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

[John Ackermann N8UR]

Marcus D. Leech said the following on 10/13/2011 09:18 PM:
> 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.
[ snip ]

> 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'm starting with 4, but if my harebrained scheme works, want to 
increase to whatever the CPU will allow.

I've attached a screenshot of my test flowgraph.  It's a linear 
translator that takes a chunk of spectrum down to baseband, then 
retransmits it on a different frequency range -- similar to what the 
amateur satellites do.

What I'm playing with is whether I can improve the transmit efficiency 
by dividing the passband into multiple, independently squelched channels 
so that I'm not amplifying and retransmitting noise where there is no 
real signal present.  For best results, you'd want to have many channels 
(and possibly some means to select adjacent channels), but to start with 
4 is enough to see whether this idea makes any sense at all.

John

> 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).

translator.grc.png
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