Hi
> On Jul 8, 2022, at 10:35 AM, Mike Monett via time-nuts > <time-nuts@lists.febo.com> wrote: > > Bob, you wrote: > >> Mike. One concern I have with active components as mixer is noise. >> For an SA I designed only a passive DB diode mixer had low enough >> output noise. Would a PF detector as being an active component, >> not create more noise as output? Erik > >> Yes, you are correct. The only thing with a low enough noise floor >> for good phase noise measurements (via the quadrature technique) >> is some sort of mixer. Normal digital phase detectors have way to >> high a noise floor. > >> Bob > > You are talking about old technology. Old tecnology PFD's were built with > discrete circuits and probably suffered from crosstalk, deadband, ground > bounce, VCC noise, and noisy input oscillator signals. > > Modern PFD's have very low noise. For example, the Hittite HMC984LP4E > digital phase-frequency detector has -231 dBc/Hz of noise and goes up to > 350MHz: > https://www.analog.com/media/en/technical-documentation/data-sheets/hmc984.pdf Hi The noise floor of the double balanced mixer (used as a phase detector at 100 MHz) is in the -165 go -170 dbc / Hz range. I’ve used the parts you are talking about. Their floor is *way* higher. Bob > > Too bad the price jumped enormously when Analog bought Hittite. > > The MC100EP140 Phase-Frequency Detector has 200 femtoseconds of jitter and > goes up to 2GHz. That is not going to match the HMC984LP4E but will be > adequate in many applications: > https://www.onsemi.com/pdf/datasheet/mc100ep140-d.pdf > > Modern synthesizer IC's have PFD's as the frequency detector and offer very > low noise. > > You also forget that double-balanced mixers are also very noisy. For > example, most receivers need a good low noise preamp in front of the mixer > to get an acceptable noise figure. I am told that part of the reason for > the high DBM noise is multiple harmonics are generated by the internal > signals, which combine as part of the output signal. > > Mike > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe send an email to time-nuts-le...@lists.febo.com _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send an email to time-nuts-le...@lists.febo.com