Near Field Distribution of Hollow Dielectric Wall Diagonal Horn Antennas

Abstract

Aperture/near-field distributions of hollow dielectric wall diagonal horn antennas have been studied theoretically and experimentally. Solutions of the Helmholtz equation are obtained for TE to x and TE to y modes using separation of variables technique for the horn assumed to be made of an equivalent homogeneous dielectric material of dielectric constant equal to the effective dielectric constant of dielectric slabs and inner free space region bounded by these slabs. Transcendental equations for the transverse components of propagation constants are obtained by applying proper boundary conditions, i.e. the continuity of the electric and magnetic fields at the interfaces each between the dielectric region and outer free space region. These transcendental equations are solved for the transverse propagation constants for the fundamental mode for five horns each of axial length = 12.8 cm and flare angle = 8.5° at 9.418 GHz in the x-band. The dielectric constant of the dielectric slabs used in fabricating the five horns are equal to 2.54, 2.56, 2.56, 2.80 and 3.03 and respective slab thicknesses are equal to 0.15, 0.15, 0.32, 0.32 and 0.32 cm. The theoretical aperture-field distributions obtained for Hx11, and Hy11modes propagating in these antennas are compared with corresponding experimental ones.