Agilent 8904A

Multifunction Synthesizerdc to 600 kHz

Build complex waveforms from common signals

The Agilent Technologies 8904AMultifunction Synthesizer uses thelatest VLSIC technology to createcomplex signals from six fundamentalwaveforms. The standard 8904A digi-tally synthesizes precise sine, square,triangle, ramp, white noise, and dcwaveforms and routes these signals to a single output. Option 001 addsthree more identical internal synthe-sizers (channels) which can eithermodulate the first synthesizer or besummed to the output. Frequency,amplitude, waveform, phase, and des-tination can be independently set foreach synthesizer. Available modula-tion types for channel A include AM,FM, FM, DSBSC, and pulse modula-tion. Option 002 adds a second 50 Ωoutput, providing a second separatesignal for two channel applications.Option 003 adds fast hop and digitalmodulation capability to the 8904A.Option 005 allows multiple 8904As tobe phase synchronized for applica-tions which require the use of morethan one 8904A. Option 006 changesoutput 1 of the 8904A from a 50 Ωfloating output to a 600 Ω, high-powerbalanced output. With this option, the8904A can deliver 10 volts rms into a600 Ω load from 30 Hz to over 100 kHz.All this unique capability makes the8904A a powerful tool for demandingapplications like VOR, ILS, FM Stereo,and communications signaling.

. . . Begins with . . .

Function synthesizerThe Agilent 8904A Multifunction Syn-thesizer delivers synthesizer accuracy,along with six waveforms in a compact,economical package. Broad sinewavefrequency coverage from 0.1 Hz to 600 kHz with 0.1 Hz resolution makethe 8904A ideal for a number of low-frequency applications. In addition tosinewave generation, the 8904A hasfive other standard functions: square,triangle, ramp, dc, and Gaussian whitenoise. Of these five, square, ramp, andtriangle functions are available from 0.1 Hz to 50 kHz. All waveform valuesin the 8904A are DIGITALLY calculatedin real time by Agilent’s Digital Wave-form Synthesis IC. The use of this chipresults in signals with very well-definedaccuracy and exact repeatability. Thismeans unprecedented performance atan unexpectedly low price. Comparedwith analog technologies, drift is elim-inated, accuracy is improved, and thenumber of required adjustments isgreatly reduced.

Modulation source For demanding modulation require-ments, where internal modulationsources of signal generators don’tmeasure up, use the Agilent 8904AMultifunction Synthesizer. With itsdigitally synthesized accuracy andresolution, the 8904A is an ideal, yetlow cost, external modulation sourcefor signal generators. Besides com-mon sinewave modulation, the func-tions of the 8904A can be used to cre-ate more complex modulating signals.For example, use the 8904A to exter-nally modulate a signal generatorwith the noise function while at thesame time using internal modulation.Using this technique accurate degra-dation of the modulation signal-to-noise ratio can be achieved. To accom-modate applications requiring remoteoperation for system use, the 8904Acomes with GPIB as a standard feature.

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The Agilent 8904AMultifunction Synthesizer . . .

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Stimulus for audio circuits The 8904A has many characteristicsand features which make it well suitedas a stimulus for audio circuits. Theoutput of the 8904A is characterizedby low spurious and harmonic content.Total harmonic distortion plus noise(including all spurs) can be as low as–78 dBc. With low distortion, the8904A can be used to test many highperformance audio devices. Anotherunique characteristic of the 8904A isits 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 perform-ance is a real plus for high perform-ance audio test applications. Groundloops can be one of the most difficultproblems to correct in audio tests.The 8904A is equipped with an elec-tronically floating, 50 Ω output ampli-fier which makes overcoming groundloops easy.

Two outputsOption 002 adds a second, identicalsynthesizer and floating output sectionto make the 8904A TWO synthesizersin one half-rack width instrument.Frequency, amplitude, waveform, andphase can be independently set foreach of the two synthesizers. Theflexibility provided by two sources isneeded in a variety of applications.When simultaneous external modula-tion of a signal generator is required,the 8904A Option 002 provides anaccurate, low-cost method of generat-ing two independent modulating sig-nals. Many two-input applications,such as differential amplifier testing,can benefit from the ability of the8904A Option 002 to generate twoindependent test signals at the sametime. Modern ATE systems designedto test complex systems or productsrequire a number of sources to fullystimulate the device being tested. Inthese cases one or more 8904A Option002 Multifunction Synthesizers can beused to provide multiple test signals.Two instruments provide four synthe-sizers and occupy only one 5.25-inchfull rack space.

