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