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FIR and Tstep

Question asked by xamilla_enst on Dec 5, 2007
Latest reply on Dec 6, 2007 by xamilla_enst
Hi, I have designed a lowpass FIR (order 256) with passband of 30 kHz in the digital filter designer. When I pass a spectrum of signals (from 25 kHz to 150 kHz)through this FIR and plot the spectrum at the output using a spectrum analyzer the FIR acts differently depending on the Tstep size of the FloatToTimed component placed right after the FIR. If  Tstep of 1 us=> only the 25 kHz signal passes, Tstep of 2 us => nothing passes, Tstep of 0.1 us=> all signals passes.

How should this Tstep size be set for the filter to act correctly?

Best regards, Xamilla  

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