From the fig. 1, the operational concept of a typical 2.45
GHz rectenna can be understood. The incident 2.45 GHz RF
signal is received by an antenna, which operating frequency
must be same as the signal frequency. The power of the
incident RF signal is converted to dc signal by the rectifier
circuit. Between the antenna and rectifier, an impedance
matching network composed of inductive and capacitive
elements is introduced, which ensures the maximum power
delivery from antenna to rectifier [8]. These impedance
matching network and rectifier circuit are jointly called RF
energy harvesting circuit.