On Sat, Oct 5, 2019 at 01:13 PM, Oristo wrote:
do SA612s not feed I and Q into ADC?
Indeed. Two separate signals. For IQ mixing the LO inputs would have to be 90 degrees out of phase and the input must be the same. Both are not the case.
The nanoVna needs to measure two independent signals at the same time. Actually three. But the adc is stereo so one input is switched between reflection and transmission signal
* does not mixing always generate sum and difference frequencies..??
sin A cos B = (sin(A + B)+sin(A - B))/2
Indeed. Here the difference is zero e.g. DC and the output is averaged which is a very effective low pass filter so the sum at 10kHz is eliminated
No need for other filters
