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Reply-To: "Kevin Aylward"
From: "Kevin Aylward"
References: <3DDED492.2B9873B0@webaccess.net> <3DDF16D8.90072F5@webaccess.net> <3DDF229B.B85180DD@ieee.org>
Subject: Re: Phase locked loops and confusion.
X-Newsreader: Microsoft Outlook Express 6.00.2800.1106
Date: Sat, 23 Nov 2002 07:27:07 -0000
NNTP-Posting-Date: Sat, 23 Nov 2002 07:27:14 GMT
> Chuck Simmons, John Larkin wrote in part:
>> We looked at an equivalent because the digital team considered that
>> simple. I pointed out that it would limit cycle with larger
>> amplitude than the deadband from somewhat more linear methods. The
>> simulations of the bang bang were unimpressive given the fact that
>> we are locked to edges coming at most at f/6 and on the average of
>> f/12. We are essentially in harmonic lock but the harmonic varies
>> from 6 to a maximum of 28 from edge to edge. Harmonic locking with
>> the additional complication of a loop divider of around 200 makes it
>> really interesting. The bang bang seemed to have trouble with that
>> so we decided to change our approach.
> What are you ultimately controlling with your circuit, an oscillator
> for some sort of communications device? Am I correct in assuming that
> the device frequency being controlled is quite high since you are both
> dividing it by 200 (256?) and locking onto anywhere from the 6th to
> well more than the 12th subharmonic of an already 200X reduced
> frequency? Why do you need to lock onto subharmonics anyway? Are you
> doing frequency hopping as part of an encryption scheme?
> Could you please provide more background information and design
> specifications for whatever it is you are up to. Thanks.
Its pretty standard to lock a GHz clock to a lower frequency one. e.g.
in parallel to serial to parallel communication systems. The || data
might be at say 100Mhz, and the serial line may be at 2.5Ghz.
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