| Reflector antennas are widely used in radar,communication,astronomical observation and other fields.The surface accuracy of antenna reflector has an important impact on the electromagnetic performance.With the trend of large aperture,high frequency band and high accuracy,the impact of surface accuracy is more significantly.How to ensure the high surface accuracy under all working conditions is an extremely challenging for the antenna design and commissioning.For example,the QTT 110m antenna is building in Qitai County,Xinjiang,China,with a diameter of 110 meters and a working frequency up to 115GHz.In order to meet its electrical performance,the surface accuracy needs to be better than 0.2mm.For this kind of 100m fully steerable high-precision antenna,in order to achieve the surface shape accuracy of 0.2mm,in addition to the structure homologous design,the advanced active structure compensation technology is also needed,which can compensate the structural deformation by the adjusting mechanism to ensure the high surface accuracy of the antenna under all working conditions.Antenna is a typical electromechanical equipment.The antenna structure is not only the carrier and guarantee of the electromagnetic performance,but also often restricts the realization and improvement of the electromagnetic performance.With the development of antenna to high frequency,high gain,fast response and high pointing accuracy,the strong coupling characteristics are presented between structure and electromagnetic performance.Therefore,the QTT110m antenna is needed to be investigated immediately from the electromechanical coupling theory.For this,the accuracy analysis,compensation and reconstruction of surface deformation are studied deeply in this thesis,and the main research is described as fo Ilows.A multi-scale error description method based on spatial distribution characteristics is proposed.This method mainly aims at the multi-scale problem of large reflector antenna surface error.According to the structural and error distribution characteristics of the antenna,the surface error distribution is divided into three scales: large scale,small scale and micro scale based on the principle of multi-scale division based on the electromechanical coupling.According to the distribution characteristics,the large-scale and small-scale errors are described by orthogonal circular polynomials and circular harmonic triangles polynomials.The micro scale error is described by statistical characteristics.Based on the principle of statistical sampling superposition,the synthetical distribution model of multi-scale error is obtained.By analyzing the influence of different scale errors and comprehensive errors on the antenna electromagnetic performance,the law of the influence of different types and scale errors on the antenna electromagnetic performance is found out,and it lays a theoretical foundation for the design,development,compensation and surface reconstruction of large high-precision antenna such as QTT.Based on the electromechanical coupling model,a method for adjusting the pose and shape of the subreflector is proposed.Aiming at the problem of residual phase error after the pose adjustment of the rigid body,based on the electromechanical coupling theory,the subreflector is regarded as a deformable surface,so that the residual error can be effectively compensated.Firstly,the influence models of the pose of the rigid body on the electrical performance is established,and the residual phase error of the aperture field with subreflector rigid displacement is analyzed.Secondly,the deformation of subreflector is described as the expression of the inverse distance weighting function related to the displacement of the adjustable point based on structural analysis and simulation,the relationship between the shape and the optical path difference of the surface is established.Finally,the adjustment amount of the actuators are obtained by minimizing the residual optical path difference after the shape adjustment of the subreflector surface.The effectiveness of the method is verified by numerical simulation.A rapid adjustment method of active surface for the large reflector antenna considering the elastic deformation of the adjustable element is proposed.Aiming at the problem that the elastic deformation of the adjustable element is not fully considered in the common adjustment methods,which affects the adjustment accuracy of the active main reflector,the analytical expressions of displacement of the adjustable point and the reflector deformation are derived based on the thin plate bending theory,and the relationship between the adjustment amount and the electromagnetic performance of the antenna is further clarified,and a method of rapid adjustment of active surface based on electromechanical coupling theory is established.In this method,the structural characteristics of independent adjustment mode and shared adjustment mode of active surface are considered,and the corresponding adjustment models are established respectively,so that when different forms of active surface are used,the surface shape can be adjusted quickly and accurately.The results of numerical experiments verify the correctness and effectiveness of the model and method.A multi-resolution integrated phase retrieval reconstruction method is proposed.When the antenna is in service,the accuracy of the reflector surface will decline.At this time,the adjustment of the actuators stored in the storage should be modified,and the phase distribution of the actual reflector is obtained quickly for this.The Misell and OOF algorithms are used in the conventional phase retrieval method.However,the conventional methods are not only sensitive to the initial value selection,but also have the fixed resolution.Therefore,starting from the antenna near-field and far-field transformation model,a modified Misell algorithm combined with the OOF algorithm is proposed,so that the multiresolution phase distribution can be quickly reconstructed from the fixed far-field amplitude distribution.Based on the principle of Chirp Z-Transform,the near-field and far-field transform model with adjustable resolution is established,and then the near-field and farfield transform operation in the Misell algorithm is replaced,so that it has the ability of phase retrieval with adjustable resolution,and the phase distribution with different resolution can be reconstructed from the fixed far-field amplitude data.Simulation results show the effectiveness of the method.More importantly,it provides important support for the construction of active surface reference database in service. |
PDF Full Text Request