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Mismatching between MATLAB filter design wizard and Linux IIO Scope when halfband filters is used

Question asked by Ivan-Rusov Employee on Nov 21, 2014
Latest reply on Nov 24, 2014 by dpu



I have a following request.


Latest MATLAB filter design wizard 3.0 is used for creating 4 MHz low-pass filter. file is saved to the USB drive. Then it is used for FIR configuration in IIO Scope.

When half-band filters are not used I get normal spectrum. Data rate is 12.288 MSPS.

When 8x half band filters are switched on in debug tab (0xCC in Register 0x2):

I get following spectrum:

When I write 0xDE to Registers 0x2 and 0x3:

And write 0x03 to Register 0xA:

I get:

Where is my mistake? Why when I turn on the HB filters I get distorted spectrum of my signal? Could you please help me to resolve the issue?


My created file you can find in attachment. Xilinx Zync 702 + AD-FMCOMMS3-EBZ is used for evaluation.