Wideband Vertically Polarized Planar Endfire Antenna Based on Spoof Surface Plasmon Polaritons

A novel wideband vertically polarized planar endfire antenna based on the first and the second high-order modes of spoof surface plasmon polaritons (SSPPs) is proposed in this letter. A double-sided SSPP transmission line (TL) is used to produce vertically polarized radiation. By replacing the uniform stub in the conventional SSPP cells with a step-impedance-resonator (SIR) shaped stub, the bandgap between the first and the second high-order modes is eliminated. The double-sided SIR-shaped SSPP cells are tilted to make the maximum radiation point in the endfire direction. Dielectric covers perforated with air vias are added to the top and bottom surfaces of the SSPP TL to generate endfire radiation and enhance antenna gain. A grounded coplanar waveguide to double-sided parallel-strip line transition is designed to feed the radiator. A prototype of the proposed antenna has been fabricated and measured. The proposed antenna achieves a fractional bandwidth of 91.6% from 12.9 to 34.6 GHz and a peak gain of 17.3 dBi.