Re: what diode do i use?
At 2.45 GHz, only low-power detector Schottky diodes work well. Some manufacturers even offer tiny encapsulated diode quads you can connect as a bridge rectifier.
In general do not expect a high efficiency. If you like experimenting, read about "rectenna" concepts. You can connect your bridge rectifier to a dipole, add a reflector to its back, and use any suitable low-power 2.45 GHz transmitter to find what DC output you can achieve from a given RF transmitted power over a short distance. With only a voltmeter load everything looks fine- you can read a volt over almost one meter distance. Once you decide to add a lower-resistance load, the DC power will be very small. Recently there are companies promising to feed DC power this way to small sensors; one can slowly charge a 1 microfarad capacitor and obtain one short blink of a LED. That is all.
Let me know if you can do better. When you overload your rectifier, it will saturate and reflect the RF power back. So far the world is waiting for a better rectifier.