Agilent Technologies 33120A User Manual

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Service Guide

Publication Number 33120-90017 (order as 33120-90104 manual set) Edition 6, March 2002

For Safety information, Warranties, and Regulatory information,

see the last page in this manual.

Agilent 33120A 15 MHz Function /

Arbitrary Waveform Generator

Note: Unless otherwise indicated, this manual applies to all Serial Numbers.

The Agilent Technologies 33120A is a high-performance 15 MHz synthesized function generator with built-in arbitrary waveform capability. Its combination of bench-top and system features makes this function generator a versatile solution for your testing requirements now and in the future.

Convenient bench-top features

 10 standard waveforms

 Built-in 12-bit 40 MSa/s arbitrary waveform capability

 Easy-to-use knob input

 Highly visible vacuum-fluorescent display

 Instrument state storage

 Portable, ruggedized case with non-skid feet

Flexible system features

Warning

 Four downloadable 16,000-point arbitrary waveform memories

 GPIB (IEEE-488) interface and RS-232 interface are standard

 SCPI (Standard Commands for Programmable Instruments) compatibility

 Agilent IntuiLink Arb Waveform Generation Software for

Microsoft

The procedures in this manual are intended for use by qualified, service-trained personnel only.

Windows

Agilent 33120A 15 MHz Function /

Arbitrary Waveform Generator

The Front Panel at a Glance

1 Function / Modulation keys 2 Menu operation keys 3 Waveform mod ify keys 4 Single / Internal Trigger key

(Burst and Sweep only)

5 Recall / Store instrument state key 6 Enter Number key 7 Shift / Local key 8 Enter Number “units” keys

Front-Panel Number Entry

You can enter numbers from the front-panel using one of three methods.

Use the knob and the arrow keys to modify the displayed number.

Use the arrow keys to edit individual digits.

Increments the flashing digit.

Decrements the flashing digit.

Moves the flashing digit

to the right.

to the left.

Use the “Enter Number” mode to enter a number with the appropriate units.

Use “Enter” for those operations that do not require units to be specified (AM Level, Offset, % Duty, and Store/Recall State).

The Front-Panel Menu at a Glance

The menu is organized in a top-down tree structure with three levels.

A: MODulation MENU

1: AM SHAPE Õ 2: AM SOURCE Õ 3: FM SHAPE Õ 4: BURST CNT Õ 5: BURST RATE Õ

Õ 6: BURST PHAS Õ 7: BURST SRC Õ 8: FSK FREQ Õ 9: FSK RATE Õ 10: FSK SRC

B: SWP (Sweep) MENU

1: START F Õ 2: STOP F Õ 3: SWP TIME Õ 4: SWP MODE

C: EDIT MENU

1: NEW ARB Õ [ 2: POINTS ] Õ [ 3: LINE EDIT ] Õ [ 4: POINT EDIT ] Õ [ 5: INVERT ] Õ [ 6: SAVE AS ] Õ 7: DELETE

The commands enclosed in square brackets ( [ ] ) are “hidden” until you make a selection from the

NEW ARB command to initiate a new edit session.

D: SYStem MENU

1: OUT TERM Õ 2: POWER ON Õ 3: ERROR Õ 4: TEST Õ 5: COMMA Õ 6: REVISION

E: Input / Output MENU

1: HPIB ADDR Õ 2: INTERFACE Õ 3: BAUD RATE Õ 4: PARITY Õ 5: LANGUAGE

F: CALibration MENU

1: SECURED or [ 1: UNSECURED ] Õ [ 2: CALIBRATE ] Õ 3: CAL COUNT Õ 4: MESSAGE

The commands enclosed in square brackets ( [ ] ) are “hidden” unless the function generator

is UNSECURED for calibration.

Display Annunciators

Adrs Rmt Trig AM FM Ext FSK Burst Swp

ERROR

Offset Shift Num Arb

Function generator is addressed to listen or talk over a remote interface. Function generator is in remote mode (remote interface). Function generator is waiting for a single trigger or external trigger (Burst, Sweep). AM modulation is enabled. FM modulation is enabled. Function generator is set for an external modulation source (AM, FSK, Burst). FSK (frequency-shift keying) modulation is enabled. Burst modulation is enabled. Sweep mode is enabled. Hardware or remote interface command errors are detected. The waveform is being output with an offset voltage. “Shift” key has been pressed. Press “Shift” again to turn off. “Enter Number” mode is enabled. Press “Shift-Cancel” to disable. Arbitrary waveform function is enabled. Sine waveform function is enabled. Square waveform function is enabled. Triangle waveform function is enabled. Ramp waveform function is enabled.

To review the display annunciators, hold down the Shift key as you turn on the function generator.

The Rear Panel at a Glance

1 Chassis ground 2 Power-line fuse-holder assembly 3 Power-line voltage setting

4 AM modulation input terminal

Use the front-panel Input / Output Menu to:

5 External Trigger / FSK / Burst modulation

input terminal

6 GPIB (IEEE-488) interface connector 7 RS-232 interface connector

 Select the GPIB or RS-232 interface (see chapter 4 in User’s Guide).  Set the GPIB bus address (see chapter 4 in User’s Guide). 

Set the RS-232 baud rate and parity (see chapter 4 in User’s Guide).

In This Book

Specifications Chapter 1 lists the function generator’s specifications and describes how to interpret these specifications.

Quick Start Chapter 2 prepares the function generator for use and helps you get familiar with a few of its front-panel features.

Front-Panel Menu Operation Chapter 3 introduces you to the front-panel menu and describes some of the function generator’s menu features.

Calibration Procedures Chapter 4 provides calibration, verification, and adjustment procedures for the function generator.

Theory of Operation Chapter 5 describes block and circuit level theory related to the operation the function generator.

Service Chapter 6 provides guidelines for returning your function generator to Agilent for servicing, or for servicing it yourself.

Replaceable Parts Chapter 7 contains a detailed parts lists of the function generator.

Schematics Chapter 8 contains the function generator’s block diagram, schematics, disassembly drawings, and component locator drawings.

For information on using the Phase-Lock Option for the 33120A, refer to the User’s and Service Guide included with the Option 001.

If you have questions relating to the operation of the 33120A, call 1-800-452-4844 in the United States, or contact your nearest Agilent Technologies Sales Office.

If you believe your 33120A has failed, refer to “Operating Checklist”, “Types of Service Available”, and “Repackaging for Shipment” at the beginning of chapter 6.

Chapter 1 Specifications

Chapter 2 Quick Start

To prepare the function generator for use 21 If the function generator does not turn on 22 To adjust the carrying handle 24 To set the output frequency 25 To set the output amplitude 26 To set a dc offset voltage 27 To set the duty cycle 28 To output a stored arbitrary waveform 29 To output a dc voltage 30 To store the instrument state 31 To rack mount the function generator 33

Chapter 3 Front-Panel Menu Operation

Front-panel menu reference 37 A front-panel menu tutorial 39 To select the output termination 44 To output a modulated waveform 45 To unsecure the function generator for calibration 47

Contents

Chapter 4 Calibration Procedures

Agilent Calibration Services 51 Calibration Interval 51 Time Required for Calibration 51 Automating Calibration Procedures 52 Recommended Test Equipment 52 Test Considerations 53 Performance Verification Tests 54 Frequency Verification 56 Function Gain and Linearity Verification 56 DC Function Offset Verification 57 AC Amplitude Verification 57 Amplitude Flatness Verification 60 AM Modulation Depth Verification 61 Optional Performance Verification Tests 62

Contents

Chapter 4 Calibration Procedures (continued)

Calibration Security Code 64 Calibration Count 66 Calibration Message 66 General Calibration/Adjustment Procedure 67 Aborting a Calibration in Progress 69 Frequency and Burst Rate Adjustment 69 Function Gain and Linearity Adjustment 70 AC Amplitude Adjustment (High-Z) 70 Modulation Adjustment 72 AC Amplitude Adjustment (50 DC Output Adjustment 76 Duty Cycle Adjustment 77 AC Amplitude Flatness Adjustment 77 Output Amplifier Adjustment (Optional) 80 Error Messages 81

Chapter 5 Theory of Operation

Block Diagram Overview 85 Output Attenuator 86 Output Amplifier 87 AM Modulation 89 Pre-attenuator 90 Square Wave and Sync 90 Filters 92 Waveform DAC/Amplitude Leveling/Waveform RAM 93 Direct Digital Synthesis (DDS ASIC) 95 System DACs 96 Floating Logic 97 Earth-Referenced Logic 98 Power Supplies 98 Display and Keyboard 100

W) 73

Contents

Chapter 6 Service

Operating Checklist 103 Types of Service Available 104 Repackaging for Shipment 105 Cleaning 105 Electrostatic Discharge (ESD) Precautions 106 Surface Mount Repair 106 To Replace the Power-Line Fuse 107 To Replace the Output Protection Fuse (F801) 107 Troubleshooting Hints 108 Self-Test Procedures 110

Chapter 7 Replaceable Parts

Replaceable Parts 113

Chapter 8 Schematics

33120A Block Diagram 129 Mechanical Disassembly 130 Floating Logic Schematic 131 Digital Waveform Data Synthesis 132 System DAC Schematic 133 Waveform DAC Schematic 134 Filters Schematic 135 Sync, Square Wave, and Attenuator Schematic 136 Output Amplifier Schematic 137 Output Attenuator Schematic 138 Earth Reference Logic Schematic 139 Power Supplies Schematic 140 Display and Keyboard Schematic 141 33120-66521 Component Locator Diagram 142 33120-66502 Component Locator Diagram 143

Contents

Specifications

Chapter 1 Specifications

Agilent 33120A Function Generator

WAVEFORMS

Standard Waveforms:

Sine, Square, Triangle, Ramp, Noise, DC volts, Sine(x)/x, Negative Ramp, Exponential Rise, Exponential Fall, Cardiac

Arbitrary Waveforms:

Waveform Length: Amplitude Resolution: Sample Rate: Non-Volatile Memory:

8 to 16,000 points 12 bits (including sign) 40 MSa / sec Four 16,000-point waveforms

FREQUENCY CHARACTERISTICS

Sine: Square: Triangle: Ramp: Noise (Gaussian): Arbitrary Waveforms:

8 to 8,192 points: 8,193 to 12,287 points: 12,288 to 16,000 points:

Resolution:

Accuracy:

Temperature Coefficient:

Aging:

Hz – 15 MHz

100

Hz – 15 MHz

100

Hz – 100 kHz

100

Hz – 100 kHz

100 10 MHz bandwidth

Hz – 5 MHz

100

Hz – 2.5 MHz

100

Hz – 200 kHz

100

Hz or 10 digits

10 ppm in 90 days, 20 ppm in 1 year,



C – 28C

< 2 ppm /



< 10 ppm / yr

SINEWAVE SPECTRAL PURITY (into 50

SIGNAL CHARACTERISTICS

Squarewave

Rise/Fall Time: Overshoot: Asymmetry: Duty Cycle:

Triangle, Ramp, Arb

Rise/Fall Time: Linearity: Settling Time: Jitter:

OUTPUT CHARACTERISTICS

(4)

(3)

Amplitude (into 50 Accuracy (at 1 kHz): Flatness < 100 kHz: 100 kHz to 1 MHz: 1 MHz to 15 MHz: 1 MHz to 15 MHz:

Offset (into 50 Accuracy:

Output Impedance:

Resolution:

Output Units:

Isolation:

)

Protection:

< 20 ns < 4% 1% + 5 ns 20% to 80% (to 5 MHz) 40% to 60% (to 15 MHz)

40 ns (typical) < 0.1% of peak output < 250 ns to 0.5% of final value < 25 ns

(2)

50 mVpp – 10 Vpp



1% of specified output

(sine wave relative to 1 kHz)



1% (0.1 dB)



1.5% (0.15 dB)



2% (0.2 dB) Ampl  3Vrms



3.5% (0.3 dB) Ampl < 3Vrms



5 Vpk ac + dc



2% of setting + 2 mV

50 ohms fixed

3 digits, Amplitude and Offset

Vpp, Vrms, dBm

42 Vpk maximum to earth

Short-circuit protected



15 Vpk overdrive < 1 minute

(1)

Harmonic Distortion

DC to 20 kHz: 20 kHz to 100 kHz: 100 kHz to 1 MHz: 1 MHz to 15 MHz:

Total Harmonic Distortion

DC to 20 kHz:

Spurious (non-harmonic) Output (DC to 1 MHz): Output (> 1 MHz):

Phase Noise:

-70 dBc

-60 dBc

-45 dBc

-35 dBc

< 0.04%

< -65 dBc < -65 dBc + 6 dB/octave

< -55 dBc in a 30 kHz band

(1) Add 1/10th of output amplitude and offset specification



C for operation outside of 18C to 28C range

per (1-year specification).

(2) 100 mVpp – 20 Vpp amplitude into open-circuit load.



(3) Offset

2 X peak-to-peak amplitude.

(4) For square wave outputs, add 2% of output amplitude additional error.

Chapter 1 Specifications

Agilent 33120A Function Generator

MODULATION CHARACTERISTICS

AM Modulation Carrier -3 dB Freq:

Modulation: Frequency:

Depth: Source:

FM Modulation Modulation: Frequency:

Peak Deviation: Source:

Burst Modulation Carrier Frequency: Count: Start Phase: Internal Rate: Gate Source: Trigger Source:

FSK Modulation

Frequency Range:

Internal Rate: Source:

10 MHz (typical) Any internal waveform plus Arb 10 mHz to 20 kHz (

2.5 kHz, then decreases linearly



0.4% at upper limit)

to 0% to 120% Internal / External

Any internal waveform plus Arb 10 mHz to 10 kHz ( 600 Hz, then decreases linearly



0.8% at upper limit)

to 10 mHz to 15 MHz Internal Only

5 MHz max. 1 to 50,000 cycles, or Infinite



to +360

-360 10 mHz to 50 kHz 1% Internal or External Gate Single, External, or Internal Rate

10 mHz to 15 MHz ( 600 Hz, then decreases linearly



4% at upper limit)

to 10 mHz to 50 kHz Internal / External (1 MHz max.)



