Theoretical and Practical Analysis of MIMO Simultaneous Wireless Information and Power Transfer Over Inductively Coupled Circuits

The number of wireless devices continues to increase, and this growth will be further fueled by the Internet of Things (IoT). There is an urgent need to develop new techniques to both wirelessly transfer power to and communicate with these devices. Recently, inductive power transfer has gained much attention as a potentially efficient wireless powering solution for short- and medium-distance charging scenarios. In this article, we consider multiple-input multiple-output (MIMO) simultaneous wireless information and power transfer (SWIPT) using inductive coupling. While an analysis of SWIPT requires a model that correctly captures transmit power, harvested power, and information capacity, the majority of previous studies have overlooked the relationship between the mathematical signal representations and the real-world physical quantities. To overcome this challenge, we propose a framework in which signals and channels are represented by traveling waves and scattering parameters. The optimal covariance matrices of the transmit traveling waves are derived for three different working scenarios. We propose a simple estimation procedure to determine unknown scattering parameters and noise distribution. The rate-energy (R-E) regions and the magnetic field strengths are computed for two inductively coupled MIMO models based on the finite element method (FEM).