Radiation patterns of dielectric loaded rectangular horns

A Novel Horn Radiator With High Aperture Efficiency and Low Cross-Polarization and Applications in Arrays and Multibeam Reflector Antennas

“…The expression for is given by (11) with , , . For most of the antenna applications, the incident mode at the horn input is the TE mode; therefore, for all the modes on the aperture unless the rotational symmetry of the circular horn is perturbed.…”

“…Therefore, the aperture field of a high efficiency circular horn with the TE incident mode at the horn input can be represented as (12) Assuming the principal polarization along the -direction, the aperture field for maximum efficiency is written as Substituting (13) in (12) and using orthogonality, we obtain (14) After performing the integration we get a closed-form expression for TE as (15) The first three roots of are , , ; therefore the ratio of the modal voltages for the first three TE modes calculated using (15) is (16) The phases of the propagating modes are identical. 3 For evanescent modes, the phase angles are 90 ; the positive or negative sign depends on the sign used for the normalization factor in (11). In practice, only the propagating modes arrive at the aperture plane, so the radiated fields are contributed by propagating modes only.…”

“…This horn is the rectangular equivalent of the "Potter horn;" therefore, it also has low aperture efficiency. In [10] and [11], dielectric loading was used to enhance the aperture efficiency of a rectangular horn. Such horns are heavy, have fabrication complexity, and may have surface charge accumulation on the dielectric surface leading to electrostatic discharge.…”