Re: Digital PLLs: State Space or Classic?

On 3 Jul 2006 20:23:25 -0700, "Randy Yates" <yates@xxxxxxxx> wrote:

Tim Wescott wrote:
[...]
If it's a simple PLL, and if you have to ask, then you should probably
implement the filter in the classic form.

Thanks for responding, Tim.

If anyone can intelligently and informatively discuss the pro's and
con's of each approach, I would appreciate the chance to interact and
learn.

Not sure how much I can add, but I've always used a classic approach
that's consistent with Gardner's PLL analysis. That being said,
there's more than one way to do that, and they're not quite the same.

Gardner's classic analysis was done for continuous, analog loops and
when converting the analysis via LaPlace transforms one must elect
which method to use, e.g., step-invariant, impulse-invariant, etc. The
resulting loops overall behaviors will be quite similar but will
differ in some details.

And I agree with Tim, getting the detector gain sorted out accurately
is pretty important and can be problematic at times. Once you get a
methodology down the loop filter design is trivial, but only if you
get the detector gain right.
Eric Jacobsen
Minister of Algorithms, Intel Corp.
My opinions may not be Intel's opinions.
http://www.ericjacobsen.org
.

Relevant Pages

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