Research On Optimization Of Reflector Antenna Based On Actual Feed

Reflector antennas are widely used in deep space communication,radar imaging fields etc.,while comparing with other antennas,they can meet the requirements of high gain and broadband characteristics at a lower cost.In practical application,its performance is affected inevitably by the electromagnetic environment,and thus the beam-shaping technology for the reflector antenna is generally used to enhance the anti-interference ability.However,the ideal or the simulated feeds are often adopted in the present beam-forming techniques,and the errors between the corresponding results of these feeds and that of the actual feed exist,which may lead to inaccurate beam-forming results.Therefore,a beam-shaping optimized technique based on actual feed for reflector antenna is proposed in this thesis,and then a low sidelobe and three-beam shaped reflector antennas are designed.The main contents of this thesis are as follows:1)The investigation of actual feed technique and the construction technique of actual feed using amplitude pattern and phase center.Depending on the different beam characteristics of feeds,two methods are proposed to construct the amplitude pattern,and three antennas are designed for verification.The results show that the method of the proposed principal plane pattern to calculate the amplitude pattern is suitable for beams with rotational symmetry,and the test method can accurately describe the influence of the fabrication error on the amplitude pattern,then,the principal plane's phase data is brought into the ray-tracing method to solve the phase center.Comparing with the phase center obtained in the electromagnetic simulation software CST,this method has high accuracy and fast solution speed.Finally,an actual feed is constructed for the dielectric rod antenna used to optimize the reflector antenna.2)Research of optimized technique based on actual feed is proposed for the reflector antenna.The novel optimized technique to the reflector antenna is proposed depending on the combination of the actual feed technique with some other algorithms.First,the geometric optics method is used to calculate the incident field from the actual feed to the non-uniform rational B-spline(NURBS)reflector surface;then,the physical optics(PO)method is adopted to calculate the scattering field caused by the surface current of the reflector surface,and also combining with the Gauss-Legendre quadrature(GLQ)method to speed up the scattering field calculation;finally,the Nelder-Mead optimization algorithm is used to adjust the reflector to obtain the desired pattern.Simultaneously,an offset reflector with a diameter of 300 mm is fabricated according to the technique mentioned above,and the result shows that the actual feed model is more accurate than the simulated feed.3)Research on the validation of the actual-feed beam-forming technique is proposed.According to the above techniques,the low sidelobe optimization objective function and the three-beam optimization objective function are proposed.For the shaped reflector antenna of the former situation,the corresponding sidelobe is reduced by at least 4.99 dB;while for the latter,the final gain of the three beams is about 24 dBi,and the sidelobes among beams are below-20 dB.Experiments indicate that the shaping results obtained from the actual feed are more accurate than the simulated.