[time-nuts] Re: uncertainty/SNR of IQ measurements

[Tom Holmes]

Now, re-reading my response and thinking a little longer, I understand your question a little better, maybe. I see where you
are coming from if RF and LO are the same frequency, and it's not totally clear to me yet what happens as the phase changes.
My quick back of the napkin (yes, I actually used one!) suggested outputs from a single DBM at zero phase difference of 0 *
Flo, and the input noise plus the LO noise would seem to me to be additive, not multiplied. Basically a phase detector. But
then I recalled that for PN measurements, the LO and test signal have to be maintained at 90 degrees shift for there to be a
zero volts DC component to use for steering but the noise sidebands are then what is measured.

I guess I really need to go play in the lab a bit.

Tom Holmes, N8ZM

-----Original Message-----
From: Tom Holmes <tholmes at woh.rr.com> 
Sent: Thursday, August 26, 2021 2:27 PM
To: 'Discussion of precise time and frequency measurement' <time-nuts at lists.febo.com>
Subject: [time-nuts] Re: uncertainty/SNR of IQ measurements

HI Jim...