[time-nuts] Another question about PHASE and DMTD

[Paul A. Cianciolo]

Folks,

I know I am going to regret asking this but you only live once.

Please accept my assumptions during this question 


Say we have a DMTD system that uses the same freq. for the common LO and the
F Ref and the FDUT 10 Mhz.
Further ... these oscillators are all synchronous, and in phase because they
are all derived from the same source.
This is all in a perfect world of course. No phase delays anywhere.

There should be 4 outputs from the mixers:

Fref
Fdut
Fref+ Fdut
Fref- Fdut

Perfect mixer so Fref and Fdut never make out of the mixer and cancel
perfectly.
Leaving:

Fref + Fdut   20 Mhz  at 2 times the level I assume?

And now ... all phases being equal...

Fref - Fdut should equal zero.

Now introduce a 90 phase shift in Fdut using a coax cable or some stable
lumped device.
I did this in excel and it yields a voltage of approx..1.5 times the mixer
output level and still at 10 MHz.

SO if.. and I say if... that is true and we return the Fdut back to an
oscillator in question in other words an actual dut, would associated phase
shifts be detectable and record able in an analog fashion?

I suppose in the real world the wave forms and phase delay's in the circuit
would be too high to make something like this worth while.

And the only advantage I can see does really not needing an offset LO...

I guess I am just living in the analog domain...   Edges are probably far
easier to count and more reliable.




Paul A. Cianciolo
W1VLF
http://www.rescueelectronics.com/
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