[time-nuts] Phase Detectors/Mixers for DMTD and PN measurements

[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 <richard at 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
> 
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