0.05% to



0.05% to





0.05% to

(1)

SYSTEM CHARACTERISTICS

Configuration Times

Function Change: Frequency Change: Amplitude Change: Offset Change: Select User Arb: Modulation Parameter Change:

Arb Download Times over GPIB:

Arb Length Binary ASCII Integer ASCII Real

16,000 points 8 sec 81 sec 100 sec 8,192 points 4 sec 42 sec 51 sec 4,096 points 2.5 sec 21 sec 26 sec 2,048 points 1.5 sec 11 sec 13 sec

Arb Download Times over RS-232 at 9600 Baud:

Arb Length Binary ASCII Integer ASCII Real

16,000 points 35 sec 101 sec 134 sec 8,192 points 18 sec 52 sec 69 sec 4,096 points 10 sec 27 sec 35 sec 2,048 points 6 sec 14 sec 18 sec

(3)

(2)

(3)

80 ms 30 ms 30 ms 10 ms 100 ms < 350 ms

(4)

(5)

(6)

FREQUENCY SWEEP

Type: Direction: Start F / Stop F: Time: Source:

Linear or Logarithmic Up or Down 10 mHz to 15 MHz 1 ms to 500 sec Single, External, or Internal

REAR-PANEL INPUTS

External AM Modulation:

External Trigger/FSK Burst Gate:

Latency: Jitter:

(1)



5 Vpk = 100% Modulation

Input Resistance

5 k

TTL (low true)

1.3 25 ns



0.1% (1) Trigger source ignored when External Gate is selected.

(2) Time to change parameter and output the new signal.

(3) Modulation or sweep off.

(4) Times for 5-digit and 12-digit numbers.

(5) For 4800 baud, multiply the download times by two; For 2400 baud, multiply the download times by four, etc.

(6) Time for 5-digit numbers. For 12-digit numbers, multiply the 5-digit numbers by two.

Chapter 1 Specifications

Agilent 33120A Function Generator

GENERAL SPECIFICATIONS

Power Supply:

(1)

Power-Line Frequency:

Power Installation:

Power Consumption:

Operating Environment:

Storage Environment:

State Storage Memory:

Dimensions (W x H x D)

Bench Top: Rack Mount:

Weight:

100V / 120V / 220V / 240V



10%

(switch selectable)

50 Hz to 60 Hz 400 Hz



10% and

10%. Automatically

sensed at power-on.

CAT II

50 VA peak (28 W average)



C to 55C

80% Relative Humidity to 40



Indoor or sheltered location

-40



C to 70C

Power-off state automatically saved. Three (3) UserConfigurable Stored States, Arbitrary waveforms stored separately.

254.4 mm x 103.6 mm x 374 mm

212.6 mm x 88.5 mm x 348.3 mm

4 kg (8.8 lbs)

Safety Designed to:

EMC:

Vibration and Shock:

Acoustic Noise:

Warm-Up Time:

Warranty:

Remote Interface:

Programming Language:

Accessories Included:

N10149

EN61010, CSA1010, UL-1244

EN61326, 1:1997 + 1A:1998

MIL-T-28800E, Type III, Class 5 (data on file)

30 dBa

1 hour

3 years standard

IEEE-488 and RS-232 standard

SCPI-1993, IEEE-488.2

User’s Guide, Service Guide, Quick Reference Card, IntuiLink Arb software, RS-232 cable, Test Report, and power cord.

(1) For 400 Hz operation at 120 Vac, use the 100 Vac line-voltage setting.

Chapter 1 Specifications

Agilent 33120A Function Generator

PRODUCT DIMENSIONS

TOP

All dimensions are shown in millimeters.

Quick Start

One of the first things you will want to do with your function generator is to become acquainted with its front panel. We have written the exercises in this chapter to prepare the function generator for use and help you get familiar with some of the front-panel operations.

The front panel has two rows of keys to select various functions and operations. Most keys have a shifted function printed in blue above the key. To perform a shifted function, press turn on). Then, press the key that has the desired label above it. For example, to select the

Shift AM (the shifted version of the key).

AM (amplitude modulation) function, press

Shift (the Shift annunciator will

If you accidentally press

Shift , just press it again to turn off the Shift

annunciator.

Most keys also have a number printed in green next to the key. To enable the number mode, press

Enter Number (the Num annunciator will turn on).

Then, press the keys that have the desired numbers printed next to them. For example, to select the number “10”, press (next to the

If you accidentally press off the

and Recall keys).

Enter Number , just press Shift Cancel to turn

Num annunciator.

Enter Number 1 0

Chapter 2 Quick Start

To prepare the function generator for use

The following steps help you verify that the function generator is ready for use.

1 Check the list of supplied items.

Verify that you have received the following items with your function generator. If anything is missing, contact your nearest Agilent Technologies Sales Office.

One power cord.

One RS-232 serial cable.

One User’s Guide.

This Service Guide.

One folded Quick Reference card.

Certificate of Calibration.

Agilent IntuiLink Arb Waveform Generation Software.

2 Connect the power cord and turn on the function generator.

If the function generator does not turn on, see chapter 6 for troubleshooting information. The front-panel display will light up while the function generator performs its power-on self-test. The displayed. Notice that the function generator powers up in the sine wave function at 1 kHz with an amplitude of 100 mV peak-to-peak (into a 50 termination).

To review the power-on display with all annunciators turned on, hold down

3Perform a complete self test.

The complete self-test performs a more extensive series of tests than those performed at power-on. Hold down switch to turn on the function generator; hold down the key for more than 5 seconds. The self-test will begin when you release the key.

If the self-test is successful, “ If the self-test is not successful, “ annunciator turns on. See chapter 6 for instructions on returning the function generator to Agilent for service.

Shift as you turn on the function generator.

PASS” is displayed on the front panel.

FAIL” is displayed and the ERROR

GPIB bus address is

Shift as you press the Power

Chapter 2 Quick Start

If the function generator does not turn on

Use the following steps to help solve problems you might experience when turning on the function generator. If you need more help, see chapter 6 for instructions on returning the function generator to Agilent for service.

1 Verify that there is ac power to the function generator.

First, verify that the function generator’s Power switch is in the “On” position. Also, make sure that the power cord is firmly plugged into to the power module on the rear panel. You should also make sure that the power source you plugged the function generator into is energized.

2 Verify the power-line voltage setting.

The line voltage is set to the proper value for your country when the function generator is shipped from the factory. Change the voltage setting if it is not correct. The settings are: 100, 120, 220, or 240 Vac (for 230 Vac operation, use the 220 Vac setting).

See the next page if you need to change the line-voltage setting.

3 Verify that the power-line fuse is good.

The function generator is shipped from the factory with a 500 mAT fuse installed. This is the correct fuse for all line voltages.

See the next page if you need to change the power-line fuse.

To replace the 500 mAT fuse, order Agilent part number 2110-0458.

Chapter 2 Quick Start

If the function generator does not turn on

1 Remove the power cord. Remove the fuse-holder assembly from the rear panel.

3 Rotate the line-voltage selector until the

correct voltage appears in the window.

2 Remove the line-voltage selector from

the assembly.

Fuse: 500 mAT (for all line voltages) Part Number: 2110-0458

4 Replace the fuse-holder assembly in the rear panel.

100, 120, 220 (230), or 240 Vac

Verify that the correct line voltage is selected and the power-line fuse is good.

Chapter 2 Quick Start

To adjust the carrying handle

To adjust the position, grasp the handle by the sides and pull outward. Then, rotate the handle to the desired position.

Bench-top viewing positions Carrying position

Chapter 2 Quick Start

To set the output frequency

At power-on, the function generator outputs a sine wave at 1 kHz with an amplitude of 100 mV peak-to-peak (into a 50

The following steps show you how to change the frequency to 1.2 MHz.

Freq 1 Enable the frequency modify mode.

The displayed frequency is either the power-on value or the previous frequency selected. When you change functions, the same frequency is used if the present value is valid for the new function.

1.000,000,0 KHz

W termination).

Enter Number 2 Enter the magnitude of the desired frequency.

1 2 . Notice that the Num annunciator turns on and “ENTER NUM” flashes on

the display, indicating that the number mode is enabled.

1.2

MHz m Vpp

To cancel the number mode, press

3 Set the units to the desired value.

Shift Cancel .

The units are selected using the arrow keys on the right side of the front panel. As soon as you select the units, the function generator outputs the waveform with the displayed frequency. To turn off the flashing digit,

move the cursor to the left of the display using the arrow keys.

1.200,000,0 MHz

You can also use the knob and arrow keys to enter a number.

Chapter 2 Quick Start

To set the output amplitude

At power-on, the function generator outputs a sine wave with an amplitude of 100 mV peak-to-peak (into a 50

The following steps show you how to change the amplitude to 50 mVrms.

Ampl 1 Enable the amplitude modify mode.

The displayed amplitude is either the power-on value or the previous amplitude selected. When you change functions, the same amplitude is used if the present value is valid for the new function.

100.0 mVPP

W termination).

Enter Number 2 Enter the magnitude of the desired amplitude.

5 0 Notice that the Num annunciator turns on and “ENTER NUM” flashes on

the display, indicating that the number mode is enabled.

To cancel the number mode, press

Shift 3 Set the units to the desired value.

kHz m Vrms

The units are selected using the arrow keys on the right side of the front panel. As soon as you select the units, the function generator outputs the

Shift Cancel .

waveform with the displayed amplitude. To turn off the flashing digit, move the cursor to the left of the display using the arrow keys.

50.00 mVRMS

You can also use the knob and arrow keys to enter a number.

Chapter 2 Quick Start

To set a dc offset voltage

At power-on, the function generator outputs a sine wave with a dc offset voltage of 0 volts (into a 50 how to change the offset to –1.5 mVdc.

Offset 1 Enable the offset modify mode.

The displayed offset voltage is either the power-on value or the previous offset selected. When you change functions, the same offset is used if the present value is valid for the new function.

+0.000 VDC

W termination). The following steps show you

Enter Number 2 Enter the magnitude of the desired offset.

1 . 5 Notice that the Num annunciator turns on and “ENTER NUM” flashes on



the display, indicating that the number mode is enabled. Notice that toggles the displayed value between + and – .

-1.5

To cancel the number mode, press

Shift 3 Set the units to the desired value.

kHz m Vrms

At this point, the function generator outputs the waveform with the displayed offset. Notice that the

Shift Cancel .

Offset annunciator turns on, indicating

that the waveform is being output with an offset. The annunciator will turn on when the offset is any value other than 0 volts. To turn off the

flashing digit, move the cursor to the left of the display using the arrow keys.

-01.50 mVDC



You can also use the knob and arrow keys to enter a number.

Chapter 2 Quick Start

To set the duty cycle

Applies only to square waves. At power-on, the duty cycle for square waves is 50%. You can adjust the duty cycle for a square waveform from 20% to 80%, in increments of 1% (for frequencies above 5 MHz, the range is 40% to 60%). The following steps show you how to change the duty cycle to 45%.

1 Select the square wave function.

Notice that the annunciator turns on, indicating that the square wave function is enabled.

Shift % Duty 2 Enable the duty cycle modify mode.

The displayed duty cycle is either the power-on value or the previous value selected.

50 % DUTY

This message appears on the display for approximately 10 seconds. Repeat this step as needed.

Enter Number

4 5 Notice that the Num annunciator turns on and “ENTER NUM” flashes on

3 Enter the desired duty cycle.

the display, indicating that the number mode is enabled.

To cancel the number mode, press

Enter 4 Output the waveform with the displayed duty cycle.

Shift Cancel .

45 % DUTY

You can also use the knob and arrow keys to enter a number.

Chapter 2 Quick Start

To output a stored arbitrary waveform

There are five built-in arbitrary waveforms stored in non-volatile memory for your use. You can output these waveforms directly from non-volatile memory. The following steps show you how to output an “exponential rise”

waveform from memory.

Shift Arb List 1 Display the list of arbitrary waveforms.

The list contains the five built-in arbitrary waveforms (sinc, negative ramp, exponential rise, exponential fall, and cardiac). The list may also contain up to four user-defined arbitrary waveform names. The first choice on this level is “

SINC

This message appears on the display for approximately 10 seconds. Repeat this step as needed.

> 2 Move across to the EXP_RISE choice.

SINC”.

EXP_RISE

Enter 3 Select and output the displayed arbitrary waveform.

Notice that the

Arb annunciator turns on, indicating that the output is an

arbitrary waveform. The waveform is output using the present settings for frequency, amplitude, and offset unless you change them.

The selected waveform is now assigned to the

Arb key. Whenever you

press this key, the selected arbitrary waveform is output.

You can also use the knob to scroll left or right through the choices in the list.

Chapter 2 Quick Start

To output a dc voltage

In addition to generating waveforms, you can also output a dc voltage in the range

how to output +155 mVdc.

 5 Vdc (into a 50W termination). The following steps show you

1 Press the key and hold it down for more than 2 seconds.

To enter the dc voltage mode, press the of function keys and

Offset

Offset key or any key in the top row

hold it down for more than 2 seconds. The displayed

voltage is either the power-on value or the previous offset voltage selected.

DCV

+0.000 VDC

Enter Number

1 5 5 Notice that the Num annunciator turns on and “ENTER NUM” flashes on

2 Enter the magnitude of the desired voltage.

the display, indicating that the number mode is enabled.

155

To cancel the number mode, press

Shift 3 Set the units to the desired value.

Shift Cancel .

kHz m Vrms

At this point, the function generator outputs the displayed dc voltage. Notice that the

Offset annunciator turns on (all other annunciators are

off), indicating that a dc voltage is being output. The annunciator will turn on when the offset is any value other than 0 volts.

+155.0 mVDC

You can also use the knob and arrow keys to enter a number.

