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Re: [Discuss-gnuradio] atsc_cpll finally works

From: Charles Swiger
Subject: Re: [Discuss-gnuradio] atsc_cpll finally works
Date: Sun, 25 May 2008 08:15:22 -0400

On Sat, 2008-05-24 at 21:13 -0400, Achilleas Anastasopoulos wrote:
> Chuck, Eric,
> I think there is a way to perform the cPLL at 8 complex Msps and 
> upsample to 16Msps only at the very end when you want to get the Real 
> signal out for further processing. I believe this works (i didn't see 
> any point where there is a possibility for aliasing) and it can result 
> in some savings in complexity without sacrifising performance.
> Hopefully I didn't miss anything big...
> Take a look at the block diagram here:
> http://www.eecs.umich.edu/~anastas/gnuradio/pll.png

That is interesting - for what it's worth, from empirical testing,
Eric's interpolator actually worked with a rx-clock / symbol rate ratio
of 1.487 = 16 / 10.76, altho with a few more visible errors, and using a
really good signal (a 17 element beam a few hundred yards away from a
100kw transmitter ;).


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