Phase offset Although both synthesizers are inde-pendent, the relative phase betweenthe two outputs can be precisely con-trolled. Either synthesizer can be var-ied in phase from 0 degrees to 359.9degrees with a resolution of 0.1 degree.Direct digital synthesis ensures accu-rate, repeatable phase differentials.Phase accuracy between outputs isspecified to be better than ±0.1 degreeor 30 ns (whichever is greater) up to100 kHz. Testing phase detectors, servosystems, shaft encoders, sonar, andother phase-sensitive two-port devicesis easy and accurate with the 8904AOption 002. One unique application ofthe 8904A’s phase capabilities is indriving balanced loads or lines. Byoperating the two synthesizers 180degrees out of phase, the 8904A canfunction as a balanced source withmuch higher voltage output capability.In this configuration, the 8904A candeliver +23.8 dBm (12 volts rms) intoa balanced 600 Ω load with a 100 Ωeffective source impedance.

. . . And . . .

Then add another . . .

Complex signal generation By adding three more internal synthe-sizers (two with Option 002) which canmodulate or be summed with synthe-sizer A (channel A), Option 001 is thekey to complex signal generation forthe Agilent 8904A Multifunction Syn-thesizer. All four internal synthesizerscan be set to generate different wave-forms, frequencies, amplitudes, andphases at the same time. These signalscan then be DIGITALLY summed beforerouting to the output. If Option 002 ispresent, channels may be routed toeither of the two outputs. In addition

to summing, Option 001 allows chan-nels B, C, and D to be used as modula-tion sources for channel A. The allow-able modulation types for channel Aare: AM, FM, f M, DSBSC (DoubleSideband Suppressed Carrier), andpulse modulation. Channels B, C, andD can be used to generate up to threeindependent forms of modulation atthe same time, or can be summed priorto channel A modulation. Using sum-mation and modulation, the 8904AOption 001 can generate many complexwaveforms.

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

AM FM F M DSB Pulse

Output 1

Output 2

With Option 002, two units provide fourindependent outputs in one full width rackspace.

CHANNEL B

CHANNEL C

CHANNEL D

S

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

CHANNEL A

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VOR/ILS VOR (VHF Omni Range) signals areused by modern aircraft for naviga-tion. To create accurate VOR com-posite signals, a generator must haveprecise frequency modulation andextremely accurate phase settability.Agilent 8904A Option 001 meets theseneeds easily with mathematically cal-culated frequency modulation and therepeatability of digital phase offsetcontrol. For VOR, channel B is usedto frequency modulate channel A,while channel C is summed with themodulated channel A. The bearingangle can then be changed by alteringthe relative phase of channel C. Theminimum bearing angle resolution is0.1 degree. Since the entire VOR com-posite waveform is “calculated” in realtime by the Digital Waveform SynthesisIC, the 8904A Option 001 can delivertypical bearing accuracy on the orderof ±0.05 degrees. This state-of-the-artperformance is repeatable and driftfree unlike older technology analog VORgenerators. ILS (Instrument LandingSystem) composite signals can also begenerated with digital accuracy withthe 8904A Option 001.

Audio testing With Option 001, the 8904A can gen-erate many different types of test sig-nals used in audio applications. Bysumming or modulating with the fourinternal channels, the 8904A can gen-erate intermodulation test signalswhich conform to international stan-dards. CCIF twin-tone, DIN, andSMPTE intermodulation test signalscan be created with the 8904A. Typicalresidual intermodulation distortion isless than –70 dB. With independentcontrol of all four internal synthesiz-ers, almost any type of IM test signalcan be generated. Another complexsignal often used to test amplifierpower reserves is the IHF DynamicHeadroom test signal. The 8904A cangenerate this signal with synthesizerprecision, low distortion, and exacttiming. In fact, any sinewave burstsignal can be created which will beglitch free with phase continuoustransitions within the frequency reso-lution of the 8904A (0.1 Hz). Anotheruseful signal is a phase-continuouslinear sweep. By using a ramp wave-form to frequency modulate channelA, a linear phase continuous sweepcan be created. Sweep time can bevaried from 10 seconds (ramp at 0.1 Hz)to 20 microseconds (ramp at 50 kHz).Special functions can be set which willreverse the modulating ramp waveformto produce sweeps which change thesweep direction.

