ISAR autofocusing image reconstruction of sea target

Abstract

This work deals with the implementation of ISAR method to extract an image of a sea target with high resolution. Three dimensional ISAR scenario, including radar and a target of interest, is depicted in one and the same 3-D Cartesian coordinate system and duly considered. The sea target is presented as an assembly of discrete point scatteres which intensities are interpreted as an image function of the object observed. Analytical geometrical expressions to define a range distance from the radar to each point scatterer from the object space are derived. In order to realize high range resolution on the line of sight an informative linear frequency modulated waveform is applied. An ISAR signal model as a superposition of signals reflected from target's point scatterers is described and graphicaly illustrated. Image extraction from ISAR signal returns is performed by implementation of Fourier transformation on both range and cross-range coordinates. Image enhancement is accomplished by iterative polynomial focusing procedure and entropy as a cost function. In order to verify the supposed algorithm a numerical experiment is performed.