Field theory CAD of profiled corrugated rectangular or circular horns by an efficient full-wave modal-S-matrix method

A full-wave combined modal expansion and aperture field integration method is applied for the efficient design of profiled corrugated horns with circular, rectangular or combined cross-section. The generalized modal S-matrix combination of adequate key building blocks, i.e., the circular, rectangular, or rectangular-to-circular waveguide step discontinuity, takes the influence of the higher-order modes and the aperture effect rigorously into account. An optimized broadband profiled corrugated circular horn design example utilizing 40 varying slot elements with a rectangular waveguide input section demonstrates the usefulness of the method by achieving more than 26dB return loss, about 20 dB gain, and less than -30dB cross-polarization for a bandwidth of about 1.7:1. The theory is verified by comparison with available measurements.<>