Re: [Discuss-gnuradio] GRC Polyphase Channelizer examples?

[Marcus D. Leech]

On 10/13/2011 09:11 PM, John Ackermann N8UR wrote:
> Is there a (hopefully simple) example of using the polyphase 
> channelizer block in grc?
>
> I'm trying to do a simple case of dividing a 250 kHz wide stream from 
> USRP into a small number (initially 4) of contiguous channels.  Given 
> my generally ignorant status, I'm stumped on setting the parameters.
>
> e.g. --
>
> (a) is the "taps" param an integer or is it a firdes function as in 
> the xlating FIR filter?
>
> (b) what is the oversample param used for?
>
> (c) what is the sample rate of each of the output channels -- it 
> doesn't appear to be the same at the sample rate at the input, or 
> alternatively my parameters are so far off that what's coming out of 
> the thing is absolute junk (when I feed it into a USRP sink set to 
> 250ksamples, I get screens of underruns).
>
> Thanks,
>
> John
If it's only 250Khz wide, and you only need four, have you tried 4 
discrete freq-xlating FIR filters?  They're fairly easy to use, and can
  produce a baseband output at a decimated rate.

I haven't yet figured out how to use the polyphase channelizer because I 
almost never have the N equi-spaced channels problem in
  my fields of interest.  So, discrete filters it is (sometimes a 
hierarchy of discrete filters).


>


--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org