2012/7/15 Michael Karcher <osmosdr(a)mkarcher.dialup.fu-berlin.de>de>:
Good point, but actually, I am sure it is not an
effect of the tuner
output filter. My USB stick contains a fc0012 tuner, which is always set
to 6MHz bandwidth. The bandwidth of the suspected anti-alias filter
changes clearly when I change the sample rate, though, on the other
hand, if I manipulate the FIR coefficients to contain sharp dips in the
range of hundred kHz, the dip position does not change when I change the
sample rate. This makes me cofident that the suspected anti-alias filter
has to be located in or after the resampling unit.
The only thing I can think of
now is the raised cosine filter used in
digital modulation receivers, but IMHO that should be implemented in
the FIR filter.
--
Francesco Gugliuzza
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