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PSA opt. B7J, saving IQ waveforms

Question asked by hudla on Oct 6, 2008
Latest reply on Nov 7, 2008 by hudla
Hi all,

I'm wondering what are the details of capturing IQ traces with opt. B7J of a PSA spectrum analyzer. In the manual I read that the input signal is first downsampled (to which frequency? the IF frequency 321.4 MHz?) and then sampled with an arbitrary sample rate according to user setting. When I'm capturing RF modulated signals with low symbol rates (e.g. 50 ksymbols/s), then the captured I, Q traces exported to a text file always contain some higher-frequency superimposed signal (I guess around 1.7 MHz) and I have to manually filter the data to obtain actual I, Q components of the signal. The IF BW is set to max. (8 MHz) and the captured signal is e.g. a basic 16QAM signal, filtered RRC 0.35 with bandwidth much lower than 8 MHz, so B7J should be able to capture this signal properly. The epoch length was 15000 samples (1 ms).

I don't have opt. 241 for calculating signals' error parameters so I need to capture the I, Q traces as precise as possible to make the analysis by my own (of course, the I, Q traces which I see on the screen were obtained by some complicated digital processing and contain some sources of error, however I have to "trust" PSA that this job was done properly).

Thanks for any suggestions,
Martin  

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