Optimal Design of Decoupling Networks to Improve MIMO Microwave Wireless Power Transfer

Long range wireless power transfer (WPT) is envisioned to employ multiple-input multiple-output (MIMO) systems to control the current distribution on a large antenna, allowing for a more accurate beam-forming. Presence of multiple antenna elements creates mutual coupling between them which reduces the WPT efficiency. To improve this, a decoupling network (DN) can be used in a similar way that impedance matching networks are used in single-input single-output (SISO) WPT systems. The design method of a DN has been established by many different works for a MIMO antenna in communication systems, but WPT systems exhibit a loading effect that is not considered in these works. Therefore, the resulting DN from them can only achieve suboptimal efficiency in WPT. In this paper, we present an algorithm to simultaneously synthesize a DN for both the generator antenna array and the receiver antenna array which considers the loading effect problem. Through a co-simulation of an electromagnetic simulator and a circuit simulator, we demonstrate how the proposed DN design algorithm outperforms the analytic DN design for communication antennas.