Hi If the 1 PPS is from something like a Maser ( so it’s not all over the place) *and* the 100 MHz is from something like an OCXO (so it also is reasonably stable), this all gets down to PLL design.
Since it’s 1 pps in, you need a process that will resolve the input phase reliably to << 1 ns. That is not trivial, but it can be done. You also need a stable way to get from 100 MHz to 1 pps. The “just do it with an FPGA” does not cover all the issues there…. there are a number of delays that are going to vary. Once you have that worked out, there *will* be some time period over which you will achieve your 1 ns number to some level of confidence. There will never be an absolute guarantee. Bob > On Jun 29, 2018, at 9:13 AM, Martyn Smith <[email protected]> wrote: > > Hello, > > > > 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 > synchronisation. > > > > 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 > > > > Martyn > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://lists.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://lists.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
