Commands

ed and the frequency will be set to the maximum allowed for the new function. If modulation is enabled and the current modulation parameters are incompatible with the selected function the modulation will be disabled and then the function will be set. The FUNC? query returns the current function.

Function

SINE

SQUARE

TRIANGLE

RAMP

NOISE

ARBITRARY

INVT (?) i

The INVT command turns output inversion on (i = 1) and off (i=0). The INVT? query returns the current inversion status.

OFFS (?) x

The OFFS command sets the output's DC offset to x volts. The OFFS? query returns the current value of the DC offset. The DC offset voltage plus the peak AC voltage must be less than 5 Volts.

PCLR

The PCLR command sets the waveform phase value to 0 degrees.

PHSE (?) x

The PHSE command sets the waveform output phase to x degrees. X has

0.001 degree resolution and may range from 0.001 to 7199.999 degrees. This command will produce an error if the function is set to either NOISE or ARB, or if a frequency sweep, FM, or phase modulation is enabled. The PHSE? query returns the current waveform phase.

Modulation Control Commands

note:

All modulation parameters may be set at any time. For the changes to have an effect be sure that the

modulation type is set correctly and that modulation is enabled (see the MTYP and MENA commands).

*TRG

The *TRG command triggers a burst or single sweep. The trigger source must be set to SINGLE.

BCNT (?) i

The BCNT command sets the burst count to i (1 to 30000). The maximum value of i is limited such that the burst time does not exceed 500s (that is, the burst count * waveform period <= 500s). The BCNT? query returns the current burst count.

DPTH (?) i

The DPTH command sets the AM modulation depth to i percent ( 0 to 100 %). If i is

negative

the modulation is set to double sideband suppressed carrier modulation (DSBSC) with i % modulation. The DPTH? query returns the current modulation depth.

FDEV (?) x

The FDEV command sets the FM span to x Hertz. The maximum value of x is limited so that the frequency is never less than or equal to zero or greater than that allowed for the selected function. The FM waveform will be centered at the front panel frequency and have a deviation of ±span/2. The FDEV? query returns the current span.

MDWF (?) i

The MDWF command sets the modulation waveform to i. The correspondence of i to waveform is shown in the table below. If i is a value not allowed by the current modulation type an error will be generated. The MDWF?

3-4

query returns the current modulation waveform.

Waveform

SINGLE SWEEP

RAMP

TRIANGLE

SINE

SQUARE

ARB

NONE The value i = 5 = ARB may only be set for AM, FM, and PM. The arbitrary waveform must be downloaded via the AMOD? query. If no waveform has been downloaded and modulation is enabled with the waveform set to ARB an error will be generated. Once the waveform has been loaded changing the modulation type or waveform will erase that pattern. The value i = 6 = none will be returned for modulation types that don't have an associated waveform, such as burst mode. The waveform

may not

be set to i=6=none.

MENA (?) i

The MENA command enables modulation if i=1 and disables modulation if i =

0. If any of the modulation parameters are incompatible with the current instrument settings an error will be generated. The MENA? query returns the current modulation enable status.

MKSP

The MKSP command sets the sweep markers to the extremes of the sweep span. That is, the marker start frequency is set to the sweep start frequency and the marker stop frequency is set to the sweep stop frequency.

MRKF (?) i{,x}

The MRKF command sets the sweep marker frequency to x. If i = 0 the marker start frequency will be set, if i = 1 the stop frequency will be set, if i = 2 the marker center frequency will be set, and if i=3 the marker span will be set. The MRKF? i query will return marker frequency i.

MTYP (?) i

The MTYP command sets the modulation type to i. The correspondence of i to type is shown in the table below. The MTYP? query returns the current modulation type.

Waveform

LIN SWEEP

LOG SWEEP

INTERNAL AM

BURST

PDEV(?) x

The PDEV command sets the span of the phase modulation to x degrees. x may range from 0 to 7199.999 degrees. Note that the phase shift ranges from

-span/2

to span/2. The PDEV? query returns the current phase shift.

RATE (?) x

The RATE command sets the modulation rate to x Hertz. x is rounded to 2 significant digits and may range from 0.001 Hz to 10 kHz. The RATE? query returns the current modulation rate.

SPAN (?) x

The SPAN command sets the sweep span to x Hertz. An error will be generated if the sweep frequency is less than or equal to zero or greater than allowed by the current function. The sweep will be from center freq - span/2 to

Programming Commands

3-5

Programming Commands

center freq + span/2. A negative span will generate a downward sweep, from maximum to minimum frequency. The SPAN? query returns the current sweep span.

SPCF (?) x

The SPCF command sets the sweep center frequency to x Hertz. An error will be generated if the sweep frequency is less than or equal to zero or greater than allowed by the current function. The SPCF? query returns the current sweep center frequency.

SPFR (?) x

The SPFR command sets the sweep stop frequency to x Hertz. An error will be generated if the sweep frequency is less than or equal to zero or greater than allowed by the current function. The SPFR? query returns the current sweep stop frequency. If the stop frequency is less than the start frequency (the STFR command) a downward sweep from maximum to minimum frequency will be generated.

SPMK

The SPMK command sets the sweep span to the sweep marker frequency. That is, sets the start frequency to the start marker frequency, and the stop frequency to the stop marker frequency.

STFR (?) x

The STFR command sets the sweep start frequency to x Hertz. An error will be generated if the sweep frequency is less than or equal to zero or greater than allowed by the current function. The STFR? query returns the current sweep start frequency. If the start frequency is greater than the stop frequency (the SPFR command) a downward sweep from maximum to minimum frequency will be generated.

TRAT (?) x

The TRAT command sets the trigger rate for internally triggered single sweeps and bursts to x Hertz. x is rounded to two significant digits and may range from 0.001 Hz to 10 kHz. The TRAT? query returns the current trigger rate.

TSRC (?) i

The TSRC command sets the trigger source for bursts and sweeps to i. The correspondence of i to source is shown in the table below. The TSRC? query returns the current trigger source.

Waveform

SINGLE

INTERNAL RATE

+ SLOPE EXTERNAL

- SLOPE EXTERNAL

LINE

For single sweeps and bursts the *TRG command triggers the sweep.

Arbitrary Waveform and Modulation Commands

AMRT(?) i

The AMRT command sets the arbitrary modulation rate divider to i. i may range from 1 to 223-1. This controls the rate at which arbitrary modulations are generated. Arbitrary AM takes 0.3 µs per point, arb FM takes 2 µs per

point, and arb PM takes 0.5 µs per point. The AMRT? query returns the current divider.

3-6

Programming Commands

The following commands allow downloading arbitrary waveform and modulation patterns. The commands have several things in common: First, the data are sent as multi-byte

binary

(not ASCII) data and the binary

data is followed by a checksum to ensure data integrity. The data is sent least significant byte

first

. The

checksum is just the sum of the data values sent, ignoring carries. Second, the commands are

queries-

that is, after the command is received and processed the DS345 will return the ascii value 1 indicating that it is ready to receive the binary data stream. When using these commands the program should wait for return value before sending the binary data. During the downloading of the binary data there is a 10 second receive data timeout. That is, if more than 10 seconds elapses between successive data values an error will be generated and downloading aborted.

AMOD? i

The AMOD? query allows downloading arbitrary modulation patterns. The modulation type must be set to AM, FM, or PM. i is the number of points to be downloaded and is limited to 10000 AM points, 1500 FM points, and 4000 PM points. To generate an arbitrary modulation follow the following steps:

1) Send the query AMOD? i where i is the number of points in the waveform.

2) Wait until the DS345 returns "1" indicating that it is ready to receive data.

3) Send the modulation data (discussed below). The i data points are sent least significant byte first. There should be i data points sent.

4) Send the checksum (the sum of i data points) least significant byte first. Arbitrary AM:

Each arbitrary AM point is a 16bit integer value. This value is the fraction of front panel amplitude to be output. The values range from 32767 = 1.0 * full amplitude to -32767 = -1.0 * amplitude. The value for a desired modulation fraction is easily calculated from the formula: value = 32767 * fraction. For normal AM the values should range from 0 to 32767 (1.0), while for DSBSC the -32767 (-1.0) to 32767 (1.0) range is used. The i data values should be followed by a 16-bit checksum- simply the 16-bit sum of the data values. Thus, a total of i+1 16-bit values will be sent. When modulation is enabled each modulation point takes N*0.3µs to execute, where N is the arbitrary modulation rate divider (see the AMRT command). The MODULATION OUTPUT will output the modulation waveform when modulation is enabled, +5.0 V corresponds to 100% output and -5.0V corresponds to -100% modulation.

Arbitrary FM: Each arbitrary FM point is a 32 bit integer value. This value is the frequency to be output. If the frequency is not allowed for the currently selected waveform an error will be generated. The 32 bit value is calculated from the formula: value = 232*(frequency/40 MHz). Thus, the j data points form a list of j frequencies to be output. The i data values should be followed by a 32-bit checksum- simply the 32-bit sum of the data values. Thus, a total of i +1 32bit values will be sent. When modulation is enabled each modulation point takes N*2.0µs to execute, where N is the arbitrary modulation rate divider (see the AMRT command). The MODULATION OUTPUT will output the modulation waveform when modulation is enabled, with 0 V corresponding to the minimum frequency and 5.0 V corresponding to the maximum frequency in the modulation pattern.

3-7

Programming Commands

Arbitrary PM: Each arbitrary PM point is a 32 bit integer value. This value is the phase shift to be made relative to the current phase. The values may range from -180° to +180°. The 32 bit value is calculated from the formula: value = 231* (phase shift/180°). Negative values are expected in 2's complement format (bit 31 is the sign bit). Thus, the i data points form a list of i phase shifts to be executed. The i data values should be followed by a 32-bit checksumsimply the 32-bit sum of the data values. Thus, a total of i+1 32-bit values will be sent. When modulation is enabled each modulation point takes N*0.5µs to execute, where N is the arbitrary modulation rate divider (see the AMRT command). The MODULATION OUTPUT will output the modulation waveform when modulation is enabled, with 0 V corresponding to the minimum phase shift and 5.0 V corresponding to the maximum phase shift in the modulation pattern.

LDWF? i,j

The LDWF? query allows downloading arbitrary waveforms in either point (i=0) or vector (i=1) format. In point mode j is the number of points in the waveform (16300 maximum), while in vector format j is the number of vertices (6144 maximum). The data is sent as 16 bit binary data words. The data must be followed by a 16 bit checksum to ensure data integrity. The checksum is the 16bit sum of the data words that have been sent. If the checksum sent does not match the one calculated by the DS345 an error will be generated. If the data sent is valid and the DS345's function is set to ARB the waveform will automatically be output. Otherwise, the function must be set to ARB to output the downloaded waveform. To load a waveform follow these steps:

1) Send the query LDWF? i,j where i and j are appropriate for the waveform type and number of points desired.

