Arbitrary waveform and function generators

01

Map the signal to sample rate, bandwidth and resolution

Berkeley Nucleonics' AWG selection chapter starts from the worst-case signal and maps it to specifications: highest frequency sets sample rate, edges set bandwidth, dynamic range sets bits, duration sets memory and parallel emitters set channel count. Nyquist (more than twice the highest frequency) is the floor; it suggests 2.5 times the highest frequency for clean sine reconstruction and 3–5 times for edge fidelity, so a 500 MHz signal calls for 1.25–2.5 GS/s rather than 1 GS/s. [1]

It separates analog bandwidth from sample rate, using rise time × bandwidth ≈ 0.35 (a 110 ps edge needs about 3.2 GHz), and notes the failure modes differ: too little sample rate aliases energy into spurs that move with frequency, too little bandwidth rounds edges and sags amplitude at the top of the band. A 16-bit DAC splits its range into 65,536 levels against 256 for 8-bit, lowering quantisation noise and improving spurious-free dynamic range, but very deep and very fast converters are hard to build together. [1]

Siglent describes vertical resolution as the smallest programmable voltage step, set by the DAC's bits, and notes that maximum sine frequency is not the square-wave limit: its SDG2122X reaches 120 MHz for sine but 25 MHz for square waves, because fast transitions need much more bandwidth. [2]

Give the supplier the highest frequency and fastest edge, amplitude range and load, dynamic range or spur limits, waveform types and modulation, sequence length and sample rate, channel count and synchronisation, triggering, and interfaces.

02

Size memory and check waveform limits

Berkeley Nucleonics' arithmetic: playing one millisecond at 6 GS/s needs six million samples per channel, and one second needs six billion. [1] Siglent gives output frequency = sample rate ÷ samples, so a 1,000-sample waveform at 10 MSa/s repeats at 10 kHz; its SDG2000X series samples at a nominal 1.2 GSa/s and supports point-by-point output of 8 points to 8 Mpts. [2]

Editorial calculation: an 8 Mpt waveform played at 1.2 GSa/s lasts 8 × 10⁶ ÷ 1.2 × 10⁹ ≈ 6.7 ms, repeating at about 150 Hz; reproducing a 300 MHz component at 3–5× would need 0.9–1.5 GS/s by the Berkeley Nucleonics rule. [2] [1]

Rigol lists waveform generators, including multi-channel waveform generation products, among its instruments. [3]

03

Check limits per waveform in a full function generator data sheet

Tektronix's AFG3000C Series data sheet, for a range it states is no longer sold new, shows how one family's limits change by waveform and model. Sine output reaches 10, 25, 50, 100, 150 or 240 MHz by model, square waves stop lower at 5, 25, 40, 50, 100 or 120 MHz, and arbitrary waveforms use 14-bit resolution at 250 MS/s, 1 GS/s or 2 GS/s. On the 240 MHz AFG3251C, square-wave rise and fall time is 2.5 ns or less, harmonic distortion at 1 V p-p is below −60 dBc from 10 Hz to 1 MHz and below −30 dBc from 25 to 240 MHz, and amplitude flatness widens from ±0.15 dB below 5 MHz to ±2.0 dB from 200 to 240 MHz. Every model has ±1 ppm frequency stability from 0 to 50 °C and ±1 ppm per year aging. The general data list 100–240 V supply, under 120 W consumption, a 20-minute warm-up, 0 to +50 °C operating and −30 to +70 °C storage temperature, up to 80% humidity at or below 40 °C, 329.6 × 156 × 168 mm (W × H × D) and 4.5 kg net. [4]

Editorial calculation: ±1 ppm on a 10 MHz output is ±10 Hz. Using the 0.35 rule cited above, a 2.5 ns edge corresponds to about 140 MHz of bandwidth, consistent with a square-wave limit of 120 MHz on a 240 MHz sine model; so a pulse or clock application should be sized on the square and pulse rows, not the headline sine figure. [4] [1]

04

Compare what suppliers offer

The suppliers linked to this page list waveform generators; their cards link to the pages reviewed.

Ask any supplier for sample rate and analog bandwidth per channel, sine, square and pulse limits, rise time, vertical resolution and spurious-free dynamic range, memory depth and sequencing, amplitude range and accuracy, channel synchronisation, modulation types and interfaces.

05

Trace the generator blocks

This is a functional reference built from the sources cited; it is not one maker's specification.

06

Fill the specification fields with values for your signals

A waveform generator quotation needs values for your signals. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.

07

Send the signal and timing data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Signal: [highest frequency; fastest edge; waveform types]
Level: [amplitude; load; dynamic range]
Timing: [sequence length; sample rate]
Channels: [count; synchronisation; triggers]
Interface: [LAN; USB; software]

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