Ultra-Wideband High-Gain Planar End-Fire Antenna Utilizing Higher-Order Modes of Spoof Surface Plasmon Polaritons

This letter introduces an ultra-wideband high-gain planar end-fire antenna utilizing the first four higher-order modes of spoof surface plasmon polariton (SSPP). By adjusting the width of the four interdigital branches near the opening of the meandered slot SSPP unit, bandgaps between the higher-order modes were eliminated without increasing size, facilitating ultra-wideband performance, which is a key innovation of this work. A flare slot was formed by linearly increasing the gap between two SSPP transmission lines (TLs), effectively reducing antenna sidelobes. Additionally, a metamaterial array with flower-shaped units was designed to enhance gain. A prototype was fabricated, showing measured and simulated impedance bandwidths of 113.5% from 13.8 to 50 GHz, with peak gains of 20.3 dBi and 20.6 dBi, respectively. The results are in good agreement.