Eric, Another problem I forgot to mention, the exclusive-or phase detector has a severe output ripple. This will cause frequency shift in the oscillator frequency which will show up in the measurements. The phase-frequency detector has zero ripple at lock. There is a small transient at the sample time, but this is easily filtered with a simple low pass filter. With zero ripple in the output, the PFD will not cause any shift in the oscillator frequency. This will not cause any error in the measurements.

Mike, He was using an analog mixer, but your comment about XOR mixer does not apply to analog mixers. Your oversimplification that analog mixer and XOR gates being the same thing does not apply here, and thus the assigned missbehavior does not carry over to the analog mixer case. Cheers, Magnus On 2022-07-05 12:27, Mike Monett via time-nuts wrote: > Eric, > > Another problem I forgot to mention, the exclusive-or phase detector has a > severe output ripple. This will cause frequency shift in the oscillator > frequency which will show up in the measurements. > > The phase-frequency detector has zero ripple at lock. There is a small > transient at the sample time, but this is easily filtered with a simple low > pass filter. > > With zero ripple in the output, the PFD will not cause any shift in the > oscillator frequency. This will not cause any error in the measurements. > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-leave@lists.febo.com

On Tue, July 5, 2022 5:27 am, Mike Monett via time-nuts wrote: > The phase-frequency detector has zero ripple at lock. The PF detector also locks at 0 degrees offset. How do you get the demodulated phase noise out of that? The point of the a diode mixer is that it locks at quadrature, and the output is 0V DC at that point, but any instantaneous phase offset (i.e. phase noise from reference and DUT) shows up as AC signal at the output. -- Chris Caudle