Near-Field Power-Focused Directional Radiation in Microwave Wireless Power Transfer System

This article presents a novel architecture of power generator in microwave power transmission (MPT), which serves as the transmitter with directional radiation in the MPT system. A new structure based on quadrature modulation and demodulation technique is proposed, which features low cost, easy implementation, and high performance. Full amplitude and phase control of the radio frequency (RF) power is realized, providing the chance to achieve the direction functions of the MPT system. To radiate microwave power into free space, a
$2\times 2$
phased array antenna is used in this article. Since the operation frequency is 915 MHz and energy focusing in the near field, the distance difference between each array elements with the target cannot be ignored. Therefore, based on the transmitter, a new strategy of directional radiation in the near field for power focusing is also presented in this article. The current phase difference between the array elements is calculated by using the proposed strategy. Finally, a prototype with 16-channel 100-W/915-MHz power transmitter, phased array antennas, and receiver are constructed in the laboratory to verify the theoretical analysis and test overall efficiency. The simulation and experimental results are shown to verify the effectiveness of presented power generator and its directional radiation strategy.