Figure 1.

(a) Structure of the metallic patch on a grounded dielectric substrate, in which the blue and orange areas are dielectric and metal. The period of square lattice is a = 3 mm, and the gap size varies from 0.2 to 1.0 mm. F4B is chosen as the dielectric substrate with the relative permittivity 2.2 and the thickness 1.57 mm. (b) The dispersion curves of unit cells with different gap sizes. The black oblique line is the light line.