RTL2832U FIR filter

Stefan Sydow st at metafly.info
Sat Jul 14 23:59:55 UTC 2012


Hello Michael,

Am 14.07.2012 21:23, schrieb Michael Karcher:
> This filter has a quite flat passband in the interesting range for DAB
> (-768kHz..+768kHz) but by far not enough attenuation at 1280kHz (which
> will alias to 768kHz at a sampling rate of 2048kHz) to get satisfactory
> adjacent channel rejection. The experimentally observed alias rejection
> is good enough, which lead to the conclusion that there is another
> low-pass filter, which might be part of the resampling unit.

I've got a passband of nearly 2MHz with the original coefficients.
Did I miss a factor 2 somewhere? I tried to construct a narrower filter
using the gnuradio function.

Here is a python script to construct the FIR register and plot the
frequency
response. Maybe the script is also helpful to you.

Regards,
   Stefan
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