Chapter 2 Quick Start

To store the instrument state

You can store up to three different instrument states in non-volatile memory. This enables you to recall the entire instrument configuration with just a few key presses from the front panel. The following steps show

you how to store and recall a state.

1 Set up the function generator to the desired configuration.

The state storage feature “remembers” the function, frequency, amplitude, dc offset, duty cycle, as well as any modulation parameters.

Shift Store 2 Turn on the state storage mode.

Three memory locations (numbered 1, 2, and 3) are available to store instrument configurations. The instrument configuration is stored in non-volatile memory and is remembered when power has been off.

STORE 1

This message appears on the display for approximately 10 seconds. Repeat this step as needed.

3 Store the instrument state in memory location “2”.

Use the up and down arrow keys to select the memory location.

STORE 2

To cancel the store operation, press time-out after 10 seconds.

Enter 4 Save the instrument state.

The instrument state is now stored. To recall the stored state, turn to the next page.

You can also use the knob or “enter number” mode to enter a memory location.

Shift Store again or let the display

Chapter 2 Quick Start

To store the instrument state

To verify that the state was stored properly, you can turn the power off before recalling the state.

Recall 5 Recall the stored instrument state.

To recall the stored state, you must use the same memory location used previously to store the state. Use the up and down arrow keys to change the displayed storage location.

RECALL 2

To cancel the restore operation, press

This message appears on the display for approximately 10 seconds. Repeat this step as needed.

Enter 6 Restore the instrument state.

The function generator should now be configured in the same state as when you stored the setup on the previous page.

When power is turned off, the function generator automatically stores its state in memory location “0”. You can recall the power-down state, but you cannot store the state to location “0” from the front panel.

Use the POWER ON ENABLE command in the SYS MENU to automatically recall the power-down state when power is turned on. See chapter 3 for more information on using the front-panel menus.

Recall again.

Chapter 2 Quick Start

To rack mount the function generator

You can mount the function generator in a standard 19-inch rack cabinet using one of three optional kits available. Instructions and mounting hardware are included with each rack-mounting kit. Any Agilent System II instrument of the same size can be rack-mounted beside the 33120A Function Generator.

Remove the carrying handle, and the front and rear rubber bumpers, before rack-mounting the function generator.

To remove the handle, rotate it to the vertical position and pull the ends outward.

Front Rear (bottom view)

To remove the rubber bumper, stretch a corner and then slide it off.

Chapter 2 Quick Start

To rack mount the function generator

To rack mount a single instrument, order adapter kit 5063-9240.

To rack mount two instruments side-by-side, order lock-link kit 5061-9694 and flange kit 5063-9212.

To install one or two instruments in a sliding support shelf, order shelf 5063-9255, and slide kit 1494-0015 (for a single instrument, also order filler panel 5002-3999).

Front-Panel Menu Operation

By now you should be familiar with some of the basic features of the front panel. Chapter 2 shows you how to prepare the function generator for use and describes a few of the front-panel features. If you are not familiar with this information, we recommend that you read chapter 2, “Quick Start,” starting on page 19.

Chapter 3 introduces you to the use of the front-panel menu. This chapter does not give a detailed description of every front-panel key or menu operation. It does, however, give you an overview of front-panel menu operations related to verification, adjustment and service. See chapter 3 “Features and Functions” in the User’s Guide for a complete discussion of the function generator’s capabilities and operation.

If you purchased the Phase-Lock Option for the 33120A, an additional menu

(G: PHASE MENU) is available from the front panel. For inform-

ation on using the Phase-Lock Option, refer to the User’s and Service Guide included with Option 001.

Chapter 3 Front-Panel Menu Operation

Front-panel menu reference

A: MODulation MENU

1: AM SHAPE Õ 2: AM SOURCE Õ 3: FM SHAPE Õ 4: BURST CNT Õ 5: BURST RATE Õ

Õ 6: BURST PHAS Õ 7: BURST SRC Õ 8: FSK FREQ Õ 9: FSK RATE Õ 10: FSK SRC

1: AM SHAPE Selects the shape of the AM modulating waveform. 2: AM SOURCE Enables or disables the internal AM modulating source. 3: FM SHAPE Selects the shape of the FM modulating waveform. 4: BURST CNT Sets the number of cycles per burst (1 to 50,000 cycles). 5: BURST RATE Sets the burst rate in Hz for an internal burst source. 6: BURST PHAS Sets the starting phase angle of a burst (-360 to +360 degrees). 7: BURST SRQ Selects an internal or external gate source for burst modulation. 8: FSK FREQ Sets the FSK “hop” frequency. 9: FSK RATE Selects the internal FSK rate between the carrier and FSK frequency. 10: FSK SRC Selects an internal or external source for the FSK rate.

B: SWP (Sweep) MENU

1: START F Õ 2: STOP F Õ 3: SWP TIME Õ 4: SWP MODE

1: START F Sets the start frequency in Hz for sweeping. 2: STOP F Sets the stop frequency in Hz for sweeping. 3: SWP TIME Sets the repetition rate in seconds for sweeping. 4: SWP MODE Selects linear or logarithmic sweeping.

C: EDIT MENU *

1: NEW ARB Õ 2: POINTS Õ [3: LINE EDIT] Õ [4: POINT EDIT] Õ [5: INVERT] Õ [6: SAVE AS] Õ 7:DELETE

1: NEW ARB Initiates a new arb waveform or loads the selected arb waveform. 2: POINTS Sets the number of points in a new arb waveform (8 to 16,000 points). 3: LINE EDIT Performs a linear interpolation between two points in the arb waveform. 4: POINT EDIT Edits the individual points of the selected arb waveform. 5: INVERT Inverts the selected arb waveform by changing the sign of each point. 6: SAVE AS Saves the current arb waveform in non-volatile memory. 7: DELETE Deletes the selected arb waveform from non-volatile memory.

* The commands enclosed in square brackets ( [ ] ) are “hidden” until you make a selection from the NEW ARB

command to initiate a new edit session.

Chapter 3 Front-Panel Menu Operation

Front-panel menu reference

D: SYStem MENU

1: OUT TERM Õ 2: POWER ON Õ 3: ERROR Õ 4: TEST Õ 5: COMMA Õ 6:REVISION

1: OUT TERM Selects the output termination (50 2: POWER ON Enables or disables automatic power-up in power-down state “0”. 3: ERROR Retrieves errors from the error queue (up to 20 errors). 4: TEST Performs a complete self-test. 5: COMMA Enables or disables a comma separator between digits on the display. 6: REVISION Displays the function generator’s firmware revision codes.

or high impedance).

E: Input / Output MENU

1: HPIB ADDR Õ 2: INTERFACE Õ 3: BAUD RATE Õ 4: PARITY Õ 5: LANGUAGE

1: HPIB ADDR Sets the GPIB bus address (0 to 30). 2: INTERFACE Selects the GPIB or RS-232 interface. 3: BAUD RATE Selects the baud rate for RS-232 operation. 4: PARITY Selects even, odd, or no parity for RS-232 operation. 5: LANGUAGE Verifies the interface language: SCPI.

F: CALibration MENU *

1: SECURED Õ [1: UNSECURED] Õ [2: CALIBRATE] Õ 3: CAL COUNT Õ 4: MESSAGE

1: SECURED The function generator is secured against calibration; enter code to unsecure. 1: UNSECURED The function generator is unsecured for calibration; enter code to secure. 2: CALIBRATE Performs individual calibrations; must be UNSECURED. 3: CAL COUNT Reads the total number of times the function generator has been calibrated. 4: MESSAGE Reads the calibration string (up to 11 characters) entered from remote.

* The commands enclosed in square brackets ( [ ] ) are “hidden” unless the function generator is UNSECURED for

calibration.

Chapter 3 Front-Panel Menu Operation

A front-panel menu tutorial

This section is a step-by-step tutorial which shows you how to use the front-panel menu. We recommend that you spend a few minutes with this tutorial to get comfortable with the structure and operation of the menu before attempting verification, calibration, or adjustments.

The menu is organized in a top-down tree structure with three levels (menus, commands, and parameters). You move down the menu tree to get from one level to the next. Each of the three levels has several horizontal choices which you can view by moving left or right

> .

Menus

Commands

or up

Parameters

The menu is organized in a top-down tree structure with three levels.

 To turn on the menu, press Shift Menu On/Off .

 To turn off the menu, press Shift Menu On/Off .

 To execute a menu command, press Enter .

 To recall the last menu command that was executed,

press

Shift Recall Menu .

 To turn off the menu at any time without saving changes,

press

Shift Cancel .

Chapter 3 Front-Panel Menu Operation

A front-panel menu tutorial

Messages Displayed During Menu Use

TOP OF MENU You pressed

¾ while on the “MENUS” level; this is the top

level of the menu and you cannot go any higher.

To turn off the menu, press

a level, press

MENUS

COMMANDS

< or > . To move down a level, press

You are on the “MENUS” level. Press < or > to view the choices.

You are on the “COMMANDS” level. Press < or > to view the

Shift Menu On/Off . To move across the choices on

¿ .

command choices within the selected menu group.

PARAMETER You are on the “

PARAMETER” level. Press < or > to view

and edit the parameter for the selected command.

MENU BOTTOM You pressed

¿ while on the “PARAMETER” level; this is the

bottom level of the menu and you cannot go any lower.

To turn off the menu, press

ENTERED The change made on the “ displayed after you press

MIN VALUE The value you specified on the “

Shift Menu On/Off . To move up a level, press

PARAMETER” level is saved. This is

Enter (Menu Enter) to execute the command.

PARAMETER” level is too small for

¾ .

the selected command. The minimum value allowed is displayed for you to edit.

MAX VALUE The value you specified on the “

PARAMETER” level is too large for

the selected command. The maximum value allowed is displayed for you to edit.

EXITING You will see this message if you turn off the menu by pressing

Shift Menu On/Off or Shift Cancel . You did not edit any values on the

“

PARAMETER” level and changes were NOT saved.

NOT ENTERED You will see this message if you turn off the menu by pressing

Shift Menu On/Off or Shift Cancel . You did some editing of parameters but

the changes were made on the “

NOT saved. Press Enter (Menu Enter) to save changes

PARAMETER” level.

Chapter 3 Front-Panel Menu Operation

A front-panel menu tutorial

Menu Example 1 The following steps show you how to turn on the menu, move up and

down between levels, move across the choices on each level, and turn off the menu. In this example, you will restore the function generator to the

power-on default state. This procedure is recommended before performing the verification procedures in chapter 4.

Shift 1 Turn on the menu.

Menu On/Off You enter the menu on the “MENUS” level. The MOD MENU is your first

choice on this level.

A: MOD MENU

> > > 2 Move across to the SYS MENU choice on this level.

There are six menu group choices available on the “MENUS” level. Each choice has a letter prefix for easy identification (

A: , B: , etc.).

D: SYS MENU

¿ 3 Move down to the “COMMANDS” level within the SYS MENU.

The

OUT TERM command is your first choice on this level.

1: OUT TERM

> 4 Move across to the POWER ON command on this level.

There are six command choices available in the SYS MENU. Each choice on this level has a number prefix for easy identification (

1: , 2: , etc.).

2: POWER ON

You can also use the knob to scroll left or right through the choices on each level of the menu.

Chapter 3 Front-Panel Menu Operation

A front-panel menu tutorial

¿ 5 Move down a level to the “PARAMETER” choices.

The first parameter choice is “ (“

DEFAULT” is the factory setting and is stored in non-volatile memory).

DEFAULT” for the POWER ON command

DEFAULT

> 6 Move across to the “LAST STATE” choice.

There are two parameter choices for POWER ON.

LAST STATE

Enter 7 Save the change and turn off the menu.

The function generator beeps and displays a message to show that the change is now in effect. You are then exited from the menu.

ENTERED

8 Cycle the power to restore the default values.

Turn the function generator OFF and then ON. The default output state will now be in effect (1 kHz sine wave, 100 mV peak-to-peak, 50

W termination).

You can also use the knob to scroll left or right through the choices on each level of the menu.

Chapter 3 Front-Panel Menu Operation

A front-panel menu tutorial

Menu Example 2 Some commands in the menu require that you enter a numeric

parameter value. The following steps show you how to enter a number in the menu. For this example, you will change the output amplitude.

Ampl 1 Select amplitude adjustment

The function generator displays the current output amplitude.

100.0 mVPP

< 2 Move the flashing cursor over to edit the first digit.

The cursor movement wraps around.

100.0 mVPP

^ ^ ^ 3 Increment the first digit until 300.0 mVPP is displayed.

The output amplitude of the function changes as you adjust the displayed value.

300.0 mVPP

You can also use the knob and arrow keys to enter a number.

Chapter 3 Front-Panel Menu Operation

To select the output termination

The function generator has a fixed output impedance of 50 ohms on the OUTPUT terminal. You can specify whether you are terminating the output into a 50 between the source and load will result in an output amplitude or dc offset which does not match the specified value.

Shift 1 Turn on the menu.

Menu On/Off A: MOD MENU

W load or an open circuit. Incorrect impedance matching

> > > 2 Move across to the SYS MENU choice on this level.

D: SYS MENU

¿ 3 Move down a level to the OUT TERM command.

1: OUT TERM

> 4 Move down a level and then across to the HIGH Z choice.

With the output termination set to “HIGH Z”, the function generator allows you to set the unloaded (open circuit) output voltage.

HIGH Z

Enter 5 Save the change and turn off the menu.

The function generator beeps and displays a message to show that the change is now in effect. You are then exited from the menu.

You can also use the knob to scroll left or right through the choices on each level of the menu.

Chapter 3 Front-Panel Menu Operation

To output a modulated waveform

A modulated waveform consists of a carrier and a modulating waveform. In

AM (amplitude modulation), the amplitude of the carrier is varied by

the amplitude of the modulating waveform. For this example, you will

output an AM waveform with 80% modulation depth. The carrier will be a 5 kHz sine wave and the modulating waveform will be a 200 Hz sine wave.

