There are a number of NIST papers on this: https://tf.nist.gov/general/publications.htm
You can also simulate the effect of a capacitive IF port load. However a capacitive load can also degrade the isolation and RF and LO port mismatch. One can also use diode connected BJTs instead if lower close in PN is desired at least for frequencies up to 10MHz or so. There is a NIST paper on this as well: https://tf.nist.gov/general/pdf/2556.pdf Bruce > On 11 December 2019 at 22:55 Tobias Pluess <tobias.plu...@xwmail.ch> wrote: > > > Hi colleagues > > In parallel to my GPSDO project I am also thinking about a DMTD measurement > system which should also be capable of doing phase noise measurements. This > will be necessary to measure the stability and phase noise of my own GPSDO. > > There is the paper from W. J. Riley, "A small DMTD system". He uses TUF-R3SM+ > mixers. The HP 11729C carrier noise test set uses a custom HP part as phase > detector, and a lot of other publications I found use the HP 10514A, either > as mixer or as phase detector. > I wonder, which criteria are relevant to select a mixer for this application > (besides the frequency range). Are there devices which are better when used > as mixers, or phase detectors, or are there even devices which are good for > both purposes? Of course, we want low noise, but for most if not all > commercial mixers, only the isolation and conversion loss is specified, but I > never saw a mixer datasheet having information about the mixer's noise > contribution. So there must be other criteria people use when selecting a > mixer for a DMTD or phase noise measurement system. > > Further. in this paper "OPTIMIZATION OF DUAL-MIXER TIME-DIFFERENCE > MULTIPLIER" from Sojdr I even found a reference "The mixer output has a > capacitive loading (22 nF) that increases the zero-crossing slope". The > "Small DMTD system" from Riley also does have this capacitive loading. Can > somebody explain why this does help to improve the zero crossing slope? > > > Tobias > HB9FSX > > _______________________________________________ > 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.
