Re: simple frequecny multiplier

On Thu, 07 Apr 2005 04:33:04 GMT, "colin"
<no.spam.for.me@xxxxxxxxxxxx> wrote:

>basicaly its one of those projects where it needs to be as good as i can get
>without going to extremes (atomic clocks are too expensive) and the phase
>noise is integrated over 100ms or so. but nevertheless needs to be
>ridiculously small. the reason for multiplying the frequency is to increase
>the sensitivity of the phase detector to phase changes in the 40mhz signal
>to detect phase change coresponding to changes in delays of less than a
>picosecond.
>


Why are picosecond delays interesting here?

1 ps RMS jitter over 100 ms time will be very difficult. A good
crystal oscillator can do a few tens of ps over 100 ms; a very good
ocxo can hit 1 ps over that time. Any following circuitry must be very
good to not add picoseconds of jitter.

If you're trying to characterize the phase change of a 40 MHz signal,
multipling may not make things better and could well make things a lot
worse. Measuring anything analog to one part in 25,000 will always be
tricky.

What's the application?

John


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