An Ultra-Thin and Compact Band-Pass Filter Based on Spoof Surface Plasmon Polaritons

Liaori Jidi,Jun Gao,Tong Li,Huanhuan Yang,Xiangyu Cao,Sijia Li

doi:10.1109/access.2020.3024596

Abstract

In this work, we report an ultra-thin and compact SSPPs-based waveguide band-pass filter with metals etched on the top surface of substrate, and the side and bottom surfaces of substrate also are covered with metals. The size of this filter is $1.07\lambda _{0}\times 0.32\lambda _{0}\times 0.02\lambda _{0}$ (where $\lambda _{0}$ is the wavelength at center frequency). This proposed filter can inherit the merits of rectangular waveguide and SSPPs structure, and its lower cut-off frequency can be tuned by the width of rectangular waveguide, while the upper cut-off frequency can be tuned by the length of complementary comb-like structure. Gradient groove depths are also used to form a smooth transition from rectangular waveguide to SSPPs structure, realizing a good momentum match. The dispersion curves and electric field distributions have been thoroughly investigated to reveal the SSPP-based waveguide filter mechanism. A prototype is fabricated and measured. Both simulations and measurements validate that the band-pass filter proposed in this work has high-efficiency and low-loss transmission properties.

Highlights

At optical frequencies, metals behave as plasmons and have negative permitivities, while dielectric media have positive permittivities, so surface plasmon polaritons (SPPs) can be propagated in the interface between metal and dielectric media and decay exponentially in the direction vertical to the interface [1]–[4]
We report a kind of simple ultra-thin and compact SSPPs-based waveguide filter with metals etched on the top surface of substrate, and the side and bottom surfaces of substrate are covered with metals, which has high-efficiency and low-loss features and realizes a controllable band-pass performance
In conclusion, an ultra-thin and compact SSPPs waveguide filter is proposed in this work, which has a different working principle with its former counterparts

Summary

INTRODUCTION

Metals behave as plasmons and have negative permitivities, while dielectric media have positive permittivities, so surface plasmon polaritons (SPPs) can be propagated in the interface between metal and dielectric media and decay exponentially in the direction vertical to the interface [1]–[4]. Some microwave filters based on the merits of SSPPs structures have been proposed, but among them the majorities are the low-pass filters [4], [8]–[12], [23]–[26]. We report a kind of simple ultra-thin and compact SSPPs-based waveguide filter with metals etched on the top surface of substrate, and the side and bottom surfaces of substrate are covered with metals, which has high-efficiency and low-loss features and realizes a controllable band-pass performance. The proposed filter has the following several merits: (1) Compact and miniaturized size (1.07λ0 × 0.32λ0 × 0.02λ0, where λ0 is the wavelength at center frequency); (2) Working band is controllable by varying the geometrical parameters; (3) Covering the bottom surface of substrate with metals to make it convenient in the traditionally integrated circuits design; (4) High-efficiency and low-loss properties

DESIGN AND ANALYSIS OF UNIT CELL

CONCLUSION