Keysight 33522A Function Generator

We have there are no issues of importance with the reference device. This signal generator is what it sets out to be and it functions in the same way too. However, for professional equipment of this rank you should expect to pay a good €3,000 / £2,775 / $3,580.

Sine-wave signals are generated up to 30 MHz with a sample rate of 250 MHz. The ratio of 12 % allows more than eight grid points per period. The D-to-A converter provides 16-bit resolution. The maximum amplitude amounts to 20 Vpp (Hi-Z) up to 30 MHz without any restriction.

Squarewave signals and pulses are possible up to 30 MHz. Rise and fall times are fixed for square-wave at 8.4 ns; for pulses you can also select larger values.

Ramps are limited to a maximum frequency of 200 kHz here.

Using the DC function you can produce an adjustable DC voltage in the range ±10 V.

The PRBS (pseudo-random bit stream) function is available exclusively on the Keysight product. A noise signal of this kind is very handy for determining bandwidth.

The Keysight generator is the only device that has the sync output on the front panel. There is no frequency restriction, nor any visible jitter.

As to modulation, using the external input signals can be modulated with frequencies up to 100 kHz.

Frequency counter

All three products under review have an integrated frequency counter with a bandwidth of up to 200 MHz. I measured
the sensitivity of each at three different frequencies. Table 1 shows the results. The levels in dBm are valid for Hi-Z (= high-impedance). The last line shows additionally the maximum frequency up to which each counter still works.

All three products can switch between AC and DC coupling. It is also feasible to activate a low-pass filter and set the trigger level. On the PeakTech device you can set the sensitivity in three steps, although this requires a higher level than on the other two examples. Furthermore, only six settings were given — a drawback versus the Rigol product with seven and the generator from Siglent with yet eight positions. There’s another restriction with the frequency counter on the PeakTech device: only the direct frequency is displayed, whereas both of the others can indicate the center, minimum and maximum values. The Rigol function generator shines out as very practical,
with its counter input on the front panel.

For me what is missing on all three devices is a switchable 50-Ω terminating resistor. To avoid signal reflections you will need to use a through-pass termination where appropriate.

Signal quality
For comparing signal quality on each product I set up sinewave signals at 1 and 10 kHz with a level of 1 V RMS and measured them with an audio analyzer. Table 2 indicates the harmonic distortion and Table 3 the headroom between the wanted signal and the combination of distortion and noise. Although the harmonics differed by more than 10 dB, from my point of view not one of the generators is fit to serve as a low-distortion signal source for audio measurements without additional
filtering.

Spectrum test
The spectra of a 10 MHz signal with a level of 0 dBm were measured using a spectrum analyzer. When you make direct measurements the bulk of the first harmonic is attributable directly to the spectrum analyzer account, so a 20 MHz high-pass filter was connected in series. The latter attenuates the 10 MHz signal, making it possible to raise the sensitivity of the spectrum analyzer.

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10. June 2019 by sam
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