Optimized Mode Coefficients of Multimode Horn with Square Aperture Achieving Constant Beamwidths for Multiband Use

This paper proposes directivity synthesis for multimode horns with square-waveguide aperture based on quadratic programming approach using radiation patterns for each mode for obtaining axial-symmetric beam and low cross-polarization components, and also for realizing desired constant beamwidth. As a design example, we present a 11/14/20/30-GHz primary horn with square aperture and also show effectiveness of the proposed method by evaluating electric force lines of aperture distribution and 15-dB beamwidth of radiation patterns.