The research developed in this paper lies in the framework of the Wireless Power Transportation (WPT) applied to the RFID. The carried study aims at to obtain the best efficiency of the collecting/rectifying part of the WPT system (rectenna) where recovery of the microwave energy into continuous energy takes place. The optimization is performed on an equivalent circuit approach of the rectenna with the use of only a single non-linear circuit simulator environment. Furthermore, this method allows for the physical origin of the energy losses in the system to be quantified. Thereby, it will then be possible to improve the efficiency of the rectenna by working onto each element of the circuit.