1 Select the function, frequency, and amplitude of the carrier.

For the carrier waveform, you can select a sine, square, triangle, ramp, or arbitrary waveform. For this example, select a

an amplitude of

Shift AM 2Select AM.

Notice that the

Shift 3 Use the menu to select the shape of the modulating waveform.

< Recall Menu After you enable the AM function, the “recall menu” key will

automatically take you to the

1: AM SHAPE

5 Vpp.

AM annunciator turns on.

AM SHAPE command in the MOD MENU.

5 kHz sine wave with

Chapter 3 Front-Panel Menu Operation

To output a modulated waveform

¿ 4 Move down a level verify that “SINE” is selected.

For the modulating waveform, you can select a sine, square, triangle, ramp, noise, or arbitrary waveform. For this example, you will modulate the carrier with a sine waveform. Notice that the indicating that the displayed parameter is for

AM annunciator flashes,

AM.

SINE

Enter 5 Save the change and turn off the menu.

The modulating waveform is now a sine waveform.

ENTERED

Shift Freq 6 Set the modulating frequency to 200 Hz.

Notice that the

AM annunciator flashes, indicating that the displayed

frequency is the modulating frequency. Also notice that the modulating frequency is displayed with fewer digits than the carrier frequency.

MOD 200.0 Hz

This message appears on the display for approximately 10 seconds. Repeat this step as needed.

Shift Level 7 Set the modulation depth to 80%.

Notice that the percentage is the

AM annunciator flashes, indicating that the displayed

AM depth (also called percent modulation).

080 % DEPTH

This message appears on the display for approximately 10 seconds. Repeat this step as needed.

At this point, the function generator outputs the specified modulation parameters.

AM waveform with the

Chapter 3 Front-Panel Menu Operation

To unsecure the function generator for calibration

The function generator can use a calibration security code to prevent unauthorized or accidental calibration. This procedure shows you how to unsecure the function generator for calibration.

Shift 1 Turn on the menu.

Menu On/Off A: MOD MENU

< 2 Move across to the CAL MENU choice on this level.

F: CAL MENU

¿ 3 Move down a level to the SECURED command.

1: SECURED

If the display shows UNSECURED, you do not need to perform this procedure to execute a calibration.

Chapter 3 Front-Panel Menu Operation

To unsecure the function generator for calibration

¿ 4 Move down to the “parameters” level.

^000000:CODE

0 3 3

1 2 0 5 Unsecure the function generator by entering the security code.

ENTER

^033120:CODE

The security code is set to “HP33120” when the function generator is shipped from the factory. The security code is stored in non-volatile memory and does not change when the power has been off or after a remote interface reset.

To enter the security code from the front panel, enter only the six digits. To enter the security code from the remote interface, you may enter up to 12 characters. Use the knob or arrow keys to move left or right between digits. Use the up or down arrow keys to change the digits.

To re-secure the function generator following a calibration, perform this procedure again.

Additional information about the calibration security feature is given on page 64.

Calibration Procedures

This chapter contains procedures for verification of the function generator’s performance and adjustment (calibration). The chapter is divided into the following sections:

 Agilent Calibration Services . . . . . . . . . . . . . . 51

 Calibration Interval . . . . . . . . . . . . . . . . . . . 51

 Time Required for Calibration . . . . . . . . . . . . . 51

 Automating Calibration Procedures . . . . . . . . . . 52

 Recommended Test Equipment . . . . . . . . . . . . . 52

 Test Considerations . . . . . . . . . . . . . . . . . . . 53

 Performance Verification Tests . . . . . . . . . . . . . 54

 Frequency Verification . . . . . . . . . . . . . . . . . 56

 Function Gain and Linearity Verification . . . . . . . 56

 DC Function Offset Verification . . . . . . . . . . . . 57

 AC Amplitude Verification . . . . . . . . . . . . . . . 57

 Amplitude Flatness Verification . . . . . . . . . . . . 60

 AM Modulation Depth Verification . . . . . . . . . . . 61

 Optional Performance Verification Tests . . . . . . . . 62

 Calibration Security Code . . . . . . . . . . . . . . . . 64

 Calibration Count . . . . . . . . . . . . . . . . . . . . 66

 Calibration Message . . . . . . . . . . . . . . . . . . . 66

 General Calibration/Adjustment Procedure . . . . . . 67

 Aborting a Calibration in Progress . . . . . . . . . . . 69

 Frequency and Burst Rate Adjustment . . . . . . . . 69

 Function Gain and Linearity Adjustment . . . . . . . 70

 AC Amplitude Adjustment (High-Z) . . . . . . . . . . 70

 Modulation Adjustment . . . . . . . . . . . . . . . . . 72

 AC Amplitude Adjustment (50W) . . . . . . . . . . . . 73

 DC Output Adjustment . . . . . . . . . . . . . . . . . 76

 Duty Cycle Adjustment . . . . . . . . . . . . . . . . . 77

 AC Amplitude Flatness Adjustment . . . . . . . . . . 77

 Output Amplifier Adjustment (Optional) . . . . . . . 80

 Error Messages . . . . . . . . . . . . . . . . . . . . . 81

Chapter 4 Calibration Procedures

Agilent Calibration Services

Closed-Case Electronic Calibration The function generator features closed-case electronic calibration since no internal mechanical adjustments are required for normal calibration. The function generator calculates correction factors based upon the input reference value you set. The new correction factors are stored in non-volatile memory until the next calibration adjustment is performed (non-volatile memory does not change when power has been off or after a remote interface reset).

Agilent Calibration Services

When your function generator is due for calibration, contact your local Agilent Service Center for a low-cost recalibration. The 33120A Function Generator is supported on automated calibration systems which allow Agilent to provide this service at competitive prices. Calibrations to MIL-STD-45662 are also available at competitive prices.

Calibration Interval

The function generator should be calibrated on a regular interval determined by the measurement accuracy requirements of your application. A 1- or 2-year interval is adequate for most applications. Agilent does not recommend extending calibration intervals beyond two years for any application.

Whatever calibration interval you select, Agilent recommends that complete re-adjustment should always be performed at the calibration interval. This will increase your confidence that the 33120A will remain within specification for the next calibration interval. This criteria for re-adjustment provides the best long-term stability. Performance data measured using this method can be used to extend future calibration intervals.

Time Required for Calibration

The 33120A can be automatically calibrated under computer control. With computer control you can perform the complete calibration procedure and performance verification tests in less than 15 minutes. Manual calibrations using the recommended test equipment will take approximately 45 minutes.

Chapter 4 Calibration Procedures

Automating Calibration Procedures

You can automate the complete verification and adjustment procedures outlined in this chapter if you have access to programmable test equipment. You can program the instrument configurations specified for each test over the remote interface. You can then enter readback verification data into a test program and compare the results to the appropriate test limit values.

You can also enter calibration constants from the remote interface. Remote operation is similar to the local front-panel procedure. You can use a computer to perform the adjustment by first selecting the required setup. The calibration value is sent to the function generator and then the calibration is initiated over the remote interface. The function generator must be unsecured prior to initiating the calibration procedure. For further detailing on programming the function generator, see chapters 3 and 4 in the Agilent 33120A User’s Guide.

Recommended Test Equipment

The test equipment recommended for the performance verification and adjustment procedures is listed below. If the exact instrument is not available, use the accuracy requirements shown to select substitute calibration standards.

Instrument Requirements Recommended Model Use*

50 W feedthrough load 50 W  0.1 W

6 1/2 digit Digital Multimeter (DMM)

Thermal Voltage Converter (50 W termination type) or Power Meter or Wideband ACrms Meter

Frequency Meter 1 ppm accuracy Agilent 53131A Q,P,T

Oscilloscope 100 MHz Agilent 54624A T

Spectrum Analyzer Response to 90 MHz Agilent 8560EC O

* Q = Quick Verification O= Optional Verification Tests

P = Performance Verification Tests T = Troubleshooting

20 Vdc  0.01%

Integrating ACrms

10 Vacrms  0.1%

1kHz to 15 MHz

100 kHz to 15 MHz

1 VAC rms  0.5%

1 kHz to 20 MHz

Agilent 34401A Q,P,T

3 Volt

Agilent E4418A with

Agilent 8482A

and 20 dB attenuator

—

Q,P,O,T

Q,P

Chapter 4 Calibration Procedures

Test Considerations

To ensure proper instrument operation, verify that you have selected the correct power line voltage prior to attempting any test procedure in this chapter. See page 22 in chapter 2 for more information.

For optimum performance, all test procedures should comply with the following recommendations:

 Verify the function generator is set to the default power on state

(power on default). A procedure is given on page 41.

 Make sure that the calibration ambient temperature is stable and

between 18

 Make sure ambient relative humidity is less than 80%.

C and 28 C.

 Allow a 1-hour warm-up period before verification or adjustment.

 Use only RG-58 or equivalent 50W cable.

 Keep cables as short as possible, consistent with the impedance

requirements.

Chapter 4 Calibration Procedures

Performance Verification Tests

The performance verification tests use the function generator’s specifications listed in chapter 1, “Specifications,” starting on page 13.

You can perform four different levels of performance verification tests:

 Self-Test A series of internal verification tests that give a high

confidence that the function generator is operational.

 Quick Verification A combination of the internal self-tests and

selected verification tests.

 Performance Verification Tests An extensive set of tests that are

recommended as an acceptance test when you first receive the function generator or after performing adjustments.

 Optional Verification Tests Tests not performed with every

calibration. These tests can can be used to verify additional instrument specifications following repairs to specific circuits.

Self-Test

A brief power-on self-test occurs automatically whenever you turn on the function generator. This limited test assures that the function generator is capable of operation.

To perform a complete self-test hold down the Power switch to turn on the function generator; hold down the key for more than 5 seconds (a complete description of these tests can be found in chapter 6). The function generator will automatically perform the complete self-test procedure when you release the key. The self-test will complete in approximately 5 seconds.

You can perform many tests individually (or all tests at once) using the

TEST command in the SYS MENU. You can also perform a self-test from

the remote interface (see chapter 3 in the Agilent 33120A User’s Guide).

 If the self-test is successful, “PASS” is displayed on the front panel.

 If the self-test fails, “FAIL” is displayed and the ERROR annunciator

turns on. If repair is required, see chapter 6, “Service,” for further details.

 If all tests pass, you have a high confidence (90%) that the function

generator is operational.

Shift key as you press the

Chapter 4 Calibration Procedures

Performance Verification Tests

Quick Performance Check

The quick performance check is a combination of internal self-test and an abbreviated performance test (specified by the letter Q in the performance verification tests). This test provides a simple method to achieve high confidence in the function generator’s ability to functionally operate and meet specifications. These tests represent the absolute minimum set of performance checks recommended following any service activity. Auditing the function generator’s performance for the quick check points (designated by a Q) verifies performance for “normal” accuracy drift mechanisms. This test does not check for abnormal component failures.

To perform the quick performance check, do the following:

 Set the function generator to the default power on state (power on default).

A procedure is given on page 41.

 Perform a complete self-test. A procedure is given on page 21.

 Perform only the performance verification tests indicated with

the letter Q.

If the function generator fails the quick performance check, adjustment or repair is required.

Performance Verification Tests

The performance verification tests are recommended as acceptance tests when you first receive the function generator. The acceptance test results should be compared against the 1 year test limits. After acceptance, you should repeat the performance verification tests at every calibration interval.

If the function generator fails performance verification, adjustment or repair is required.

Chapter 4 Calibration Procedures

Frequency Verification

This test verifies the frequency accuracy of the two sources in the function generator. All output frequencies are derived from a single generated frequency, and only one frequency point is checked. The second test verifies the burst rate frequency.

Set the function generator for each output indicated in the table below. Use a frequency meter to measure the output frequency. Compare the measured results to the test limits shown in the table. This is a 50 output termination test.

Agilent 33120A Measurement

Function

Q Sine wave

Q Square wave

OUT TERM

50 W

Ampl Freq

3.5 Vrms 1.00 kHz — — 1.00 kHz

3.5 Vrms 1.00 kHz 500 Hz 1 CYC 500 Hz

BURST

RATE

BURST

CNT

Nominal Error

 0.02 Hz

 5 Hz

Function Gain and Linearity Verification

This test verifies the output amplitude accuracy specification for sine wave, triangle wave, ramp, and square wave outputs.

Set the function generator for each output indicated in the table below. Use a DMM to measure the function generator ACrms output voltage. Compare the measured results to the test limits shown in the table. This is a HIGH Z output termination test.

Agilent 33120A Measurement

Function OUT TERM

Q Sine wave HIGH Z 7.0 Vrms 1.0 kHz 7.0 Vrms

Sine wave HIGH Z 5.7 Vrms 1.0 kHz 5.7 Vrms

Triangle wave HIGH Z 5.7 Vrms 100 Hz 5.7 Vrms

Ramp wave HIGH Z 5.7 Vrms 100 Hz 5.7 Vrms

Q Square wave HIGH Z 10.0 Vrms 100 Hz 10.0 Vrms

Square wave HIGH Z 8.0 Vrms 100 Hz 8.0 Vrms

Output termination set using front panel controls. HIGH Z assumes no load on output. 50W assumes a 50W  0.1W load on output.

Ampl Freq Nominal Error

 0.07 Vrms

 0.057 Vrms

 0.1 Vrms

 0.08 Vrms

Chapter 4 Calibration Procedures

DC Function Offset Verification

This test verifies the DC offset and DC output specifications.

Set the function generator for each output indicated in the table below. Use a DMM to measure the function generator dcV output. Compare the measured results to the test limits shown in the table. This is a HIGH Z output termination test.

Agilent 33120A Measurement

Function OUT TERM

Q DC Volts HIGH Z 10.0 Vdc 10.0 Vdc

DC Volts HIGH Z -10.0 Vdc -10.0 Vdc

Ampl Nominal Error

 0.20 Vdc

AC Amplitude Verification

This procedure is used to check the output amplitude calibration of the function generator. Verification checks are performed to check the accuracy of the pre-attenuator and post attenuator. Make sure you have

read “Test Considerations” on page 53.

