Atec 8904A User Manual

Agilent 8904A

Multifunction Synthesizer
dc to 600 kHz

Build complex waveforms from common signals

The Agilent Technologies 8904A
Multifunction Synthesizer uses the
latest VLSIC technology to create
complex signals from six fundamental
waveforms. The standard 8904A digi­tally synthesizes precise sine, square,
triangle, ramp, white noise, and dc
waveforms and routes these signals
to a single output. Option 001 adds
three more identical internal synthe­sizers (channels) which can either
modulate the first synthesizer or be
summed to the output. Frequency,
amplitude, waveform, phase, and des­tination can be independently set for
each synthesizer. Available modula­tion types for channel A include AM,
FM, F M, DSBSC, and pulse modula-

tion. Option 002 adds a second 50 Ω

output, providing a second separate
signal for two channel applications.
Option 003 adds fast hop and digital
modulation capability to the 8904A.
Option 005 allows multiple 8904As to
be phase synchronized for applica­tions which require the use of more
than one 8904A. Option 006 changes

output 1 of the 8904A from a 50 Ω
floating output to a 600 Ω, high-power

balanced output. With this option, the
8904A can deliver 10 volts rms into a

600 Ω load from 30 Hz to over 100 kHz.

All this unique capability makes the
8904A a powerful tool for demanding
applications like VOR, ILS, FM Stereo,
and communications signaling.

. . . Begins with . . .

Function synthesizer

The Agilent 8904A Multifunction Syn­thesizer delivers synthesizer accuracy,
along with six waveforms in a compact,
economical package. Broad sinewave
frequency coverage from 0.1 Hz to
600 kHz with 0.1 Hz resolution make
the 8904A ideal for a number of low­frequency applications. In addition to
sinewave generation, the 8904A has
five other standard functions: square,
triangle, ramp, dc, and Gaussian white
noise. Of these five, square, ramp, and
triangle functions are available from

0.1 Hz to 50 kHz. All waveform values
in the 8904A are DIGITALLY calculated
in real time by Agilent’s Digital Wave­form Synthesis IC. The use of this chip
results in signals with very well-defined
accuracy and exact repeatability. This
means unprecedented performance at
an unexpectedly low price. Compared
with analog technologies, drift is elim­inated, accuracy is improved, and the
number of required adjustments is
greatly reduced.

Modulation source

For demanding modulation require­ments, where internal modulation
sources of signal generators don’t
measure up, use the Agilent 8904A
Multifunction Synthesizer. With its
digitally synthesized accuracy and
resolution, the 8904A is an ideal, yet
low cost, external modulation source
for signal generators. Besides com­mon sinewave modulation, the func­tions of the 8904A can be used to cre­ate more complex modulating signals.
For example, use the 8904A to exter­nally modulate a signal generator
with the noise function while at the
same time using internal modulation.
Using this technique accurate degra­dation of the modulation signal-to­noise ratio can be achieved. To accom­modate applications requiring remote
operation for system use, the 8904A
comes with GPIB as a standard feature.

2

The Agilent 8904A
Multifunction Synthesizer . . .

3

Stimulus for audio circuits

The 8904A has many characteristics
and features which make it well suited
as a stimulus for audio circuits. The
output of the 8904A is characterized
by low spurious and harmonic content.
Total harmonic distortion plus noise
(including all spurs) can be as low as
–78 dBc. With low distortion, the
8904A can be used to test many high
performance audio devices. Another
unique characteristic of the 8904A is
its exceptional level flatness. From

0.1 Hz to 100 kHz, the 8904A offers
±0.009 dB level flatness relative to
1 kHz. This state-of-the-art perform­ance is a real plus for high perform­ance audio test applications. Ground
loops can be one of the most difficult
problems to correct in audio tests.
The 8904A is equipped with an elec-

tronically floating, 50 Ω output ampli-

fier which makes overcoming ground
loops easy.

Two outputs

Option 002 adds a second, identical
synthesizer and floating output section
to make the 8904A TWO synthesizers
in one half-rack width instrument.
Frequency, amplitude, waveform, and
phase can be independently set for
each of the two synthesizers. The
flexibility provided by two sources is
needed in a variety of applications.
When simultaneous external modula­tion of a signal generator is required,
the 8904A Option 002 provides an
accurate, low-cost method of generat­ing two independent modulating sig­nals. Many two-input applications,
such as differential amplifier testing,
can benefit from the ability of the
8904A Option 002 to generate two
independent test signals at the same
time. Modern ATE systems designed
to test complex systems or products
require a number of sources to fully
stimulate the device being tested. In
these cases one or more 8904A Option
002 Multifunction Synthesizers can be
used to provide multiple test signals.
Two instruments provide four synthe­sizers and occupy only one 5.25-inch
full rack space.

Phase offset

Although both synthesizers are inde­pendent, the relative phase between
the two outputs can be precisely con­trolled. Either synthesizer can be var­ied in phase from 0 degrees to 359.9
degrees with a resolution of 0.1 degree.
Direct digital synthesis ensures accu­rate, repeatable phase differentials.
Phase accuracy between outputs is
specified to be better than ±0.1 degree
or 30 ns (whichever is greater) up to
100 kHz. Testing phase detectors, servo
systems, shaft encoders, sonar, and
other phase-sensitive two-port devices
is easy and accurate with the 8904A
Option 002. One unique application of
the 8904A’s phase capabilities is in
driving balanced loads or lines. By
operating the two synthesizers 180
degrees out of phase, the 8904A can
function as a balanced source with
much higher voltage output capability.
In this configuration, the 8904A can
deliver +23.8 dBm (12 volts rms) into

a balanced 600 Ω load with a 100 Ω

effective source impedance.

. . . And . . .

Then add another . . .

Complex signal generation

By adding three more internal synthe­sizers (two with Option 002) which can
modulate or be summed with synthe­sizer A (channel A), Option 001 is the
key to complex signal generation for
the Agilent 8904A Multifunction Syn­thesizer. All four internal synthesizers
can be set to generate different wave­forms, frequencies, amplitudes, and
phases at the same time. These signals
can then be DIGITALLY summed before
routing to the output. If Option 002 is
present, channels may be routed to
either of the two outputs. In addition

to summing, Option 001 allows chan­nels B, C, and D to be used as modula­tion sources for channel A. The allow­able modulation types for channel A
are: AM, FM, fM, DSBSC (Double
Sideband Suppressed Carrier), and
pulse modulation. Channels B, C, and
D can be used to generate up to three
independent forms of modulation at
the same time, or can be summed prior
to channel A modulation. Using sum­mation and modulation, the 8904A
Option 001 can generate many complex
waveforms.

4

Then add two more . . . and sum . . . and modulate . . .

AM FM F M DSB Pulse

Output 1

Output 2

With Option 002, two units provide four
independent outputs in one full width rack
space.

CHANNEL B

CHANNEL C

CHANNEL D

S

Option 001 adds three internal synthesizers
(two in conjunction with Option 002) which
can modulate or be summed with channel A.

CHANNEL A