Ultrawideband and Miniaturized Endfire Antenna With Gain Enhancement Incorporating SSPPs Mode and Vivaldi Mode

In this communication, we propose a method of incorporating spoof surface plasmon polariton (SSPP) mode and Vivaldi mode for significantly improving the bandwidth, miniaturization, gain, and aperture efficiency of endfire antenna. The radiation of the proposed endfire antenna is mainly generated by the SSPP mode (within the low-frequency band) and the Vivaldi mode (within the high-frequency band), respectively. We utilize the strengthened low-pass property of SSPPs to effectively suppress the interference between the two radiation modes without loading additional structures, achieving stable endfire pattern over the whole operating band. This dual-mode antenna is fabricated and measured, showing the ultrawide measured band from 2.04 to 23.1 GHz (167.5%) with an improved realized gain of 8.56–16.96 dBi. Meanwhile, the proposed antenna achieves a high aperture efficiency of 91.72% at the lowest frequency with a small size of $0.41\lambda _{0} \times 1.71\lambda _{0} \times 0.0035\lambda _{0}$ ( $\lambda _{0}$ is the free-space wavelength at 2.04 GHz). The simulated and measured results verify the enhanced antenna performance and the effective mode combination in the antenna design.