Hi There are a wide range of OCXO’s listed for this project. I certainly do not have a sample of ever single one of them. For the ones that I *do* have samples of, a properly done CMOS gate sine to square converter will not degrade the close in phase noise or ADEV of the OCXO. Based on TimePod measurements, I believe it would be adequate for all the ones I’ve seen specs for.
With far removed phase noise spec’d into the “past 180 dbc/Hz” range on some parts - no logic is going to handle that. Since the CPLD on the board will floor out well before that, doing a “perfect” conversion and then degrading it as soon as you hit the bulk logic does not make a lot of sense. Bob > On Oct 23, 2015, at 5:31 AM, Charles Steinmetz <[email protected]> wrote: > > Bruce wrote: > >> Your statement about the PN of comparators conflicts with my measurements. >> The LTC6957 evaluation board had an 18dBc/Hz lower phase noise floor than a >> comparator circuit with 10MHz 15dBm inputs. However I only measured a single >> comparator circuit. The Holzworth sine to CMOS converter had a comparable PN >> to the LTC6957-4. >> I haven't, as yet measured the PN of an optimised Wenzel circuit.My setup >> for this measurement had a PN floor of around -180dBc/Hz. > > There are many, many ways of getting unnecessarily poor PN performance from > comparators (including Wenzel-style squarers) -- one has to make sure not to > make any of myriad mistakes in both design and execution. You didn't say > which comparator you tried, or in what circuit, so I'm not in a position to > suggest things to check (or to confirm that the comparator you tried performs > similarly poorly in my tests, if that is the case). > > One sanity check you can try -- disable the filtering on your 6957 eval > board. According to the LT data presented in the chart I posted, which > agrees very closely with my test results, at 10MHz/15dBm there should be > essentially no change in the PN compared to the results you obtained with > filtering enabled. If you see a significant difference, then something is > causing anomalous results. > > Best regards, > > Charles > > > ps. You often respond to one message by replying to a different message, as > you did in this case. It would be helpful for someone who just joins a > thread, and for continuity in general, if you would reply to the message to > which you are actually responding. That way, readers who are new to the > thread will have the context they need, and your interlocutor will have his > or her previous message conveniently available to refer to in any further > message. > > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
