Design of LF-WPT systems of sympathetic connection employing non-resonant grounded antennas and external circuits which emulate the systems employing self-resonant electrically small antennas

A design method of WPT systems for use in EV wireless charging is developed. The proposed loops and the external circuit configurations are in the form of equivalent circuit for WPT systems with self-resonant antennas, and the explicit design formulae for the external capacitors and inductors are given in terms of the magnetic coupling coefficient k between two coils, working frequency f₀ and the port impedances R₀. Aggressive targets are set, such as smaller loops, longer spacing between loops, lighter systems weight, and so on. k and the Q´s of the coils and the external circuit are the key parameters determining the obtainable power transfer efficiency. Higher magnetic coupling coefficient is possible by employing thicker conducting pipes for making coils. A design example for a system in 150kHz band with rectangular loops with side-length less than 40cm, loops separation 19cm, transmitor or receiver weight less than 5 kg including ground plates, is tested by simulation and experiment. The usefulness of the design theory has been verified, and the directions towards the future efforts are described.