Re: Software PLL (SPLL)

Started by Ron N. February 9, 2006
Terry Given wrote:
> Ron N. wrote: > > Tim Wescott wrote: > >>Implementing a PLL in software uses the same basic theory as > >>implementing a PLL in hardware -- you compare your synthesized signal to > >>a reference, generate a phase difference, then servo the frequency of > >>your synthesized signal to your reference.
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> > Why? Isn't a software PLL just a forward interpolator. Why not just > > estimate (statistical, FFT, phase vocoder or otherwise) the frequency, > > phase, derivatives of phase, etc.; generate a forward interpolation of > > the input reference using that information, and call that the output of > > the PLL NCO? Recalculate periodically (every sample if the compute > > power is available).
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> you would have to work quite very to match, let alone beat, the > performance you can get from a software PLL, requiring negligible > computational overhead. > > swatting flies with Howitzers often causes more problems than it solves.
If a simple feedback PLL is such a good solution, why isn't it used more often for general frequency estimation and interpolation problems? IMHO. YMMV. -- rhn A.T nicholson d.0.t C-o-M