Waveguide for electromagnetic radiation

A waveguide for electromagnetic radiation, which is a substrate integrated waveguide which is basically a laminate of planar layers comprising: - a substrate layer of dielectric material; - a bottom layer and a top layer of an electrically conductive material provided on the respective bottom surface and top surface of the substrate layer; - a multitude of pillars of electrically conductive material which extend through the substrate layer from its bottom to its top surface and which are electrically connected to the bottom and top layer; wherein at least one of the bottom and top layer contains at least one part that is void of electrically conductive material, which part is referred to as a slot