Received December 21, 2020, accepted December 22, 2020, date of publication December 25, 2020, date of current version January 6, 2021. Digital Object Identifier 10.1109/ACCESS.2020.3047485 Analysis and Experiment on Multi-Antenna-to- Multi-Antenna RF Wireless Power Transfer JE HYEON PARK, (Student Member, IEEE), DONG IN KIM , (Fellow, IEEE), AND KAE WON CHOI , (Senior Member, IEEE) Department of Electrical and Computer Engineering, College of Information and Communication Engineering, Sungkyunkwan University, Suwon 16419, South Korea Corresponding author: Kae Won Choi (
[email protected]) This work was supported in part by the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (MSIP), Korean Government under Grant 2014R1A5A1011478, and in part by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Korean Government (MSIP) under Grant NRF-2020R1A2C1014693. ABSTRACT In this paper, we provide a tool for predicting the power transfer efficiency of radio-frequency (RF) wireless power transfer (WPT). With its capability of long-range wireless power transfer, RF WPT is considered as a very promising recharging technique for powering low-power internet of things (IoT) devices. The prediction of the power transfer efficiency is a prerequisite for setting up a proper design goal of RF WPT systems. We propose an analytic method that enables to calculate the efficiency in various multi- antenna-to-multi-antenna WPT scenarios with arbitrary positions and attitudes of antenna arrays. We have built a prototype RF WPT system with 64 transmit and 16 receive antennas, the operating frequency of which is 5.8 GHz, and verified the accuracy of the proposed analysis.