Circularly polarized dual‐band zeroth order epsilon negative antenna using asymmetric unit cells

Abstract

In this paper, a dual-band zeroth order resonance (ZOR) circularly polarized epsilon negative antenna is proposed for the case where shunt ZOR (fsh) is higher than series ZOR (fse). Epsilon negative unit cells resonate fsh, while a pseudo-open termination unit cell with a series capacitance resonate fse, resulting in a dual-band ZOR. The pseudo-open termination unit cell can be placed anywhere around the epsilon negative unit cells for proper matching. Circular polarization (CP) is achieved by creating orthogonal components using asymmetric unit cells (AUCs). Zeroth order resonator inherently provides 90° phase shift between two orthogonal polarizations. Left hand circular polarization (LHCP) is achieved by adding stubs to the unit cells with two 90° right bends. Electric field distribution is used to verify the resonances for zeroth order and it is found that both the resonances follow zeroth order characteristics. The measured resonances are 4.11 GHz (fse) and 4.60 GHz (fsh) with measured average axial ratio of 2.4 dB at fse and 1.5 dB at fsh, respectively. The measured LHCP peak gain for fse is 1.53 dBic and for fsh is 2.34 dBic. The proposed design covers a frequency range of 3.6 to 4.6 GHz by varying the length of the stubs.