Dual-band crossed-Yagi antenna for RF-based power transmitters with polarization and harmonic detection functions

This paper presents a dual-band crossed-Yagi antenna for RF-based wireless power transfer applications. The proposed antenna has the capability of adjusting the polarization direction and detecting the second-harmonic reflected by the power receiver. To implement the design, two individual planar Yagi-Uda antennas with a dual-band operation feature, are set in an orthogonal structure. By properly controlling the input power ratios between the two antennas, the resulted polarization directions can be aligned from 0° to 90°. The reflected second-harmonic signal strength can be enhanced by more than 19 dB when the polarization of the receiver antenna is tracked.