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In this letter, a novel dual section or two step flare horn antenna for working at 1.5–8 GHz is presented. Novelty of this design is through utilizing of double flare section in horn so that the adverse effects of diffractions caused by ridges on radiation are decreased. The proficiency of new design is indicated in terms of location of the phase center, radiation pattern, and VSWR. Similarity of pattern for the two main polarizations over 10 dB beamwidth at 45° slant rotation is a feature of this antenna for applications that need similar amplitude patterns for two horizontal and vertical polarizations in the main beam. One prototype of antenna has been fabricated and tested with excellent agreement between measured and simulated results. Amplitude radiation patterns of this antenna for vertical and horizontal polarizations and also distance of the phase center from aperture versus frequency are illustrated.

In this paper, a structure and design procedure of a novel double ridged horn antenna with a Gaussian amplitude radiation pattern and stable phase center for two-element direction finding arrays is presented. The radiation properties of the structure are improved through appropriate profiling of the ridge taper and utilization of an elliptical aperture. Furthermore, rigorous numerical optimization is employed to adjust the antenna geometry parameter values. The achieved impedance bandwidth (VSWR < 2) is from 1.5 GHz to 12 GHz (8:1). The antenna exhibits 7 dBi to 20 dBi gain, better than 85% aperture efficiency, > 10 dB side lobe level, as well as low phase center variation (< 5 cm over the operating band). The aforementioned features make the proposed antenna suitable for the amplitude and phase hybrid direction finding applications. The design is validated numerically in CST Microwave Studio.