Research On Beam Sharpening Method Of Airborne Forward-looking Scanning Radar

Airborne forward-looking scanning radar has great application value in the fields of autonomous landing,terrain avoidance and ground attack.However,the azimuth resolution of the airborne forward-looking scanning radar is relatively low due to the limitation of the real aperture.As a result,the terrain and the clustery targets in the forward-looking area of the vehicle cannot be detected effectively.Therefore,it is of great importance to explore new approaches to sharpen the real beam and improve the azimuth resolution of the airborne forward-looking scanning radar.Focusing on the problem of beam sharpening method of airborne forward-looking scanning radar,this dissertation has studied the sharpening method,algorithm realization and distortion correction based on the statistical optimization method and the regularization method.The main contents are as follows:1.Based on I/Q channel noise modeling,a maximum likelihood beam sharpening method is proposed.It alleviates the noise sensitive problem caused by the mismatch of echo statistic model in the traditional method,and effectively suppresses the parasitic ripple and false targets in the imaging results.2.A maximum posterior beam sharpening method based on the square Laplace constraint is proposed.It solves the iterative semi convergence problem caused by the noise amplification phenomenon in sparse scene,and improves the stability of the beam sharpening algorithm while realizing the accurate inversion of the sparse targets.3.A two-channel regularization strategy is proposed and the corresponding sharpening methods have been constructed.It breaks the limitation of the existing regularization method to deal with the single characteristic scene,and solves the problem of losing the the background outline while resolving the the clustery targets.4.To solve the problem of slow convergence of the iterative regularization method,an accelerated iterative threshold shrinkage method based on three-point vector extrapolation is proposed.It lays a technical foundation for the efficient implementation of the regularization beam sharpening method and facilitates the engineering realization of the algorithm.5.Aiming at the problem of beam distortion in high-speed motion of the vehicle,the analytic relation between the motion velocity and the distortion pattern is established.Besides,the regularization correction algorithm based on block processing is used to improve the result of beam sharpening under the condition of high-speed motion of the machine.The theories and methods above have been validated by simulations and measured data.The results demonstrate that the methods above can effectively solve the problem of the engineering application of the beam sharpening method of airborne forward-looking scanning radar.