Variable permittivity dielectric material loaded stepped-horn antenna

45Figure 4.1 Input reflection coefficient versus frequency for dielectric (εr = 2.63) loadedopen-ended waveguide radiator with length of L = 9.51mmand bA = 29.21 mm and length of the horn is L = 51 mm. Three different dielectricloading configurations are compared. First uniform dielectric loading is applied. In thisconfiguration, both feed waveguide and tapered section of the horn are loaded with thesame dielectric material, εr. Then step loading is applied. This configuration leaves thefeed waveguide empty and loads the tapered section with dielectric medium (εr). And lastconfiguration that was tested is a linear profile configuration. From feed waveguide towardthe aperture, dielectric constant εr changes linearly from 1 to pre-determined value of εr .The value of a dielectric constant εr = 1.5 is chosen to load the 10 dB standard gain hornantenna.Results presented in Figure 4.3 to Figure 4.6 depict comparison for input reflectioncoefficient, gain, aperture efficiency and cross-polarization characteristics between thesethree configurations and an empty horn antenna. From input reflection coefficient comparisons