High gain dual-band zeroth order omnidirectional circularly polarized antenna

Abstract

A dual-band omni directionally circularly polarized zeroth order resonance (ZOR) antenna is proposed in this paper. Shunt ZOR (fsh) is excited by an Epsilon Negative Transmission Line (ENG TL), whereas Series ZOR (fse) is excited by two Pseudo-Open Termination (P-OT) unit cells. To resonate an omnidirectional fsh, ENG TL is required, while to resonate an omnidirectional fse, the two P-OT unit cells require similar series capacitances. Higher vertical and horizontal components are created by applying Asymmetric Unit Cells (AUCs) concept, in order to achieve Circular Polarization (CP) and high gain. The 90° phase is provided by the ZOR. By combining the feature of omnidirectional and CP at ZOR, omnidirectional CP is achieved at both fsh and fse. Since ENG TL and P-OT unit cells have two 90° right bends in the extended stubs, fsh and fse resonate with Left Hand CP (LHCP). The measured ZORs occur at 4.54 GHz (fsh) and 3.86 GHz (fse) with fractional bandwidths of 1.55% and 1.3%, respectively. The measured peak LCHP gains of the proposed antenna at fsh and fse are 3.34 dBic and 3.05 dBic, respectively. In the 10-dB impedance bandwidth range, the measured average axial ratio is less than 3-dB.