resonance-based wireless power transfer (R-WPT)||resonance frequency||power transfer efficiency (PTE)||3-coil system||steady-state matrix analysis||Class-E power amplifier||wireless power transfer (WPT) system||output characteristics||strength||coupling coefficient||impedance matrix||multiple coils||mutual inductance||scattering matrix||transfer impedance||wireless power transfer||design optimization||finite element analysis||gallium nitride||gradient methods||inductive power transmission||power measurement||transformer cores||wireless charging||circuit modeling||numerical analysis||capacitive wireless power transfer||resonance||power-transfer efficiency||multiports||multiple-input single-output||wireless power transmission||electric field||shielded-capacitive power transfer||design guidelines||resonant||inductive coupling||optimal load||single-input multiple-output||power gain