I'm trying to calculate the relative change in permittivity of a capacitor. I have created a circuit that feeds a 80MHz square wave signal into a first order low pass filter.
I don't know the capacitance of said low pass filter, but I don't think I care as I just want the relative change in permittivity.
The output of the low pass filter is then feed into a envelope detector (ADL5910). I then measure the voltage on the VCALC pin and converts that voltage to dBm.
This is where I'm currently stuck...
My question is; Is it possible to calculate the change in capacitance/relative-permittivity of the capacitor in the low pass filter from the change in dBm and if so, how would one calculate this?
VCALC measurement 1 in medium A: 302mV - 2.0dBm
VCALC measurement 2 in medium B: 233mV - -0.5dBm