(A) study on estimating scattering centers & ISAR image of a target using high resolution techniques in radar target recognition

Abstract

Radar is a system that uses electromagnetic waves to identify the range, altitude, direction, or speed of the objects such as aircrafts, ships, weather formations, and so on. Hence, a radar system is often used in radar target recognition. The basic aim of radar target recognition is classification and recognition of an unknown target by analyzing backscattered waves from the target using a radar system. The scattering centers and inverse synthetic aperture radar (ISAR) image of a target provide a physically relevant description of the target and are thus good candidates in automatic target recognition. Besides, they are widely used for target scattering analyses, radar signature modeling, and radar target recognition. Accordingly, scattering centers extraction and ISAR image formation of a target are very challenging tasks in radar target recognition. In this dissertation, we present high resolution techniques of scattering centers extraction and ISAR image formation from a radar backscattered signal in radar target recognition. In general, the inverse fast Fourier transform-based method is used to estimate not only the locations and amplitudes of scattering centers but also ISAR image of targets. This method is computationally efficient, but is weak in term of resolution. To achieve the good resolution, the radar system should have wide bandwidth and the target should be observed over a large angular domain. However, in real applications, the radar system has narrow and limited bandwidth and the target may not be observed over a large angular sector. To overcome these drawbacks with the IFFT-based method, various high resolution techniques have been developed. High resolution technique takes advantage of the autocorrelation matrix eigenstructure resulting in the decomposition of the space into two orthogonal subspaces, called the signal and noise subspace. High resolution techniques offer good resolution with narrow bandwidth and a small aspect angle. Thi...