Tunable Dual-Band High Impedance Coil for Wireless Power Transfer Applications

Earlier, we engineered a wireless power transfer (WPT) system whose key element is a self-activating and self-decoupling transmitting (Tx) antenna called the high-impedance coil (HIC) that grants a high efficiency for a receiving (Rx) antenna with a free position in front of the Tx array. When the Rx antenna is located in front of the Tx one, the input impedance of the last one drastically decreases, which results in efficient power transfer. This impedance is initially so high that the Tx antenna in the absence of the Rx one does not accept power, which implies negligible open-circuit losses. This feature grants the automatic activation/deactivation of the WT system. In the present work, we suggest the qualitative modification of the HIC-based WPT system aiming its operation at two very different frequencies. The upper frequency is above 500 MHz which was earlier considered technically not achievable for HICs. To analytically engineer and describe our new HIC, in which the cable is replaced by a stripline, we developed a comprehensive semianalytical model. This model is quite general and can be used for further modifications of such antennas.