[time-nuts] PLL Digital Loop Filter
paulswedb at gmail.com
Tue Mar 21 11:19:22 EDT 2017
Have to say a search for PLL book by Best generates lots of stuff. None of
it about PLLs. Better hint please? I think Lyons may be a bit better.
On Tue, Mar 21, 2017 at 7:39 AM, Attila Kinali <attila at kinali.ch> wrote:
> On Mon, 20 Mar 2017 21:32:28 -0700
> James Peroulas <james at peroulas.com> wrote:
> > I'm trying to understand how to design and analyze the loop filters in a
> > digital PLL. Specifically, because of digital processing delays, the
> > offset measured at time t will only produce a change on the VCXO input at
> > time t+T, where T is the sampling period of the digital loop.
> You have the same delays in analog filters as well. As a rule of thumb
> you can assume that the delays are in the same order of magnitude as
> with the equivalent analog filters, not accounting for the delays due to
> pre- and post-processing of the signal.
> The analysis of digital PLLs works the same as with analog ones, you
> just exchange the Laplace transform with the Z-transform. You can add
> arbitrary delays due to pre/post-processing as a simple multiplication
> by 1/z for each clock cycle of delay.
> > I've found plenty of texts describing analog loop filters. Are there any
> > recommendations for digital loop filter PLL design?
> The PLL book by Best contains two chapters on how to design digital PLLs.
> I can also recommend "Understanding digital signal processing" by Lyons,
> which is a very hands-on description how to do filters and perform other
> signal processing tasks.
> Attila Kinali
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