A Study Of Error Calibration For Space Large Aperture Antenna Array

Space array antenna,which is an important part of satellite systems,is widely used in the satellite communications,earth observation and anti-missile warnings.Large aperture space array is a form of space antenna with rapid development and great application potential due to its advantages such as high gain and narrow beam.However,space antennas are in the extreme space thermal environment.Temperature changes cause the deformation of space large aperture antennas and the distortion of the array element response.The existing array errors affect the performance of the phased array antennas and the signal processing seriously.Typical calibration methods include two steps of deformation measurement and electrical calibration.In order to monitor the shape of the array surface in real time,several measurement sensors are distributed on the space large aperture arrays.However,factors such as thermal load and device aging cause the measurement sensors on the array to fail.Therefore,the recovery methods for the measurement data are needed to be studied.Based on the mechanical calibration,the array should be further corrected combining with the signal processing technologies.The deformation errors of space arrays vary with the space and time,so the structural model should be established reasonably and accurately to improve the accuracy of the error estimation.The pattern synthesis technology for large aperture arrays faces the problems such as high computational complexity and less robust in the presence of array errors.Therefore,it is necessary to study the robust and fast pattern synthesis technology.This paper focuses on the key problems such as monitoring sensor failure,structural errors,thermal deformation errors,the pattern synthesis for the large aperture arrays,and then studies the analysis of the deformation mechanism for large space arrays,the recovery of the array measurement data,the estimation and calibration of array errors,and the fast pattern synthesis method for large aperture arrays.The main research contents are summarized as follows: 1.Aiming at the problem of failure of the measurement sensors in large aperture space array,a recovery method for measurement data based on graph signal processing is proposed.By establishing the graph signal model of the array surface structure,the Laplacian matrix of the measurement data is obtained.Based on the matrix completion theory,the data recovery model is established.Then the alternating iterative method is used to solve the corresponding regularization optimization problem.The method utilizes the graph structural characteristics of the array,and can recover the measurement data with high precision in the presence of sensor failure and measurement error without any other prior information.Robustness analysis and theoretical simulations show that the proposed method can obtain more accurate data recovery results than other matrix completion methods,and the robustness of the method in condition of large failure rate is analyzed.2.The large aperture space array with a diameter of several tens or even hundreds of square meters is composed of multiple panels.Aiming at the problem of the large number of parameters to be estimated,a method to estimate the error model parameters directly is proposed.The array position errors generated during the assembly,splicing and development of the panels are different from the traditional random error.The structural errors are with a low-order error model,so the model can be used to improve the accuracy of the error estimates.Based on the analysis of the structure of the antenna,the position error model is established at the panel level and the sensor level.By analyzing the range/Doppler ambiguities in the main lobe,the constraints of the radar operating parameters are derived.Using the calibration source data extracted from the clutter echo,the error model and the calibration algorithm are combined to calculate the error model parameters directly.The simulation results show that the proposed method can achieve high-precision position error estimation and compensate the patterns well.3.Typical calibration methods for the space large aperture arrays include two methods: deformation measurement and electrical calibration.The monitoring system of the array shape is limited by the installation accuracy of the measurement equipment,and there are ambiguities of the electrical calibration when the deformation errors are large.Aiming at this problem,based on the consideration of satellite array monitoring system and actual thermal deformation characteristics,an error estimation method combining mechanical measurement and signal processing technologies is proposed.According to the measured data of the measurement sensors in the monitoring system,the order deformation model order and the initial positions of the array elements are obtained.By analyzing the geometric relationship of the satellite and the ground,the calibration source signals are extracted from the ambiguous clutter data.Then the estimates with a more accurate for the element positions can be obtained in iteration.Robustness analysis and theoretical simulations show that the proposed method can estimate the thermal deformation errors effectively and quickly,which still has good robustness in condition of a large deformation error.4.Traditional pattern synthesis technology is difficult to be applied to large aperture arrays and less robust in the presence of array errors.Aiming at this problem,an improved iterative Discrete Fourier transform(DFT)method is proposed.By using Taylor expansion to remove the coupling relationship between the position of the element and the scanning angle,the compensation matrix for the pattern function and the array weighted vector in case of amplitude and position errors are derived.The conversion relationship between the array error and the array weight is corrected in the iterative process.Thereby the correct prospective pattern can be obtained.The theoretical simulation experiments verify the effectiveness and robustness of the proposed method for the linear array and planar array pattern synthesis.The influence of Taylor expansion order on the pattern synthesis results is analyzed,which provides guidance for the subsequent selection of parameters in actual engineering.