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

From: Bob McGwier N4HY
Subject: Re: [Discuss-gnuradio] first attempt at gnuradio - ssb phasing demod
Date: Fri, 10 Mar 2006 11:40:51 -0500
User-agent: Mozilla Thunderbird 1.0.6 (Windows/20050716)

I missed this question for 3 days.  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


Charles Swiger wrote:

On Sun, 2006-03-05 at 00:48 -0500, Robert McGwier wrote:
Almost. Translate the carrier to where you want it to be and then use a complex bandpass filter to pick off the sideband.

make the filter edges    L  < H for your favorite bandwidth  (H-L)

for USB,  make a complex filter   with edges  L, H

for LSB, make a complex band pass filter with edges

-H, -L

Take the real part, make imaginary part = real part.

send complex signal to sound card.

Do we have tools to make complex (negative freq) filter coeffecients?
(other than externally in matlab etc).  I see 'optfir' but looks like
it makes float taps too.


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