Characterizing the Dynamic Behavior of a Both-Sides Retrodirective System for the Control of Microwave Wireless Power Transfer

Long distance wireless power transfer is achieved by large antenna systems which employ a number of antenna elements. The larger the antenna, the longer the distance that can be achieved. To maximize the power transfer, the amplitude and phase of each antenna element must be controlled precisely according to the values that are predicted by an S-parameter view. Iterative approaches to control them are considered to compensate for the time-varying behavior of the wireless channel but these methods rapidly increase in computational complexity as the system grows in size. The use of retrodirective antenna arrays on both the power generator antennas and the receiver antennas have been proposed as an alternative. The feedback looping mechanism of this method enables a highly efficient power transfer. In this paper, we analyze the dynamic behavior of this proposed system in terms of its zero-input response and step response. We show that at marginal stability, the proposed system can achieve maximum theoretical efficiency. The theoretical analysis is validated by a time-domain simulation and results show agreement with theoretical predictions.