2) Wait until the DS345 returns "1" indicating that it is ready to receive data.

3) Send the waveform data (discussed below). There should be j data points sent.

4) Send the 16 bit checksum (the sum of j data points). The waveform data is send as 16 bit

binary

data. In point mode each data

point consists of a 16 bit amplitude word. Each value should be in the range

-2047to +2047. In vector mode each data point consists of a 16 bit x vertex word and a 16 bit y vertex word (for a total of 2*j 16 bit words). Each x value must be in the range 0 to 16299 and must be greater than or equal to the value of the previous x value. Each y value must be in the range -2047 to +2047. The checksum is the 16 bit sum of the j words sent in point mode or the 2*j words sent in vector mode.

3-8

Setup Control Commands

*IDN?

The *IDN common query returns the DS345's device configuration. This string is in the format: StanfordResearchSystems,DS345,serial number,version number. Where "serial number" is the five digit serial number of the particular unit, and "version number" is the 3 digit firmware version number.

*RCL i

The *RCL command recalls stored setting number i, where i may range from 0 to 9. If the stored setting is corrupt or has never been stored an execution error will be generated.

*RST

The *RST common command resets the DS345 to its default configurations.

*SAV i

The *SAV command saves the current instrument settings as setting number i.

Status Reporting Commands

(See tables at the end of the Programming section for Status Byte definitions.)

*CLS

The *CLS common command clears all status registers. This command does not affect the status enable registers.

*ESE (?) i

The *ESE command sets the standard event status byte enable register to the decimal value i.

*ESR? {i}

The *ESR common command reads the value of the standard event status register. If the parameter i is present the value of bit i is returned (0 or 1). Reading this register will clear it while reading bit i will clear just bit i.

*PSC (?) i

The *PSC common command sets the value of the power-on status clear bit. If i = 1 the power on status clear bit is set and all status registers and enable registers are cleared on power up. If i = 0 the bit is cleared and the status enable registers maintain their values at power down. This allows the production of a service request at power up.

*SRE (?) i

The *SRE common command sets the serial poll enable register to the decimal value of the parameter i.

*STB? {i}

The *STB? common query reads the value of the serial poll byte. If the parameter i is present the value of bit i is returned (0 or 1). Reading this register has no effect on its value as it is a summary of the other status registers.

DENA (?) i

The DENA command sets the DDS status enable register to the decimal value i.

STAT? {i}

The STAT? query reads the value of the DDS status byte. If the parameter i is present the value of bit i is returned. Reading this register will clear it while reading bit i will clear just bit i.

Programming Commands

3-9

Programming Commands

Hardware Test and Calibration Commands

NOTE:

These commands are primarily intended for factory calibration use and should never be needed dur-

ing normal operation.

Incorrect use of some of these commands can destroy the calibration of the

DS345.

*CAL?

The *CAL? common query initiates the DS345's self calibration routines. When the calibration is complete the status of the calibration is returned. The status may have the following values (see

TROUBLESHOOTING

sec-

tion for more detail):

Status value

Meaning

No Error

DS345 not warmed up. At least 2 minutes must elapse between power on and calibration.

Self-Test Fail. The DS345 must pass its self tests before calibration.

A/D Cal Error. The DS345's A to D converter could not be calibrated.

DC Offset Fail. The DS345 was unable to calibrate its DC offset.

Amplitude Cal Fail. The DS345 was unable to calibrate its amplitude control circuitry.

Doubler Cal Fail. The DS345 was unable to calibrate the doubler offset or the gain of the doubler/square wave signal path.

*TST?

The *TST? common query runs the DS345 internal self-tests. After the tests are complete the test status is returned. The status may have the following values (see the

TROUBLESHOOTING

section for more details):

Status value

Meaning

No Error

CPU Error. The DS345 has detected a problem in its CPU.

Code Error. The DS345's ROM firmware has a checksum error.

Sys RAM Error. The system RAM failed its test.

Cal Data Error. The DS345's calibration data has become corrupt.

Function Data Error. The waveform RAM failed its test.

Program Data Error. The modulation program RAM failed its test.

Trigger Error. The trigger detection circuits failed their test.

A/D D/A Error. Either the A/D or one of the D/A's failed its test. The front panel message is more specific.

Signal Error. Either the waveform DAC, amplitude control, or the output amplifier has failed.

Sync Error. The sync signal generator has failed.

Doubler Error. The frequency doubler has failed.

$ATD? i,j

The $ATD? query uses the DS345 A/D converter to measure the voltage on analog channel i. The parameter j = 0 returns the raw data value, j=1 returns the value corrected for the A/D's offset, and j=2 returns the value corrected for the A/D's offset and gain errors.

3-10

Programming Commands

$ATN(?) i

The $ATN command sets the DS345's output attenuators to range i. The ranges go for 0dB attenuation (i=0) to 42dB attenuation (i=7) in 6dB steps. Resetting the amplitude will return the attenuators to their normal position. The $ATN? query returns the current attenuator position.

$FCL

The $FCL command recalls the factory calibration bytes. This command will generate an error if calibration is not enabled.

$MDC i

The $MDC command sets the mimic DAC to the value i (0 to 255). If the DS345 has modulation enabled this command will have no effect.

$WRD (?) j{,k}

The $WRD command sets the value of calibration word j to k. Parameter j may have a value from 0 to 509, while k may range from -32768 to +32767. This command will generate an error if calibration is not enabled.

NOTE:

this command will alter the calibration of the the DS345. To correct the calibration the factory calibration bytes may be recalled (see the $FCL command).

3-11

Programming Commands

STATUS BYTE DEFINITIONS Status Reporting

The DS345 reports on its status by means of three status bytes: the serial poll byte, the standard status byte, and the DDS status byte.

On power on the DS345 may either clear all of its status enable registers or maintain them in the state they were in on power down. The action taken is set by the *PSC command and allows things such as SRQ on power up .

Serial Poll Status Byte:

bit

name

usage

Sweep Done

set when no sweeps are in progress

Mod Enable

set when modulation is enabled

User SRQ

set if the user sends a SRQ from the front panel

DDS

An unmasked bit in the DDS status register has been set.

MAV

The gpib output queue is non-empty

ESB

An unmasked bit in the standard status byte has been set.

RQS/MSS

SRQ (Service Request)bit.

No Command

There are no unexecuted commands in the input queue

The DDS and ESB bits are set whenever any unmasked bit (bit with the corresponding bit in the byte enable register set) in their respective status registers is set. They are not cleared until the condition which set the bit is cleared. Thus, these bits give a constant summary of the enabled status bits. A service request will be generated whenever an unmasked bit in the serial poll register is set. Note that service requests are only produced when the bit is first set and thus any condition will only produce one service request. Accordingly, if a service request is desired every time an event occurs the status bit must be cleared between events.

Standard Event Status Byte:

bit

name

usage

unused

Query Error

Set on output queue overflow

unused

3-12

Programming Commands

Execution err

Set by an out of range parameter, or non-completion of some command due a condition such as an incorrect waveform type.

Command err

Set by a command syntax error, or unrecognized command

URQ

Set by any key press

PON

Set by power on

This status byte is defined by IEEE-488.2 (1987) and is used primarily to report errors in commands received over the communications interfaces. The bits in this register stay set once set and are cleared by reading them or by the *CLS command.

DDS Status Byte:

bit

name

usage

Trig'd

Set when a burst or sweep is triggered.

Trig Error

Set when a trigger rate error occurs.

Ext Clock

Set when the DS345 is using an external clock source

Clk Error

Set when a external clock error occurs.

Warmup

Set after the warmup period has expired.

Test Error

Set if a self test error occurs.

Cal Error

Set if a self cal error occurs

mem err

the stored setting were corrupt on power up.

The Ext Clk bit will be set whenever the DS345 is locked to an external clock source. The Warmup bit will be set and remain set after the warmup period has expired. The rest of the bits in this register are set when the corresponding event occurs and remain set until cleared by reading this status byte or by the *CLS command.

3-13

Programming Commands

3-14

Program Examples

Introduction The following examples demonstrate interfacing the DS345 via the GPIB in-

terface using the National Instruments GPIB card. Using a different brand of card or the RS232 interface would be similar except for the program lines that actually send the data. These examples are intended to demonstrate the syntax of the DS345's command set.

To successfully interface the DS345 to a PC via the GPIB interface, the instrument, interface card, and interface drivers must all be configured properly. To configure the DS345, the GPIB address must be set in the GPIB menu. The default GPIB address is 19; use this address unless a conflict occurs with other instruments in your system.

Make sure that you follow all the instructions for installing the GPIB card. The National Instruments card cannot be simply unpacked and put into your computer. To configure the card you must set jumpers and switches on the card to set the I/O address and interrupt levels. You must run the program "IBCONF" to configure the resident GPIB driver for you GPIB card. Please refer to the National Instruments manual for information. In this example, the following options must be set with IBCONF:

Device name: ds345 Device address: 19 EOS character: 0Ah (linefeed)

Once all the hardware and GPIB drivers are configured, use "IBIC". This terminal emulation program allows you to send commands to the DS345 directly from your computer's keyboard. If you cannot talk to the DS345 via "IBIC", then your programs will not run.

Use the simple commands provided by National Instruments. Use "IBWRT" and "IBRD" to write and read from the DS345. After you are familiar with these simple commands, you can explore more complex programming commands.

3-15

Program Examples

EXAMPLE 1: Arbitrary Amplitude Modulation.

This program downloads an arbitrary AM pattern to the DS345. The modulating waveform is a sine wave. The range of amplitude values will be -100% to +100% of full output, making DSBSC modulation. The program calculates the AM pattern values, sets the modulation type to AM, modulation waveform to ARB, downloads the pattern, and enables modulation. The program is written in C.

