US Patent 11031824 Apparatus and method for RF energy harvesting

An RF energy harvesting apparatus comprising an energy harvesting antenna carried on a substrate for fixing the antenna to an electrical device, wherein the antenna comprises a coil of conductive material carried on the substrate, wherein the coil provides two loops of conductive material on the substrate, the coil comprising a second loop inside a first loop; and wherein the coil comprises at least one segment arranged to reduce spatial variations in the H-field in an area circumscribed by the first loop.