Adaptive impedance matching of rectifier for a 100 MHz microwave power transfer system

Abstract

Microwave power transmission (MPT) has been one of the most promising systems in the far-field wireless power transmission system. In MPT system, the harmonic energy generated by conventional diode rectifying circuit has great impact on the overall efficiency. Moreover, the passive impedance network leads to power reflection, which is the other factor leading to the overall efficiency decline. In this study, a 10 W output 100 MHz two-stage adaptive impedance-matching rectifying circuit is proposed which can make input impedance constant. About 100 MHz belongs to the band of radio frequency (RF) and the conception of microwave. The first-stage rectifier is modelled mathematically, which plays an essential role in constructing the initial input impedance and designing the control method of second-stage converter. By adjusting the duty cycle of the second-stage converter, the impedance of the whole rectifier realises 50 Ω under various input and the output conditions by means of simulations and experiments. The simulation and experimental results are shown to verify the effectiveness of the proposed RF to direct current converter and its control method. The overall efficiency with full load is up to nearly 65%.