/* program to demonstrate arbitrary AM modulation. Will generate a DSBSC sine wave signal. Written in Microsoft C and uses National Instruments GPIB card. Assumes DS345 is installed as device name DS345. */

#include <stdio.h> #include <string.h> #include <stdlib.h> #include <dos.h> #include <math.h> #include <float.h>

#include <decl.h> /* National Instruments header file */ void main(void); /* function declaration */ int ds345;

unsigned data[10000]; /* up to 10000 points 2 bytes each */ void main ()

{ char cmd[40]; int i,number,sum; double t;

if ((ds345 = ibfind("DS345")) < 0) /* open National driver */ { printf ("Cannot find DS345\n"); exit(1);

}

number = 1000; /* 1000 points */ sum = 0; /* initialize checksum */

/* now we will calculate 2-byte amplitude data, each point is given by value = 32767 * % full amplitude */ for (i = 0 ; i < number ; i++)

{ t = 32767.0 * sin ((6.2831853*(double)i)/(double)number); /* sine wave */ data[i] = (int)(t + 0.5); /* convert to int */ sum += data[i]; /* add to checksum */ }

data[number] = sum; /* store checksum */

sprintf (cmd,"MENA0;MTYP2;MDWF5\n"); /* make sure modulation off until after loading, set AM, arb WF */

ibwrt (ds345,cmd,strlen(cmd)); /* send commands */ sprintf (cmd,"AMOD?%d\n",number); /* arb modulation command */

ibwrt (ds345,cmd,strlen(cmd)); ibrd (ds345,cmd,40); /* read back reply before sending data */

ibwrt (ds345,(char *)data,(long)2*number+2); /* number of bytes = 2 per data

point + 2 for checksum */

3-16

Program Examples

sprintf (cmd,"MENA1\n"); /* turn modulation on */ ibwrt (ds345,cmd,strlen(cmd)); }

EXAMPLE 2: Arbitrary Frequency Modulation.

This program downloads an arbitrary FM pattern to the DS345. The modulating waveform is a sine wave. The program calculates the FM pattern values, sets the modulation type to FM, modulation waveform to ARB, downloads the pattern, and enables modulation. The program is written in C.

/* program to demonstrate arbitrary FM modulation. Will generate a sine wave FM of 50kHz carrier with 10 kHz span. Written in Microsoft C and uses National Instruments GPIB card. Assumes DS345 is installed as device name DS345. */

#include <stdio.h> #include <string.h> #include <stdlib.h> #include <dos.h> #include <math.h> #include <float.h>

#include <decl.h> /* National Instruments header file */ void main(void); int ds345;

unsigned long data[1500]; /* up to 1500 points 4 bytes each */ void main ()

{ char cmd[40]; int i,number; long sum; double t,center,span,s;

if ((ds345 = ibfind("DS345")) < 0) /* open National driver */ { printf ("Cannot find DS345\n"); exit(1);

}

number = 1000; /* 1000 points */ sum = 0l; /* initialize checksum */ s = pow (2.0,32.0); /* scale factor */ center = 50.0E3; /* 50 kHz center freq */ span = 10.0E3; /* 10 kHz span */

/* now we will calculate 4-byte frequency data, each point is given by value = 2^32 * ( freq/40 MHz) */ for (i = 0 ; i < number ; i++)

{ t = span/2.0 * sin ((6.2831853*(double)i)/(double)number); /* delta freq */ t += center; /* + center freq = output frequency */ t /= 40.0E6; /* ratio to 40 MHz */ data[i] = (long)(s*t); sum += data[i]; }

data[number] = sum; /* store checksum */

sprintf (cmd,"MENA0;MTYP3;MDWF5\n"); /* make sure modulation off until after loading, set FM, arb WF */

3-17

Program Examples

ibwrt (ds345,cmd,strlen(cmd)); /* send commands */ sprintf (cmd,"AMOD?%d\n",number); /* arb modulation command */

ibwrt (ds345,cmd,strlen(cmd)); ibrd (ds345,cmd,40); /* read back reply before sending data */

ibwrt (ds345,(char *)data,(long)4*number+4); /* number of bytes = 4 per data

point + 4 for checksum */

sprintf (cmd,"MENA1\n"); /* turn modulation on */ ibwrt (ds345,cmd,strlen(cmd)); }

EXAMPLE 3: Arbitrary Phase Modulation.

This program downloads an arbitrary PM pattern to the DS345. The modulating waveform is a sine wave. Since the DS345 expects a list of phase

changes

we calculate the initial phase of the waveform and then take differences from that phase. The program calculates the PM pattern values, sets the modulation type to PM, modulation waveform to ARB, downloads the pattern, and enables modulation. The program is written in C.

/* program to demonstrate arbitrary PM modulation. Will generate a sine wave with span of 90deg (-45 deg to +45 deg). Written in Microsoft C and uses National Instruments GPIB card. Assumes DS345 is installed as device name DS345. */

#include <stdio.h> #include <string.h> #include <stdlib.h> #include <dos.h> #include <math.h> #include <float.h>

#include <decl.h> /* National Instruments header file */ void main(void); int ds345;

unsigned long data[4000]; /* up to 4000 points 4 bytes each */ void main ()

{ char cmd[40]; int i,number; long sum; double t,s,span,old,new;

if ((ds345 = ibfind("DS345")) < 0) /* open National driver */ { printf ("Cannot find DS345\n"); exit(1);

}

number = 1000; /* 1000 points */ sum = 0l; /* initialize checksum */ s = pow (2.0,16.0); /* scale factor */ span = 90.0; /* 90 deg span */

3-18

Program Examples

/* since list is of phase CHANGES need to calculate initial phase of waveform and then calculate phase shifts */ old = 0.0; /* initial sine wave value = 0 = sin (0) */

/* calculate 4-byte data values. each value = 2^16 * delta phase */ for (i = 0 ; i < number ; i++)

{

new = span * sin ((6.2831853*(double)(i+1))/(double)number)/2.0;/*new phase */ t = new - old; /* phase change */ old = new; /* save new phase for next time */ data[i] = (long)(s*t); sum += data[i]; /* update checksum */ }

data[number] = sum; /* store checksum */

sprintf (cmd,"MENA0;MTYP4;MDWF5\n"); /* make sure modulation off until after loading, set PM, arb WF */

ibwrt (ds345,cmd,strlen(cmd)); /* send commands */ sprintf (cmd,"AMOD?%d\n",number); /* arb modulation command */

ibwrt (ds345,cmd,strlen(cmd)); ibrd (ds345,cmd,40); /* read back reply before sending data */

ibwrt (ds345,(char *)data,(long)4*number+4); /* number of bytes = 4 per data

point + 4 for checksum */

sprintf (cmd,"MENA1\n"); /* turn modulation on */ ibwrt (ds345,cmd,strlen(cmd)); }

EXAMPLE 4: Point Mode Arbitrary Waveform.

This program downloads an arbitrary in point edit mode. The data is just a list of the amplitude value at each waveform RAM point. The program is written in C.

/* program to donwload point mode arb wf to DS345. The waveform is a simple ramp. Written in Microsoft C and uses National Instrument GPIB card. Expects DS345 to be installed as DS345 in IBCONF */

#include <stdio.h> #include <string.h> #include <stdlib.h> #include <dos.h>

#include <decl.h> /* National Instruments header file */ void main(void); int ds345;

int data[10000]; /* up to 10000 points */ void main ()

{ char cmd[40]; int i,sum,j,number;

3-19

Program Examples

if ((ds345 = ibfind("DS345")) < 0) /* open National driver */ { printf ("Cannot find DS345\n"); exit(1);

}

sum = 0; /* initialize checksum */ j = -2048; /* initial ramp value (-full scale)*/ number = 8192; /* number of points in waveform */

/* will make a 8192 point ramp, increment y value every other point */ for (i = 0 ; i < number ; i++)

{ data[i] = j; /* y value */ sum += data[i]; /* add to checksum */ if (i&1)j++; /* increment y value if i is odd */ }

data[number] = sum; /* checksum */ sprintf (cmd,"LDWF?0,%d\n",number); /* command to load waveform */

ibwrt (ds345,cmd,strlen(cmd)); ibrd (ds345,cmd,40); /* read back reply before sending data */

ibwrt (ds345,(char *)data,(long)2*number+2); /* number of bytes = 2 per data

point + 2 for checksum */

sprintf (cmd,"FUNC5\n"); /* arb wf output */ ibwrt (ds345,cmd,strlen(cmd)); }

EXAMPLE 5: Vector Mode Arbitrary Waveform.

This program downloads an arbitrary in vector edit mode. The data is just a list of x values (waveform RAM addresses) and amplitude values. The program generates a triangle wave whose amplitude linearly grows in time (the vertex y values grow and alternate in sign). The program is written in C.

/* program to donwload vector mode arb wf to DS345. The waveform is a triangle wave linearly increasing in amplitude (a "christmas tree" on its side). Written in Microsoft C and uses National Instrument GPIB card. Expects DS345 to be installed as DS345 in IBCONF */

#include <stdio.h> #include <string.h> #include <stdlib.h> #include <dos.h>

#include <decl.h> /* National Instruments header file */ void main(void); int ds345;

int data[10000]; /* up to 10000 points */ void main ()

{ char cmd[40]; int i,sum,number;

3-20

Program Examples

if ((ds345 = ibfind("DS345")) < 0) /* open National driver */ { printf ("Cannot find DS345\n"); exit(1);

}

sum = 0; /* initialize checksum */ number = 250; /* 250 verteces */

/* each vertex has an x and y value, we will step x in increments of 50 and y in increments of 8 with alternating sign (zig-zag up and down */

for (i = 0 ; i < number ; i++)

{ data[2*i] = 50*i; /* x */ data[2*i+1] = 8*i*(-1 + 2*(i%2)); /* y */ sum += (data[2*i] + data[2*i+1]); /* add x and y to checksum */

} data[2*number] = sum; /* checksum */ sprintf (cmd,"LDWF?1,%d\n",number); /* command to load waveform */

ibwrt (ds345,cmd,strlen(cmd)); ibrd (ds345,cmd,40); /* read back reply before sending data */

ibwrt (ds345,(char *)data,(long)4*number+2); /* number of bytes = 4 per data

point(x and y) + 2 for checksum */

sprintf (cmd,"FUNC5\n"); /* arb wf output */ ibwrt (ds345,cmd,strlen(cmd)); }

3-21

Program Examples

3-22

Message

Meaning

AC-DC Error

The output |Vac| + |Vdc| > 5V. Adjust either the offset or amplitude.

Arb Corrupt

The stored arbitrary modulation pattern is corrupt. The pattern is automatically erased by power down, self-test, autocal, or changing the modulation type or waveform.

Arb Edit Err

An out of range value during editing of an arbitrary waveform. Such as y value out of -2048 to +2047 range, vertex x value < previous vertex x value, or vertex x value > 16299.

Arb Error

Tried to download more than 16300 points or 6144 vectors.

Arb Fn Bad

The stored arbitrary waveform has been corrupted. Not a problem unless occurs frequently. Can be due to faulty battery or memory glitch.

