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Re: [Discuss-gnuradio] first attempt at gnuradio - ssb phasing demod

From: Robert W McGwier
Subject: Re: [Discuss-gnuradio] first attempt at gnuradio - ssb phasing demod
Date: Fri, 10 Mar 2006 14:24:04 -0500
User-agent: Mozilla Thunderbird 1.0.6 (X11/20050715)

We are giving away all the secrets. The only secrets in SDR DSP are how to make a complex filter and how to overlap-NNN based convolution of an FIR. All the rest is glue logic.



Charles Swiger wrote:
On Fri, 2006-03-10 at 11:40 -0500, Bob McGwier N4HY wrote:
I missed this question for 3 days.

it took 3 days to hit the list

Yes we do.  And here is how it works

It makes a real, low pass filter with cutoff


and then spins the coefficients to the correct frequency using a complex sinusoid.

It is used in a few places in usrp_wfm_rcv_pll.py

Oh - found it - cool. There it is in blksimpl/wfm_rcv_pll.py:

    stereo_carrier_filter_coeffs = gr.firdes.complex_band_pass(20.0,

can make this beautiful response:

Voila, single-sideband.

BTW I recently fixed a broken decimation rate (11 -> 16) in Mike's
examples apps/hf_radio - now is sounds much better.


Robert W. McGwier, Ph.D.
Center for Communications Research
805 Bunn Drive
Princeton, NJ 08540

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