Analysis on power harvesting circuits with tunable matching network for improved efficiency

This paper presents the necessity and potential of using tunable matching network in UHF RFID transponders. A compact I/V model for diode-connected MOSFET in strong inversion and sub-threshold regions, which is based on the UMC 0.13-¿m technology, is utilized to analyze the influence of the dynamic load to the performance of the power harvesting circuit. A direct dependence of the voltage sensitivity on the varying load current has been found and formulated. The dependence suggests the necessity of optimizing dynamically the impedance matching network between the antenna and the rectifier according to the transponder operation status. A concept of the operation-controlled tunable matching network is finally proposed.