Omni-Directional Microstrip Ring Antenna Based On a Simplified Left-Handed Transmission Line Structure

In this paper we present a novel microstrip ring antenna based on a simplified left-handed transmission line (TL) structure. We simplify the widely used composite right/left-handed TL structure by taking away the series capacitors to reduce both the size and the structure complexity. The analysis shows that such simplified TL structure still possesses zero phase propagation constant. We investigate the resonance at which the phase propagation constant is zero through both the finite element method (FEM) based full-wave electromagnetic simulation and experiment. Operated at the resonant frequency, the antenna features an omni-directional radiation pattern which is similar to a vertical half-wavelength dipole. With the advantages of low-profile, compactness and omni-directional radiation, we believe this antenna would have potential applications in various wireless communication applications.