Exploiting Third Harmonic of Differential Charge Pump for Wireless Power Transfer Antenna Alignment

Wireless power transfer (WPT) always suffers from the antenna radiation direction and polarization misalignments between the base station and the WPT terminal. In this letter, the third harmonic of a differential charge pump is exploited for antenna alignment with only one pair of antennas. Due to the intrinsic nonlinearity of diodes, the third harmonic can be generated and reflected by the differential charge pump. A ring coupler is employed to distribute the received fundamental frequency power for rectification by the differential charge pump and couple the third-harmonic generation back to its input port. Such third-harmonic power is feedback by a dual-band antenna operating at the third-harmonic frequency. In consequence, the WPT antennas can be aligned by obtaining the maximum third-harmonic feedback at the base station. The whole system is theoretically analyzed and experimentally validated.