Design of a portable wireless charging system based on relay technology

Four coupling coil structure was proposed in the paper. they are used in relay wireless charging system of portable devices. The frequency response and transmission efficiency of relays are evaluated and compared with each other based on the coupling resonance filter analytical method, then we can calculate and gained a minimum volume coupling coil - square spiral coil, it has great in-band flatness and high transmission efficiency, and can be installed easily at the bottom of the portable equipment, meanwhile it has a smaller effect on communication quality in portable devices. The transmission efficiency of square spiral relays system with 8 cm diameter is over 90% in 30 cm distance.