Summary form only given. For wide-angle scanning planar arrays, the magnitude of the reflection coefficient may change substantially with scan angle, scan plane and wave polarization. The conventional solution to this problem consists in the use of wide-angle impedance matching (WAIM) structures made up of a stack of dielectric layers. Much greater flexibility may be achieved by employing anisotropic slabs with controllable spatial dispersivity. Artificially structured materials (or metamaterials) make this approach feasible by allowing the simultaneous control of dielectric and magnetic properties in the different directions (S.Sajuyigb et al., IET Microw. Antennas Propag., 4(8), 1063-1072, 2010).