Wideband, lowloss, low-cost, quasi-TEM metamaterial-based local waveguides in air gaps between parallel metal plates

The paper presents a new waveguide appearing in the air gap between two parallel metal plates. One of the plates has a metal texture, and confined local waves follow ridges in the texture whereas they are prohibited from propagating in other directions by metal pins in the texture. The pins (or bed of nails) provide a high impedance surface that creates a stop band when used together with a metal surface, i.e. a parallel plate cut-off. The principle performance of the ridge gap waveguide is explained by numerical simulations of the dispersion diagram, both to show the parallel plate cut-off generated by the pin surface, but also to see the quasi-TEM wave propagating along the ridge. The performance is validated by numerical simulations and experimentally of a ridge gap waveguide with two 90 deg bends, including transitions to coaxial connectors. The ridge gap waveguide has a large potential for use up to THz because it can be realized without conducting joints between metal parts, and it lends itself to co-design and integration with active components.