Design of Self-Matched Planar Loop Resonators for Wireless Nonradiative Power Transfer

An impedance-matching technique for magnetically coupled planar-loop resonators employing transmission lines and capacitive stubs is presented for application in wireless nonradiative power transfer (WNPT). These distributed components can be incorporated into the planar resonator itself, thereby eliminating external matching networks. The theory behind the impedance-matching technique is given in detail. Parameter tradeoffs are explored and a design procedure is provided. Two different planar loop designs are presented. The first design yields a loop-to-loop power transfer efficiency of 91% at a coupling distance of 15 cm (1.67 loop radii). The second design yields 85% efficiency at a coupling distance of 20 cm (2.22 loop radii). These results show that planar self-matched loop resonators enable compact efficient WNPT.