A Wideband High-Gain Endfire Antenna Based on Spoof Surface Plasmon Polaritons

A novel endfire antenna based on spoof surface plasmon polaritons (SSPPs) is proposed in this letter. The main radiator of the antenna is excited by the SSPP waveguide, due to the high transmission performance of the SSPP waveguide, which is realized by etching a series of periodic corrugated grooves on the metal strip. The gradient corrugated grooves are used as the transition to transform the quasi-TEM mode in the microstrip line to the SSPP mode and get maximum impedance matching. In the bottom layer of the proposed antenna, to improve the front-to-back ratio of the endfire antenna, an extended U-shaped metal plane is positioned to act as the reflector of the antenna. Three printed metal strips are designed as the directors of the endfire antenna and improve the directivity. A prototype of the endfire antenna was fabricated and measured in this letter. The simulation and measurement results demonstrate that the gain of the antenna is about 9.1 dBi at the designed frequency 7 GHz, the fractional bandwidth of the antenna is up to 31%. The endfire antenna, which is implemented on a single layer dielectric substrate has the advantages of high efficiency, good directivity, high gain, wide band, easy fabrication, and compact size.