Mechanical Modeling And Performance Evolution Of A Reflector Antenna With Radome

Reflector antennas are widely used in manned spaceflight,deep space exploration,radio astronomy and other fields due to their simple structure,high reliability,high gain,and low side lobes.Due to the wide range of applications,it often faces complex service environments such as high and low temperature,ice and snow,typhoons and vibration shocks.Under the external load,the main reflector,sub-reflector and feed position of the antenna will be deformed,which will lead to the continuous deterioration of its electrical performance until it cannot meet the service conditions.This requires accurate evaluation of its performance in the antenna design stage,especially for composite antennas that are difficult to model.Due to the use of new materials and processing techniques,it is particularly important to achieve accurate evaluation of service reliability.At present,the laboratory cannot simultaneously measure the electromagnetic performance of the antenna under the condition of simulating the external load.Most of the methods for evaluating the performance of reflector antennas are based on finite element simulation.For composite materials with large errors in material parameters,this method cannot be achiev an accurate assessment for its performance.In order to solve these problems,the main research contents of this thesis are as follows:(1)A finite element model of a reflector antenna with radome is established,and its statics and dynamics are simulated and analyzed.According to the structural characteristics and material properties of the antenna,an appropriate element type is selected for the skin,and a sandwich equivalent method is introduced for the honeycomb structure modeling,which not only reduces the modeling difficulty,but also reduces the number of finite element meshes.Based on the established finite element model,the statics and dynamics simulation analysis was carried out,and the maximum deformation position and maximum stress position of the antenna structure during service were found through the statics simulation results;through dynamic modal simulation analysis and experimental testing,it is found that there is a large error in the first five-order natural frequencies of the two,which pave the way for the correction of the model introduced below.(2)A two-stage model updating method for composite structures based on surrogate model is proposed.This method combines the traditional dynamic model-based model correction method and the statics-based model correction method,the model modification of large composite structure is realized.in the first stage,the sub-assemblies and the overall structure were modified based on the dynamic parameters,and the updating results were verified by using the static parameters;in the second stage,the combined modification was carried out based on the dynamic and static characteristics.In this thesis,a reflector antenna with radome is taken as the object to correct the model to verify the effectiveness of the method.The results show that the method proposed in this thesis reduces the error sum of the first fiveorder natural frequencies from 55% to 23%,and finally to 13.6%,which is much smaller than the 26% of the traditional direct correction method.After the first-stage correction is completed,the statics error is reduced from 44.6% to 5.9%,which proves the effectiveness of the updating method proposed in this thesis,and the method allocates the parameter errors to the sub-assemblies reasonably,reducing the parameters of each optimization,the optimization algorithm is more likely to find the optimal solution.(3)A method for analyzing the evolution of antenna performance by fusing simulated and measured data is proposed.The method combines the test results based on the physical model and the finite element simulation,and solves the problem that the structure and electromagnetic life cannot be evaluated under the service conditions of the antenna.Firstly,an experimental device for simulating static wind load is developed,which can measure the precise deformation information of the radome,main reflector and sub-reflector under different wind speeds.The deformation and strength information of the physical model is obtained through the experimental test,and the strength information can be converted into the allowable stress of the material,which provides the limit threshold for the finite element simulation of the structure;the deformation information is used to updating the finite element model to obtain accurate displacement field information and to calculate the electromagnetic performance of the antenna under load.Through the method proposed in this thesis,it is found that the maximum stress position of the antenna can serve normally for 15 years under the simulated random vibration environment,and its strength performance evolution curve has no obvious attenuation phenomenon;under the extreme wind load of 65m/s,the maximum gain loss of the antenna is 0.098 d B,and the sidelobe level is reduced by 0.265 d B,which meets the requirements of electromagnetic performance indicators during service.