Coaxial‐fed high‐gain triple‐band zeroth‐order circularly polarized antenna using pseudo‐open termination and asymmetric unit cells

Abstract

A coaxial-fed tri-band zeroth-order resonance (ZOR) circularly polarized antenna with higher gains for all the excited ZORs is designed and analyzed in this paper. Epsilon negative transmission line (ENG TL) and pseudo-open termination (P-OT) unit cells with different series capacitances (CS and CS1) resonate shunt ZOR (fsh) and two series ZORs (fse and fse1), respectively. Asymmetric unit cell concept is applied to ENG-TL and P-OT unit cells to create vertical and horizontal components, and the 90° phase shift is provided by the ZOR, resulting in circular polarization (CP). Left-hand CP (LHCP) is achieved by creating two 90° right bends to the extended stubs in ENG TL and P-OT unit cells. Higher gains for all the excited ZORs are achieved by shifting the shorting pins of ENG TL and P-OT unit cells far away from the center position. After fabrication, the measured resonances occur at 4.64 GHz (fsh), 4.04 GHz (fse), and 3.86 GHz (fse1) with fractional bandwidths of 1.62%, 1.73%, and 1.6%, respectively. The measured LHCP peak gains are 4.05 dBic (fsh), 3.85 dBic (fse), and 3.94 dBic (fse1). The average axial ratio obtained is less than 3-dB in the 10-dB fractional bandwidth of the proposed antenna.