Body-Proximity Effects on the Input Impedance of a Complex-Conjugate SWIPT Textile Rectenna

Abstract

While a range of Simultaneous Wireless Information and Power Transfer (SWIPT) rectennas were proposed for wearables, the human-proximity effects on a complex-conjugate matching network-free rectenna remain mostly unknown. This paper reports for the first time the impact of human proximity on a complex conjugate rectenna's impedance. The impedance of a dual-mode SWIPT microstrip/dipole rectenna is measured experimentally for varying separation from the body and on different body positions. The measured input impedance is used to simulate the rectifier's RF-to-DC efficiency using a non-linear model showing the effects of the power level, load, and frequency on the DC output for different on-body impedances.