Wireless power transfer system for external memory hard by using small magnetic coils

A miniature magnetic resonance coil for an external memory disk is presented. The proposed resonance coils are derived from a spiral structure and two capacitors through the analysis of input impedance. The measured resonance frequency and efficiency are 1.78 MHz and 82.3% at normalized distance 6 cm and the diameter size of the Rx spiral coil is 7cm.