Optimization of a horn-parabolic excitation unit of a planar dielectric waveguide

Antennas built around the surface-to-space wave conversion have become firmly established as a particular class in antenna technology. They mainly consist of a dielectric waveguide, which forms a slow surface wave, and a diffraction grating, which serves to convert the surface wave into a space one. The variable coupling between the grating and the dielectric waveguide field determines the amplitude distribution in the antenna aperture along the surface wave propagation. Considering that the requirements upon width and sidelobe level of the antenna radiation pattern are usually made on both orthogonal planes, and that the amplitude distribution in the antenna aperture across the surface wave propagation direction is fully controlled by the amplitude distribution in the dielectric waveguide cross section, there is a need to resolve a further, no less important problem of forming a desired amplitude distribution in the dielectric waveguide. A new approach is suggested by the authors in which a special dielectric insertion is set in the open end of a standard flanged hollow metal waveguide as part of the exciter. Being a dielectric rod antenna bifurcated at the tip, the insertion improves greatly the illumination of the reflector sides.