High-efficiency harmonically-terminated rectifier for wireless powering applications

In wireless powering, the rectifier efficiency has a large effect on overall system efficiency. This paper presents an approach to high-efficiency microwave rectifier design based on reduced conduction angle power amplifier theory. The analysis for an ideal rectifying device is derived to predict efficiency dependence on optimal dc load. A class-C 2.45 GHz Schottky-diode rectifier with short-circuit 2^nd and 3^rd harmonic terminations is designed using source-pull measurements, and demonstrates a maximum RF-DC conversion efficiency of 72.8% when matched to 50Ω. The approach is applied to integration of a rectifier with a dual-polarization patch antenna in a non 50Ω environment and free-space measurements demonstrate a lower bound on efficiency of 56% at 150 µW\cm² power density which includes matching circuit and mismatch losses.