Dilemma of Microwave Wireless Power Transfer and Fully Passive Receiver Finding Utilizing Multi-Antenna Technologies

There is a dilemma in microwave wireless power transfer (MWPT): if a receiver (Rx) runs out of battery or loses communication capability, a transmitter (Tx) cannot find Rx, resulting in extremely low transfer efficiency. To overcome this problem, this paper presents fully passive Rx-finding methods for open- and enclosed-space MWPT by utilizing i) the nonlinear response of rectennas and ii) the unique behavior of parasitic antennas in a shielded cavity. The experiments successfully demonstrate high-accuracy Rx-finding performance using the proposed methods with a simple Rx configuration.