Arb Not Clr

The arbitrary waveform must be cleared before the edit mode can be changed.

Burst Error

The programmed burst time is outside of 1 µs → 500 s range. Also if the frequency of a burst waveform is > 1 MHz.

Cntr F Error

The programmed center sweep frequency would put the sweep frequencies either below zero or greater than that allowed for the current function.

Count Error

Attempt to set burst count to 0 or greater than 30000.

4-1

TROUBLESHOOTING

If Nothing Happens on Power On

Make sure that the power entry module on the rear panel is set for the proper ac line voltage for your location, that the correct fuse is installed, and that the line cord is inserted all the way into the power entry module. The selected line voltage may be seen through the clear window, just below the fuse.

When the unit is plugged in and turned "ON", the unit's firmware version number and serial number will be briefly displayed. The self tests should then execute.

Cold Boot If the unit displays no sensible message, the "cold boot" procedure may fix

the problem. To do a "cold boot", turn the unit off. Then, while holding the "CLR" button, turn the unit "ON". This procedure initializes the RAM and recalls all factory calibration values. The "Autocal" procedure should be run after the unit warms up (see INSTRUMENT SETUP section).

ERROR MESSAGES The following lists explain all of the error messages that the DS345 can gen-

erate. The messages are divided into operational errors, self-test errors, and autocal errors. The messages are listed alphabetically.

Operational Errors These error messages may appear during normal front panel operation and

generally are warnings of illegal parameter entries.

Troubleshooting

Depth Error

Attempt to set AM depth outside of -100 % to +100% range.

Edit Error

Attempt to set front-panel edit point value past end of arb waveform. Can only edit the existing waveform points + 1 new one.

Freq Error

Attempt to set output frequency outside of range allowed for current function, set sweep markers <= 0 Hz or > 30.2 MHz, or attempting to set frequency for NOISE function.

Funct Error

Attempting to modulate NOISE; attempting to download ARB modulation pattern if not AM, FM, or PM; or attempting sweeps, FM, or PM of ARB waveforms.

Load Error

Timeout during loading of ARB waveform or modulation. The can be no more than 10s between successive data points. Check that the correct number of bytes are sent.

Load CS Error

The checksum calculated by the DS345 is different than that received from the computer on downloading of ARB waveform or modulation. Check that the computer is sending the correct # points and calculating sum correctly.

Load Rng Error

Arb AM value outside of ±32767 range (-32768 is illegal). Arb FM frequency > 30.2 MHz. Arb PM phase shift > ±180 degrees. Arb waveform y value outside of -2048 to + 2047 range. Arb waveform vertex x value < previous vertex x value. Arb waveform vertex x value > 16299.

No Interface

Cannot access GPIB and RS232 menus if option board is not installed.

Offset Error

DC output offset outside of ±5V range.

Phase Error

Phase or PM deviation set outside of ±7199.999° range.

Range Error

Parameter in command is out of allowed range for that command.

Rate Error

Modulation rate out of range (0.001 Hz to 1kHz for sweeps, 0.001 Hz to 10 kHz for other). Trigger rate out of range (0.001Hz to 10kHz).

Recall Error

Parameter memory corrupt on power up, stored setting corrupt. Not a worry unless this error occurs frequently. Check the battery if so.

Span F Error

Sweep or FM span set so that frequency is <= 0 Hz or > max allowed for the current function. Also if SPAN=MRK function has same effect.

Strt F Error

The sweep start frequency is out of range ( 0 < Freq < max for function).

Stop F Error

The sweep stop frequency is out of range ( 0 < Freq < max for function).

Syn Error

The command syntax is invalid. See PROGRAMMING section for correct command syntax.

UART Error

The DS345 has detected an error on its computer interface option board.

4-2

Troubleshooting

Units Error

The units set with AMPL command are not Vpp,V

rms

, or dBm.

Volt Error

The output voltage is outside of 0.01Vpp to 10V

range.

Self-Test Errors

These errors may occur during the DS345's self- test. In general, these messages indicate DS345 hardware problems. If the errors occur repeatedly the unit may have an electrical problem. The messages are listed alphabetically, also listed is the status value returned by the *TST? command.

Message

Status Value

Meaning

AD Offs Err

The DS345's A/D converter has an excessive DC offset (> ± 75mV). This can mean a problem with the D/A or A/D circuits.

AD Gain Err

The DS345's A/D converter has the wrong gain (A/D measures the 5.00V reference voltage). Can be a problem with the D/A or the A/D multiplexer.

Cal Data Err

The RAM calibration data has become corrupt. The factory values will be reloaded from ROM. This message is not a problem unless it occurs frequently, which could indicate a problem with the battery backup circuits.

Code Err XX

The DS345's ROM has a checksum error. XX is the checksum value.

CPU Error

The DS345 has detected a problem in its Z8800 Cpu.

DAC OFF Err

The waveform DAC output offset control (carrier null) doesn't work (should have 75mV to 225mV range at output BNC).

DDS DAC 1 Er

Error in linearity of ASIC controlled gain DAC (U412A). Checked at full, 1/2, 1/4, and 1/8 scale.

DDS DAC 2 Er

Error of ASIC controlled offset DAC (U412B). Checked at 0V, ±full scale.

DDS DAC 3 Er

Error in linearity of mimic DAC (U401). Checked at full, 1/2, 1/4, and 1/8 scale.

Doubler Error

Error in frequency doubler circuitry or Cauer filter.

Fn Data Err x

Error in read/write to waveform RAM. x = 1 = U305, 2 = U306, 3 = U307. Can indicate problem with RAMs, ASIC, or bus interface circuits.

Func DAC Err

The waveform DAC (U500) cannot generate ±full scale output.

Func Off Err

The waveform DAC or amplitude control multiplier (U500 and U702) have excessive DC offset (> ±200mV or ±450mV respectively).

Gain Ctl Err

The amplitude control multiplier (U702) has linearity problem. Checked at full, 1/2, and 1/4 scale.

Gain FS Err

Amplitude control DACs (U109B and U412A) full scale output is > ±20% from nominal.

note:

this error can be caused by a signal being applied to the ex-

ternal AM input.

4-3

Troubleshooting

Gain Off Err

Amplitude control DAC's (U109B and U412A) have excessive DC offset (> ±100mV).

Offset G Error

The DC offset function gain is more than ±10% from nominal. Can be a problem with DAC or output amplifier.

Offset O Err

Output has excessive DC offset when set to 0 (>±100mV). Can be a problem with offset control or output amplifier.

Out Gain Err

Full scale output is more than ±30% from nominal. Can be due to incorrectly set waveform DAC reference voltage (VR500 should output -1.00V), bad Bessel filter, bad amplitude control multiplier, or output amplifier problem.

Prg Data Err

Read/write test of modulation RAM (U301) failed. Can be bad RAM, ASIC, or bus problem.

Sync Cpr Err

Sync generator does not produce ±full scale output.

Sys Data Err

CPU RAM (U204) failed read/write test.

Sys G DAC Err

System amplitude control DAC (U109B) linearity error. Checked at full, 1/2, 1/4, and 1/8 scale.

Trig Error X

Error in trigger detection circuits. If x = 1 = triggered signal error, x = 2 = trigger error signal error, and x = 3 = sweeping signal error.

Autocal Errors

These errors messages can be generated by autocal. If the DS345 fails autocal try running the procedure again. Repeated failure can indicate a hardware problem. The parameter limits and number of iteration allowed by autocal are fixed and are set so that all units should easily calibrate within those limits. The messages are listed alphabetically, also listed is the status value returned by the *CAL? command.

Message

Status Value

Meaning

AD Gain Err

The A/D converter gain is more than ±5% from nominal.

AD Offs Err

The A/D converter offset is too large.

Bes G Cal Er

The DC gain of Bessel signal path is outside of -40% to +25% from nominal, or the calibration did not converge after the maximum allowed number of iterations.

Cal Dly Err

The DS345 is not warmed up. Wait until warmed up for at least two minutes befor starting autocal.

DAC Off Err

The waveform DAC's output offset calibration did not converge or went outside the ±50mV allowed range.

DBL ERR xx

The frequency doubler output offset calibration failed at frequency xx. Output frequency = 312500 Hz * xx.

Offset Cal Err1

The dc output offset control offset calibration did not converge, or went out of range.

4-4

Troubleshooting

Offset Cal Err2

The dc output offset control gain calibration did not converge, or went out of range.

Offset Cal Err3

The ASIC amplitude DAC (U412A) offset calibration did not converge.

Offset Cal Err4

The system amplitude DAC(U109B) offset calibration did not converge.

Sine DC G Er

The sine wave path DC gain is outside of -40% to +25% from nominal, or the calibration did not converge after the maximum allowed number of iterations.

Sqr DC G Err

The square wave path DC gain is outside of -40% to +25% from nominal, or the calibration did not converge after the maximum allowed number of iterations.

GPIB PROBLEMS

First, make sure that the GPIB interface is enabled. Press [SHIFT][GPIB] to display the enable status line. GPIB should be "ON". If not, turn GPIB on using the MODIFY keys. Second, the GPIB address of the DS345 must be set to match that expected by the controlling computer. The default GPIB address is 19, and so it is a good idea to use this address when writing programs for the DS345. Any address from 0 to 30 may be set in the GPIB menu. To check the GPIB address, press [SHIFT][GPIB] twice to view the GPIB address. The entry keys or MODIFY keys may be used to set the GPIB address.

The DS345 will ignore its front panel key pad when Remote Enable (REN) has been asserted by the GPIB. This "REMOTE" state is indicated by the REM LED. To return to LOCAL operation (ie. to enable the front panel) press [STEP SIZE]. Controlling programs may inhibit the ability to return to LOCAL operation by asserting the Local-Lockout state (LLO).

A linefeed character is sent with and End or Identify (EOI) to terminate strings from the DS345. Be certain that your GPIB controller has been configured to accept this sequence.

RS-232 PROBLEMS

First, make sure that the RS232 interface is enabled. Press [SHIFT][RS232] to display the enable status line. RS232 should be "ON". If not, turn RS232 on using the MODIFY keys. Second, the RS-232 baud rate must be set to match that expected by the controlling computer. The default baud rate is 9600 baud. The DS345 always sends two stop bits, 8 data bits, and no parity, and will correctly receive data sent with either one or two stop bits.

When connecting to a PC, use a standard PC serial cable, not a "nullmodem" cable. The DS345 is a DCE (Data Communications Equipment) device, and so should be connected with a "straight" cable to a DTE device (Data Terminal Equipment). The "minimum" cable will pass pins 2,3 and 7. For hardware handshaking, pins 5 and 20 (CTS and DTR) should be passed. Occasionally, pins 6 and 8 (DSR and CD) will be needed: these lines are always asserted by the DS345.

