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Re: [Discuss-gnuradio] CPM timing recovery

From: Achilleas Anastasopoulos
Subject: Re: [Discuss-gnuradio] CPM timing recovery
Date: Thu, 07 Jun 2007 09:15:51 -0400
User-agent: Mozilla Thunderbird 1.0.2 (Windows/20050317)


as I explained in my earlier email,
the power you have to raise your signal is not always 2.
If h = 1/4 you need to raise your signal to the power 4.
In general ig h=N/D, you raise it to D.


David Scaperoth wrote:

    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? david
           #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 ()

Achilleas Anastasopoulos                        
Associate Professor
EECS Department               Voice : (734)615-4024
UNIVERSITY OF MICHIGAN        Fax   : (734)763-8041
Ann Arbor, MI 48109-2122      E-mail: address@hidden
URL: http://www-personal.engin.umich.edu/~anastas/      

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