Cecil Moore wrote:
On Apr 27, 10:30 am, Wimpie wrote:
Depending on the frequency resolution of your VSA, the frequency of
the injected signal can be well within 1 kHz of the carrier, so LC
filters in the PA will not distort the measurement. In case of a 100W
PA and injection of about 100 mW, the difference in wanted signal and
signal to be rejected is 30 dB (not that large).

Would any competent optical physicist suggest that it is valid to
study the conditions associated with interfering coherent light waves
inside an interferometer by introducing an incoherent light source
into the system? Why would any competent RF engineer suggest that the
system source conditions associated with interfering coherent RF waves
can be studied by introducing an incoherent test signal?

Interestingly, it's NOT an incoherent test signal. It's a carefully
chosen coherent test signal with a frequency difference. It's the same
idea as having an interferometer with dithering piezo transducer on a
mirror or a modulator in one of the paths.