Wideband Circularly Polarized Antenna with Enhanced Gain and Wide Beamwidth for Energy Harvesting Applications

This paper presents a high gain wideband circularly polarized antenna. The antenna is a small single element antenna, which consists of a partially grounded printed monopole design loaded with a circular split ring resonator. The antenna radiates over a wide frequency band (from 4.8 to 6 GHz), covering 5.2 GHz (Wi-Fi) and 5.8 GHz (ISM). Two circular strips are inserted into the patch; the antenna gain has slightly increased, but the significant gain enhancement (from 2.2 to 8.1 dBi) is obtained by adding a metallic reflecting surface underneath the ground plane at an optimum position. The patch resonator with the circulating current has excited the reflector to operate as a second radiator, and generate the circular polarization (CP) over a wideband. Also, the proposed structure achieves a wide beamwidth which ensures a flat-top angular coverage from −50° to +50° throughout a high gain of a range from 4 to 8.1 dBi. As a result, that antenna is proposed as a rectifying antenna (rectenna), as it guarantees good rectification efficiency. The antenna can be utilized harvest RF energy from Wi-Fi and ISM bands. CST Microwave Studio has been used to simulate the antenna. There is good agreement between simulated and measured results of reflection coefficient and radiation pattern.