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From:
Ghost Op <address@hidden>
Date: Fri, May 5, 2017 at 1:31 PM
Subject: Frequency vs time domain Filtering Anomaly
To:
address@hidden
Hi everyone,
I'm trying to sort out a discrepancy I'm seeing between a
frequency domain and time domain version of the same
filter. What I'm running into is that my frequency domain
implementation is a match for the GNURadio response,
however in the time-domain version, while the filter band
looks the same, the frequency domain version seems to
remove more of the out-of-band signal by about 35 dB.
You can see it in the screenshot below:
In my experience with code my first assumption is I'm
doing something wrong. But before I go on a bug hunt, I
wanted to check with those of you who have worked with
both time and frequency filters to see if my assumption
that the two should be exact matches is accurate or if
the result is as expected. My understanding is that
applying the same filter in either the time or frequency
domain should produce the same output, and this doesn't
quite look "the same" enough to me. Does the
forward/reverse FFT process in the frequency domain
version cause some resolution/loss?
Any thoughts?