Surface plasmonic waveguide and ultra-wideband bandpass filter using double-layered glide symmetric corrugated lines

Abstract

In this paper, an ultra-wideband high-efficiency bandpass filter based on a surface plasmonic waveguide (SPW) is proposed. The novel SPW consists of double-sided glide symmetric periodic corrugated metal. The dispersion characteristics of the double-layered glide symmetric SPW are analyzed. By using glide symmetry technology, the dispersion curve for the two lowest-order modes of the proposed SPW is a degeneracy at the Brillouin zone boundary, resulting in a higher propagation constant than the traditional symmetric structure with the same geometry. The dispersion relation of the SPW when glide symmetric conditions are broken is also investigated. Based on the proposed double-layered glide symmetric SPW, we design a bandpass filter working in an ultrawide range of frequencies. To realize the high-efficient transmission of the bandpass filter, the matching structure composed of double-layer grooves with gradient variation is designed for the effective mode conversion of quasi-transverse electromagnetic waves and spoof surface plasmonic polariton. The upper cutoff frequency of the passband can be tuned by adjusting the geometric parameters of the corrugated metal unit, and the lower cutoff frequency can be controlled by modifying the coupling distance with the bottom layer. A prototype of an ultra-wideband bandpass filter has been manufactured and measured, showing a reasonable agreement with simulations. The proposed novel UWB bandpass filter with glide symmetry can be widely used in microwave and millimeter wave related communication systems, and may play an important role in the fabrication of advanced plasma functional devices and circuits.