Direction-of-Arrival Estimation by Utilizing Harmonic Reradiation from Rectenna

We propose a new direction-of-arrival (DoA) method for wireless power transfer (WPT) by utilizing harmonic reradiation from rectenna. A feature of the proposed method is needlessness of a pilot signal oscillator in the receiving site, then the receiving system can be configured without any power supplies and batteries. We developed and experimentally investigated the harmonic-reradiated DoA estimation system. We verified that the measurement results were comparable with a conventional DoA estimation and simulation results, except for the interference with the direct incoming waves from the WPT transmitter. We discussed error factors from viewpoints of mutual coupling effects on receiving antennas, and asymmetric property of the receiving antennas including feeding points, as well as the interference with the WPT transmitter. By calibrating the measured data, the harmonic-reradiated DoA estimation errors were mitigated within the range from -2.1° to 3.5°.