[time-nuts] 1 pps sync'ing

Martyn Smith martyn at ptsyst.com
Fri Jun 29 09:13:10 EDT 2018



My colleague Steve asked a question about wanting to generate a 10 MHz and
100 MHz squarewaves with both rising edges aligned to a reference 1 pps
input (to within 5ns).


We already have a product that can do this (at 10 MHz), but it is very
complicated, and Steve's job is to fine an easier approach.


I'm not trying to achieve 1-5 ns to UTC as that's not possible as already
pointed out, just 1 to 5 ns to a reference 1 pps (from Hydrogen Maser).


We definitely need all rising edges synchronised.  Of course, we will have
to be very careful with cabling lengths etc otherwise we will lose all this


So starting at 100 MHz and dividing down is a good idea, except the 100 MHz
needs to be synchronised in the first place, which brings me back to the
first problem.


Our existing product generates 48 bit BCD time code all synchronised to a 1
pps inputs.  This was designed ages ago for a customer.  So, the last bit of
the 48 bit is 100ns in time or 10 MHz in frequency. 


So we could use this board and then lock the 100 MHz to the 10 MHz.  


But it's not very elegant!!


Anyway, the research continues.


Best Regards




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