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

Previous work has demonstrated that very narrow beam radiation patterns can be obtained from a simple source embedded within multiple dielectric layers of appropriate thicknesses above a ground plane. The configuration consists of dielectric layers having permittivities epsilon1 and epsilon2 stacked in an alternating arrangement, With epsilon2 > epsilon1. This narrow-beam effect is attributable to weakly attenuated leaky waves that exist on the structure. Employing a new approach, simple asymptotic formulas for the propagation and attenuation (leakage) constants are derived which show how the beamwidth varies with the number of layers and the material constants. The exact radiation pattern is compared with the leaky-wave pattern for a specific case to demonstrate the role of the leaky waves in determining the total pattern.