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Re: [Discuss-gnuradio] Hardware sampling rates
From: |
Johnathan Corgan |
Subject: |
Re: [Discuss-gnuradio] Hardware sampling rates |
Date: |
Mon, 22 Mar 2010 07:47:29 -0700 |
On Mon, Mar 22, 2010 at 01:49, Charles Brain <address@hidden> wrote:
> I have tried the fractional interpolator and it just sucks too many CPU
> cycles.
There is one more thing you can try--use the polyphase resampler.
This is a new block by Tom Rondeau based on the Harris book. It
hasn't gotten a lot of use yet, but it is working so far and is very
efficient.
gr.pfb_arb_resampler_ccf(resample_rate, taps, size)
'resample_rate' is your desired interpolation rate
'taps' is the vector of FIR taps to use as the interpolation filter
'size' is the number of phases to use in resampler (default=32)
You can use gr.firdes.* to design a filter to create 'taps'; but the
sample rates to use require special calculation. See:
http://gnuradio.org/redmine/repositories/entry/gnuradio/gnuradio-examples/python/pfb/interpolate.py
...for an example using both the polyphase integral interpolator and
the polyphase arbitrary resampler.
In your case, if I recall correctly, your final output filter is a
root-raised-cosine filter. So you'd use the arbitrary resampler to
upsample to your final output sample rate, and use the RRC tap
generator to create the taps for it.
Johnathan