4-5

Troubleshooting

4-6

PERFORMANCE TESTS

INTRODUCTION

NECESSARY EQUIPMENT The following equipment is necessary to complete the tests. The suggested

Instrument Critical Specifications Recommended Model

Analog Oscilloscope 350 MHz Bandwidth Tektronix 2465 Time Interval Counter Frequency Range: 20 MHz min. SRS SR620

FFT Spectrum Analyzer Frequency Range: DC to 100 kHz SRS SR760

RF Spectrum Analyzer Frequency Range: 1 kHz to 100 MHz Anritsu MS2601/ HP4195A

DC/AC Voltmeter 5 1/2 Digit DC accuracy Fluke 8840A

The procedures in this section test the performance of the DS345 and compare it to the specifications in the front of this manual. The first set of tests test the basic functionality of the DS345 from the front panel. The second set of tests actually measure the DS345's specifications. The results of each test may be recorded on the test sheet at the end of this section.

equipment or its equivalent may be used.

Time Interval Accuracy: 1ns min

Amplitude Accuracy: ±0.2 dB Distortion: < 75 dB below reference

Amplitude: ±0.5 dB Distortion and Spurious: < -70 dB

True RMS AC to 100 kHz

Thermal Converter Input Impedance: 50

Input Voltage: 3 Vrms Frequency: DC to 30 MHz Accuracy: ±0.05dB

10 MHz Frequency Standard Frequency: 10 MHz ± .001 ppm SRS FS700

Phase Noise: < -130 dBc @ 100Hz

50 Ω Terminator 50 Ω ± 0.2 %, 1 Watt HP 11048C

Doubly Balanced Mixer Impedance: 50 Ω Mini-Circuits ZAD-3SH

Frequency: 1 - 20 MHz

1 MHz Lowpass Filter -50 dB min at f > 15 MHz TTE, Inc. Model J85

15 kHz Lowpass Filter 11.0 kΩ, 0.0015 µF Homemade

Ω Ballantine 1395A-3-09

5-1

Performance Tests

FUNCTIONAL TESTS

These simple tests verify that the DS345's circuitry is functional. They are not intended to verify the DS345's specifications.

Front Panel Test

This test verifies the functionality of the front panel digits, LED's, and buttons.

1) Turn on the DS345 while holding down [FREQ]. A single segment of the leftmost digit should light.

2) Use [MODIFY DOWN ARROW] to light each segment (7 of them) and the decimal point of the leftmost two digits. Only a single segment should be on at a time. [MODIFY UP ARROW] will step backward through the pattern.

3) Push the down arrow key again and all of the segments of all 12 digits should light.

4) Press the down arrow key repeatedly to light each front panel indicator LED in turn, top to bottom, left to right. At any time only a single LED should be on.

5) After all of the LEDs have been lit further pressing of the front panel keys will display the key code associated with each key. Each key should have a different keycode.

Internal Self-Tests

The internal self tests test the functionality of the DS345 circuitry.

1) Turn on the DS345. The ROM firmware version number, and the serial number should be displayed for about 3 seconds. The self tests will execute and the message "TEST PASS" should be displayed. If an error message appears see the TROUBLESHOOTING section for a description of the errors.

Sine Wave

This procedure visually checks the sine wave output for the correct frequency and any visible irregularities.

1) Connect the DS345's output to the oscilloscope input and terminate in 50Ω.

2) Set the DS345 to sine, 10 MHz, 10 Vpp. Set the scope to 2 V/div vertical, and 100ns/div horizontal.

3) The scope should display a sine wave with one cycle per horizontal division and about five divisions peak-to-peak. There should be no visible irregularities in the waveform.

Square Wave

This procedure checks the square wave output for frequency, rise time, and aberrations.

1) Connect the DS345's output to the oscilloscope input and terminate in 50Ω.

2) Set the DS345 to square wave, 1 MHz, 10 Vpp. Set the scope to 2V/div

5-2

Performance Tests

vertical, and 200ns/div horizontal.

3) The scope should show two square waves about 5 division peak-to-peak.

4) Increase the scope sensitivity to 1V/div and measure the size of the overshoot at the beginning of the square wave. It should be less than 0.5V peakto-peak.

5) Adjust the scope to 2 V/div and 5ns/div. Measure the 10% to 90% rise time of the square wave. It should be less than 15ns.

Amplitude Flatness

This test provides a visual indication of the sine wave amplitude flatness.

1) Connect the DS345's output to the oscilloscope input and terminate in 50Ω.

2) Set the DS345 to sine wave, 10Vpp. Modulation to linear sweep with a sawtooth waveform. Set the start frequency to 1Hz, stop frequency to 30MHz, and the rate to 100Hz. Turn the DS345's sweep ON.

3) Set the scope to 2V/div vertical, and 1ms/div horizontal. Trigger the scope on the falling edge of the DS345's SWEEP output.

4) The scope should show a sweep that is essentially flat. The peak-to-peak variations should be less than ±3.3%. Ignore any dc variations, using the peak-to-peak measurements for flatness comparison.

Output Level

This test provides a visual check of the DS345's output level control.

1) Connect the DS345's output to the oscilloscope input and terminate in 50Ω.

2) Set the DS345 to sine wave, 1MHz, 10Vpp. Set the scope to 2V/div vertical and 1µs/div horizontal.

3) Verify that the DS345's output is about 10V pk-to-pk.

4) Set the DS345 to 5Vpp verify the output.

5) repeat step 4 at 1Vpp, 0.5 Vpp, 0.1 Vpp, and 0.05 Vpp. Adjust the scope as necessary.

This completes the functional tests

5-3

Performance Tests

5-4

Performance Tests

PERFORMANCE TESTS

These tests are intended to measure the DS345's conformance to its published specifications. The test results may be recorded on the test sheet at the end of this section. Allow the DS345 at least 1/2 hour to warm up, run the DS345's autocal procedure, and proceed with the tests.

FREQUENCY ACCURACY

This test measures the accuracy of the DS345's frequency. If the frequency is out of specification the DS345's timebase frequency should be adjusted (see CALIBRATION section).

specification: ± 5 ppm of selected frequency

1) Turn the DS345 on and allow it to warm up for at least 1/2 hour. Set the DS345 for sine wave, 10 MHz, 1 Vpp.

2) Attach the output of the DS345 to the frequency counter. Terminate into 50Ω. Attach the reference frequency input of the counter to the frequency standard. Set the counter for a 1s frequency measurement.

3) The counter should read 10MHz ± 50Hz. Record the result.

AMPLITUDE ACCURACY

The following tests measure the accuracy of the DS345 output amplitude. There are separate tests for sine, square, and ramp/triangle. The tests measure the accuracy of the amplitude as a function of frequency. The sine wave test also measures the performance of the attenuators. There is only a single test for triangle and ramp functions because they have the same signal path.

Frequency < 100 kHz

Connect the DS345 output to the voltmeter through the 50Ω terminator. After the DS345 has had at least 1/2 hour to warm up, run the autocal procedure.

Then perform the following tests.

Sine Wave specification: ±0.2 dB (±2.3%), amplitude > 5V

±0.3 dB (±3.4%), amplitude < 5V

1) Set the DS345 to sine wave, 100Hz, 3.54 Vrms (10Vpp).

2) Read the AC voltage on the voltmeter. Repeat at 1kHz and 10kHz, and 100 kHz. The readings should be between 3.459 and 3.621 Vrms (± 2.3%). Record the results.

3) Set the DS345 to 1 kHz. Set the amplitude to 1 Vrms. Read the voltmeter and record the results. The amplitude should be between 0.966 and 1.034 Vrms. Repeat at 0.5 Vrms, 0.25 Vrms, 125 mVrms, 75 mVrms, 40 mVrms, and 25 mVrms. Record the results. They should be within ±3.4% of the set values.

5-5

Performance Tests

Square Wave specification: ±3%

1) Set the DS345 to square wave, 100Hz, 5Vrms (10 Vpp).

2) Read the AC voltage on the voltmeter. Repeat at 1 kHz and 10kHz. The readings should be between 4.85 and 5.15 Vrms.

Triangle/Ramp Waves specification: ±3%

1) Set the DS345 to triangle wave, 100Hz, 2.89Vrms (10 Vpp).

2) Read the AC voltage on the voltmeter. Repeat at 1 kHz and 10kHz. The readings should be between 2.80 and 2.97 Vrms.

Frequency > 100 kHz

Sine Waves specification: ±0.2 dB (±2.3%), frequency < 20 MHz

±0.3 dB (±3.4%), frequency > 20 MHz

1) Connect the DS345's output to the thermal converter (because the convertor has a 50Ω impedance no terminator is needed). Connect the thermal converter output to the voltmeter using the most sensitive voltmeter range

since the nominal signal level is about 7mV DC. Allow the DS345 at least 1/ 2 hour to warm up.

2) Set the DS345 to sine wave, 1 kHz, 3.00 Vrms. Allow the thermal converter 15 seconds to stabilize and record the result as the 1kHz reference value.

3) Step the DS345's frequency in 2 MHz steps from 1kHz to 30.001 MHz. Allow the thermal converter to stabilize at each frequency and record the results.

4) Verify that the readings are within ±4.2 % of the 1 kHz reading for frequencies below 20 MHz and within ±6.3% for frequencies above 20 MHz.

Square Waves specification: ±6%, frequency < 20 MHz

±15%, frequency > 20 MHz

1) Connect the DS345's output to the oscilloscope with a 50Ω terminator. Set the DS345 to square wave, 1 kHz, 10Vpp. Set the scope to 2V/div and

0.1ms/div.

2) Step the DS345's frequency in 2 MHz steps from 1kHz to 30.001 MHz.

5-6

Performance Tests

3) Verify that the DS345's output is within ±6% of the 1kHz amplitude for frequencies less than 20 MHz, and within ±15% for frequencies from 20 to 30 MHz.

DC OFFSET ACCURACY

This test measures the accuracy to the DS345's DC offset function.

DC Only

specification: 1.5% of setting + 0.2mV

1) Connect the DS345's output to the voltmeter with a 50Ω terminator. Set the DS345 to 0.0V amplitude

2) Set the DS345 to 5V offset. Read the voltmeter and record the result. The result should be between +4.925V and +5.075V.

3) Set the DS345 to -5V offset. Read the voltmeter and record the result. The result should be between -5.075V and -4.925V.

4) Set the DS345 to 0V offset. Read the voltmeter and record the result. The result should be between -0.2 mV and +0.2mV.

