We report our experimental and theoretical studies on a metamaterial substrate consisting of a quasi-periodic metallic planr pattern and a flat metal sheet, interconnected through metallic vias.We show that this structure possesses multiple in-phase reflection frequency regimes and spectral gaps for transverse-magnetic surface waves, whereas the transverse-electric surface waves are suppressed in all frequencies. In particular, an antenna put on top of this planar structure radiates with very high directivity sD=240d at some frequencies. This phenomenon is mainly governed by the inhomogeneity of the structure, which is a collective effect of perfect magnetic and electric conductors operating simultaneously at the frequency.