Research On Fast Shaping Technology Of Reflector Antenna Based On Quasi-Actual Feed

Reflector antennas have been widely employed in a variety of applications including radio astronomy and satellite communication because of their advantages of high gain and low side-lobe.With the development of wireless communication technology,the electromagnetic environment where the antennas are located becomes increasingly complicated.In order to continue take advantages in this new environment,the beam characteristics of reflector antennas need to be optimized by using beam-forming technology.However,the traditional beam-forming technology for reflector antennas always adopt ideal point source as the feed,and the errors between the ideal point source and actual feed may cause the imprecise beam-forming results.Given this situation,a fast beam-forming technology based on quasi-actual feed for reflector antennas is proposed in this thesis.Based on this technology,a low side-lobe and a flat-top beam-shaped reflector antennas are designed to prove the validity of the proposed technique.The main research contents of this thesis are as follows:1.A beam-forming technology based on quasi-actual feed is proposed for reflector antennas.The quasi-actual feed technique based on simulation data is studied,and then the quasi-actual feed technique is combined with a variety of algorithms and technique to constitute a beam-forming technology for reflector antennas.In this beam-forming technology,a quasi-actual feed is adopted to excite a reflector generated by NURBS(nonuniform rational B-spline non-uniform rational B-spline)technique;and then,the geometric optics,the physical optics,and the Gauss-Legendre methods are employed to quickly analyze the scattering field of the NURBS reflector;finally,the Nelder-Mead algorithm is applied to optimize the shape of the NURBS reflector to obtain the desired pattern.2.Beam-forming reflector antennas are designed to prove the feasibility of the proposed technique.First,a reflector antenna working at 14.5GHz-15.5GHz is designed to as the initial antenna,which includes an offset NURBS reflector whose aperture diameter is 300.0mm and a small hollow dielectric rod feed antenna whose length is 115.0mm.Then,(1)a low side-lobe objective function is proposed and is combined with the beamforming technique proposed in this thesis to optimize the initial antenna,and the side-lobe of the shaped antenna is reduced by at least 4.3d B;(2)a flat-topped beam objective function is proposed and is combined with the beam-forming technique to optimize the initial antenna.Compared with the original antenna,the 1d B beam-width of the optimal antenna is more than doubled,and the first side-lobe level does not increase significantly.Both of the objective functions have simple form and flexible controllable parameters.Moreover,the design of the beam-forming reflector antennas verify that the beam-forming technology proposed in this thesis has the advantages of fast calculation speed,smooth forming surface,and accurate forming result.