DC+AC

specification: < ±80mV at full output

1) Connect the DS345's output to the voltmeter with a 50Ω terminator. Set the DS345 to sine wave, 1 kHz, 10Vpp, 0V offset. Set the voltmeter to meas-

ure DC voltage.

2) Measure the offset voltage and verify that it is between -80mV and +80mV. Record the result.

3) Repeat step 2 at 100kHz, 1MHz, 10 MHz, 20MHz, and 30MHz. Record the results and verify that the offset is between -80mV and +80mV at all of the frequencies.

SUBHARMONICS

This test measures the subharmonic content of the DS345's sinewave output. This is residual carrier feedthrough from the DS345's frequency doubler. The frequencies in this test are picked such that spurious frequencies from the DDS process do not fall on the carrier position.

specification: <-50 dBc

1) Connect the DS345 to the RF spectrum analyzer. Set the DS345 to sine wave, +23.98dBm (10Vpp), 0V offset.

2) Set the DS345 to to 102 kHz. Set the spectrum analyzer to 51 kHz center frequency, 10 kHz span. The carrier amplitude at 51 kHz should be less than

-26.02 dBm. Record the result.

5-7

Performance Tests

3) Set the DS345 to 1.002 MHz, and the spectrum analyzer to 501 kHz. Measure and record the amplitude of the 501 kHz carrier. It should be less that -26.02 dBm.

4) Repeat step 3 with the DS345 and spectrum analyzer set to the following frequencies: 10.002 MHz and 5.001 MHz, 20.002 MHz and 10.001 MHz, and

30.002 MHz and 15.001 MHz. Record the results and verify that the carrier levels are below -26.02 dBm.

SPURIOUS SIGNALS

These tests measure the spurious signals on the DS345's sine wave outputs. They check both close-in and wide band spurs.

specification: < -50 dBc at full output

1) Connect the DS345 to the RF spectrum analyzer. Set the DS345 to sine wave, +23.98dBm (10Vpp), 0V offset.

2) Set the DS345 to 26.662 MHz. Set the spectrum analyzer to 26.662 MHz center frequency, 100 kHz span. Measure the amplitude of the spurious signals and verify that they are < -50 dBc.

3) Set the DS345 to 20.004 MHz. Set the spectrum analyzer to 20.004 MHz, 100 kHz span. Measure the amplitude of the spurious signals and verify that they are < -50 dBc.

4) Set the DS345 to 18 MHz. Set the spectrum analyzer to sweep from 1kHz to 100 MHz. Ignoring the harmonics of the fundamental at 36MHz, 54 MHz, 72 MHz, and 90 MHz, measure the amplitude of the spurious signals and verify that they are < -50 dBc.

HARMONIC DISTORTION

This test measures the DS345's sine wave harmonic distortion. specification: < -55 dBc, frequency < 100 kHz

< -45 dBc, frequency 0.1 to 1 MHz < -35 dBc, frequency 1 to 10 MHz < -25 dBc, frequency 10 to 30 MHz

1) Connect the DS345 output to the FFT analyzer input with a 50Ω terminator. Set the DS345 to sine wave, 100Hz, 1 Vpp.

2) Adjust the FFT analyzer to view the fundamental and its harmonics. Verify that all harmonics are below -55 dBc.

3) Repeat step 3 at 1 kHz and 10 kHz.

4) Connect the DS345 output to the RF spectrum analyzer input. Set the DS345 to 50 kHz. Verify that the harmonics are at least -55 dBc.

5) Set the DS345 to 500 kHz, 5 MHz, 15 MHz, and 30 MHz and verify that all harmonics are at least -45 dBc, -35 dBc, -25 dBc, and -25 dBc respectively. Record the results.

5-8

PHASE NOISE

This test measures the integrated phase noise of the DS345's output in a 15 kHz band about carrier. This test is performed at 10 MHz to minimize the contribution of discrete spurs to the measurement.

specification: < -50 dBc in a 15 kHz band centered about the carrier, exclusive of discrete spurious signals.

1) Connect the equipment as shown in the diagram below. The 1 MHz filter removes the sum frequency mixer output, and the 15 kHz filter sets the noise bandwidth of the measurement.

2) Set the DS345 to sine wave, 10.001 MHz, +13 dBm. The frequency standard should be 10 MHz, > +10 dBm.

3) Record the AC voltage reading.

4) Set the DS345 to 10.0 MHz. Measure the DC signal from the mixer. Use the DS345's PHASE control to minimize the DC voltage value.

5) Set the voltmeter to AC and measure the mixer output. Calculate the ratio of this voltage to that obtained in step 3 ( dB = 20 log (V5/V3)). Add -6 dB to

this value to compensate for the mixer. This value should be less than -55 dB. Record the result.

OUTPUTS

FUNCTION

SYNC

REM SRQ ACT ERR

EXT ERR

ARB

NOISE

BURST

AM (INT)

LOG SWP

LIN SWPmTRIG'D SINGLE

ARB

MOD/SWP SHIFT

Hz dBm

DEG Vrms

% Vpp

FREQ AMPL OFFS PHASE TRIG STEP SPAN RATE MRK STRT f STOP f

ON/STBY

SRS

STANFORD RESEARCH SYSTEMS MODEL DS345 30MHz SYNTHESIZED FUNCTION GENERATOR

TIMEBASE

STATUS

Ω

40V max.

TTL

ECL

TTL

REL=0

TRIG SWP CF

BRST CNT

STOP f

MRK START

GPIB

TRIG SOURCE

MRK STOP

SRQ

TRIG RATE

ARB EDIT

MRK CF

RS232

MRK=SPAN

DEFAULTS

MRK SPAN

DATA

SPAN=MRK

CALIBRATE

LOCAL

AMPL

FREQ

OFFST

PHASE

RATE

SWEEP ON/OFF

SPAN (DEPTH)

START FREQ

SHIFT STO RCL CLR

DEG

MHz dBm

kHz Vrms

Hz Vpp

STEP SIZE

+/-

FUNCTION

MODULATION

FUNCTION SWEEP/MODULATE MODIFYENTRY

10.000000000 MHz

Frequency Standard

Mixer

1 MHz Lowpass Filter

11.0 kΩ 1%

15 kHz Lowpass Filter

Ω

1.23 V

AC/DC Voltmeter

Figure 6-1. Phase Noise Measurement

Performance Tests

DS345

0.0015 µF 5%

5-9

Performance Tests

SQUARE WAVE RISE TIME

This test measures the rise time and aberrations of the square wave output. specification: rise time < 15 ns

overshoot < 5% of peak-to-peak output

1) Connect the output of the DS345 to the 350 MHz oscilloscope with a 50

Ω

terminator. Set the DS345 to square wave , 1 MHz, 10 Vpp.

2) Set the oscilloscope to 2 V/div vertical and 5 ns/div horizontal. Measure the time between the 10% and 90% points and verify that it is less than 15ns. Record the results.

3) Set the oscilloscope to 1 V/div vertical and 100 ns/div horizontal. Verify that the overshoots and undershoots are less than ± 500 mV. Record the results.

SQUARE WAVE SYMMETRY

This test measures the symmetry of the square wave output. specification: < 1% of period + 4ns

1) Connect the output of the DS345 to the A input of the time interval counter and terminate into 50Ω. Set the DS345 to square wave, 1 MHz, 5 Vpp.

2) Set the time interval counter to measure the positive width of the A input. Record the reading.

3) Set the time interval counter to measure the negative width of the A input. This reading should be equal to the reading in step 2 < ±14 ns. Record the result.

AM ENVELOPE DISTORTION

This test measures the distortion of the envelope when the DS345 is amplitude modulating its output.

specification: < -35 dB at 1 kHz

1) Connect the DS345's output to the RF spectrum analyzer. Set the DS345 to sinewave, 1 MHz, 10 Vpp. Set the modulation to AM, sine wave, 1 kHz rate, 80% depth. Turn the modulation on.

2) Set the spectrum analyzer to 1 MHz center frequency, 20 kHz span.

3) The 1 MHz fundamental output and the two modulation sidebands1 kHz away should be visible. Verify than any harmonics of the sidebands (at 2kHz, 3 kHz, ... offset) are less than -35 dB down. Record the results.

THIS COMPLETES THE PERFORMANCE TESTS

5-10

DS345 PERFORMANCE TEST RECORD

Serial Number: __________

Date:____________

Tested By:______________ Comments:

Pass

Fail

Functional Tests

Front Panel Test

_____

Self Tests

_____

Sine Wave

_____

Square Wave

_____

Amplitude Flatness

_____

Output Level

_____

Minimum

Actual

Maximum

Performance Tests

Frequency Accuracy

9,999,950 Hz

____________

10,000,050 Hz

Amplitude Accuracy

sine, 100 Hz, 3.54 Vrms

3.459 Vrms

____________

3.621 Vrms

sine, 1 kHz, 3.54 Vrms

3.459 Vrms

____________

3.621 Vrms

sine, 10 kHz, 3.54 Vrms

3.459 Vrms

____________

3.621 Vrms

sine, 100 kHz, 3.54 Vrms

3.459 Vrms

____________

3.621 Vrms

sine, 1 kHz, 1 Vrms

0.966 Vrms

____________

1.034 Vrms

sine, 1 kHz, 0.5 Vrms

0.483 Vrms

____________

0.517 Vrms

sine, 1 kHz, 0.25 Vrms

0.242 Vrms

____________

0.259 Vrms

sine, 1 kHz, 125 mVrms

121 mVrms

____________

129 mVrms

sine, 1 kHz, 75 mVrms

72.5 mVrms

____________

77.6 mVrms

sine, 1 kHz, 40 mVrms

38.6 mVrms

____________

41.4 mVrms

sine, 1 kHz, 25 mVrms

24.15 mVrms

____________

25.85 mVrms

square, 100 Hz, 5 Vrms

4.85 Vrms

____________

5.15 Vrms

square, 1 kHz, 5 Vrms

4.85 Vrms

____________

5.15 Vrms

square, 10 kHz, 5 Vrms

4.85 Vrms

____________

5.15 Vrms

triangle, 100 Hz,2.89 Vrms

2.80 Vrms

____________

2.97 Vrms

triangle, 1 kHz, 2.89 Vrms

2.80 Vrms

____________

2.97 Vrms

triangle, 10 kHz, 2.89 Vrms

2.80 Vrms

____________

2.97 Vrms

sine, 1 kHz, 3 Vrms reference = X

____________

Tolerance ±4.2% of X

___________

__________

(0.958X)