FM stereo mode In conjunction with an RF signal gen-erator, the 8904A Option 001 can gen-erate the signals required to test com-mercial FM broadcast stereo receivers.The FM stereo mode included withOption 001 transforms the 8904A intoa dedicated FM stereo encoder. Singlekeystrokes control the audio test tonefrequency, composite signal level, testsignal mode, pilot on/off, and pilotlevel in terms of % of composite level.Test signal modes include Left=Right,Left=– Right, Left Only, and Right Only.The pilot tone amplitude, frequencyand phase, as well as subcarrier fre-quency are fully adjustable. Audiotest tone frequency can be set from20 Hz to 15 kHz in 0.1 Hz increments.Three pre-emphasis curves ensurecompliance with all international stan-dards: 25 µsec, 50 µsec, and 75 µsec.Digital synthesis combined with superbanalog performance yields typicalstereo separation of greater than 65 dBover the full 20 Hz to 15 kHz audiobandwidth. The digital nature of thestereo test signals generated by the8904A eliminates such signal by-prod-ucts as subcarrier leakage and pilottone/subcarrier phase error found inanalog stereo encoders.

. . . And you get complex signal generation . . .

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Communication signaling In addition to the extra channels,Option 001 also adds four sequencemodes to the 8904A: tone sequencemode, DTMF sequence mode, digitalsequence mode, and Hop Ram sequencemode. These modes make the 8904A apowerful tool for generating sequencesused in communications signaling.Tone sequence mode allows entry of16 unique sine wave tones, each withan “on-time” and “off-time.” Fromthese 16 tones, sequences can be builtup to a length of 750 tones. The mini-mum on and off time duration is 800 µswith 10 µs resolution, while the maxi-mum value is 655.35 ms. Timing accu-racy is better than ±20 µs. When no off-time is specified, tone sequence modewill switch to the next tone frequencyin a phase continuous manner withoutdiscontinuities.

DTMF (Dual Tone Multi Frequency)mode allows generation of sequencesup to 750 telephone type signals inlength. In DTMF mode, the 8904A cangenerate the 16 standard frequencypairs as defined by Bell Telephone (Belltechnical reference publication No.48005). Minimum timing periods forDTMF are 1 ms, with 10 µs resolution.

Digital sequence mode can generatedigital bit streams up to 3,000 bits inlength. Minimum period in the digitalmode is 100 µs with 10 µs resolution.On and off “levels” in the digital modecan be set to any value for simulatingdifferent logic families and asserted“high” or asserted “low” logic conven-tions. For ease of entry, data may beentered in binary, octal, or hexadeci-mal formats. All three modes containextensive sequence-editing features,and three control modes: single se-quence, continuously repeat sequence,and manual step-through sequence.

Hop Ram sequence mode offers a mixof the capabilities of the tone and dig-ital sequence modes. This mode allowsentry of 16 signal states, each with anassociated amplitude, frequency, andphase value. Sequences of up to 750tones can be built if all 16 states areused, or up to 3,000 tones if only twoof the states are used. A unique burstfunction allows the pattern to be re-peated a specified number of timesfrom 1 to 127. Unlike the other se-quence modes, Hop Ram sequencemode allows you to use any of the sixstandard waveforms available in the8904A: sine, square, ramp, triangle, dcor white Gaussian noise. Instead ofselecting the timing in terms of milli-seconds, Hop Ram sequence mode setstiming in terms of frequency. Thisallows the generation of patternswhich have precise baud rates suchas 1200, 2400, 4800, or 9600.

