Study on a Metal Closet Based Wireless Power Transfer System for Smart Suit Charging

This paper investigates a metal closet-based wireless power transfer system designed to ensure the wireless charging of batteries incorporated into a smart suit. The closet walls are made of steel, and the dimensions are such that several modes with commensurate amplitudes are excited simultaneously. The fields inside the closet are excited by a sine wave source at an operating frequency of 865.5 MHz, which belongs to the standard sub-GHz ISM band. Several receiving and transmitting antenna configurations are examined, including the one involving a classical dipole antenna printed on an FR-4 substrate acting as the transmitter. The receiving dipole antenna is embedded into a cotton suit model. Additionally, two configurations with single and two Yagi-like antennas are studied. The WPT system power transfer efficiency is estimated by means of commercially available software Ansys HFSS. The simulation results obtained for different antenna configurations are compared to show their advantages and shortcomings. The results show that the use of Yagi-like antennas at both the transmitting and the receiving ends results in the highest efficiency reaching 65% and improves the field uniformity inside the closet, thus relaxing the requirement for precise suit placement.