[time-nuts] Phase Detectors/Mixers for DMTD and PN measurements
Joseph Gwinn
joegwinn at comcast.net
Thu Dec 12 01:40:38 UTC 2019
On Wed, 11 Dec 2019 12:00:02 -0500, time-nuts-request at lists.febo.com
wrote:
Re: time-nuts Digest, Vol 185, Issue 17
> ------------------------------
>
> Message: 4
> Date: Wed, 11 Dec 2019 23:36:29 +1300 (NZDT)
> From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
> To: Discussion of precise time and frequency measurement
> <time-nuts at lists.febo.com>
> Subject: Re: [time-nuts] Phase Detectors/Mixers for DMTD and PN
> measurements
> Message-ID: <1772914487.1926367.1576060590010 at webmail.xtra.co.nz>
> Content-Type: text/plain; charset=UTF-8
>
> 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
I recall that Enrico Rubiola wrote a paper on the care and feeding of
diode-ring mixers. It will be on Enrico's rubiola.org website.
Joe Gwinn
>> On 11 December 2019 at 22:55 Tobias Pluess <tobias.pluess at 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?
>
> End of time-nuts Digest, Vol 185, Issue 17
> ******************************************
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