Optimal Coupling to Achieve Maximum Output Power in a WPT System

In the wireless power transfer systems, a coupling coefficient is one of the measures of performance. In particular, the coupling coefficient at critical coupling does not ensure maximum system energy efficiency but guarantee maximum output power to the load. As the coupling coefficient goes beyond the critical-coupled state, output power begins to decline. In this letter, we propose a method to maximize output power even in an overcoupled state as in the critical-coupled state by adjusting the capacitance of the resonator. Our proposal is verified by comparing the calculations and simulations with measurements, and they are in good agreement.