Re: [Discuss-gnuradio] SSB demodulation

[Eric Blossom]

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