Redefining the Channel Bandwidth for Simultaneous Wireless Power and Information Transfer

The ideal simultaneous wireless power and information transfer (SWPIT) system should share the same source and channel bandwidth. However, the requirements of the channel bandwidth between wireless power transfer (WPT) and wireless information transfer are different. In order to alleviate the effect of communications on the WPT, three bandwidths are redefined based on traditional communication systems, namely the modulation bandwidth, channel bandwidth and demodulation bandwidth. A square wave circuit is built to track the frequencies of signals at the receiver power coil, and the harmonic components in the same square wave are used to recreate information source to transmit data. Since the harmonic components can enlarge the deviations of the fundamental component, the needed channel bandwidth is decreased. The transmitter power coil and the receiver power coil still work under the quasi-resonant state with online communications. The communication function shows a strong immunity to various disturbances, such as distances, loads and input voltages. Based on the proposed method, two typical SWPIT systems in near-field and far-field are built, and the experimental data are consistent with the analytical results. The proposed SWPIT achieves a good tradeoff between efficiency and data transfer rate.