The aim of this paper is to demonstrate that it is possible to perform a waveguide using parallel plates and some metamaterial surfaces. The lack of lateral metallic walls in the waveguide is replaced by the effect of these metamaterials. An AMC-PEC-AMC structure is designed, simulated and prototyped. The advantage of this structure is due to the planar architecture and its low cost. In this paper, we use the structure described as if it were the feeding part of a planar slot antenna, in order to demonstrate the chance of using this structures in this antennas. Reflection and radiation pattern measurements are presented.