Using a envelope detector to demodulate low voltage signal
I would suggest using a bias tee for adding DC to your RF signal. More than 600 mV of DC voltage would be required, or your diode will only open at the maximum of the signal.



(picture from Wikipedia)

You need to be careful about selecting the L and C values, so that the inductance represents a high enough impedance at the desired RF frequency but the capacitor's impedance should be lower than the characteristic impedance of the transmission line (coaxial cable or whatever you use).