Set the function generator for each output indicated in the table on the next page. Use a DMM to measure the ACrms output voltage of the function generator. Compare the measured results to the test limits shown in the table. This is a HIGH Z output termination test.

Output termination set using front panel controls. HIGH Z assumes no load on output. 50W assumes a 50W 0.1W load on output.

Chapter 4 Calibration Procedures

AC Amplitude Verification

Agilent 33120A Measurement

Function OUT TERM

Q Sine wave HIGH Z 7.0 Vrms 1.00 kHz 7.0 Vrms

Sine wave HIGH Z 5.7 Vrms 1.00 kHz 5.7 Vrms

Sine wave HIGH Z 5.5 Vrms 1.00 kHz 5.5 Vrms

Sine wave HIGH Z 4.4 Vrms 1.00 kHz 4.4 Vrms

Sine wave HIGH Z 3.5 Vrms 1.00 kHz 3.5 Vrms

Sine wave HIGH Z 2.8 Vrms 1.00 kHz 2.8 Vrms

Sine wave HIGH Z 2.2 Vrms 1.00 kHz 2.2 Vrms

Sine wave HIGH Z 1.7 Vrms 1.00 kHz 1.7 Vrms

Sine wave HIGH Z 1.4 Vrms 1.00 kHz 1.4Vrms

Sine wave HIGH Z 1.1 Vrms 1.00 kHz 1.1 Vrms

Q Sine wave HIGH Z 0.88 Vrms 1.00 kHz 0.88 Vrms

Sine wave HIGH Z 0.70 Vrms 1.00 kHz 0.70 Vrms

Sine wave HIGH Z 0.55 Vrms 1.00 kHz 0.55 Vrms

Sine wave HIGH Z 0.44 Vrms 1.00 kHz 0.44 Vrms

Sine wave HIGH Z 0.35 Vrms 1.00 kHz 0.35 Vrms

Sine wave HIGH Z 0.28 Vrms 1.00 kHz 0.28 Vrms

Sine wave HIGH Z 0.22 Vrms 1.00 kHz 0.22 Vrms

Sine wave HIGH Z 0.17 Vrms 1.00 kHz 0.17 Vrms

Sine wave HIGH Z 0.14 Vrms 1.00 kHz 0.14 Vrms

Sine wave HIGH Z 0.11 Vrms 1.00 kHz 0.11 Vrms

Q Sine wave HIGH Z 0.088 Vrms 1.00 kHz 0.088Vrms

Sine wave HIGH Z 0.070 Vrms 1.00 kHz 0.070 Vrms

Sine wave HIGH Z 0.055 Vrms 1.00 kHz 0.055 Vrms

Sine wave HIGH Z 0.044 Vrms 1.00 kHz 0.044 Vrms

Q Sine wave HIGH Z 0.036 Vrms 1.00 kHz 0.036 Vrms

Ampl Freq Nominal Error

 0.070 Vrms

 0.057 Vrms

 0.055 Vrms

 0.044 Vrms

 0.035 Vrms

 0.028 Vrms

 0.022 Vrms

 0.017 Vrms

 0.014 Vrms

 0.011 Vrms

 0.0088 Vrms

 0.0070 Vrms

 0.0055 Vrms

 0.0044 Vrms

 0.0035 Vrms

 0.0028 Vrms

 0.0022 Vrms

 0.0017 Vrms

 0.0014 Vrms

 0.0011 Vrms

 0.00088 Vrms

 0.00070 Vrms

 0.00055 Vrms

 0.00044 Vrms

 0.00036 Vrms

Output termination set using front panel controls. HIGH Z assumes no load on output. 50W assumes a 50W  0.1W load on output.

Chapter 4 Calibration Procedures

AC Amplitude Verification

Install the 50W feedthrough load between the DMM and the function generator output. Set the function generator for each output indicated in the table on the next page. Use a DMM to measure the ACrms output voltage of the function generator. Compare the measured results to the test limits shown in the table. This is a 50

Function OUT TERM

Q Sine wave

Sine wave

Q Sine wave

Sine wave

Q Sine wave

Sine wave

W output termination test.

Agilent 33120A Measurement

Ampl Freq Nominal Error

50 W

3.5 Vrms 1.0000 kHz 3.5 Vrms

2.8 Vrms 1.0000 kHz 2.8 Vrms

2.2 Vrms 1.0000 kHz 2.2 Vrms

1.7 Vrms 1.0000 kHz 1.7 Vrms

1.4Vrms 1.0000 kHz 1.4Vrms

1.1 Vrms 1.0000 kHz 1.1 Vrms

0.88 Vrms 1.0000 kHz 0.88 Vrms

0.70 Vrms 1.0000 kHz 0.70 Vrms

0.55 Vrms 1.0000 kHz 0.55 Vrms

0.44 Vrms 1.0000 kHz 0.44 Vrms

0.35 Vrms 1.0000 kHz 0.35 Vrms

0.28 Vrms 1.0000 kHz 0.28 Vrms

0.22 Vrms 1.0000 kHz 0.22 Vrms

0.17 Vrms 1.0000 kHz 0.17 Vrms

0.14 Vrms 1.0000 kHz 0.14 Vrms

0.11 Vrms 1.0000 kHz 0.11 Vrms

0.088Vrms 1.0000 kHz 0.088Vrms

0.070 Vrms 1.0000 kHz 0.070 Vrms

0.055 Vrms 1.0000 kHz 0.055 Vrms

0.044 Vrms 1.0000 kHz 0.044 Vrms

0.035 Vrms 1.0000 kHz 0.035 Vrms

0.028 Vrms 1.0000 kHz 0.028 Vrms

0.022 Vrms 1.0000 kHz 0.022 Vrms

0.018 Vrms 1.0000 kHz 0.018 Vrms

 0.035 Vrms

 0.028 Vrms

 0.022 Vrms

 0.017 Vrms

 0.014 Vrms

 0.011 Vrms

 0.0088 Vrms

 0.0070 Vrms

 0.0055 Vrms

 0.0044 Vrms

 0.0035 Vrms

 0.0028 Vrms

 0.0022 Vrms

 0.0017 Vrms

 0.0014 Vrms

 0.0011 Vrms

 0.00088 Vrms

 0.00070 Vrms

 0.00055 Vrms

 0.00044 Vrms

 0.00035 Vrms

 0.00028 Vrms

 0.00022 Vrms

 0.00018 Vrms

Output termination set using front panel controls. HIGH Z assumes no load on output. 50W assumes a 50W  0.1W load on output.

Chapter 4 Calibration Procedures

Amplitude Flatness Verification

This test verifies the output amplitude flatness specification at selected frequencies. If you use a TVC (recommended) or a wide band ACrms voltmeter (with a 50 described. If you are using a measurement device that requires a transfer measurement (for example, a power meter), make the transfer in the reference measurement at 100 kHz.

Set the function generator to the first output indicated in the table below and make a reference measurement. Select each function generator output in the table below and adjust the function generator output amplitude until the measured output is at the reference measurement. Compare the amplitude level set on the front panel to the test limits shown in the table. This test is a 50

Function

Q Sine wave

Sine wave

Q Sine wave

Sine wave

Q Sine wave

OUT TERM

W feed through load), perform this procedure as

W output termination test.

Agilent 33120A Measurement

50 W

Ampl Freq Nominal Error

3.0 Vrms 1.00 kHz <reference>

3.0 Vrms 100.00 kHz <reference>

3.0 Vrms 500.00 kHz <reference>

3.0 Vrms 1.00 MHz <reference>

3.0 Vrms 3.00 MHz <reference>

3.0 Vrms 5.00 MHz <reference>

3.0 Vrms 7.00 MHz <reference>

3.0 Vrms 9.00 MHz <reference>

3.0 Vrms 11.00 MHz <reference>

3.0 Vrms 13.00 MHz <reference>

3.0 Vrms 15.00 MHz <reference>

 0.03 Vrms

 0.045 Vrms

 0.06 Vrms

Output termination set using front panel controls. HIGH Z assumes no load on output. 50W assumes a 50W 0.1W load on output.

Chapter 4 Calibration Procedures

AM Modulation Depth Verification

This test verifies the modulation depth specification.

Select each function generator output in the table below. Use a DMM to measure the function generator ACrms output voltage. Compare the measured results to the test limits shown in the table. This is a HIGH Z output termination test.

Agilent 33120A Measurement

AM Modulation

Function

Q Sine wave HIGH Z 1.0 Vrms 1.00 kHz Sinewave 100 Hz 0% 0.50 Vrms

Sine wave HIGH Z 1.0 Vrms 1.00 kHz Sinewave 100 Hz 100% 0.61 Vrms

OUT TERM

Ampl Freq Shape Freq Depth Nominal Error

 0.005 Vrms

 0.0061 Vrms

Output termination set using front panel controls. HIGH Z assumes no load on output. 50W assumes a 50W  0.1W load on output.

Chapter 4 Calibration Procedures

Optional Performance Verification Tests

These tests are not intended to be performed with every calibration. They are provided as an aid for verifying additional instrument specifications.

Square Wave Duty Cycle Verification

This test verifies the duty cycle specification of the squarewave output.

Select each function generator output in the table below. Use an integrating DMM to measure the Vdc output of the function generator. Compare the measured results to the test limits shown in the table. This is a HIGH Z output termination test.

Agilent 33120A Measurement

Function

Square wave HIGH Z 1.0 Vrms 300.00 Hz 50% 0.00 Vdc

Square wave HIGH Z 1.0 Vrms 300.00 Hz 25% - 0.50 Vdc

Square wave HIGH Z 1.0 Vrms 300.00 Hz 75% + 0.50 Vdc

OUT TERM

Ampl Freq

Duty

Cycle

Nominal Error

 0.020 Vdc

The DMM used for this test must be an integrating multimeter. If the first step does not measure 0 Vdc, use an oscilloscope for this test.

Do not use an auto-ranging function on the DMM for this test. Fix the DMM measurement range at 10 Vdc.

Output termination set using front panel controls. HIGH Z assumes no load on output. 50W assumes a 50W  0.1W load on output.

Function

Sine wave

Chapter 4 Calibration Procedures

Optional Performance Verification Tests

Distortion Verification

This test checks the Harmonic Distortion at selected frequencies and harmonics. This test requires the use of a spectrum analyzer with dynamic range, frequency range, and resolution bandwidth adequate for the measurement.

Select each function generator output in the table below. Use a spectrum analyzer connected to the function generator output. Set the fundamental frequency reference to 0 dB and measure the 2nd through 5th harmonic frequencies relative to this reference. This test is a 50 termination test.

Agilent 33120A Measurement

harmonic

OUT TERM

50 W

Ampl Freq Fundamental 2nd 3rd 4th 5th

1.1 Vrms 20.00 kHz reference 40 kHz 60 kHz 80 kHz 100 kHz < 70 dB

1.1 Vrms 100.00 kHz reference 200 kHz 300 kHz 400 kHz 500 kHz < 60 dB

1.1 Vrms 1.00 MHz reference 2 MHz 3 MHz 4 MHz 5 MHz < 45 dB

1.1 Vrms 15.00 MHz reference 30 MHz 45 MHz 60 MHz 75 MHz < 35 dB

W output

Value below

reference

Output termination set using front panel controls. HIGH Z assumes no load on output. 50W assumes a 50W  0.1W load on output.

Chapter 4 Calibration Procedures

Calibration Security Code

This feature allows you to enter a security code (electronic key) to prevent accidental or unauthorized calibrations of the function generator. When you first receive your function generator, it is secured. Before you can adjust calibration constants you must unsecure the function generator by entering the correct security code. A procedure to unsecure the function generator is given on page 47.

 The security code is set to “HP033120” when the function generator is

shipped from the factory. The security code is stored in non-volatile memory, and does not change when power has been off or after a remote interface reset.

 To secure the function generator from the remote interface, the security

code may contain up to 12 alphanumeric characters as shown below. The first character must be a letter, but the remaining characters can be letters or numbers. You do not have to use all 12 characters but the first character must always be a letter.

A _ _ _ _ _ _ _ _ _ _ _ (12 characters)

 To secure the function generator from the remote interface but allow it to

be unsecured from the front panel, use the eight-character format shown below. The first two characters must be “HP” and the remaining characters must be numbers. Only the last six characters are recognized from the front panel, but all eight characters are required. (To unsecure the function generator from the front panel, omit the “HP” and enter the remaining numbers.)

H P _ _ _ _ _ _ (8 characters)

 If you forget your security code, you can disable the security feature by

adding a jumper inside the function generator, and then entering a new code. See the procedure on the following page.

WARNING

Chapter 4 Calibration Procedures

Calibration Security Code

To Unsecure the Function Generator Without the Security Code

To unsecure the function generator without the correct security code, follow the steps below. A procedure to unsecure the function generator is given on page 47. Also see “Electrostatic Discharge (ESD) Precautions” in chapter 6 before beginning this procedure.

SHOCK HAZARD. Only service-trained personnel who are aware of the hazards involved should remove the instrument covers. The procedures in this section require that you connect the power cord to the instrument with the covers removed. To avoid electrical shock and personal injury, be careful not to touch the power-line connections.

1 Disconnect the power cord and all input connections (front and rear terminals).

2 Remove the instrument cover. Refer to the disassembly drawing on page 130.

3 Connect the power cord and turn on the function generator.

4 Apply a short between the two exposed metal pads on JM101 (located

near U106 and U205) as shown in the figure below.

5 While maintaining the short, enter any unsecure code. The function

generator is now unsecured.

6 Remove the short at JM101.

7 Turn off and reassemble the function generator.

8 The function generator is now unsecured and you can enter a new

security code. Be sure you take note of the new security code.

Chapter 4 Calibration Procedures

Calibration Count

The calibration count feature provides an independent “serialization” of your calibrations. You can determine the number of times that your function generator has been calibrated. By monitoring the calibration count, you can determine whether an unauthorized calibration has been performed. Since the value increments by one for each calibration, a complete calibration increases the value by approximately 85 counts.

