Analytical Dispersion Characteristic of a Gap-Groove Waveguide

Abstract|A new type of waveguide based on the gap waveguideconcept is here proposed and called gap-groove waveguide. Its designis based on the realization of a groove on a metal, facing an arti¯cialsurface which creates a high impedance surface (HIS) boundarycondition. This condition is achieved here by employing a structure ofclosely packed metallic pins, known as bed of nails. The type of modesthat can propagate in the gap-groove waveguide are similar to the onesof a standard waveguide but in this case there is no need of electricalconnection. This is a potential advantage, especially when workingat high frequencies. The dispersion characteristic of the gap-groovewaveguide is derived by solving an eigenvalue problem, settled througha resonance condition at the interface between the groove and the bedof nails. The eigenvalues are associated with the modes propagatingin the waveguide, and their dispersion characteristic is analyzed andcompared with full wave simulations. A procedure to maximize thebandwidth is also provided, based on an appropriate choice of thegeometrical parameters. Furthermore, the ¯eld distribution and themodal impedance of the fundamental mode are investigated.