Design of microwave circuits in ridge-gap waveguide technology

This paper presents recent advances is a new waveguiding 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 waves. In these waveguides there are no mechanical joints. The gap waveguides have lower losses than microstrip lines, and they are completely shielded by metal so no additional packaging is needed. The gap waveguides are realized in a narrow gap between two parallel metal plates by using a texture on one of the surfaces. The waves follow metal ridges in the textured surface. All wave propagation in other directions is prohibited by realizing a high impedance through the textured surface. The paper studies the characteristic impedance of the line and presents simulations and measurements of circuits designed using this technology.