Dual band omnidirectional circularly polarized antenna using EZR and MZR modes

Abstract

A dual band omnidirectional circularly polarized (CP) antenna is presented based upon new concept of combining two orthogonal modes of epsilon-zero resonance (EZR) and mu-zero resonance (MZR) in this article. The antenna has the CP characteristic by two circularly ring-structured double negative (DNG) transmission lines. One DNG transmission line has higher frequencies of EZR and lower frequency of MZR while the other DNG transmission line has higher frequencies of MZR and lower frequency of EZR. The EZR and MZR modes at the same frequency have a vertical and a horizontal polarization with 90 degrees phase difference, respectively. In the EZR mode, a vertical polarization is generated like an electric monopole so that the EZR antenna radiates omnidirectionally. The MZR antenna makes a horizontal polarization by the circular ring current like a magnetic dipole loop which also radiates omnidirectionally. The analysis and design of the antenna are performed according to theory and simulation based on a dispersion diagram and E-field distribution. Finally, the reasonable performances of the antenna such as a reflection coefficient, a CP gain, an axial ratio, and a far-field radiation pattern are obtained in dual band.