Multi-helix inductor of wireless power transfer system for 3-D stacked package

In this paper, the performance of package-level wireless power transfer (WPT) is compared and with respect to Z21 and voltage transfer ratio (VTR). The Z21 (transfer impedance) of three different types of inductors is analyzed and the transferred voltage is measured by applying a signal corresponding to a parallel-resonant frequency. The size of these inductors is implemented within 8 mm × 8 mm in which the parallel resonance is designed with a frequency band of 100 MHz ~300 MHz. When applying a sinusoidal signal generated from a signal generator, the proposed multi-helix inductor shows a VTR efficiency of 56.25 %. The proposed structure of the multi-helix inductor represents the most excellent VTR performance and is the most proper configuration of a package-level WPT system.