Characterization of a resonant capacitively coupled wireless power transfer system for communication purposes at 6 MHz

Abstract

This work characterizes a wireless power transmission (WPT) system operating at the 6 MHz frequency band for wireless information transfer purposes. To perform the characterization, the channel is modelled using its 2-port network scattering parameters. Then, a long string of symbols encoded with on-off keying and modified Miller encoding is passed through the channel model at various data rates. The original data is recovered from the channel output signal using a software-defined receiver. Bit error rate curves and eye diagrams are created for each encoding scheme and data rate. To verify the simulated results, the aforementioned data strings are transferred through the actual WPT system and output signals are post-processed in the digital domain with the same software-defined receiver. For comparison purposes, the performance of the WPT channel is compared to that of a conventional wireless communication channel with a flat additive white Gaussian noise model. The simulation and measurement results demonstrate that the provided WPT system can be used for data transfer with an acceptable error rate. 1 INTRODUCTION With emerging advances in RFID, wireless sensor networks (WSN), and biomedical implants, there is a push for systems that are able to power up batteryless devices and enable bidirectional communication with them [1] in order to send control signals and receive sensor data. However, wireless power transfer (WPT) and wireless communication/information transfer (WIT) differ in the metrics that each attempts to maximize [2]. WPT attempts to transfer maximum power with high efficiency, which often requires highly resonant (high Q) structures to increase power output [3, 4]. On the other hand, WIT attempts to increase data rate, which requires large bandwidths. Thus, there are two opposing design parameters: highly resonant but narrowband designs for WPT and wideband designs for wireless communication. This trade-off motivates designs in which WPT and WIT are separated either spatially [5] (such that each purpose has its own set of antennas) or in frequency as in [6-8]. This separation in designs is effective but requires dedicated hardware for each purpose. Thus, there is merit in having a This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.