Analysis of Received Power in RF Wireless Power Transfer System With Array Antennas

In this paper, a method for calculating the received power in a radio-frequency wireless power transfer system with array antennas is proposed. The received power is derived based on the superposition of the electric fields that radiate from individual transmitter (Tx) elements and are captured by each receiver (Rx) element. That is expressed in a finite series form with the radiation patterns of an element considering mutual coupling in the array and corresponding distances between the elements of Tx and Rx. Unlike conventional methods (such as the Friis and Goubau formulas), this approach is able to calculate the received power precisely in both Fresnel and far-field regions. It is also efficiently applicable to various cases, such as those involving beamforming and with varying positions of Rx. The calculated results using this method are applied to a 5.2 GHz WPT system with array antennas and verified through comparisons with both simulation and experimental results.