Stanford Research Systems DS345 Specifications Sheet

DS345

1290-D Reamwood Ave, Sunnyvalle, CA 94089
Phone [phone], Fax [phone]
e-mail: info @thinkSRS.com, www.thinkSRS.com

30 MHz Synthesized
Function Generator

DS345
30 MHz Synthesized
Function Generator

$1595

(U.S. list)

Status indicators show
activity over the IEEE-488 or
RS232 interfaces. An error
indicator lights when an
improper external reference
is applied.

Sync provides a TTL pulse
synchronous with the
Function output. Both
outputs are isolated from
the chassis ground.

• 30 MHz direct digitally
synthesized source

-6

• 10

Hz resolution

• 12 bit, 40 Msample/s
arbitrary waveforms

• Low phase noise and
distortion

• Fast, phase continuous
frequency switching

• Sine, square, ramp and
triangle waveforms

• Internally synthesized FM,
AM and phase modulation

• Arbitrary and burst
modulation

• Linear and Log sweeps

• Flexible triggering - rates
from .001 Hz to 20 kHz

• Optional IEEE-488 and RS232
interfaces with Arbitrary
Waveform Composer
software

Select the output waveform
and choose the displayed
signal parameter.

ntroducing the DS345
30 MHz Synthesized

I

Function Generator from SRS.
The affordable solution to all
your signal generator needs.

The DS345 uses direct digital
synthesis to generate outputs
up to 30 MHz with 1 ∝Hz res-
olution. And thanks to the
innovative architecture, the
DS345 is a remarkably agile
source. The output can be
modulated at rates up to 20
kHz, and frequency switching
is phase continuous and takes
only 25 ns.

The standard waveforms ­sine, square, ramp and trian­gle - may be frequency, ampli­tude, phase or burst modulated
by the internal source. The
modulation source is digitally

Set the type of sweep and
modulation waveform. The
up/down keys allow easy
access to all selections.

synthesized and provides
either standard or arbitrary
modulation waveforms. The
modulation function is availa­ble from the rear panel. The
signal output can also be
amplitude modulated by an
external signal.

The ability to generate fast,
high resolution arbitrary wave­forms is another advantage of
the direct digital design. Pat­terns are generated at sample
rates up to 40 Msamples/s with
12 bits (.025%) of vertical res­olution. Records as long as
16k points can be stored in the
DS345. Waveforms can be
point or vector edited from the
front panel, or created and
downloaded using the Arbi­trary Waveform Composer
software package.

Large, easy to read 12 digit display
shows the selected parameter. The
parameter type and units are also
indicated.

Store and recall up to 10
different instrument setups in
non-volatile memory.

Values may be adjusted with
the highlighted digit cursor or
incremented and decremented
by user defined steps. The
cursor position and step size
are stored along with each
parameter.

Units may be entered as
engineering values,
reducing the number of
required keystrokes.

Sweeps are specified by choosing either the
center frequency and span or the start and
stop frequencies. Sweep rate, burst count and
trigger rate are easily programmed.

utputs have the low phase

O

noise inherent to direct
digital synthesis. Wideband
amplifiers provide low distortion
as well as excellent pulse
response. The squarewave output
can drive 10Vpp into a 50Ω load
with less than a 10 ns risetime.
Amplitude and offset are set with

0.2 dB accuracy from 1 µHz to
30 MHz. The amplitude may be
entered in Vpp, Vrms or dBm, or
set directly to TTL or ECL levels.

Linear and log frequency sweeps
are quickly specified by entering
the center frequency and span or
the start and stop frequencies.
Sweep marker outputs are
available on the rear panel.

Direct keyboard entry simplifies parameter entry.
Shifted numeric keys select less commonly used
parameters. Back panel functions like marker
functions are set and controlled through the front

Sweeps and bursts can be
triggered from the front panel, the
internal rate generator, or the
external trigger input. Bursts of
any waveform, including arbitrary
waveforms, may be triggered.

Parameter values are either
entered numerically, adjusted
using the cursor, or incremented
and decremented by user defined
steps. Up to 10 complete
instrument configurations may be
stored in non-volatile memory for
quick setup.

