Metamaterial Loaded Endfire Circularly Polarized High-Gain Microstrip Patch Antenna for L Band Frequency Applications

In this paper, a circularly polarized wideband and high-gain microstrip patch antenna is presented. A coplanar-waveguide-feed square patch microstrip antenna is chosen as a reference design. The bandwidth of the antenna is improved by truncating the ground plane, and circular polarization is obtained by making two diagonally placed plus-shaped slots in the radiator. These slots are orthogonally distributing the current resulting in circular polarization. The truncation of the ground plane yields a wideband response but an omnidirectional pattern thus lowering the directivity and gain. The measured realized gain of the proposed antenna is improved by 7.3 dBi using a novel wideband metamaterial electronic bandgap structure (EBG) placed beneath the antenna. The integration of this metamaterial is also transforming the omnidirectional pattern to the endfire radiation. The simulation and characterization of the proposed wideband circularly polarized antenna and metamaterial are done using a full-wave electromagnetic simulator. The prototype of the antenna is built and tested. The measured -10 dB impedance bandwidth is 67%, -3 dB axial ratio bandwidth of the antenna is 57%, and peak realized gain is 10.5 dBi. The antenna has stable performance over the operating frequency range.