Please help!!!!! Capacitor for Rectenna

Hi,
I am trying to build a rectenna. I already have my microstrip patch antenna design done and now I'm focusing on my rectifying circuit which consists of a diode and a capacitor. I am having trouble deciding what the size of my capacitor should be if I am operating at a resonating frequency of 2.4 GHz. Is there a formula or rule of thumb?

thankkkss