LEAKY-WAVE PROPAGATION AND RADIATION FOR A NARROW-BEAM MULTIPLE-LAYERDIELECTRIC STRUCTURE

Previous work has demonstrated that very narrow beam radiation pattern s can be obtained from a simple source embedded within multiple dielec tric layers of appropriate thicknesses above a ground plane. The confi guration consists of dielectric layers having permittivities epsilon1 and epsilon2 stacked in an alternating arrangement, With epsilon2 > ep silon1. This narrow-beam effect is attributable to weakly attenuated l eaky waves that exist on the structure. Employing a new approach, simp le asymptotic formulas for the propagation and attenuation (leakage) c onstants are derived which show how the beamwidth varies with the numb er of layers and the material constants. The exact radiation pattern i s compared with the leaky-wave pattern for a specific case to demonstr ate the role of the leaky waves in determining the total pattern.