[time-nuts] DMTD - analog multiplier vs. diode mixer ?
alexpcs at ieee.org
Sun Jan 10 16:47:00 EST 2016
and there was also a frequency/phase detector from Analog Devices, which
took care about that dead zone
On 1/10/2016 10:53 AM, Richard (Rick) Karlquist wrote:
> Phase frequency detectors (starting with the legendary MC4044)
> being made out of flip flops, had metastability and/or race
> conditions. Motorola showed a block diagram made of gates,
> as if it were combinatorial logic, but because of the feedback,
> it is actually a state machine, as described in the MC4044
> data sheet. It had a dead zone around zero phase that came
> to light when Fairchild introduced the competing 11C44 PFD
> using Eric Breeze's patent to fix the dead zone. The
> 11C44 data sheet showed their dead zone, vs Brand M.
> Even that improved chip still had a "funny" zone, it just
> never went to zero gain.
> Fast forward to today, we are now seeing PFD's made
> with samplers. They too have a bunch of issues with
> phase noise floors. None of them come close to a mixer.
> In the 5071A, I used a mixer as a phase detector that
> had some flip flops only used for acquisition, so they
> were non players in terms of phase noise. I still think
> I would do that even if I had to do over 25 years later.
> Rick Karlquist N6RK
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