AM FM F M DSB Pulse

Output 1

Output 2

CHANNEL B

CHANNEL C

CHANNEL D

S

External . Freq Phase AmpTiming

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. . . Fast hop Option 003 adds the ability to hop the8904A in frequency, phase, and/oramplitude. Up to 16 frequency/phase/amplitude states can be entered intothe “Hop Ram” memory. To hop, anexternal device must address the four-bit TTL-level address bus provided onthe digital port connector on the rearpanel. As the address supplied to thebus is varied, the 8904A will hop tothe frequency/phase/amplitude statethat corresponds to that address of theHop Ram memory. Fast hop can onlybe performed on channel A. Phasecontinuous frequency switching canbe done in as little as 8 µs. Since thesignals are digitally created, there is no

settling time like traditional PLL syn-thesizers. Only the cycle time of theDigital Waveform Synthesis IC deter-mines the switching speed. Controlfunctions allow you to enable or disableany one of the three hop parameters.For example, phase and amplitude hopcan be disabled to produce only fre-quency hopping without having toremove the phase and amplitude hopdata from the Hop Ram. If Option 001and 003 are installed, the other threechannels can be used while hopping.Channel B, for example, could be set tophase modulate channel A with noisewhile channel A is hopping. This setupallows controlled amounts of “phasenoise” to be added to the hopping signal.

. . . Digital modulation One application for Option 003 is thecreation of digital modulation formats.By hopping frequency, FSK and otherfrequency switching type modulationformats with up to 16 frequencies canbe generated. BPSK, QPSK, and otherphase shifting formats can be made byhopping just phase. With a combina-tion of amplitude and phase hopping,the 8904A Option 003 can generateQAM signals with up to 16 phaseamplitude states. The digital datamust be supplied to the digital con-trol port in a four-bit wide parallelword to control the timing.

Add external timing control to get . . .

Option 003 adds externaltiming control for fast hopor digital modulation

CHANNEL A

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. . . Phase synchronization With Option 005, multiple 8904As canbe phase synchronized to provide morethan two channels of phase relatedoutputs. In the synchronous mode,one unit is specified to be the “master”and all others are designated “slaves.”Two signals from the master unit (syncclock and phase reset) are routed toexternal power splitters which dividethe signals to the slave units. When aphase reset command is issued fromthe master, via the front panel or GPIB,all units reset to their specified phaserelationships. In this mode all con-nected units are phase locked andwill not drift relative to each other.Whenever the frequency, destination,or angle modulation amplitude arechanged on any of the units, a phasereset must be issued on the masterunit to restore proper phase. In thesynchronous mode, the phase accuracyfrom unit to unit is specified as anadditional 30 ns error for frequenciesfrom 0.1 Hz to 100 kHz. This yields atotal specification of the larger of ±0.1 degree or 60 nsec for the samefrequency range. Using low-loss powersplitters, up to eight units can be syn-chronized for a total of 16 phaserelated outputs if the units have Option 002. If more signals are desired,amplifiers can be inserted before thepower splitters to increase the numberof synchronized units. Because theextra cables required for synchronousoperation use the mounting holesnormally reserved for rear panel out-puts, Option 004 (rear panel outputs)cannot be ordered with Option 005.Option 005 solves many tough testingproblems by providing a high perform-ance yet low cost solution to generat-ing many phase related signals. Forexample, testing three phase powerline devices requires the generationof three voltage and three currentwaveforms which are phase related.With Option 005, three 8904As with

Option 002 and 005 can be used togenerate the required signals. Acousticsand sonar work also require largenumbers of phase related signals. WithOption 005, the 8904A can be used toprovide a cost effective solution forthese demanding applications.

Or add 600 Ω balanced outputOption 006 replaces the standard 50 Ωelectronic floating output (output oneonly) with a transformer coupled 600 Ωoutput, This balanced, fully floatingoutput delivers higher power into 600 Ω loads than the standard 50 Ωoutput. The maximum signal level is afull 10 volts rms into a 600 Ω load (20volts rms open circuit). The Option 006output is specified for sinewaves onlyand covers the frequency range of 30 Hz to 100 kHz.

Output frequencies above 100 kHz areavailable up to 200 kHz with a typicalrolloff of –4 dB at 200 kHz. Option 006is ideal for applications requiring truebalanced operation or the higher signallevels commonly required in 600 Ωaudio systems. Because of the band-limited nature of a transformer cou-pled output, Option 006 cannot pass dcor low frequency signals, and causeswaveform distortion when passingsquare or ramp waveforms. The trans-former adds little distortion above 300 Hz preserving the excellent spec-tral purity of the standard 8904A. TheOption 006 output also has degradedphase linearity compared to the excel-lent phase linearity of the standard 50 Ω output. Option 004, rear paneloutputs is not available when Option006 is ordered.

