Research On The Design Of Smooth-walled Spline-profile Horn Antenna

Smooth-walled spline-profile horns,with the advantages of low cross-polarization level,low sidelobe level and axisymmetric beam,have been widely used in satellite communication,radio telescopes and microwave remote sensing system.Based on the theories of multimode horns,this paper focuses on the design,simulation and optimization of smooth-walled spline-profile horns.The main work is as follows:Firstly,several function curves suitable for the design of smooth-walled horns are illustrated.The horns profiled by these curves are simulated by HFSS while the input radius,length,and output radius are fixed.After comsidering the radiation characteristics of these horns,the tangential-profile horn is chosen to be modeled and optimized.Though the sidelobe level is less than-28 d B at the center frequency 53 GHz,the cross-polarization is poor and the operating band of the horn is narrow.Secondly,a smooth-walled spline-profile horn constituted by sinusoid profile and gaussian profile is designed and optimized.The antenna gain is more than 23.2d Bi,the-3d B beamwidth is less than 15?,as well as the beam is axisymmetric above-15 d B in the 50-56 GHz band.In the 52-56 GHz band,the sidelobe level and cross polarization level are less than-30 d B,which achieve the requirements of a feed.The disadvantage of the horn is that the sidelobe and cross polarization are poor in the 50-52 GHz band.Thirdly,a dual-polarized smooth-walled spline-profile horn is designed by using Piecewise Cubic Hermite Interpolating Polynomial(PCHIP)curve.The HFSS-MATLAB-API functions are applied to generate the VB scripts to construct a 3D model of the horn.The electrical size of the horn is properly selected to improve the performance of this horn.This horn reaches the goals that the antenna gain is higher than 20.1d Bi,the-3d B beamwidth is less than 15?,the beam is axisymmetric above-30 d B,the sidelobe level is less than-29.3d B and the cross polarization level is less than-29 d B across the frequency range of 50-56 GHz.Finally,an optimum proposal based on differential evolution algorithm is presented to design and optimize a dual-polarized smooth-walled horn.The node radii and the adaptive function,generated by computer programs,are employed to construct a closed-loop optimization structure,which has the advantages of fast speed and high accuracy.The optimized horn reaches the targets that the antenna gain is higher than 22.8d Bi,the-3d B beamwidth is less than 15?,the beam is axisymmetric above-20 d B,the sidelobe level is less than-30.5d B and the cross polarization level is less than-28.8d B in the 50-56 GHz band.The horn is more compact than the other horns designed in this paper.