Research On Airborne ISAR Ship Imagingusing Real Data

Inverse synthetic aperture radar(ISAR) is a kind of high-resolution imaging radar for non-cooperative target, which has a broad prospect in both military and civilian fields. Ships are important military targets. With the growing demand for the development of naval equipment in recent years, the imaging and identification requirements of the large ships such as aircraft carrier are constantly increasing. The existing ISAR ship imaging technology still needs to be improved. This thesis mainly studies the ISAR imaging algorithm, analyzes extensive airborne ISAR real data and provides sufficient signal processing experiences for practical application. The specific work is arranged as follows:Firstly, the introduction reviews the development background and current research status of ISAR, briefly elaborates the basic principle of ISAR imaging, the technique of motion compensation and ISAR imaging algorithm, and summarizes the main work in this paper.Secondly, Chapter 2 studies airborne ISAR ship imaging which is based on optimal time selection. This chapter introduces two optimal-time-selection-based imaging methods for ship targets, which use the Doppler Centroid Frequency Estimation and Doppler Spread Estimation. The airborne ISAR real data based processing validates the applicability of the two methods, and the comparison and analysis between the two methods are also presented.Thirdly, the airborne ISAR ship imaging based on estimation of multicomponent quadratic frequency-modulated signals is studied. The method estimates parameters of the signal phase component at one time by building a new mathematical model which is the conjugate multiplication of autocorrelation function and relatively simple arithmetic such as Fourier transform, then we can calculate the instantaneous Doppler frequency of each scattering points and obtain ISAR instantaneous image. This method is different from traditional instantaneous imaging method. It reduces the computational complexity and improves the estimation precision reasonably. In this chapter, the feasibility of the algorithm is verified by the simulation of ship model firstly. Then, the processing results of the airborne ISAR measured data validate the algorithm and the performance is analyzed.Then Chapter 4 studies airborne ISAR ship imaging based on high-order match Fourier transform. In this algorithm, the estimation of the high-order phase component coefficients is compared with the traditional method. The estimation precision is improved and the image quality of the ships becomes better. Finally, the effectiveness of the algorithm of ISAR ship imaging using high-order match Fourier transform is verified by simulation and real data processing.At the end, the work of the thesis is concluded. The issues to be studied next are pointed out.