[time-nuts] Basic question regarding comparing two frequencies
jfor at quik.com
Sun Jul 25 17:02:10 UTC 2010
The splitter makes two identical signals from Ref 1
The quadrature hybrid makes two signals out of Ref 2, but with a 90 degree
phase shift between the signals.
It's essentially a QPSK Demodulator, but set up to run in the linear
region, rather than clipping. It's also sometimes called an I-Q detector.
There is some closely related info here:
> My attempt to understand your diagram, not sure about how the quadrature
> is connected.
> ----- Original Message ----
> From: J. Forster <jfor at quik.com>
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Sent: Sun, July 25, 2010 10:29:23 AM
> Subject: Re: [time-nuts] Basic question regarding comparing two
> There is a cute way to use a scope.
> It requires a power splittere, a quadrature hybrid, and two mixers (all
appropriate for the frequencies you are comparing), and an X-Y scope.
Mini-Circuits sells appropriate parts. The stuff is hooked up like this:
> X Axis
> S | H
> P ---- MIX ---- Y
> REF 1--L B -- REF2
> I ---- MIX ---- R
> T | I
> Y Axis D
> The 'scope display will be roughly a circle if the frequencies are a bit
different and the spot will go around CW or CCW depending on which Ref
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