(1.042X)

sine, 2.001 MHz, 3 Vrms

____________

sine, 4.001 MHz, 3 Vrms

____________

sine, 6.001 MHz, 3 Vrms

____________

Performance Tests

5-11

Performance Tests

sine, 8.001 MHz, 3 Vrms

____________

sine, 10.001 MHz, 3Vrms

____________

sine, 12.001 MHz, 3 Vrms

____________

sine, 14.001 MHz, 3 Vrms

____________

sine, 16.001 MHz, 3 Vrms

____________

sine, 18.001 MHz, 3 Vrms

____________

Tolerance ±6.3% of X

___________

__________

(0.937X)

(1.063X)

sine, 20.001 MHz, 3 Vrms

____________

sine, 22.001 MHz, 3 Vrms

____________

sine, 24.001 MHz, 3 Vrms

____________

sine, 26.001 MHz, 3 Vrms

____________

sine, 28.001 MHz, 3 Vrms

____________

sine, 30.001 MHz, 3 Vrms

____________

square, 10 Vpp

____________

___________

Pass

Fail

DC Offset Accuracy (DC only)

5.0 V

4.925 V

___________

5.075 V

-5.0 V

-5.075 V

___________

-4.925 V

0.0 V

-0.0002 V

___________

0.0002 V

DC Offset Accuracy (DC + AC)

1 kHz, 10 Vpp, 0 Vdc

-0.08 V

___________

0.08 V

100 kHz, 10 Vpp, 0 Vdc

-0.08 V

___________

0.08 V

1 MHz, 10 Vpp, 0 Vdc

-0.08 V

___________

0.08 V

10 MHz, 10 Vpp, 0 Vdc

-0.08 V

___________

0.08 V

20 MHz, 10 Vpp, 0 Vdc

-0.08 V

___________

0.08 V

30 MHz, 10 Vpp, 0 Vdc

-0.08 V

___________

0.08 V

Subharmonics

sine, 102 kHz, 23.98 dBm

___________

-26.02 dBm

sine, 1.002 MHz,23.98 dBm

___________

-26.02 dBm

sine, 10.002 MHz, 23.98 dBm

___________

-26.02 dBm

sine, 20.002 MHz, 23.98 dBm

___________

-26.02 dBm

sine, 30.002 MHz, 23.98 dBm

___________

-26.02 dBm

Spurious Signals

sine, 26.662 MHz

___________

-50 dBc

sine, 20.004 MHz

___________

-50 dBc

sine, 18 MHz

___________

-50 dBc

Harmonic Distortion

sine, 100 Hz, 1 Vpp

___________

-55 dBc

sine, 1 kHz, 1 Vpp

___________

-55 dBc

sine, 10 kHz, 1 Vpp

___________

-55 dBc

sine, 50 kHz, 1 Vpp

___________

-55 dBc

sine, 500 kHz, 1 Vpp

___________

-45 dBc

5-12

Performance Tests

sine, 5 MHz, 1 Vpp

____________

-35 dBc

sine, 15 MHz, 1 Vpp

____________

-25 dBc

sine, 30 MHz, 1 Vpp

____________

-25 dBc

Phase Noise

sine, 10.001 MHz, 13 dBm = V1

____________

sine, 10.0 MHz, 13 dBm = V2

____________

noise = 20 log (V2/V1) - 6 dB

____________

-55 db

Square Wave Rise Time

square, 1 MHz, 10 Vpp. 10% to 90% rise time

____________

15 ns

square, 1 MHz, 10 Vpp. Overshoots

____________

±500 mV

Square Wave Symmetry

square, 1 MHz, 5 Vpp. + pulse width

____________

square, 1 MHz, 5 Vpp. - pulse width

____________

asymmetry = (+ width) - (- width)

____________

14 ns

AM Envelope Distortion

80% depth, 1 kHz

__________

Pass

Fail

5-13

CALIBRATION

Introduction

Calibration Enable The DS345 is shipped with calibration disabled. When calibration is disabled

The calibration of the DS345 is composed of two parts: adjustment and calibration. Adjustments are actual physical adjustments to variable resistors, inductors, and capacitors to correct the DS345's oscillator, filters, and output amplifier response. Calibration is the process of determining the calibration constants ("calbytes") that the DS345 firmware uses to correct the output amplitude, etc.. The DS345's autocal procedure automatically determines the most important of these calbytes.

The settings of the adjustments are, in general, very stable and should rarely require change. If the adjustments are changed the corresponding calibrations must be performed. However, the DS345 should need only routine running of the autocal procedure and occasional complete recalibration to maintain its performance.

only autocal is allowed, and direct access to the calbytes is prevented. The internal calibration enable switch must be set to enable calibration. To set the switch remove the DS345's top cover by removing its four retaining screws (this will break the calibration seal). On units with an optional oscillator remove the mounting screw half way back on the left side of the chassis. Next, remove the two left hand screws securing the top circuit board. This board will hinge open (the optional oscillator hinges with the circuit board). In the center of the bottom circuit board is a four position DIP switch labelled SW300. Set SW300 switch 2 ON to enable calibration, and OFF to disable calibration.

Calbytes The DS345's calibration is controlled by calibration constants ("calbytes") that

the firmware uses to adjust the various output parameters. These calbytes are stored in the DS345's RAM. Recalibration of the DS345 involves determining the values of the calbytes and storing the new values in RAM. The calbyte values at the time of the DS345's production are also stored in ROM and may be recalled at any time.

Direct access to the DS345's calbytes is allowed from both the front panel and computer interfaces after calibration is enabled. From the front panel press [SHIFT][CALIBRATE] three times to display the calbyte menu line. There are two displayed parameters: on the left is the calbyte number, and on the right is the calbyte value. The calbyte number and value may be modified with either the keypad or the MODIFY keys. To select an item use the [SHIFT][RIGHT ARROW] and [SHIFT][LEFT ARROW] keys. The calbyte number may be set between 0 and 509. The calbyte value may be set between -32768 and 32767. The complete set of factory calbyte values may be recalled by pressing [CLR] any time a value is not being entered. The table on the next page lists the DS345 calbytes. Shown is the calbyte number, name, and meaning. The chart also indicates which calbytes are automatically adjusted by autocal.

6-1

Calibration

DS345 CALBYTES

Number

Name

Autocal

Meaning

Oscillator Cal

Tunes Oscillator. Range = 0 - 4095

+5 V Ref Cal

Value of +5 ref voltage. Value = 32768 *(Vref/5.00)

ADC Gain

ADC Gain correction.

ADC Offset

ADC Offset correction.

DC Offset Gain

DC ouput offset gain fix.

DC Offset offset

DC output offset offset fix.

Attenuator 0 dB

Gain correction for 0 dB attenuator

Attenuator 6 dB

Gain correction for 6 dB attenuator

Attenuator 12 dB

Gain correction for 12 dB attenuator

Attenuator 18 dB

Gain correction for 18 dB attenuator

Attenuator 24 dB

Gain correction for 24 dB attenuator

Attenuator 30 dB

Gain correction for 30 dB attenuator

Attenuator 36 dB

Gain correction for 36 dB attenuator

Attenuator 42 dB

Gain correction for 42 dB attenuator

System amp DAC

Offset of system amplitude DAC

ASIC amp DAC

Offset of ASIC amplitude DAC

Sine DC gain

Sets the sinewave DC gain

Square DC gain

Sets the squarewave DC gain

Bessel DC gain

Sets the Bessel (tri, ramp, arb) DC gain

Waveform DAC offset

Offset of waveform DAC

NOTE: The following calbytes are frequency dependent. The table value for a particular frequency is given by: TABLE BASE NUMBER + Frequency (Hz)/312500.

20-117

Sine Amplitude

Sine wave amplitude correction

118-215

Square Amplitude

Square wave amplitude correction

216-313

Doubler Offset

Frequency doubler offset fix

314-411

Carrier Null

Sine wave carrier null correction

412-509

Square Symmetry

Square symmetry fix

6-2

Calibration

NECESSARY EQUIPMENT

The following equipment is necessary to complete the adjustments and calibrations. The suggested equipment or its equivalent may be used.

Instrument

Critical Specifications

Recommended Model

Analog Oscilloscope

350 MHz Bandwidth

Tektronix 2465

Time Interval Counter

Frequency Range: 20 MHz min.

SRS SR620

Time Interval Accuracy: 1ns max

FFT Spectrum Analyzer

Frequency Range: DC to 100 kHz

SRS SR760 Amplitude Accuracy: ±0.2 dB Distortion: < 75 dB below reference

RF Spectrum Analyzer

Frequency Range: 1 kHz to 100 MHz

Anritsu MS2601/ HP4195A Amplitude: ±0.5 dB Distortion and Spurious: < -70 dB

DC/AC Voltmeter

51/2 Digit DC accuracy

Fluke 8840A True RMS AC to 100 kHz

Thermal Converter

Input Impedance: 50

Ω

Ballantine 1395A-3-09 Input Voltage: 3 Vrms

Frequency: DC to 30 MHz Accuracy: ±0.05dB

10 MHz Frequency Standard

Frequency: 10 MHz ± .001 ppm

SRS FS700 Phase Noise: < -130 dBc @ 100Hz

50 Ω Terminator

50 Ω ± 0.2 %, 1 Watt

HP 11048C

ADJUSTMENTS

The following adjustments set the values of all of the variable components in the DS345. After an adjustment has been made the associated calibrations

must

be made. All adjustments must be complete before calibration is started. First, remove the DS345's top cover by removing the four retaining screws.

On units with an optional oscillator remove the mounting screw half way back on the left side of the chassis. Next, remove the two left hand screws securing the top circuit board. This board will hinge open (the optional oscillator hinges with the circuit board). Set the "cal enable" switch (SW300 switch 2) to ON.

NOTE: The chassis ground and circuit ground float relative to each other. For voltage measurements use the FUNCTION output BNC shield as a ground reference.

Clock Adjustment

This adjustment sets the DS345's internal 40 MHz oscillator. Instructions for both standard and optional oscillators are given below. The oscillator calibration should be done after this adjustment.

1) Connect the DS345's 10 MHz output to the frequency counter input. The counter should use the frequency standard for its timebase. Be sure that the

6-3

Calibration

DS345 has had at least 1/2 hour to warm up.

2) Set calbyte number 0 to 2980. For a unit with an optional oscillator set SW300 switch 1 (bottom board) to OFF.

3) Adjust L203 (top board) so that the output U205 pin 6 is closest to 0 V DC. Adjust L204 (top board) so that the oscillator frequency is within 1 Hz of 10.0 MHz.

if the unit has an optional oscillator:

4) Set SW300 switch 1 to ON. Set calbyte 0 to 2048.

