Hi You might be surprised by the noise floor of an XOR run at 125 KHz. They are quite good at that low a frequency.
Bob On Dec 5, 2012, at 8:24 PM, John Miles <[email protected]> wrote: > That would be a good way to do it. I wouldn't use an XOR gate or other > digital phase detector for this, due to the low slew rate among other > things. Instead, you could phase lock two of your sources with a > double-balanced mixer, then run the IF through a lowpass filter and a quiet > opamp or other LNA. The baseband noise can then be viewed on a spectrum > analyzer that goes down to whatever the minimum offset of interest is. The > analyzer's noise floor doesn't matter, it just needs to be something that > can tune down to the 100 Hz-1 kHz area. An old-school HP 8566 or 8568 is > ideal. > > For calibration details, see the references in the last FAQ entry at > http://www.ke5fx.com/gpib/faq.htm , especially HP 11729B-1. > > Alternatively, I'm not sure where the noise floor of the FSUP is, but if it > is otherwise low enough, you could mix the 125 kHz with an ultra-low-noise > OCXO and measure one of the resulting sidebands. It might or might not be > necessary to filter the other sideband depending on how the FSUP works. > > You could also build a low-noise 8x active multiplier to get to 1 MHz where > the FSUP can see it, as well. This would have the advantage of not > requiring a ULN OCXO for mixing, and would also boost the PN by 18 dB for > easier measurement on the FSUP. However, you'd need to be careful with the > multiplier's residual noise, especially in the first couple of stages. > > If you need to make these measurements over and over, go with the multiplier > or mixer, otherwise I'd use an analog quadrature PLL. > > -- john > Miles Design LLC > > >> -----Original Message----- >> From: [email protected] [mailto:time-nuts- >> [email protected]] On Behalf Of Adrian >> Sent: Wednesday, December 05, 2012 4:40 PM >> To: Discussion of precise time and frequency measurement >> Subject: Re: [time-nuts] Very challenging phase noise measurement, does >> anyone have an idea?? >> >> You can always use an external mixer / phase detector and the baseband >> input of a HP 3048A or FSUP. >> >> Just to name a few: >> For low power (+7dBm) you can use a SRA-3 which goes from 25kHz to >> 200MHz >> SRA-3MH +13dBm from 25kHz to 200MHz >> SRA-3H +17dBm from 50kHz to 200MHz >> For high power signals use a RAY-3. It goes from 70kHz to 200MHz. >> The IF must be specified from DC, which for the above is the case. >> >> Between mixer and baseband input a lowpass filter is required to >> suppress the sum signal (2x f_input) sufficiently. >> >> Adrian >> >> >> Azelio Boriani schrieb: >>> Yes, I have taken a look and the FSUP is 1MHz min at the signal > analyzer. >>> Timepod? No, 500KHz min... an R&S FAM modulation analyzer? >>> >>> On Wed, Dec 5, 2012 at 10:48 PM, Bob Camp <[email protected]> wrote: >>> >>>> Hi >>>> >>>> A "3048" style measurement with the carrier suppressed by lock should >> do >>>> pretty well. If the XOR's are out, there are a lot of mixers available > that >>>> work at 125 KHz. A simple op-amp buffer and a sound card could do what >> you >>>> need to do. >>>> >>>> Bob >>>> >>>> -----Original Message----- >>>> From: [email protected] [mailto:time-nuts- >> [email protected]] On >>>> Behalf Of Adrian >>>> Sent: Wednesday, December 05, 2012 4:33 PM >>>> To: Discussion of precise time and frequency measurement >>>> Subject: Re: [time-nuts] Very challenging phase noise measurement, >> does >>>> anyone have an idea?? >>>> >>>> For phase noise the frequency range is 1MHz to 8/26.5/50GHz >>>> The spectrum analyzer works from 20Hz to max. >>>> >>>> Adrian >>>> >>>> >>>> Azelio Boriani schrieb: >>>>> Isn't the FSUP a 110K euros equipment 20Hz-50GHz capable? 125KHz >>>> shouldn't >>>>> be a problem. I had an FSUP for 25 seconds to play with... really >>>>> impressive but too limited test time to appreciate fully. >>>>> >>>>> On Wed, Dec 5, 2012 at 1:14 PM, Bob Camp <[email protected]> wrote: >>>>> >>>>>> Hi >>>>>> >>>>>> Just about any of the high speed CMOS parts should work. A 74AC86 is >>>> about >>>>>> the earliest part I would trust. Any of the fast logic families that >>>> came >>>>>> after that should do equally well. >>>>>> >>>>>> Bob >>>>>> >>>>>> On Dec 5, 2012, at 7:03 AM, Hans Rosenberg <[email protected]> >>>> wrote: >>>>>>> Hello Time-nuts, >>>>>>> >>>>>>> I have to do a phase noise measurement and I'm wondering if anyone >> here >>>>>> has any ideas on that. We have to measure the phase noise of a 125kHz >>>>>> carrier (5Vp-p signal level). The measurement system should have a >> noise >>>>>> floor that is -164dBc/Hz at a distance of 1kHz to 8kHz away from the >>>>>> carrier. >>>>>>> Our current plan is to use 2 of these sources, have one in free > running >>>>>> mode and lock the other one to the first one using an XOR gate and >> then >>>> use >>>>>> the output of the XOR gate as an output signal. However, we are >>>> wondering >>>>>> if any of you know a better idea. Maybe there is an off-the-shelf > piece >>>> of >>>>>> equipment that can do that that we could rent. Or maybe we could >>>> increase >>>>>> the frequency to a few megahertz using a pll, which means the signal >>>> comes >>>>>> into the measurement range of our FSUP phase-noise analyzer. >> Problem is, >>>>>> the phase detector would then need to have an insanely low noise- >> floor >>>> (in >>>>>> our idea the XOR also has to have this insanely low noise floor as > well >>>> off >>>>>> course) so does anyone have experience with anything like this? Does >>>> anyone >>>>>> know an XOR with these good specs? I don't have a clue what a >> standard >>>>>> 74lvc1g86 would do. Needless to say the supply of this XOR would have >> to >>>> be >>>>>> ridiculously clean, but I do have a solution for that problem. >>>>>>> Any help is greatly appreciated! >>>>>>> >>>>>>> Best regards, >>>>>>> >>>>>>> Hans Rosenberg >>>>>>> _______________________________________________ >>>>>>> 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. >>>>>> >>>>> _______________________________________________ >>>>> 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. >>>> >>>> >>>> >>>> _______________________________________________ >>>> 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. >>> >> >> >> _______________________________________________ >> 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. _______________________________________________ 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.
