RF Power Harvester With Varactor-Enabled Wide-Power-Range Capability for Wireless Power Transfer Applications

This article proposes an approach of designing a wide-power-range RF power harvester integrated with a dc – dc boost converter, in order to facilitate wireless charging driven by wireless power transfer (WPT). The approach addresses the operational constraints posed by a dc – dc boost converter with maximum power control functionality, achieving high power conversion efficiencies (PCEs) across a wide input power range. It involves the integration of a varactor to dynamically compensate for fluctuations in the input impedance of the rectifier. The direct biasing of the varactor is strategically achieved through a double-voltage rectifying structure, without any external biasing methods. The proposed rectifier demonstrates high RF-dc PCEs exceeding 50% within an input power range of 2.4–20.9 dBm in the experiment, under a constant voltage load of 3.3 V, which emulates the dc – dc boost converter effects. Our design surpasses the conventional capacitor-based approach by more than 10 dB in the operating power range without relying on external bias. Finally, a self-powered wireless sensor node is designed based on the proposed rectifier, demonstrating the stability of rectifier’s performance within a system design. It also validates the potential use of the proposed rectifier for efficiently powering wireless sensor nodes in practical scenarios.