mode "rf off" to measure only b-waves (incoming waves)?

[iptish]

I did not find any information on this topic, so I hope that opening an issue here is the correct way.

From looking at the schematic and the block diagram, I think it should possible to turn off the reference signal by disabling CLK1 of the SI5351A. Then, a kind of "two-channel spectrum analyzer" mode could be obtained when CH0 and CH1 are not calculated as S11=b1/a1 and S21=b2/a1 but just as b1 and b2.

I have some applications in mind where this could be useful: the signal with known frequency is already present but is measured via different paths and the ratio b1/b2 is the quantity of interest.

[hitstm32]

I am also very interested in this idea