Re: RF Energy Harvesting
Hello,
You should start with basic EM and antenna theory. You should know things as: power flux density (E*H), E- field strength, field attenuation versus distance, ERP, EIRP, antenna aperture, relation between antenna aperture and gain, relation between gain, size and vert & hor. beam width, polarization, LOS propagation, maybe propagation over ground (two ray model), etc.
The above enables you to figure out how much power you can extract from the environment.
Next step is to understand the diode detection (rectifying) process, rectifier topologies and losses in LC or transmission line circuits. As the output power of the antenna may be very low, you need to transform the antenna's output impedance in such a value that you have sufficient voltage to have good detection performance (but don't stress the diodes too much). You also need to know the properties of diodes to make the best match and to avoid temporary overload (as this may fry your HF schottky rectifiers).
Once you have some power available, you need to design a good converter that enables you to convert the rectified power into the desired voltage, without much loss.
You may also need band pass filtering in the RF section to avoid that harmonics due to the rectifiers reradiate into the air.
Things that will have large influence on the work to be done: wide band versus narrow band, center of frequency band and omnidirectional versus spot. If you have one strong transmitter, then a narrow band, spot approach may work best (and is relatively simple).