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Re: [Discuss-gnuradio] CQPSK and raised cosine filters
From: |
Eric Blossom |
Subject: |
Re: [Discuss-gnuradio] CQPSK and raised cosine filters |
Date: |
Wed, 27 Oct 2004 20:29:02 -0700 |
User-agent: |
Mutt/1.5.6i |
On Wed, Oct 27, 2004 at 09:33:56PM -0500, Rick Parrish wrote:
> Is anyone out there working one these?
>
> 1. CQPSK
No, but we'd love it if you did!
> 2. raised cosine (or root-raised cosine) filters
We've got root raised cosine. I though we had raised cosine too, but
apparently we haven't needed it yet. In any event, you determine the
taps using :
taps = gr.firdes.root_raised_cosine (gain, sampling_freq, symbol_rate,
alpha, ntaps)
then use
filter = gr.fir_filter_fff (decim, taps)
to instantiate the signal processing block.
See http://www.gnu.org/software/gnuradio/doc/classgr__firdes.html
> I've got a working clock pulse recovery PLL for CQPSK but I'm wondering
> if running the data through a raised cosine filter will improve S/N for
> the final decoded result. The application is APCO Project 25 two-way
> voice communications.
It's been a while since I looked at the specs, but a matching filter
on each end wouldn't be a surprise.
Eric