yes, all I care about is the signal in the middle that looks like triangle. The first peak is always there, the signal is the middle is the reflection signal that I want. I calculated the time constant based on:
capacitor-resistor combination will establish the time constant ��, which should be kept to a value above the period of the main component (carrier, 5MHz), but much lower than the modulating signal (in this case dictated by the frequency of repetition 7.8kHz).
T1 = 1/5000000 = 0.2µs
T2 = 1/7800 = 128µs
�� = R*C = 100p*220k = 22µs
∴ T1 < �� < T2