 The calibration count is stored in non-volatile memory and does not

change when power has been off or after a remote interface reset. Your function generator was calibrated before it left the factory. When you receive your function generator, read the calibration count to determine its value.

 The calibration count increments up to a maximum of 32,767 after which

it wraps around to 0. There is no way provided to program or reset the calibration count. It is an independent electronic calibration “serialization” value.

Calibration Message

You can use the calibration message feature to record calibration information about your function generator. For example, you can store such information as the last calibration date, the next calibration due date, the function generator’s serial number, or even the name and phone number of the person to contact for a new calibration.

You can record information in the calibration message only from the remote interface. You can read the message from either the front-panel menu or the remote interface.

 The calibration message may contain up to 40 characters. The function

generator can display up to 11 characters of the message on the front panel; any additional characters are truncated.

 The calibration message is stored in non-volatile memory, and does not

change when power has been off or after a remote interface reset.

Chapter 4 Calibration Procedures

General Calibration/Adjustment Procedure

The adjustment procedures described in chapter 4 use the CAL MENU to generate and set internal calibration constants. The general menu procedure is the same for all calibration setups. The following example

demonstrates making the Frequency and Burst Rate adjustments.

Shift 1 Turn on the menu.

Menu On/Off A: MOD MENU

< 2 Move across to the CAL MENU choice on this level.

F: CAL MENU

¿ 3 Move down a level to the UNSECURED command.

1: UNSECURED

If the display shows SECURED, you will have to unsecure the function generator to perform the calibration procedures. A procedure is given on page 47.

> 4 Move across to the CALIBRATE choice.

2: CALIBRATE

¿ 5 Move down one level.

The display indicates the calibration setup number. You can change this number to perform individual specification adjustments.

SETUP 00

Enter 6 Begin the Frequency and Burst Rate adjustment procedure.

Chapter 4 Calibration Procedures

General Calibration/Adjustment Procedure

< > 7 Move the flashing cursor over the digit to be edited.

¿ 8 Change the value in the display to match the measured frequency.

1.000,0040KHz

Enter 9 Calculate and save the new value.

CALIBRATING

10 Perform the next adjustment procedure.

The setup number and function generator output is automatically set for the next adjustment procedure.

SETUP ^01

You will press ENTER twice for each calibration step, once to select the setup (as described in step 6) and once to enter the adjustment (as described in step 9).

You can also use the knob to scroll left or right through the choices on each level of the menu

Chapter 4 Calibration Procedures

Aborting a Calibration in Progress

Sometimes it may be necessary to abort a calibration after the procedure has already been initiated. You can abort a calibration at any time by pressing any front-panel key (except calibration from the remote interface, you can abort a calibration by issuing a remote interface device clear message or by pressing the front-panel

LOCAL key.

Shift-Cancel ). When performing a

Frequency and Burst Rate Adjustment

The function generator stores two calibration constants related to frequency and burst rate output. The constants are calculated from the adjustment value entered and are stored at the completion of each setup.

1 Use a frequency meter to measure the function generator output

frequency for each setup in the following table. These adjustments use a 50

W output termination.

Nominal Output

SETUP FREQUENCY AMPLITUDE

00 * 1.00 kHz 10 Vpp

01 500 Hz 10 Vpp

* A new calibration (SETUP 86 – Rev 4.0) has been added as an alternative to SETUP 00. The new calibration outputs a 10 MHz sine wave, rather than the 1 kHz signal used for SETUP 00. The new calibration reduces slew rate dependent errors in the frequency measurement and is especially important when calibrating the Phase-Lock Assembly (Option 001). Note that either setup is sufficient to calibrate the carrier frequency and you don’t need to perform both.

2 Use the CALIBRATE menu to adjust the displayed frequency at each

setup to match the measured frequency and enter the value.

3 Perform the Frequency Verification procedures on page 56.

Adjustment for main frequency generator, sine wave output

Adjustment for burst rate timing, pulse output.

Chapter 4 Calibration Procedures

Function Gain and Linearity Adjustment

The function generator stores six calibration constants related to function gain and linearity. The constants are calculated from the adjustment value entered. If the calibration procedure is aborted before all setup steps

have been completed, no calibration constants are stored.

1 Use a DMM to measure the function generator ACrms output voltage for

each setup in the following table. These adjustments use a HIGH Z output termination.

Nominal Output

SETUP FREQUENCY AMPLITUDE

02 1 kHz 7.07 V rms Adjustment for sine wave gain.

03 1 kHz 5.6 V rms Adjustment for amplitude linearity.

04 100 Hz 5.6 V rms Adjustment for triangle wave gain.

05 100 Hz 5.6 V rms Adjustment for ramp gain.

06 100 Hz 10.0 V rms Adjustment for square wave gain.

07 100 Hz 1.1 Vrms Adjustment for square wave linearity.

2 Use the CALIBRATE menu to adjust the displayed amplitude at each

setup to match the measured amplitude and enter the value.

3 Perform the Function Gain and Linearity Verification procedures on page 56.

AC Amplitude Adjustment (High-Z)

The function generator stores twenty-two calibration constants related to HIGH Z output, and sixteen calibration constants related to 50 The constants are calculated from the adjustment value entered. The calibration constants are stored following completion of setup 22 (HIGH Z output) and the calibration procedure may be aborted after that point. No calibration constants are stored if the procedures are aborted at any other setup.

1 Use a DMM to measure the function generator ACrms output voltage for

each setup in the following table. These adjustments use a HIGH Z output termination.

W output.

Chapter 4 Calibration Procedures

AC Amplitude Adjustment (High-Z)

Nominal Output

SETUP FREQUENCY AMPLITUDE Adjustment for:

8 1 kHz 5.5 V rms 2 dB Output Attenuator

9 1 kHz 4.4 V rms 4 dB Output Attenuator

10 1 kHz 3.5 V rms 6 dB Output Attenuator

11 1 kHz 2.8 V rms 8 dB Output Attenuator

12 1 kHz 2.2 V rms 10 dB Output Attenuator

13 1 kHz 1.7 V rms 12 dB Output Attenuator

14 1 kHz 1.4 V rms 14 dB Output Attenuator

15 1 kHz 1.1 V rms 16 dB Output Attenuator

16 1 kHz 0.88 V rms 18 dB Output Attenuator

17 1 kHz 0.70 V rms 20 dB Output Attenuator

18 1 kHz 0.55 V rms 22 dB Output Attenuator

19 1 kHz 0.44 V rms 24 dB Output Attenuator

20 1 kHz 0.35 V rms 26 dB Output Attenuator

21 1 kHz 0.28 V rms 28 dB Output Attenuator

22 1 kHz 0.22 V rms 30 dB Output Attenuator

23 1 kHz 5.5 V rms 2 dB Pre-attenuator

24 1 kHz 4.4 V rms 4 dB Pre-attenuator

25 1 kHz 3.5 V rms 6 dB Pre-attenuator

26 1 kHz 2.8 V rms 8 dB Pre-attenuator

27 1 kHz 2.2V rms 10 dB Pre-attenuator

28 1 kHz 1.7 V rms 12 dB Pre-attenuator

29 1 kHz 1.4 Vrms 14 dB Pre-attenuator

2 Use the CALIBRATE menu to adjust the displayed amplitude at each

setup to match the measured amplitude and enter the value.

3 Perform the AC Amplitude Verification procedures on page 57.

Chapter 4 Calibration Procedures

Modulation Adjustment

The function generator stores three calibration constants related to amplitude modulation depth. The constants are calculated from the adjustment value entered. If the calibration procedure is aborted before

all setup steps have been completed, no calibration constants are stored.

1 Use a DMM to measure the function generator ACrms output voltage for

each setup in the following table. These adjustments use a HIGH Z output termination.

Nominal Output

SETUP FREQUENCY AMPLITUDE Adjustment for:

30 1 kHz 3.5 Vrms 0% modulation depth.

31 1 kHz 0.707 Vrms 50% modulation depth.

32 1 kHz 6.36 Vrms 100% modulation depth.

2 Use the CALIBRATE menu to adjust the displayed amplitude at each

setup to match the measured amplitude and enter the value.

33 Perform the AM Modulation Depth Verification procedures on page 61.

NEW CALIBRATION: A new calibration (SETUP 85 – Rev 4.0) has

been added to eliminate a small residual error in the AM amplitude system which could potentially cause a failure of the AM amplitude verification. The new calibration operates just like the other AM calibrations (SETUP 30, 31, 32) in that the external measurement is AC Vrms with no load. The new calibration is not allowed until the other AM gain calibrations (SETUP 30, 31, 32) are performed.

The new algorithm is designed such that the calibration should not be required again once the function generator has been calibrated at the factory. However, if you change any critical analog components which determine amplitude in AM modulation, you should perform the calibration again.

Chapter 4 Calibration Procedures

AC Amplitude Adjustment (50

AC Amplitude Adjustment (50W)

1 The function generator stores 16 calibration constants related to 50W

output. The constants are calculated from the adjustment value entered. The calibration constants are stored following completion of setup 49 and the calibration procedure may be aborted after that point. No calibration constants are stored if the procedures are aborted at any other setup.

Use the DMM to measure the resistance of a 50 Record the measurement for step 3. You can measure the load and cable resistance (recommended procedure) or just the load as shown below.

W feedthrough load.

3 Enter the following setup and use the calibrate menu to enter the

measured value of the 50 will be used to calculate the 50

SETUP LOAD Z

Once the value of the 50W load and cable are entered, use the SAME load and cable for all 50

W feedthrough load (and cable). This number

W output amplitude calibration constants.

Nominal Input

50 W

W tests.

Enter measured value of load.

Chapter 4 Calibration Procedures

AC Amplitude Adjustment (50

4 Use the DMM to measure the function generator ACrms output voltage

for each setup in the table on the next page. These adjustments use the 50

W load and cable measured in step 2 and connected as shown below.

Chapter 4 Calibration Procedures

AC Amplitude Adjustment (50

SETUP FREQUENCY AMPLITUDE Adjustment for:

34 1 kHz 3.5 Vrms 0 dB Output Attenuator

35 1 kHz 2.8 Vrms 2 dB Output Attenuator

36 1 kHz 2.23 Vrms 4 dB Output Attenuator

37 1 kHz 1.77 Vrms 6 dB Output Attenuator

38 1 kHz 1.41 Vrms 8 dB Output Attenuator

39 1 kHz 1.12 Vrms 10 dB Output Attenuator

40 1 kHz .887 Vrms 12 dB Output Attenuator

41 1 kHz .704 Vrms 14 dB Output Attenuator

42 1 kHz .559 Vrms 16 dB Output Attenuator

43 1 kHz .442 Vrms 18 dB Output Attenuator

44 1 kHz .350 Vrms 20 dB Output Attenuator

44 1 kHz .281 Vrms 22 dB Output Attenuator

46 1 kHz .223 Vrms 24 dB Output Attenuator

47 1 kHz .177 Vrms 26 dB Output Attenuator

48 1 kHz .141 Vrms 28 dB Output Attenuator

49 1 kHz .112 Vrms 30 dB Output Attenuator

Nominal Output

5 Use the CALIBRATE menu to adjust the displayed amplitude at each

setup to match the measured amplitude and enter the value.

6 Perform the AC Amplitude Verification procedures beginning on page 57.

Chapter 4 Calibration Procedures

DC Output Adjustment

The function generator stores nine calibration constants related to DC volts output. The constants are calculated from the adjustment value entered. The calibration constants are stored following completion of setup 59. No calibration constants are stored if the procedures are aborted at any other setup.

1 Use a DMM to measure the function generator dcV output voltage for

each setup in the following table. These adjustments use a HIGH Z output termination.

Nominal Output

SETUP DC Volts Adjustment for:

50 - 8.0 Vdc Negative offset gain

51 8.0 Vdc Positive offset gain

52 0.0 Vdc AM offset

53 0.0 Vdc 2 dB Pre-attenuator offset.

54 0.0 Vdc 4 dB Pre-attenuator offset.

55 0.0 Vdc 6 dB Pre-attenuator offset.

56 0.0 Vdc 8 dB Pre-attenuator offset.

57 0.0 Vdc 10 dB Pre-attenuator offset.

58 0.0 Vdc 12 dB Pre-attenuator offset.

59 0.0 Vdc 14 dB Pre-attenuator offset.

2 Use the CALIBRATE menu to adjust the displayed output voltage at

each setup to match the measured voltage and enter the value.

3 Perform the DC Function Offset Verification procedures on page 57.

Chapter 4 Calibration Procedures

Duty Cycle Adjustment

The function generator stores two calibration constants related to squarewave offset and two calibration constants related to squarewave duty cycle. The constants are calculated from the adjustment value entered. The calibration constants are stored following completion of setup 63. No calibration constants are stored if the procedures are aborted at any other setup.

1 Use a DMM to measure the function generator dcV output voltage for

each setup in the following table. These adjustments use a HIGH Z output termination.

For this test, the DMM must be set to a fixed range capable of measuring from +10 V to -10 V. Do not use an auto-ranging function for this test.

Nominal Output

SETUP FREQUENCY AMPLITUDE

60 — 10.0 Vdc Positive squarewave offset.

61 — -10.0 Vdc Negative squarewave offset.

62 300 Hz 0.0 Vdc 50% duty cycle squarewave.

63 300 Hz 5.0 Vdc 75% duty cycle squarewave

2 Use the CALIBRATE menu to adjust the displayed output voltage at

each setup to match the measured voltage and enter the value.

3 Perform the Squarewave Duty Cycle Verification procedures on page 62.

AC Amplitude Flatness Adjustment

The function generator stores eleven calibration constants related to AC Amplitude Flatness from 1 kHz to 15 MHz. The constants are calculated from the adjustment value entered and one of two calculation constants related to the type of measurement device you are using. The calibration constants are stored following completion of setup 82. No calibration constants are stored if the procedures are aborted at any other setup.

