title: Midfield wireless powering of subwavelength autonomous devices.
abstract: We obtain an analytical bound on the efficiency of wireless power transfer to a weakly coupled device. The optimal source is solved for a multilayer geometry in terms of a representation based on the field equivalence principle. The theory reveals that optimal power transfer exploits the properties of the midfield to achieve efficiencies far greater than conventional coil-based designs. As a physical realization of the source, we present a slot array structure whose performance closely approaches the theoretical bound.
authors.affiliation: Department of Electrical Engineering, Stanford University, Stanford, California 94305, USA.
authors.forename: Sanghoek
authors.initials: S
authors.lastname: Kim
authors.affiliation: Department of Electrical Engineering, Stanford University, Stanford, California 94305, USA.
authors.forename: John S
authors.initials: JS
authors.lastname: Ho
authors.affiliation: Department of Electrical Engineering, Stanford University, Stanford, California 94305, USA.
authors.forename: Ada S Y
authors.initials: AS
authors.lastname: Poon
mesh_terms: D011211:Electric Power Supplies; D060733:Electromagnetic Radiation; D004867:Equipment Design; D008962:Models, Theoretical; D019736:Prostheses and Implants