Cross Correlation methods are commonly used with analog mixers. Most of the high end commercial offerings use it (Holzworth, Anapico, Rhohde & Schwarz, etc.)
Bruce > On 12 December 2019 at 18:53 Gerhard Hoffmann <g...@hoffmann-hochfrequenz.de> > wrote: > > > It seems the mixer noise cannot be ignored. > > > I wonder then why nobody takes the mixer to cross correlation land, > and maybe even the driver amplifier. > > The FFT analyzer can do it anyway, a second AF pre amp costs nothing, > and other than that > > there are only another mixer and 2 power dividers on the BOM. > > In addition, each mixer gets 3 dB less power which helps the survival rate. > > One can always crank it up for bragging rights. > > > Also, high level mixers (type 2 and 3 in [1] ) have resistors in series > to each diode for biasing > > so their lower efficiency should not come as a surprise. And, the > resistors in the ring generate > > AF noise. With DC across them also 1/f, esp. for thick film. > > The usual 1nV/rt Hz op amps (LT1028, AD797, ADA4898) have the voltage > noise of a 60 Ohm resistor. > > That probably brings them to the point of diminishing return. > > The diodes in the ring themselves create only half-thermal noise. > > > Methinks one would be better off with many low level mixers and power > dividers, > > adding up the demodulated AF voltages. There is no point in power > matching the AF side. > > Maybe for RF with a RC high pass. > > SMD Wilkinson dividers are $2.50 or so now from Macom, MCL or Pulse and > > low level mixers are also cheap, or even 2 1:4 SMD transformers + diode > ring. > > Easily done when one does not have to wind the coils. > > > When verifying my links below, I stumbled across M9H for $333. > > The price for two of them is the number of the beast. =8-) ) > > > [1] > > < > https://www.jlab.org/uspas11/Reading/RF/Mixers%20-%20phase%20detectors.pdf > > > > < > https://www.google.de/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=2ahUKEwiu8Zi7pa_mAhUKQUEAHb1pAyAQFjAAegQIAxAJ&url=http%3A%2F%2Fwww.rfcafe.com%2Freferences%2Farticles%2Fwj-tech-notes%2Fmixers-theory-technology-p2-v8-3.pdf&usg=AOvVaw3fc3OZgN2H5jzPx6jXDBh9 > > > > > > Also interesting: > > < > https://www.google.de/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=2ahUKEwiFuqCvpq_mAhVTh1wKHcc2ALQQFjAAegQIAxAJ&url=http%3A%2F%2Fliterature.cdn.keysight.com%2Flitweb%2Fpdf%2F5989-8999EN.pdf&usg=AOvVaw3RFawCNg543QEv1hUsscbY > > > > > > regards, > > Gerhard, DK4XP > > > > > Am 11.12.19 um 20:29 schrieb Bob kb8tq: > > Hi > > > > There are some famous name papers showing data taken on the 3048. When > > asked about the levels involved, the next question inevitably was - “How > > many > > mixers did you fry running the test?”. > > > > Bob > > > >> On Dec 11, 2019, at 10:54 AM, Richard (Rick) Karlquist > >> <rich...@karlquist.com> wrote: > >> > >> > >> The HP 3048A phase noise system has a phase > >> detector in the HP 11848A chassis that was > >> originally a Watkins-Johnson (the original > >> company) M9H. The M9H lives on now sold by > >> MaCom Technology Solutions. "Someone" (unknown) > >> established that the Mini-Circuits JMS-5H > >> is an acceptable substitute, although not > >> an exact replacement. > >> > >> The tradeoff in picking a mixer is the LO > >> level. A high LO drive level such as the above > >> mixer have, gives higher performance, provided > >> you have a driving amplifier that has both the > >> necessary output power is itself low phase noise. > >> Depending on the test set up, some of the driver > >> amplifier phase noise will common mode out. > >> > >> Also, high drive level mixers have a narrow window > >> between high enough drive to operate vs the damage > >> level. So a third requirement on the driver > >> amplifier is that it's maximum output level is > >> less than the damage level. (Don't ask how I > >> know this :-). You can always put a pad between the > >> drive amplifier and the LO input of the mixer used > >> as phase detector to adjust the maximum possible > >> drive. > >> > >> Rick N6RK > >> > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.