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Re: [Discuss-gnuradio] CPM timing recovery

From: David Scaperoth
Subject: Re: [Discuss-gnuradio] CPM timing recovery
Date: Thu, 7 Jun 2007 09:04:45 -0400

BTW, are you using the cpm.py hierarchical block that is
on the trunk? If yes, I attach a simple python code that
demonstrates the spectral line generation for a 4-CPFSK
with h=1/2.
I definitely see the spectral lines for your case, which I believe is considered an MSK modulation.  Unfortunately, I cannot assume that the signal will be MSK.  When I change the index to another often used CPFSK index of 1/4, I noticed that the spectral lines go away...
any thoughts?

       #self.connect (self.src,self.b2B,self.mod_old,self.fft_old)
       #self.connect (self.b2B,self.mod_new ,self.fft_new)
       self.connect (self.src,self.b2B,self.mod_new,self.fft_new)
       self.connect (self.mod_new,(self.nonl,0))
       self.connect (self.mod_new,(self.nonl,1))
       self.connect (self.nonl ,self.fft_new1)

if __name__ == '__main__':
   app = stdgui.stdapp (cpm_graph, "test CPM graph")
   app.MainLoop ()

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