Design and Performance Evaluation of Energy Source for RFID Tag.

This paper presents a rectifying antenna (rectenna) for the harvesting of the microwave energy associated to UHF (Ultra- High Frequency) Radio Frequency Identification (RFID) systems. The proposed device uses a microstrip line monopole with coplanar waveguide feeding line as receiving antenna and a five-stage voltage multiplier as rectifier. Experimental results demonstrating and RF-to-DC conversion efficiency of about 54% with an input power density will be presented and discussed . A compact rectenna circuit at 2.4 GHz is presented. A matching capacitor and five Parallel diodes are introduced to the rectifying circuit so as to achieve well impedance matching. There is a RF-DC conversion efficiency difference of about 3%. The experiment DC output voltage of the rectifying circuit with this novel design achieves 3.0V at a DC load which is a RFID tag. The RF-DC conversion efficiency at desired frequencies could be optimized. Zero bias Schottkey diode model for low RF input power and moderate DC current rectifying antennas (RECTENNAs) is investigated. The model provides diode parameters at the desired output DC current level to be matched with the antenna so that optimum power transfer from antenna to the diode occurs.