Abstract—Resonant wireless power transfer (WPT) using
magneto quasi-static fields is an attractive means for delivering
power in many applications. Central to the efficient delivery
of power in these systems is the use of high-ratio impedance
transformers to impedance-match the load to the source via the
WPT network.Mini-loop transformers, which use a resonant tank
for impedance matching, have become popular as they provide
high-ratio impedance matching and low loss. Key to the low loss
is the use of high- resonators. There are two challenges with
this approach. The first is impedance matching the resonators to
source/load impedances, and the second is adjusting the center
frequency of resonance to exactly match the operating frequency,
which can be very difficult with helical coils that use their parasitic
capacitance for resonance. In this letter, we introduce a tri-coil
impedance-matching network for WPT that provides accurate
impedance matching and precise frequency tuning for highcoils
to overcome these limitations.