5) If necessary, adjust the optional oscillator coarse adjustment screw so that the frequency is within 1 Hz of 10 MHz.

Output Amplifier Bandwidth

These adjustments correct the bandwidth of the output amplifier. A complete calibration must be performed if these adjustments are changed. All of the adjustments are on the bottom PCB and may be reached through holes in the shield. Use an insulated adjusting screwdriver.

1) Set the DS345 for square wave, 8 Vpp, 10 kHz. Measure the DC voltage at the output of U600 pin 6. Adjust P600 to until this voltage is 0.0V.

2) Connect the output of the DS345 to the oscilloscope with a 50Ω terminator. Set the DS345 to square wave, 8 Vpp, 100 Hz. Set the scope to 2 V/div

vertical and 5 ms/div horizontal. Adjust R639 for the squarest output waveform.

3) Set the DS345 to 500 kHz. Set the scope to 1 µs/div. Adjust P601 for the squarest output waveform.

4) Set the scope to 200ns/div. Adjust C611 for the fastest output risetime without excessive overshoots.

5) Do a complete calibration of the DS345

Bessel Filter Adjustment

This adjustment sets the bandpass of the DS345's Bessel waveform filter. The adjustments are on the top board. Run autocal after these adjustments.

1) Press [SHIFT][DEFAULTS]. This will recall the DS345's default arbitrary waveform- a square wave. Set the DS345 to ARB waveform, 8 Vpp, 2 MHz sampling frequency. Connect the DS345's output to an oscilloscope with a

50Ω terminator. Set the scope to 2 V/div vertical and 200 ns/div horizontal.

2) Starting with C645, adjust C645, C644,C643, and C642 to make the output rise time as fast as possible while minimizing the peak-to-peak ripple. Several iterations of the capacitors may be needed to acheive optimum response.

3) Run autocal.

6-4

Calibration

Harmonic Distortion Adjust

This adjustment minimizes the DS345's 2nd, 3rd, and 5th harmonic distortion. A complete calibration is necessary after this adjustment.

1) Set the DS345 to sine wave, 8 Vpp, 15 kHz. Connect the DS345's output to the FFT analyzer with a 50Ω terminator. Set the FFT analyzer to display from DC to 100 kHz.

2) Adjust P602 (bottom board) to minimize the levels of the third harmonic at 45 kHz and the 5th harmonic at 75 kHz.

3) Readjust the AC-DCgain balance of the output amplifier (see Output Amplifier Bandwidth adjustment, step 2).

4) Recalibrate the DS345.

6-5

Calibration

CALIBRATION

The following procedures determine the values of the DS345's calbytes. Any adjustments should be done before starting calibration. Allow the DS345 at least 1/2 hour warmup before beginning calibration. The first calibration (the

5.00 V reference calibration) requires the DS345's top cover be removed. All other calibrations should be done with the DS345 completely assembled and 1/2 hour of warmup after reassembly. When the new calbyte values are determined they should be entered into the DS345's RAM. In cases where the calbyte value is determined to be greater than 32767 enter the value = calbyte value - 65536.

5.00 V Reference Calibration

This procedure measures the value of the 5.0 V reference voltage that the DS345 uses for its internal A/D converter (calbyte # 1).

1) Measure the DC voltage at U103 pin 1 (top board).

2) The new value for calbyte 1 is Calbyte 1 = 32768 * (DC voltage/5.00).

Clock Calibration

This procedure sets the frequency of the DS345's internal 10 MHz clock. The procedure is identical for standard and optional oscillators. Be sure that the DS345 has been completely reassembled and warmed up for at least 1/2 hour before this calibration is started.

1) Connect the DS345's 10 MHz output to the frequency counter input with a 50Ω terminator. Use the frequency standard as the counter's timebase.

2) Adjust the value of calbyte 0 so that the frequency is within 1 Hz of 10 MHz (0.01 Hz for optional oscillators). The range of calbyte 0 is 0 to 4095. If the clock cannot be calibrated with a value in this range do the clock adjustment procedure.

Attenuator Calibration

This procedure calibrates the DC value of the DS345's output attenuators. If the current calbyte value is negative use the value = old calbyte + 65536 in the following calculations.

1) Connect the output of the DS345 to a DC voltmeter. Do

not

use a 50

Ω

terminator. Set the DS345 to sine wave, 1 kHz, 0 Vpp, 5 V offset.

2) Record the DC voltage. Record this value, with a high impedance termination, as Vref.

3) Connect the 50Ω terminator and measure the DC voltage. The new value for calbyte 6 = old calbyte 6 * Vref/(2 * Vdc).

4) Set the DS345 to 2.5 V offset. Measure the DC output value. The new value for calbyte 7 = old calbyte 7 *Vref/ (4 * Vdc).

5) Set the DS345 to 1.25 V offset. Measure the DC output value. The new value for calbyte 8 = old calbyte 8 * Vref/(8 * Vdc).

6-6

Calibration

6) Set the DS345 to 625mV offset. Measure the DC voltage. The new value for calbyte 9 = old calbyte 9 * Vref/(16 * Vdc).

7) Set the DS345 to 312mV offset. Measure the DC voltage. The new value for calbyte 10 = old calbyte 10 * Vref/(32.05 * Vdc).

8) Set the DS345 to 156mV offset. Measure the DC voltage. The new value for calbyte 11 = old calbyte 11 * Vref/(64.1 * Vdc).

9) Set the DS345 to 78mV offset. Measure the DC voltage. The new value for calbyte 12 = old calbyte 12 * Vref/(128.21 * Vdc).

10) Set the DS345 to 39mV offset. Measure the DC voltage. The new value for calbyte 13 = old calbyte 13 * Vref/(256.41 * Vdc).

Carrier Null Calibration

This calibration nulls the carrier feedthrough of the DS345's frequency doubler. This calibration depends on frequency and is calibrated at 98 frequency points in the DS345's frequency range. This calibration must be done before the amplitude calibrations.

1) Set the DS345 to sine wave, 1 kHz, 8 Vpp, 0 V offset. Connect the DS345's output to the FFT spectrum analyzer using a 50Ω terminator. Set the analyzer to display 0 to 2 kHz.

2) Adjust calbyte 314 to minimize the 1 kHz carrier amplitude.

3) Connect the DS345's output to the RF spectrum analyzer. Set the DS345's frequency step size to 312500 Hz. Set the frequency to 313500 Hz.

At 96 frequencies between 313500 Hz and 30,001,000 Hz in 312500 Hz steps repeat the following procedure.

4) Set the spectrum analyzer center frequency to the programmed frequency/

2. Set the span to 100 kHz.

5) Adjust the appropriate calbyte to minimize the carrier frequency component at f/2 (ignore any nearby spurs). The calbyte has a range of 0 to 4095. The calbyte number for a particular frequency is: 314 + (f - 1000Hz)/312500 Hz (that is 313500 Hz = 315, 626000 Hz = 316, etc.).

6) Step to the next frequency, and reset the analyzer. Continue until 30,001,000 Hz and calbyte 410.

7) Set calbyte 411 to the same value as calbyte 410.

6-7

Calibration

Sinewave Amplitude

This calibration corrects the flatness of the DS345's sinewave output. This calibration depends on frequency and is calibrated at 98 frequency points in the DS345's frequency range. The carrier null calibration should be done before this calibration.

1) Set the DS345 to sine wave, 1 kHz, 3 Vrms, 0 V offset. Set the frequency step size to 312500 Hz. Connect the DS345's output to the thermal converter and the thermal conveter output to the DC voltmeter.

2) Set calbyte 20 to 16384.

3) Allow the thermal converter output to settle (about 10 - 15 seconds) and record the voltage as Vref (the voltage should be about 7 mV).

At 96 frequencies between 313500 Hz and 30,001,000 Hz in 312500 Hz steps repeat the following procedure.

4) Set the DS345's output frequency and allow the converter to settle. The new calbyte for this frequency is given by:

The calbyte should be in the range 8000 to 23000. The calbyte number for a given frequency is: number = 20 + (f - 1000Hz)/312500 Hz (that is 313500 Hz = 21, 626000 Hz = 22, etc.).

5) Set calbyte 117 to the same value as calbyte 116.

Square Wave Amplitude

This calibration corrects the DS345's square wave amplitude response. This calibration depends on frequency and is calibrated at 98 frequency points in the DS345's frequency range. The square wave symmetry calibration should be done after this calibration.

1) Set the DS345 to square wave, 1 kHz, 10 Vpp. Connect the DS345's output to the oscilloscope with a 50Ω terminator. Set the DS345's frequency step size to 312500 Hz. Set the oscilloscope to 2 V/div vertical and 1 ms/div

horizontal.

2) Set calbyte 118 to 16384.

3) Measure the peak-to-peak amplitude of the square wave and record as Vref.

At 96 frequencies between 313500 Hz and 30,001,000 Hz in 312500 Hz steps repeat the following procedure.

4) Set the DS345's output frequency and measure the peak-to-peak amplitude. The new calbyte value for this frequency is: new calbyte = old calbyte * (Vref/Vpp). The calbyte should be in the range 8000 to 23000. The calbyte

new

   

   

0.556

calbyte= old calbyte×

ref

6-8

Calibration

number for a given frequency is: number = 118 + (f - 1000Hz)/312500 Hz (that is 313500 Hz = 119, 626000 Hz = 120, etc.).

5) Set calbyte 215 to the same value as calbyte 214

Square Wave Symmetry

This calibration corrects the symmetry of the DS345's square wave output. This calibration depends on frequency and is calibrated at 98 frequency points in the DS345's frequency range. This calibration should be done after the square wave amplitude calibration.

1) Set the DS345 to square wave, 1 kHz, 10 Vpp. Connect the DS345's output to the counter with a 50Ω terminator. Set the DS345's frequency step size to 312500 Hz. Set the counter to measure the pulse width of the square

wave input. At 97 frequencies between 1000 Hz and 30,001,000 Hz in 312500 Hz steps

repeat the following procedure.

4) Set the DS345's output frequency. Adjust the calbyte for this frequency so that the positive pulse width of the square wave is equal to the negative pulse width. The calbyte should be in the range 0 to 4095. The calbyte number for a given frequency is: number = 412 + (f - 1000Hz)/312500 Hz (that is 1000 Hz = 412, 313500 Hz = 413, etc.).

5) Set calbyte 509 to the same value as calbyte 508.

6-9

Stanford Research Systems DS345 Users Guide

Specifications and Main Features

Frequently Asked Questions

User Manual