Substrate-integrated circuits (SICs) [1] have attracted much attention in the last several years because of their great potential. The first implementation of the concept can be found in [2] as a feeding mechanism for a slot array antenna. Deslandes and Wu [3], [4] used the term substrate-integrated waveguide (SIW) to define this waveguide integrated in a substrate where the lateral walls are synthesized with metallized via holes, and the upper and lower walls are the top and bottom metallization of the substrate.