Narrow-beam antennas using an artificial dielectric medium with permittivity less than unity

Radiation from a line source of electric current placed inside a slab of artificial dielectric medium with a permittivity less than unity has been studied. It is found that radiation patterns with single or multiple narrow beams may be obtained by the proper choice of parameters. In a typical case for ¿r=0.1378, ¿r=1.322, a beamwidth of about 1° is obtained when the thickness of artificial dielectric slab is about 2.33 times the wavelength.