Research On Beampattern Synthesis And Adaptive Beamforming For Wing Flexible Conformal Array

With the increasing demand for future electronic warfare,intelligent variable aircraft began to become the current aerospace field.It requires aircraft to have the ability of autonomous perception,active judgment and decision making,and the rapid development of electronic information technology provides possibilities for it.The wings of intelligent variable aircraft can carry out structural deformation in real time according to different flight states and flight stages,so as to meet different aerodynamic requirements and improve the overall combat performance.The array embedded in the wing is usually the flexible conformal array that can deform with it,which can be completely conformal with the surface.In this thesis,the flexible conformal array that can expand along different spatial directions is designed based on practical conditions,and the robust adaptive beamforming(RAB)of the flexible conformal array is discussed and studied.Aiming at the problem of how to ensure that the beampattern is not distorted with deformed array structure,the beampattern synthesis algorithm is studied.On the basis of the deformation parameters mismatch and the direction-of-arrival(DOA)mismatch,the RAB algorithm is studied accordingly.The effectiveness and superiority of the proposed algorithms are verified by simulation experiments.The main research work and innovation of this thesis are as follows:1.The geometric model of the wing flexible conformal array is established,and the receiving signal measurement model of the flexible conformal array is established based on Euler rotation method.In addition,the Cramér Rao lower bound(CRLB)of the estimation of elevation and azimuth angles of the receiving signal is derived based on wing flexible conformal array.Simulation experiments were conducted to analyze the effects of signal-to-noise ratio(SNR),the number of snapshots,deformation parameters and the signal direction on CRLB.2.A fast beampattern optimization algorithm based on parameter iteration is proposed.Aiming at the problems of multi-dimensional parameters and complex global optimization in the beampattern synthesis of wing flexible conformal array and the problems of distortion of the beampattern when the structure is deformed,the multiple parameters are updated by closed expressions,which is based on the idea of the alternating direction method of multipliers(ADMM).Finally,simulation experiments verify that the proposed algorithm can suppress the sidelobe level while maintaining the main lobe with low complexity.3.A RAB algorithm based on deformation parameter estimation and interference signal subspace projection is proposed.The algorithm firstly correct the deformation parameters by means of calibration signal preprocessing aiming at the mismatching of deformation parameters,which is unique to the wing flexible conformal array.Then,in the light of the corrected deformation parameters,the interference-plus-noise covariance matrix is reconstructed in the two dimensional elevation-azimuth angle domain by utilizing integral method.And then,the steering vector of the signal-of-interest is estimated based on the subspace projection of the interference signal.Finally,the robustness of the proposed algorithm is verified by simulation experiments.