Alternative ridge gap waveguide design using a mushroom-type EBG surface

The new proposed ridge gap waveguide can be implemented with different types of periodic surfaces. In this manuscript we have shown how to use the mushroom-type EBG surface to this aim besides the previously used ldquoFakir´s bed of nailsrdquo. The bandgap of the periodic structure inside the parallel plate gives the upper limit of the band of operation of the gap waveguide, being the distance to the upper plane or gap, a key parameter for the bandwidth. In both geometries, a reduction in this gap means a significant increase on the bandgap of the structure. Nevertheless, both structures have a bandwidth which is large enough for most of the applications, even if larger gap size values are considered. Due to its physical realization and volume, the pin surface is more suitable for high frequencies whereas the mushroom-type EBG surface could be used in lower frequency ranges.