Omnidirectional Circularly Polarized Zeroth Order Antenna Using Asymmetric Unit Cells

In this paper, a single-band omni-directionally circularly polarized Zeroth Order Resonance (ZOR) epsilon negative antenna is proposed. The above proposed antenna is designed for the case where the shunt ZOR is higher than series ZOR. Circular Polarization (CP) is achieved using Asymmetric Unit Cells (AUCs) which create orthogonal components. Zeroth order resonator inherently provides 90° phase shift between two orthogonal polarizations. Left Hand Circular Polarization (LHCP) is achieved by adding stubs with two 90° right bends to the unit cells. Electric field distribution is used to verify the excited resonance for zeroth order and it is found that it follows zeroth order characteristics. The simulated and the measured shunt ZOR are 4.21 GHz and 4.26 GHz, with fractional bandwidths of 1.3 % and 0.87 %, respectively. The simulated and measured LHCP gains are 2.05 dBic and 1.9 dBic, respectively.