A Self-Gating RF Energy Harvester for Wireless Power Transfer With High-PAPR Incident Waveform

In this article, we propose a self-gating radio frequency (RF) energy harvester (RFEH) for reaching a high-power harvesting efficiency (PHE) at a low incident RF power level with a high peak-to-average power ratio (high-PAPR) waveform. It includes a power switch between a cross-coupled rectifier and its supplied load to cut off the reverse leakage current in between the short power bursts. The power switch is dynamically controlled based on an indication of the ability of the RFEH to effectively charge the load at the instantaneous incident power level. This is achieved by comparing the load voltage with the open-circuit voltage of a replica rectifier. A comparator with optional proteresis (reversed hysteresis) is proposed for compensating its logic delay at the start and at the end of the short RF power bursts. As a result, the power switch is accurately turned on only during the power bursts. The self-gating RFEH was prototyped for 2.45-GHz wireless power transfer (WPT). It includes a cross-coupled rectifier with the proposed self-gating circuit fabricated in a 65-nm process, a discrete balun, a parasitic-aware-sized p matching network, and an off-the-shelf power management unit (PMU) with maximum power point tracking (MPPT). Measurement results show sensitivity as low as −26.7 dBm with a peak PHE of 32.3% at −14.1-dBm incident power. Compared with the state-of-the-art works, the proposed design significantly improves the RFEH performance at the target low average incident power.