Local Metamaterial-Based Waveguides in Gaps Between Parallel Metal Plates

TLDR

The ridge gap waveguides are planar and much cheaper to manufacture than hollow waveguides, especially at millimeter and sub‑millimeter frequencies. This letter presents a new metamaterial‑based waveguide technology called ridge gap waveguides and introduces the gap waveguide with initial simulated results. The ridge gap waveguide is realized in a narrow gap between two parallel metal plates using a textured or multilayer surface that provides high surface impedance, guiding waves along metal ridges, suppressing transverse propagation, and eliminating mechanical joints across which currents would float. The gap waveguides exhibit lower losses than microstrip lines, are fully shielded by metal eliminating packaging needs, and show no cavity resonances within the operating band, as demonstrated by initial simulated results.

Abstract

This letter presents a new metamaterial-based waveguide technology referred to as ridge gap waveguides. The main advantages of the ridge gap waveguides compared to hollow waveguides are that they are planar and much cheaper to manufacture, in particular at high frequencies such as for millimeter and sub- millimeter waves. The latter is due to the fact that there are no mechanical joints across which electric currents must float. The gap waveguides have lower losses than microstrip lines, and they are completely shielded by metal so no additional packaging is needed, in contrast to the severe packaging problems associated with microstrip circuits. The gap waveguides are realized in a narrow gap between two parallel metal plates by using a texture or multilayer structure on one of the surfaces. The waves follow metal ridges in the textured surface. All wave propagation in other directions is prohibited (in cutoff) by realizing a high surface impedance (ideally a perfect magnetic conductor) in the textured surface at both sides of all ridges. Thereby, cavity resonances do not appear either within the band of operation. The present letter introduces the gap waveguide and presents some initial simulated results.