Miniature magnetic resonance coils for wide wireless power transfer applications

A simple miniature magnetic resonance coil for wide wireless power transfer applications is presented. The proposed resonance coils are derived from a new two layered spiral structure designed through the analysis of input impedance, transmission coefficient and direction of coil current. The measured resonance frequency and efficiency are 1.8 MHz and 82.5% at normalized distance 0.68(20.4 cm) and the diameter size of the spiral coil is 30 cm (1.8λ/1000). Their performance is compared with previously reported result of helical and spiral coils.