Flexible Printed Rectenna Based on a 2.45 GHz CPW Rectifier for Energy Harvesting Applications

This paper presents a study on a novel and innovative design of a thin and flexible rectenna using a coplanar waveguide (CPW) rectifier optimized for operation in the 2.4 GHz frequency band. The substrate selected for the rectenna is a 125-μm thick Polyimide film with a 35 μm copper foil. The CPW-fed rectifier is designed to efficiently handle low RF input power levels, while the integrated antenna is capable to operate in both the 2.4 GHz and 5-8 GHz bands with a minimum gain of +2dBi. Before integration, the performances of the CPW-fed antenna and the rectifying circuit were individually characterized. The rectifier, based on a voltage doubler architecture, was extensively studied and demonstrated a power conversion efficiency of 37.4% for a low RF input power of −10 dBm. To assess the conformability of the printed rectenna, its flat and folded performance was compared and evaluated in an anechoic chamber. The overall power conversion efficiency of the rectenna, with an RF input power of −4.5 dBm, can reach 50%, resulting in a DC voltage of1.3 V across a 9.5 kΩ load. With the measured performance, the fabricated rectenna is capable of efficiently harvesting the available power density from an RF source in the 2.4 GHz ISM band, which corresponds to the Bluetooth and WIFI channels.