Re: [Discuss-gnuradio] multi-band receiver

[Matt Ettus]

>
> In this example (and indeed, in the code for the analysis_filterbank),
> we divide a 1MHz band exactly into 25 kHz channels. However, the
> channels at the edge will be attenuated (cite: Matt's email of yesterday
> 12:11 AM PST). I therefore oversampled the desired passband by 33%,
> which causes the resulting wideband signal to not divide evenly into
> channel-sized chunks.
>
> If I do some sort of 3/4 resampling should the passband quality suffer?

The simple way to think about this is that you have an RF bandwidth of
the overall composite signal (let's say 4MHz), and you have the SPACING
of each channel (not necessarily the bandwidth), say 25 kHz.  So the
math is -->  4Mhz/25kHz = 160.  So you need a 160 point filterbank.   It
doesn't matter how many of those channels are  occupied and oversampling
is not an issue.  It doesn't matter how wide the individual signals are
either.  In the case of the pagers, the signals are 16 kHz wide, but the
spacing is 25kHz, and so we use 25 kHz channels.

To be more specific, we are creating polyphase analysis and synthesis
filterbanks based on the FFT.

Matt