Analysis of Voltage Doubler Behavior of 2.45-GHz Voltage Doubler-Type Rectenna

摘要

This paper describes the voltage doubler (VD) behavior of a 2.45-GHz VD-type rectenna. An important feature of the developed VD-type rectenna is the absence of the charge pump capacitor that is present in conventional VDs. Based on the circuit simulation and measurement results, the developed VD-type rectenna shows drastic improvement to the radio frequency-to-direct current (RF–dc) conversion efficiency in comparison with a half-wave rectifier (HWR)-type rectenna at output loads exceeding 100 Ω . From the simulation, both the VD- and HWR-type rectennas show VD behavior, even without the charge pump capacitor. This behavior was found to be attributable to the electric charge stored in the junction and package capacitances of the Schottky barrier diode in the rectennas. Additionally, it was found that the improvement of the RF–dc conversion efficiency is caused by the voltage conservation in the series diode. This improvement is dependent on the microwave period and the electric discharge time constant. When the microwave period is comparable with the electric discharge time constant, the VD-type rectenna conserves a dc voltage even when the input microwave voltage is negative. These phenomena were observed by analyzing the voltage and current waveforms of the rectenna equivalent circuit obtained via circuit simulation.