A Generic Hybrid Combining Receiver for MIMO Wireless Power Transfer Considering Nonlinearities

We study the impact of nonlinear saturation effect and receiver architecture on the performance of multiple-input and multiple-output (MIMO) wireless power transfer (WPT). We propose a generic hybrid combining receiver architecture where the receive antennas are grouped into multiple subarrays, each subarray consisting of multiple energy harvesting (EH) circuits. For efficient receiver reconfiguration, a power splitter is placed in between each antenna subarray and the associated EH circuits. To improve the WPT performance, we formulate an optimization problem for joint transmit and receive beamforming design along with receiver reconfiguration, which appears non-convex fractional programming. To resolve this, the optimization problem is reformulated into equivalent semi-definite programming problem with rank-one relaxation through quadratic transform, which provides a suboptimal solution for the original problem. Then, we propose an iterative algorithm for optimizing the joint beamforming design and receiver reconfiguration. We confirm that the WPT system optimization considering the nonlinearities existing in the proposed generic receiver structure yields better performance than when the nonlinearities and resulting receiver architecture are not taken into account.