Hi Ben, I made some matlab simulation (attached here) of whole process for "compelx PFB_FIR+FFT + Transpose + 2ndFFT" for mkid application before. To just study the PFB's bin width scaling, you can simply use part of the code and play with that parameter in the code to simulate the effects with different setup. By replacing the 2nd FFT with DDC, you can also study your PFB+DDC application.
For the output of complex PFB block, I think 2^N complex input should results in 2^N complex output (some of the real fft block only output 2^(N-1)), and sequencing is same as complex FFT in matlab (output will increas from bin 1 to bin2^N (or we can understand this as from bin 0 to bin2^N -1 and consider bin0 as DC bin)). For the negative frequency bins, depends on how you define them. by switch the between complex(I,Q) and complex(I,-Q) etc, you can get the negative frequency bins at (0 to 2^(N-1)-1) or (2^(N-1) to 2^N-1). Ran > Two quick PFB/FFT questions. > > 1) The bin width scaling parameter in PFB_FIR. Can someone explain how this works? If you increase the bin width, doesn't the output rate of the > PFB need to increase? Does a value of 2 here make the bins twice as wide > as a PFB with bins that are "normally" spaced? > > 2) We are feeding the CASPER FFT complex data with 2^N points. The output > is complex data with 2^(N-1) points. Where did my negative frequencies go? Since the input is complex the negative frequencies are independent of the positive freqs, and I need them! > > Thanks, > Ben > > >
test_pfb_fft_business.m
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test_pfb_fft_business_record_pattern.m
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