[time-nuts] Very challenging phase noise measurement, does anyone have an idea??

Hans Rosenberg Hrosenberg at catena.nl
Wed Dec 5 12:03:13 UTC 2012

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

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