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Re: [Discuss-gnuradio] FLL Band-Edge Detectors: Literature?


From: Martin Braun (CEL)
Subject: Re: [Discuss-gnuradio] FLL Band-Edge Detectors: Literature?
Date: Tue, 2 Oct 2012 15:01:14 +0200
User-agent: Mutt/1.5.21 (2010-09-15)

On Mon, Oct 01, 2012 at 05:17:33PM -0400, Tom Rondeau wrote:
> Yes, harris' book is the best to start with. There is another paper
> from him called "Let's Assume the System is Synchronized" that also
> goes over it. I'm not sure if he's published a paper that discusses
> the specifics of the filter derivation, yet, though. It's based on the
> derivative of the half cosine waveform of the  RRC filter rolloff. The
> system behaves much better this way than just generating any random
> band edge filter.
> 
> In theory, this should work for any signal using an RRC pulse shaping.
> For specific constellations, you could use a Costas loop with a wider
> lock in bandwidth to handle the frequency offset.
> 
> Oh, and I might be the only one who calls this the "FLL band edge
> filter" specifically to point out that this is only one possible
> implementation of an FLL for coarse frequency tracking. Other
> algorithms are welcome :)

Thanks for these pointers. For future reference (and the mailing list
archives):

* The paper "Let's Assume the System is Synchronized" is a good
  introduction and provides a great and simple explanation.
* Harris' book "Multirate Signal Processing: for communication systems"
  is the more complete version, down to polyphase implementation
  details.
* I should have realized this is a way to implement an ML Frequency
  correction for RRC spectra without a-priori knowledge. This is more
  generally derived in "Synchronization techniques for digital
  receivers" by Mengali/D'Andrea[1], and probably many other places.

M

[1] In general, Fred Harris books and papers are more fun to read,
    though.

-- 
Karlsruhe Institute of Technology (KIT)
Communications Engineering Lab (CEL)

Dipl.-Ing. Martin Braun
Research Associate

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Phone: +49 721 608-43790
Fax: +49 721 608-46071
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KIT -- University of the State of Baden-W├╝rttemberg and
National Laboratory of the Helmholtz Association

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