I am trying to simulate aliasing effect of an 5GSa/s digitizer sample rate using my 80GSa/s oscilloscope (DSO-X 90164A). I wonder how does the oscilloscope acheive an analog bandwidth reduction from 16GHz to 4GHz? I wonder where could I find the Bode plot of the internal antialiasing filter?
Edited by: antony_css on Feb 17, 2015 8:26 PM
Edited by: antony_css on Feb 17, 2015 8:27 PM
Edited by: antony_css on Feb 17, 2015 8:26 PM
Edited by: antony_css on Feb 17, 2015 8:27 PM
- There is anti-aliasing built into the scope, but it only works at the highest sample rates. If you sample at 5GSa/sec, there is no anti-aliasing. A 2GHz sine wave will look a lot like a 3GHz sine wave, in both time and frequency domain.
- Similarly, if you decimate an 80GSa capture, here will be no anti-aliasing.
- When the scope is using "Bandwidth Limit" mode, it's doing that with a digital filter after acquisition. The A/D is still seeing full BW signals.
- Even though it appears to work, don't use reduced sample rates with "Bandwidth Limit" mode
- The Bode Plots are not available, but you can create your own. Capture a very fast edge, the faster the better. Create a function to differentiate that capture (that turns the edge into a pulse). Create a function to do an FFT of the pulse. The scope provides a fast edge on the Cal Out signal. Use the best cable and adapters you have. For best results, you should average the FFT with another function.
Some of the above is from memory. I have not gone back into the technical documents to verify everything.
Al
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