A tunable superconducting LC-resonator with a variable superconducting electrode capacitor bank for application in wireless power transfer

The frequency alignment of resonators is essential for wireless power transfer (WPT) systems to achieve strongly coupled magnetic resonances. Here, we present a novel tunable superconducting resonator for WPT applications. The tunable resonator is composed of a high-temperature superconducting (HTS) coil and a variable HTS electrode capacitor bank based on two series YBa2C3O7-x-SrTiO3-YBa2C3O7-x thin films. The HTS coil serves as a wireless transmitting tool for power delivery, while the HTS electrode capacitor bank provides a frequency-tuning element for the resonator. At 77 K, the HTS materials cause low loss and thus achieve a high quality factor, while the incipient ferroelectric SrTiO3 substrate with HTS electrodes has a nonlinear capacitance dependence on the applied electric field with no hysteresis. A voltage supply applies a continuous DC bias to both capacitors synchronously via the coil, adjusting the total capacitance and thus the resonant frequency. Our results indicate that the tunable resonator can achieve a tuning range of 12% from 775 kHz, offering a frequency-tuning functionality to superconducting WPT technology.