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Re: [Discuss-gnuradio] SSB demodulation
From: |
Eric Blossom |
Subject: |
Re: [Discuss-gnuradio] SSB demodulation |
Date: |
Wed, 8 Sep 2004 09:17:47 -0700 |
User-agent: |
Mutt/1.4.1i |
On Wed, Sep 08, 2004 at 07:50:45AM -0700, Johnathan Corgan wrote:
> cswiger wrote:
>
> >Hi All - I'm making wild stabs are writing modules to demod SSB
> >with REAL+IMAG or REAL-IMAG for upper and lower sideband, simply
> >by cloning David Carr's gr_complex_mag module:
>
> You have to phase delay the IMAG (Q) symbol stream by 90 degrees
> (Hilbert transform all-pass filter) prior to the addition or subtraction
> with the REAL (I) symbol stream. (And don't forget to keep them in time
> sync; that is, whatever the sample propagation delay through the Hilbert
> filter is for the Q stream must be accounted for in the I stream prior
> to addition or subtraction.)
See gr_hilbert_fc (python: gr.hilbert_fc). It takes a single float
stream and returns a complex stream. The real component is suitably
delayed, the imaginary component is the hilbert transform. Be sure to
use an odd tap count in the constructor. 37 should be fine.
> This is the "phasing" method of SSB modulation/demodulation, Google has
> many references.
>
> 73 de Johnathan, AE6HO
Eric