Design of Retrodirective Antenna Arrays for Short-Range Wireless Power Transmission

Application of retrodirective antenna arrays in wireless power transmission is proposed in this paper. The time reversal or phase conjugate theory and design considerations of the array factors are examined in GHz regime and meter range. The wireless power transmission efficiency is analyzed in the 2-D case with full-wave electromagnetic (EM) solution and validated by analytical array theory. The design factors of array size, array spacing, element size, and specific choice of the industrial, scientific and medical (ISM) band frequency are investigated to optimize the transmission focus. Design guidelines are provided for those factors and the impact of manufacturing variability is discussed. The proposed approach can also be extended to wireless power transfer with active retrodirective rectenna array and passive RFID systems.