Computer interfacing is simple
and direct with the IEEE-488 and
RS232 interface option. The
Arbitrary Waveform Composer
software package is included free
with the interface option.

The standard timebase provides 5
ppm frequency accuracy. The
optional ovenized oscillator
timebase provides .002 ppm
stability. Even greater long-term
stability can be achieved using an
external timebase, such as the
SRS FS700 Loran Frequency
Standard. The phase relationship
between multiple DS345's sharing
the same timebase can be adjusted
with millidegree resolution.

nd best of all, the DS345
is priced well below

A

conventional function generators
offering far less performance. So
why not move up to the DS345
today? For more information, or
to place an order, call SRS at

[phone].

Powerful Functions

Any function generator can make sine waves. But the DS345 not only makes extremely accu­rate and pure sine waves, it has extensive built in modulation features. This flexibility allows it
to produce frequency, amplitude, phase and burst modulations as well as linear and logarithmic
frequency sweeps. And the DS345 offers a choice of synthesized modulating functions - sine,
square, ramp, triangle -- even arbitrary waveshapes. The modulation or trigger rate is not limit­ed to a few fixed frequencies, but can be set from .001 Hz to 20 kHz with 2 digits of resolution.
Complex functions like pulse modulation and binary or phase shift keying are all at your
fingertips.

Linear and Log sweeps

Burst modulation

Frequency modulation

Arbitrary waveform

Arbitrary Waveform Composer

Amplitude modulation

Phase modulation

Ramps, triangles, and squares

Create Arbitrary Waveforms

Complex arbitrary waveforms of 8 to 16,300 points are easily generated with sample rates as
fast as 40 Msamples/s. Simple waveforms may be entered from the front panel point by point or
with vectors. The Arbitrary Waveform Composer software, included with the interface option,
provides a friendly window environment for the user to create, edit, and download waveforms to
the DS345. Complicated patterns
can be quickly generated by
combining many waveforms.
The software also downloads
ASCII files created with other
applications. Instrument
parameters such as triggering,
amplitude, and sample rate are
controlled with simple
keyboard commands or a

10 MHz, 1 Vpp sine into 50 Ω

Waveforms

Max Freq

Resolution

Sine

30.1 MHz

1 µHz

Square

30.1 MHz

1 µHz

Ramp

1 MHz

1 µHz

Triangle

1 MHz

1 µHz

Noise

10 MHz

(Gaussian Weighting)

OUTPUT

Source Impedance

50 Ω

Amplitude Range

10mV to 10Vpp in 8 ranges.

AmplitudeAccuracy

±0.2 dB (±2%) (sine output)

Amplitude Resolution

0.1% of full scale.

Maximum Offset

±5 VDC

Offset Resolution

0.05% of full scale.

Sync Output

TTL levels into 50 Ω.

Isolation

40V for Function and Sync.

SINE SPECTRAL PURITY

Spurious Responses<-55 dBc (non-harmonic)
Phase Noise

<

-50 dBc in a 30 KHz band
centered on the carrier.

Subharmonic

<

-50 dBc

Harmonic Distortion<-65 dBcDCto

100 kHz

<

-55 dBc

0.1to1 MHz

<

-40 dBc1to

10 MHz

<

-25 dBc10to

30 MHz

SQUARE WAVE

Rise/Fall Time

<10 ns (10% to 90%)

Asymmetry

1% + 3ns

Overshoot

<5% at full scale output.

RAMPS, TRIANGLE AND ARBITRARY

Rise/Fall Time

35 ns (10 MHz Bessel Filter)

Linearity

±0.1% of full scale output

Settling Time

100 ns to 0.5 % (Full Scale)
of final value.

ARBITRARY WAVEFORMS

Sample Rate

40 MHz/N

Waveform Length

8 to 16,300 points.

Vertical Resolution

12 bits (0.025% of full scale)

Specifications

FREQUENCY RANGE

MODULATION AND SWEEPS

Modulation Frequency, amplitude, phase
Sweeps Linear and log sweeps.

Modulation Functions Sine, ramp, triangle, square and
Modulation Rate 0.001 Hz to 20 kHz

Mod Rate Resolution 2 Digits
Modulation Span AM: 0 to 100%

Markers Two adjustable Sweep Markers.

