This paper presents an energy harvesting circuit for high efficiency performance. The proposed circuit consists of an RLC shunt resonance circuit integrated to an RF antenna. The resonance circuit is used to (i) selectively pick the desired signal whose output is fed to a Cockcroft–Walton voltage multiplier circuit; and (ii) match the impedance of the antenna with the Cockcroft–Walton voltage multiplier circuit for optimum power (DC) transfer. The proposed circuit exhibits an efficiency of 68% for an input power of 200 microwatts