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Re: [Discuss-gnuradio] PFB Filterbank & arbitrary resampler

From: Tom Rondeau
Subject: Re: [Discuss-gnuradio] PFB Filterbank & arbitrary resampler
Date: Mon, 5 Sep 2011 12:55:41 -0400

On Sun, Sep 4, 2011 at 11:33 AM, Ryan Pape <address@hidden> wrote:
We are successfully using the PFB filterbank to channelize 1-6mhz into a variety of channel widths (25K, 50K etc).
In one application, we have 25K channels which are then resampled using PFB resampler to 19.2K fed into gmsk_demod @ 9600bps with 2sps.
In this case, we may have 20-40 ports "active" (not null sink) with pfb resamplers connected to each.
Is there  way to perform this resampling in the filterbank to avoid the need for many separate resampler blocks in an effort to improve performance?
We are pushing the limits of hardware already, so any efficiencies are helpful.  We will consider a hierarchical filterbank structure if necessary, but our first goal is to do it with one filterbank, if possible.

What you are talking about is possible, but not with the current implementation of the GNU Radio channelizer. fred harris has recently published a few papers on doing arbitrary channel / arbitrary bandwidth channelizers that should meet your needs, but it would have to be programmed up.

Now, that having been said, there is a way to handle this. If you have a 9600 bps signal in a 25 ksps channel, you can switch to using the gr_pfb_clock_resampler_fff block, which allows you to specify a real number for the number of samples per symbol (2.6042 in this case) instead of integers. That should do the trick.


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