A 5.2 GHz RF Energy Harvester System Using Reconfigurable Parallel Rectenna

This paper presents a 5.2 GHz band, 67% efficiency at the input power of + 20 dBm RF Energy Harvester (EH) for IoT/wearable devices. In order to keep the high efficiency over the wide RF input range, the reconfigurable 6parallel rectenna is proposed. The configuration of rectenna is automatically changed depending on the RF input power level. Also, adaptive matching is proposed to adjust the matching network automatically depending on the number of stages of rectenna, RF input frequency, and load current. Each RF-DC converter in rectenna is implemented by two Schottky diodes in a package and with a harmonic control scheme to produce a reasonable output DC voltage. Buck-boost converter is integrated to provide a constant voltage to the IoT/wearable devices. By using reconfigurable structure, different values of efficiency and the output DC voltage can be achieved. The measured efficiency of RF EH is 67% with an output DC voltage of 6.1 V when the RF input power level is +20 dBm at the frequency of 5.2 GHz single-tone signal. It can charge the wearable devices such as G Watch, Mi band, and SmartThinQ.