Chapter 4 Calibration Procedures

AC Amplitude Flatness Adjustment

This procedure can be performed with one of three types of measurement device; a broadband ACrms voltmeter, a power meter, or a thermal voltage converter. The procedure differs slightly depending upon the type of measurement device used. These adjustments us a 50

W output termination.

1 Use a DMM to measure the ACrms output voltage of the function generator

and enter the measurement value for the setup in the table below.

Nominal Output

SETUP FREQUENCY AMPLITUDE Reference for:

64 1 kHz 3.0 V rms 1 kHz flatness DAC gain

2a. If you are using a broadband ACrms voltmeter, proceed to step 3.

b. If you are using a power meter capable of measurements at 1 kHz,

use the power meter to measure the function generator output and enter the value for the setup in the table below. (If your power meter does not measure to 1 kHz, see the transfer measurement procedure below.)

Nominal Output

SETUP FREQUENCY AMPLITUDE Reference for:

83 1 kHz 3.0 V rms V rms, dBm

Transfer Measurement Procedure

If you are using a power meter not capable of measurement to 1 kHz, you can perform the transfer measurement at a different frequency. For example, the Agilent E4418A Power Meter with the Agilent 8482A probe and 20 dB attenuator are specified to a low frequency of 100 kHz. To use this measurement device, perform step 1, then use setup 65 to obtain a 100 kHz output. Measure the output with the power meter and record the measured value. Perform setup 83 and enter the recorded value (not a new measurement). Then, perform step 3 (you will use setup 65 twice). This procedure assumes the output of the function generator is

flat from 1 kHz to 100 kHz.

c. If you are using a Thermal Voltage Converter (TVC), use the TVC to

measure the function generator output and enter the measurement for the setup in the table below (TVC values entered are in mVdc).

Nominal Output

SETUP FREQUENCY AMPLITUDE Reference for:

84 1 kHz 3.0 V rms Thermal Voltage Converter

Chapter 4 Calibration Procedures

AC Amplitude Flatness Adjustment

3 For each setup in the table below, use the CALIBRATE command to

change the displayed amplitude to match the measured amplitude.

Nominal Output

SETUP FREQUENCY AMPLITUDE Adjustment for:

65 100 kHz 3.0 V rms 100 kHz amplitude flatness

66 500 kHz 3.0 V rms 500 kHz amplitude flatness

67 1 MHz 3.0 V rms 1 MHz amplitude flatness

68 3 MHz 3.0 V rms 3 MHz amplitude flatness

69 5 MHz 3.0 V rms 5 MHz amplitude flatness

70 7 MHz 3.0 V rms 7 MHz amplitude flatness

71 9 MHz 3.0 V rms 9 MHz amplitude flatness

72 10 MHz 3.0 V rms 10 MHz amplitude flatness

73 10.5 MHz 3.0 V rms 10.5 MHz amplitude flatness

74 11 MHz 3.0 V rms 11 MHz amplitude flatness

75 11.5 MHz 3.0 V rms 11.5 MHz amplitude flatness

76 12 MHz 3.0 V rms 12 MHz amplitude flatness

77 12.5 MHz 3.0 V rms 12.5 MHz amplitude flatness

78 13 MHz 3.0 V rms 13 MHz amplitude flatness

79 13.5 MHz 3.0 V rms 13.5 MHz amplitude flatness

80 14 MHz 3.0 V rms 14 MHz amplitude flatness

81 14.5 MHz 3.0 V rms 14.5 MHz amplitude flatness

82 15 MHz 3.0 V rms 15 MHz amplitude flatness

4 Perform the Amplitude Flatness Verification procedures on page 60.

Shift Menu On/Off Completion of adjustment procedures. Return the function generator

to the normal operating mode.

EXITING

Chapter 4 Calibration Procedures

Output Amplifier Adjustment (Optional)

This adjustment procedure should only be performed following repairs to the Output Amplifier circuitry. The adjustment improves the high frequency performance of the Output Amplifier.

1 Remove the function generator power and cover as described on page 130.

2 Use a DMM to measure the ACrms voltage across J701 as shown below.

Cable Shield is Circuit Ground

3 Turn on the function generator.

4 Set the function generator for a 1 kHz, 1V rms, sine wave output.

5 Adjust R710 for a minimum reading on the voltmeter. Typical readings

are less than 0.005 Vrms.

6 Replace the covers as described on page 130.

Chapter 4 Calibration Procedures

Error Messages

The following tables are abbreviated lists of function generator’s error messages. They are intended to include errors which are likely to be encountered during the procedures described in this chapter. For a more complete list of error messages and descriptions, see chapter 5 in the Agilent 33120A User’s Guide.

System Error Messages

Error Error Message

-330 Self-test Failed

-350 Too many errors

501 Isolator UART framing error

502 Isolator UART overrun error

511 RS-232 framing error

512 RS-232 overrun error

513 RS-232 parity error

514 Command allowed only with RS-232

521 Input buffer overflow

522 Output buffer overflow

550 Command not allowed in Local

Self-Test Error Messages

Error Error Message

601 Front panel does not respond

602 RAM read/write fail

603 Waveform RAM readback failed

604 Modulation RAM readback failed

605 Serial configuration readback failed

606 Waveform ASIC failed

607 SYNC signal detection failure

608 SYNC signal detection failure

625 I/O Processor not responding

626 I/O Processor failed self-test

627 I/O Processor reset; possible low power line voltage

Chapter 4 Calibration Procedures

Error Messages

Calibration Error Messages

Error Error Message

701 Cal security disabled by jumper

702 Cal secured

703 Invalid secure code

704 Secure code too long

705 Cal aborted

706 Cal value out of range

707 Cal signal measurement out of range

708 Flatness cal failed

709 Cannot calibrate frequency while externally locked (Option 001)

760 RAM checksum failure

850 Cal setup invalid

851 Negative offset gain cal required (CAL:SETup 50)

852 Flatness DAC gain cal required (CAL:SETup 64)

853 AM cal 1 required (CAL:SETup 30)

854 AM cal 2 required (CAL:SETup 31)

855 Cal load resistance not specified (CAL:SETup 33)

856 Square wave positive offset cal required (CAL:SETup 60)

857 Square wave 50% duty cycle cal required (CAL:SETup 62)

858 AM cal 3 required (CAL:SETup 32)

Theory of Operation

This chapter is organized to provide descriptions of the circuitry contained on the schematics shown in chapter 8. A block diagram overview is provided followed by more detailed descriptions of the circuitry contained in the schematics chapter.

 Block Diagram Overview . . . . . . . . . . . . . . . . 85

 Output Attenuator . . . . . . . . . . . . . . . . . . . 86

 Output Amplifier . . . . . . . . . . . . . . . . . . . . 87

 AM Modulation . . . . . . . . . . . . . . . . . . . . . 89

 Pre-attenuator . . . . . . . . . . . . . . . . . . . . . . 90

 Square Wave and Sync . . . . . . . . . . . . . . . . . 90

 Filters . . . . . . . . . . . . . . . . . . . . . . . . . . 92

 Waveform DAC/Amplitude Leveling/Waveform RAM . . 93

 Direct Digital Synthesis (DDS ASIC) . . . . . . . . . 95

 System DACs . . . . . . . . . . . . . . . . . . . . . . 96

 Floating Logic . . . . . . . . . . . . . . . . . . . . . . 97

 Earth-Referenced Logic . . . . . . . . . . . . . . . . . 98

 Power Supplies . . . . . . . . . . . . . . . . . . . . . 98

 Display and Keyboard . . . . . . . . . . . . . . . . . . 100

The self-test procedures are described in chapter 6.

Chapter 5 Theory of Operation

Block Diagram Overview

This discussion pertains to the block diagram shown on page 129.

The function function generator’s circuitry is divided into two major blocks: the floating section and the earth (ground) reference section. All signal generation, control, and display functions are contained in the floating section. This section also contains the function generator’s main CPU.

The floating section can be viewed in two pieces; the analog signal conditioning section (System DAC, Filters, Sync, Square wave, Pre-Attenuator, Output Amp, and Output Attenuator) and the digital logic section (Floating Logic, Digital Waveform Data Synthesis, and Waveform DAC).

All signal generation, level control, and modulation functions are performed in the floating section. The waveform DAC generates two outputs, normal and inverted, between approximately 800 mVp-p and 1 Vp-p. The DAC outputs are routed through anti-alias low-pass filters to eliminate higher frequency sampling products. The nominal x10 gain of the output amplifier, combined with preattenuator and output attenuator settings, are chosen such that the desired output amplitude is produced.

The ground reference section uses a processor configured as a slave to the main CPU. This processor establishes external I/O communication with the main CPU through a bi-directional, optically isolated, serial communications link. The earth referenced processor controls low-level GPIB (IEEE-488) and RS-232 interface operation. The ground referenced, rear panel external trigger input uses a dedicated optical isolator to couple a trigger signal to the main CPU in the floating section.

Separate power supplies are provided for the floating and ground reference sections. The front panel operates from the floating section with its logic common different from the CPU logic common.

Chapter 5 Theory of Operation

Output Attenuator

Block 8 on block diagram page 129; Schematic on page 138.

The Output Attenuator provides 0 to 30 dB of signal attenuation between the output amplifier section and the output BNC connector. Output signal levels are controlled by combining coarse amplitude control from the output attenuator section and pre-attenuator section with fine amplitude control from the Waveform DAC AMP_CTL signal.

Four switched output attenuator pads are combined to achieve the desired signal attenuation as shown in the table below. Relays K801 through K804 either bypass an attenuator pad or select that attenuator. K801 selects a 2 dB attenuator, K802 selects a 4 dB attenuator, K803 selects a 8 dB attenuator, and K804 selects a 16 dB attenuator. Relays are sequenced to provide signal attenuation in 6 dB steps. Intermediate amplitude levels are controlled by selecting 0 dB, 2 dB or 4 dB of signal attenuation through the pre-attenuator solid state switches in combination with reducing the output level of the waveform DAC itself. The AMP_CTL signal provides smoothly varying control of the Waveform DAC output level over a 0 dB to -2 dB range. This operation is described further in the Waveform DAC and System DAC discussions.

Output Attenuation K801 K802 K803 K804

0 dB set set set set

6 dB reset reset set set 12 dB set reset reset set 18 dB reset set set reset 24 dB set set reset reset 30 dB reset reset reset reset

K801 through K804 are latching relays. Their set or reset state is selected by momentarily pulsing the appropriate coil of the relay. Relay coils are pulsed with 5 volts for 15 ms through relay drivers U301 and U302. The main controller, U102, writes data bytes to ASIC U103 which transmits this data to the relay drivers via the internal 3-wire serial data bus (SERCLK, SERDAT, and SERSTB) to accomplish the relay state changes.

A 30 MHz filter, composed of L801, C801, and C802, eliminates wideband noise from the function generator output. The output amplifier and output attenuators are protected from damage by clamps CR801 and CR802 and by fuse F801. The function generator is protected from accidental application of voltages <10 volts for short durations.

Chapter 5 Theory of Operation

Output Amplifier

Block 7 on block diagram page 129; Schematic on page 137.

The output amplifier drives the function generator’s signal output through the output attenuator section. The output amplifier exhibits an approximate 35 MHz bandwidth and 1000 V/ originating from the DAC+ and DAC- signal paths are combined at the input of the amplifier. The output amplifier exhibits a nominal x(-10) voltage gain from its -AMP_IN input and a nominal x12 voltage gain from its +AMP_IN input. A dc offset signal, related to the front panel output offset value, is also summed with the ac signal at the input of the amplifier. A simplified block diagram of the output amplifier is shown below.

ms slew rate. AC signals

Chapter 5 Theory of Operation

Output Amplifier

The block diagram shows four basic stages: dc amplifier, input differential amplifier, gain, and power output. The amplifier’s input differential amplifier stage and gain stage are symmetrical. The +AMP_IN and

-AMP_IN inputs are both amplified through complementary amplifiers whose outputs are summed together at the input of the power output stage. Transistors Q701, Q702, Q704 and Q707 form the complementary input differential amplifiers. Q708 and Q705 are current sources which provide bias to the input differential amplifiers. Q709 and Q710 are emitter follower amplifiers used to couple the respective differential amplifier outputs to the gain stage transistors Q711 and Q715 which provide virtually all of the amplifiers open loop gain (~ x1000).

The power output stage is a wideband, class C buffer amplifier. Emitter followers Q714 and Q716 buffer the gain stage output from loading by the power output emitter follower transistors Q713 and Q718. Idle current bias for these power output transistors is set by the ratios of R732, R726 and transistor matching between Q713, Q714 and their equivalents in the other half of the stage: R734, R727 and Q718, Q716. Transistors Q712 and Q717 are current sources which provide bias to emitter followers Q714 and Q716 respectively.

The low frequency and dc performance of the amplifier is controlled by U702. This amplifier is used to sense the dc offset present at the +AMP_IN and -AMP_IN inputs and servo the output amplifier dc offset to zero volts; to the limit of U702’s own dc offset performance. U702 also provides a means to add a desired dc offset value into the output signal path through the x (-1) gain of the OUT_OFFSET signal.

The output amplifier employs a current feedback technique to set the closed-loop gain. The emitters of Q701 and Q702 are the virtual summing node points in the amplifier. Amplifier closed loop gain is controlled predominately by the following ratios:

2 * ( R740 + R710 ) + R717

(

R715 + R716

)

and

2 * ( R740 + R710 ) + R711

(

R719 + R720

)

Variable resistor R710 is used to match the gain through the high frequency feedback path (described above) and the dc feedback path summed through resistors R705, R706. The feedback signal current is injected into the amplifier through the emitters of Q701 and Q702 respectively.

Chapter 5 Theory of Operation

AM Modulation

Blocks 3 and 6 on block diagram page 129; Schematics on pages 136 and 133.