Phase synchronization or add 600 Ω output

8904A Master

8904A Slaves

Phase Reset Sync Clock

Sync Clock Output

Phase Reset Output

Phase Reset In

Sync Clock In

Phase Reset In

Sync Clock In

Phase Reset In

Sync Clock In

Phase Reset In

Sync Clock In

Low-loss power splitters*

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Agilent digital technology:Unparalleled performance at anunprecedented priceThe Agilent 8904A’s Digital WaveformSynthesis IC uses Agilent’s propri-etary CMOS high-density VLSIprocess. With 100,000 transistors,this IC realizes four complete wave-form synthesizers, plus a host of sup-port functions, on a single chip. TheDigital Waveform Synthesis IC allowsthe 8904A to generate complex wave-forms with accuracy and repeatabilitynot found in traditional analog func-tion generators or multi-phase-lock-loop synthesizers. In addition, driftand power consumption are reducedwhile reliability is increased (over400 MSI TTL chips would be requiredto emulate the function of the DigitalWaveform Synthesis IC).

Abbreviated specifications

Frequency rangeSine wave: 0.1 Hz to 600 kHzSquare, triangle, ramp: 0.1 Hz to 50 kHz

AC amplitudeRange: 0 to 10Vp-p into a 50 Ω loadAccuracy (sine wave): 1%, 0.1 Hz to 100 kHzFlatness (>630 mVp-p, 1 kHz reference): ±0.009 dB, 0.1 Hz to 100 kHz

DC amplitudeRange: 0 to ±10V open circuit

THD+N (amplitude >50 mV rms, 80 kHz BW, sine wave)– 66 dBc rms, 20 Hz to 20 kHz (30 kHz BW to 7.5 kHz)

Phase (sine wave)Range: 0 degrees to 359.9 degrees

Gaussian noiseSpectral characteristic: Equal energy per unit bandwidth (“white”)

Option 001 specifications Modulation (with Option 001)

Modulation for channel A ONLY, and specified for sine wave carrier and modulation.External modulation is NOT possible.

Modulation types: AM, FM, f M, Pulse, and DSBSC

Summation (with Option 001)Two, three, or four channels may be summed into a single output. Two or three channelsmay be summed for modulation of channel A.

Sequence Sequence modes: Tone, DTMF, and Digital sequence modesSequence length: 250 tones for Tone and DTMF modes; 1,000 bits for Digital modeTiming resolution: 10 µs

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Backlit liquid crystal dis-play presents all informa-tion in easy-to-understandalphanumeric screens.Tone, DTMF, Digital, andHop Ram sequence modesavailable with Option 001are ideal for generating sig-nalling sequences used incommunication systems.

Softkeys provide simplecontrol of operating modesand sequence functions.Step through all displayscreens with NEXT/LASTkeys.

All waveforms, phase off-sets, frequencies, fine levelsettings, and modulationtypes are created by directdigital synthesis which yieldsoutstanding accuracy andrepeatability.

Full GPIB* control for ATEand automated productiontest.

* GPIB: Not just IEEE-488, but the hard-ware, documentation and support thatdelivers the shortest path ot a meas-urement system.

Six standard digitally createdwaveforms: sine, ramp, trian-gle, square, white Gaussiannoise, and dc. Calibrationquality AM, FM, f M, DSBSC,and Pulse Modulation onchannel A.

Thirty-five storage registerssave data for a given con-figuration, making repeti-tive tasks easy.

Keypad for entering param-eters and signallingsequences.

One electronic floating 50 Ωoutput is standard. Option002 adds a second identical50 Ω output; Option 006converts output 1 into ahigh power 600 Ω balancedoutput (30 Hz to 100 kHz).

Front panel features

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GPIB implementationincludes powerful querrymodes to determine instru-ment settings.

Digital port provides zero-crossing pulse and polaritysquarewave outputs for allfour internal channels.

With Option 001, a TTL-levelline on the digital port canbe sued to start Tone, DTMF,Digital, or Hop Ramsequences.

Option 003 adds the capa-bility to fast hop frequency,phase, and amplitude by ad-dressing the four-bit addressbus on the digital port.

Rear panel features

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