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 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

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-leave@lists.febo.com