Amplitude modulation is performed by analog multiplier U603 combining the AM_IN and +FUNCTION and -FUNCTION signals. Modulation depths from 0% to 120% are set by varying the signal at AM_IN.

When the amplitude modulation function is selected, the output of U603 is switched into the +AMP_IN signal path by K602. At the same time, the -AMP_IN signal path is grounded, cutting the output signal amplitude in half, to accommodate the more than two times peak signal levels required by >100% modulation depth.

The AM_IN signal is a combination of any external modulation inputs applied to the rear panel BNC connector and the internally generated AM signals. The function generator can internally synthesize an 8-bit modulation wave shape through DAC U313. Data from any standard or arbitrary wave shape can be used as the modulating wave shape. Modulating wave shapes are automatically expanded or compressed in length, as required, to meet the specified modulating frequency setting. Changes in the function generator output will lag changes in the modulating frequency because new modulation data must be computed and downloaded internally for every frequency change.

The AM_GAIN and AM_OFFSET dc signals are used to calibrate and vary the am modulation depth settings. AM_GAIN controls the peak-to-peak output level from U313 in response to modulation depth setting changes. Likewise, the AM_OFFSET signal varies inversely to the AM_GAIN signal, as the AM depth setting is varied, to produce a constant signal offset in the composite AM_IN modulation signal. The net AM_IN offset is independent of the modulating ac signal component or AM depth setting.

Chapter 5 Theory of Operation

Pre-attenuator

Block 6 on block diagram page 129; Schematic on page 136.

All signals, except square waves, pass through the preattenuator. The preattenuator multiplexes eight resistive 2 dB attenuators to provide attenuation from 0 dB to 14 dB in 2 dB steps. The 0 dB, 2 dB, and 4 dB attenuation steps are used for level settings between the 6 dB steps selected in the output attenuator section. Amplitude settings between these 2 dB steps are set by smoothly varying the Waveform DAC output level from 0 dB to -2 dB of its nominal level via the AMP_CTL signal. Output attenuator 6 dB steps, preattenuator 0 dB, 2 dB, and 4 dB steps, and small variations (0 dB to 2 dB) of the Waveform DAC output level are combined to produce each amplitude setting.

In the preattenuator, U601 and U602 are operated as 8-to-1 multiplexers, each providing selectable 2 dB attenuation steps. Because of the gain imbalance of the output amplifier (x 12 on +AMP_IN and x (-10) on

-AMP_IN), the +signal path U601 has an additional 2 dB attenuation always present (R601 and R602) to equalize the nominal gains in both the plus and minus signal paths.

Square Wave and Sync

Block 6 on block diagram page 129, schematic on page 136.

During square wave outputs, a sine wave signal is generated internally and squared-up by comparator U620. Square wave amplitude control is accomplished by variable gain amplifier Q603 and Q604 and switched into the output signal path through relay K601. A simplified diagram of the square wave generator is shown below.

Chapter 5 Theory of Operation

Square Wave and Sync

Transistors Q601 and Q602 buffer the output of the sine wave anti-alias filter to the input of comparator U620. Square wave duty cycles are controlled by the SQ_SYM input on the inverting input of the comparator. The squarewave outputs of U620 are amplified by variable gain amplifiers Q603 and Q604.

The amplifier gain output level is controlled by the variable current source Q605 and U307D in response to the System DAC dc signal SW_AMP. Squarewave variable gain amplifier output signal levels are unbalanced by resistors R643 and R644 to correct for the output amplifier + and - gain differences as discussed in the preattenuator section on page 90.

Latching relay K601 connects the square wave into the +FUNCTION and -FUNCTION paths. The relay set or reset state is selected by momentarily pulsing the appropriate coil. Relay coils are pulsed with 5 volts for 15 ms through relay driver U301. The main controller, U102, writes data bytes to ASIC U103 which transmits this data to the relay drivers via the internal 3-wire serial data bus (SERCLK, SERDAT, and SERSTB) to accomplish relay state changes.

Multiplexer U604 selects one of five sources for the SYNC output: off, modulation sync, square wave comparator output, RUN*, or Arbitrary waveform sync. ARB_SYNC is derived from the WA14 line through U210B. U215B and U210C control the pulse width of the ARB_SYNC (arbitrary waveform sync) signal. Square wave sync is taken from the inverting output of square wave comparator U620. U620 also generates the MOD_SYNC (modulation sync) through U217. Buffer U621 inverts the sync signal and provides the output current drive to the SYNC output BNC connector.

Chapter 5 Theory of Operation

Filters

Block 5 on block diagram page 129; Schematic on page 135.

The output of the Waveform DAC passes through one of two anti-alias filters. A 17 MHz 9th order elliptical filter is used for the sine wave and square wave output functions. A 10 MHz 7th order Bessel filter is used for filtering all other output functions, including all arbitrary waveshapes. The diagrams below show the typical frequency response of these filters.

The filters are switched in or out of the signal path by latching relays K501 and K502. Their set or reset state is selected by momentarily pulsing the appropriate coil of the relay. Relay coils are pulsed with 5 volts for 15 ms through relay drivers U301 and U302. The main controller, U102, writes data bytes to ASIC U103 which transmits this data to the relay drivers via the internal 3-wire serial data bus (SERCLK, SERDAT, and SERSTB) to accomplish these relay state changes. When K501 and K502 are set, the 10 MHz Bessel filter is selected.

Chapter 5 Theory of Operation

Waveform DAC/Amplitude Leveling/Waveform RAM

Block 4 on block diagram page 129; Schematic on page 134.

The Waveform DAC, U407, converts 12-bit digital data from waveform RAM’s U404 and U405 into positive and negative analog voltages. A simplified diagram of the Waveform DAC circuitry is shown below.

The preattenuator, filters, and associated circuits in the output signal path provide an approximate 25 DAC nominally produces a 40 mA differential output current — yielding differential 1 Vac output signals. Wave shape (amplitude) data is loaded into the waveform RAM by the main controller CPU U102. Once loaded, these data are addressed by the DDS ASIC. The rate at which addresses are incremented determines the output waveform frequency. Waveform RAM output data is latched and shifted to ECL levels by U402 and U403 for input to the waveform digital-to-analog converter (DAC) U407. DDS ASIC U206, waveform data latches U402 and U403, and the Waveform DAC U407 are clocked at 40 MHz. The 40 MHz clock is generated by oscillator U413 and ECL level-shifter U401.

W load for the Waveform DAC. The Waveform

Chapter 5 Theory of Operation

Waveform DAC/Amplitude Leveling/Waveform RAM

The Waveform DAC voltage reference is driven by U410B. This reference controls the magnitude of the nominal 0 to -40 mA DAC output current. The reference level is varied to produce 0 to -2 dB fine amplitude level control via dc signal AMP_CTL and

2 dB of dynamic amplitude flatness

correction for static and swept frequency operation via flatness correction dac U409. These reference voltage adjustments are summed together in amplifier U410B. Amplitude flatness correction data are stored in calibration memory during calibration. These data are used to produce a modulation program with corresponding 8-bit amplitude correction data values which are gated to latch U412 during operation. These data provide real-time correction of the output amplitude level as frequency changes are made. Amplifier U408 and Q401 use the waveform DAC reference voltage to center the waveform DAC output signal near 0 volts.

U404 and U405 are the high-speed waveform RAM. Together, U404 and U405 form a 16383 x 12-bit RAM. Each RAM stores and outputs 6 bits of the waveform DAC 12-bit WD data bus. RAM U404 drives the least significant 4 bits and U405 drive the most significant 8 bits of the WD data bus. Note that DAC U407 calls D1 the most-significant bit (MSB) and D12 it’s least-significant bit (LSB). Waveform RAM addresses are controlled by the DDS ASIC’s WA (waveform address) bus.

Chapter 5 Theory of Operation

Direct Digital Synthesis (DDS ASIC)

Block 2 on block diagram page 129; Schematic on page 132.

The DDS ASIC, U206, controls the WA (waveform address) and MA (modulation address) busses. The waveform address is used by the waveform RAMs U404 and U405. The modulation data bus is used by the modulation RAM U205.

The DDS ASIC is comprised of several internal registers and addressing state machines. Instructions are written to the DDS ASIC by the main CPU via memory mapped control registers U108 and U202. When loading data into Waveform RAM or Modulation RAM, addresses on the WA and MA busses are incremented by ASIC U206. ASIC addresses are incremented by each rising edge of the TRIG line while writing data into these RAM. The state of the HOST_RQ* line controls whether the main CPU or the modulation RAM U205 is sourcing instructions to the DDS ASIC internal state machines. The Modulation RAM is loaded with frequency values and amplitude flatness correction values or AM modulation data for latch U309 and AM dac U313. Data multiplexer U217 and flip-flop U215 are used to preselect and synchronize the modulation sync source available to the SYNC output terminal multiplexer U604.

The external trigger input OGEXT is optically isolated by U213 and applied to an input of trigger source multiplexer U214. The external trigger input is used for triggering the start of a frequency sweep or burst output and for externally gating the output signal on and off asynchronously. U214 selects one of seven trigger sources for use by U206 for initiating its internal program.

Chapter 5 Theory of Operation

System DACs

Block 3 on block diagram page 129; Schematic on page 133.

All output amplitudes are derived from the internal voltage reference of System DAC U303. The system dac track/hold amplifier outputs are used to provide controllable bias voltages to various analog circuits including AM modulation depth, square wave amplitude, square wave duty cycle, output dc offset, and output amplitude level. The System DAC is programmed and responds to the main controller via the internal 3-wire serial data bus SERCLK, SERRBK, and SERSTB. The System DAC is multiplexed to 7 track/hold amplifiers through U304. Each track/ hold amplifier is refreshed approximately every 3 ms to maintain its output setting. Changes to track/hold amplifier outputs are accomplished by dwelling on that position for an extended period.

Chapter 5 Theory of Operation

Floating Logic

Block 1 on block diagram page 129; Schematic on page 131.

The floating logic controls the operation of the entire function function generator. All output functions and bus command interpretation is performed by the main CPU, U102. The front panel and earth referenced logic operate as slaves to U102. The main CPU portion of the floating logic section is clocked from a 12 MHz ceramic resonator, Y101. Non-volatile EEPROM U106 stores arbitrary waveform data, calibration constants, calibration secure code, calibration count, and last instrument state.

The main CPU, U102, is a 16-bit micro controller. The 16-bit A (address) bus and 8-bit AD (address/data) bus are used to provide digital communication with the 256k byte program ROM U104, 32k byte RAM U105, 128k byte non-volatile EEPROM U106, 32k byte high speed Modulation RAM U205, 16k x 12-bit high speed waveform RAM U404 and U405 and DDS ASIC U206.

Gate array U103 provides CPU address latching and memory mapping functions. There are four internal registers in U103: a configuration register, an 8-bit counter register, a serial transmit/receive register, and an internal status register. RAM chip select signal RAMCE* and CPU port bits RAMA13 and RAMA14 are used to access 4 - 8k byte banks of program data RAM. Similarly, 4 banks of 56k non-volatile EEPROM and 2 banks of 56k non-volatile RAM are gated from CPU port bits PRG16, PRG17, and WAVA16 and U103 signal ROMCE*. Addresses on the CPU address bus are valid when the ALE line is high. Memory mapping of control of registers U107 and U202, DDS ASIC U206, data transceivers U201, U203, U204, and write enables for RAM U404 and U405 and U205 are controlled by data selector U108.

The U103 serial register controls the front panel, relay drivers U301 and U302, and System DAC U303 through a serial data bus. Front panel signals are FPDI, FPSK*, and FPDO. Interrupts from the front panel are detected by U103 and signaled to U102 by CHINT. The FPINT line from U102 signals the front panel that U103 has data to send. The internal 3-bit serial data bus (U102) uses SERCK, SERDAT, and SERSTB to send data to various registers. SERRBK (serial read back) is used by self test to verify operation of U103, relay drivers U301, U302, and System DAC shift register U305.

Chapter 5 Theory of Operation

Earth-Referenced Logic

The main CPU, U102, communicates with the earth referenced logic through an optically isolated asynchronous serial data link. U101 isolates the incoming data (OG_RXD*) from the earth referenced logic. Similarly, U901 isolates the data from U102 (OG_TXD) to the earth reference logic. Data is sent in an 11-bit frame at a rate of 187.5 k bits/second. When the RS-232 interface is selected, data is sent across the serial link at 93.75 k bits/second. The 11-bit internal data frame is configured for one start bit, eight data bits, one control bit, and one stop bit.

Earth-Referenced Logic

Block 9 on block diagram page 129; Schematic on page 139.

The earth referenced section provides all rear panel input/output capability. Microprocessor U903 handles GPIB (IEEE-488) control through bus interface chip U904 and bus receiver/driver chips U907 and U908. The RS-232 interface is also controlled through U903. RS-232 transceiver chip U906 provides the required level shifting to approximate

 9 volt logic levels through on-chip charge-pump power supplies using

capacitors C904 and C906. Communication between the earth referenced logic interface circuits and the floating logic is accomplished through an optically-isolated bi-directional serial interface. Isolator U101 couples data from U903 to microprocessor U102. Isolator U901 couples data from U102 to microprocessor U903.

Power Supplies

Block 10 on block diagram page 129; Schematic on page 140.

The power supply section, is divided into two isolated blocks similar to the floating logic and earth referenced logic sections discussed earlier. The floating supply outputs are 6 Vrms center tapped filament supply for the vacuum fluorescent display. All earth referenced logic is powered from a single +5 Vdc supply. Power-on reset signals are provided by both the floating and earth referenced power supplies. In addition, the floating section +5 Vdc supply incorporates a power failure detection circuit which provides a priority interrupt signal to the main CPU (U102).

 18 Vdc, +5 Vdc, -5.2 Vdc (VEE), and a

Agilent Technologies 33120A User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

The Front Panel at a Glance

Front-Panel Number Entry

The Front-Panel Menu at a Glance

Display Annunciators

The Rear Panel at a Glance

In This Book

Contents