Improvement of power gain for efficient wireless power transmission by using 2Tx×2Rx coil array

This paper introduced a concept of near-field array gain improvement originated from the design factor of far-field antenna array, by which an efficiently non-radiative mid-range wireless power transmission (WPT) system can be realized. Different from far-field antennas, the near-field communication needs integrative analysis including both transmitter (Tx) and receiver (Rx) antennas for the strong coupling between them to achieve the successful WPT within mid-range distance. Thus here, using a pair of dual coil arrays facing each other as energy transceivers of the WPT system, the total combined energy power gained from all elements of the Rx coil array, and the corresponding total transmission efficiency of the whole WPT system both will be increased because of the strongly coupled magnetic resonances (SCMRs) established between the Tx/Rx coil arrays. Based on the comparison between the WPT cases of Tx/Rx coil arrays and Tx/Rx coil with single elements, the gain formula of the total power harvested from Rx coil array would be presented. In this paper, the efficient WPT system working at the resonant frequency of 19.22 MHz, is composed of two coil arrays with the same three-dimensional size of 15.4 cm × 15.4 cm × 0.9 cm and the transmission separation size of 50.0 cm. As mentioned above, here a full-wave numerical method is applied for integrative analysis and the following simulation results well demonstrated that the total power transmission efficiency of much over 50% (Combined Output Power VS. Total Input Power) can be reached easily. Also, the optimized values of load resistors connected to the Rx coil array elements showed that this kind of the proposed WPT system is more feasible for application in charging a battery with lower internal resistance.