[time-nuts] How to measure Allan Deviation?

Didier Juges didier at cox.net
Mon Oct 23 00:02:33 EDT 2006


Bruce,

Thanks for the reminder. That was my intention. I was planning to use a 
74HC74, and whatever dividers I can get my hands on. I am not looking 
forward to daisy chain seven 7490s, so I will probably try something 
else. With the D flip-flop, the dividers don't really matter, as long as 
the delay is below 100nS.
I need to find the best way to go from the 10 MHz sinewave to the 
divider, probably through an LM119 comparator with modest hysteresis.
The need for a low jitter divider is the same for the GPS disciplined 
oscillator, so I should be able to reuse the divider for my frequency 
standard.

Thanks

Didier

Dr Bruce Griffiths wrote:
> Didier
>
> If you are going to use a PPS divider to divide the oscillator frequency 
> down to 1Hz, you will need to measure the inherent jitter of the divider 
> to ensure that it doesn't degrade the measurement resolution. It may be 
> necessary to resynchronise the divided output using a fast D flipflop to 
> reduce the inherent divider jitter to less than the 20ps resolution of 
> the 5370.
>
> Bruce
>   




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