Waveform generator limitations

Question

I have linked the analog output to the analog input as part of testing and getting to know the Bitscope Micro. When generating lower-end frequencies (sine wave in this case) the received waveform is quite clean.

However when setting the frequency to the top of the range, it looks like some harmonics are being introduced. Also when using square waves, there is considerable overshoot on the transitions.

Therefore, is there some practical limit to the frequency the waveform generator can be used to get 'clean' waveforms?

Alternatively, am I just seeing a poorly compensated 'probe' (especially with the square wave)? If that is gthe case, is there a way to adjust the probe compensation (as there is typically with a 'normal' DSO probe)?

Susan

scottiebabe · Accepted Answer

It appears the Bitscope Micro runs the waveform generator DAC at a sample rate of 1 MHz (Not exactly sure). So without any additional filtering on the output I wouldn't expect to see "clean" sine waves really past 10 kHz.

Depending on how detailed of an answer you are looking for, you can take a look at: https://www.analog.com/media/en/training-seminars/design-handbooks/Technical-Tutorial-DDS/Section2.pdf to define an exact distortion specification.

If you can add an RC reconstruction filter to reject some of the sample images you will see the sine distortion improve.

Probe Compensation: I have never used a Bitscope scope so I'm not really sure, but probe compensation would only apply to a 10x probe, I'm not sure if that is what is included with the scope.

All the best!

Jan Cumps · Answer

I expect that the signal integrity will be closer to expectation if it's properly terminated with 50 Ohm just before the input.

Waveform generator limitations

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