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Time resolution for EVM measurements

Question asked by robristow on Oct 8, 2007
Latest reply on Oct 9, 2007 by robristow
I'm interested to know what baseband digitiser rate we need to provide an accurate measurements of EVM. I am evaluating VSA with a standard PSA analyser which seems to be able to produce data at 15Msps, but a QPSK signal at 3.84Mcps doesn't seem to produce very good EVM results.

Does the VSA software interpolate between measurement samples when it calculates the EVM? It seems to me that if it does not then I will have to run the baseband sample rate at least 16 samples per chip to get close enough to the symbol instants.

What is the recommended sampling rate to make measurements at to get an accurate EVM?