TIMEBASE

Accuracy ±5 ppm (20 to 30 °C)
Aging 5 ppm/year
Reference Input 2.5, 5 or 10 MHz input.
Timebase Output
Optional Timebase Ovenized oscillator with

GENERAL

Rear Panel Inputs Trigger, External AM and
Rear Panel Outputs Trigger, Modulation, Timebase,
Interface Option RS232 and IEEE-488 interfaces.

Power 50 W, 100/120/220/240 VAC,
Dimensions 8.5"x3.5"x13" (W x H x D)

Weight 10 lbs
Warranty One year parts and labor on

and burst.

arbitrary.

FM and Sweeps: 30.1 MHz
PM: ±7200 degrees

.002 ppm stability and 10-9 per
day aging.

Timebase.
Blank/Lift, Marker and Sweep.
All instrument functions are

controllable over the interfaces.
Arbitrary Waveform Composer
Software (DOS) included at no
additional charge.

50/60 Hz.

materials and workmanship.

What is DDS?

1290-D Reamwood Ave, Sunnyvalle, CA 94089
Phone [phone], Fax [phone]
e-mail: info @thinkSRS.com, www.thinkSRS.com

Direct Digital Synthesis (DDS) is the third generation in waveform synthesis. First generation frequency
synthesizers use a phase-locked loop (PLL) to lock a variable oscillator to a stable reference. Wave-shaping
circuits then produce the desired function. The PLL limits the frequency resolution to about 1:106 and results in
high phase jitter and poor frequency switching response. In addition, the wave-shaping circuits produce large
amounts of harmonic distortion. Second generation arbitrary function generators use a PLL to create a variable
clock that increments an address counter. The counter addresses memory locations in a waveform RAM. The
RAM data is converted by a high speed digital-to-analog converter (DAC) to produce an analog waveform. The
waveform RAM can be filled with any pattern to produce "arbitrary" functions as well as the usual sine, triangle
and ramp. The output is then filtered to remove sampling harmonics. Since the frequency is adjusted by changing
the clock rate, the output filter cutoff frequency must also be adjustable. Second generation PLL designs suffer
from the same phase jitter, transient response and resolution problems as first generation synthesizers.

Direct digital synthesis also generates addresses that are sent to a waveform RAM to producing data for a DAC.
However, unlike previous generations, the clock is a fixed frequency reference. Instead of using a counter to
generate addresses, an adder is used. On each clock cycle, the contents of a Phase Increment Register are added
to the contents of the Phase Accumulator. The Phase Accumulator output is the address to the waveform RAM.
By changing the Phase Increment,
the number of clock cycles needed
to step through the entire waveform
RAM, and thus the frequency, is
changed. Frequency jumps can be
accomplished phase continuously
in only one clock cycle.
Additionally, the fixed clock
eliminates phase jitter and requires
only a simple fixed frequency
anti-aliasing filter at the output.

The DS345 uses a custom Application Specific Integrated Circuit (ASIC) to implement the address generation

circuitry in a single component. The frequency resolution is equal to the resolution
with which the Phase Increment can be set. In the DS345, the phase registers are 48
bits long for an impressive 1:10
modulation control CPU that operates on the Phase Accumulator, Phase Increment
and external circuitry. This allows digital synthesis and control of waveform
modulation. The Modulation CPU uses data stored in the Modulation RAM to
produce amplitude, frequency, phase and burst modulation, as well as frequency
sweeps. All modulation parameters, such as rate, frequency deviation and modulation
index, are digitally programmed.

14

frequency resolution. The ASIC also contains a

By using DDS, the DS345 has greater flexibility and power than conventional synthesizers and arbitrary

Ordering Information

DS345 OPTIONS

30 MHz Synthesized $1595 -01 RS232 and IEEE-488 interface. $495
Function Generator Arbitrary Waveform Composer Software (DOS)

(All prices U.S. list)

-02 High Stability Ovenized Timebase $650

-0345RMS Single Rack Mount Kit $85

-0345RMD Double Rack Mount Kit $85

included at no additional charge.