Frequency modes in a MIMO wireless power transfer system

In this research, we investigate the frequency splitting phenomenon in a multi-input and multi-output (MIMO) wireless power transfer (WPT) system, which consists of multiple transmitters (TX), multiple receivers (RX) and a repeater. Equivalent circuit model is presented to predict the system characteristics of the MIMO architecture. Frequency splitting is first analyzed in the conventional single-input and single-output (SISO) system. Low-mode and high-mode frequencies for the SISO system are obtained. Frequency splitting is then further demonstrated in a prototype MIMO system consisting of two TXs, two RXs and a repeater. In the experiment setup, the system is designed to operate at a center frequency of 6.78 MHz and the antennas are fabricated on the flame retardant (FR4) substrates using photolithography and etching. Both analytical and measurement results agree well demonstrating the multiple frequency modes in the MIMO wireless power transfer system.