Design considerations in planar soft surfaces

Soft surfaces have been traditionally used to suppress surface wave propagation in a given direction. In this work we analyze one type of planar soft surface which is easy to manufacture and relatively compact. The structure consists of strips with grounded vias. A parametric study has been carried out for a realistic case, showing which are the fundamental parameters of the geometry which define bandgap properties. It is shown that vias can be used to modify the bandgap frequency and also to create a dual band soft surface. Moreover, this structure is simple and more compact than mushroom-type EBG, thus it can be useful for applications in which surface waves have to be cancelled in a known direction, such as for example mutual coupling reduction or back radiation reduction in patch antennas. Some experimental results are also presented.