ISAR image reconstruction technique with stepped frequency modulation and multiple receivers

In this work, a new 3D model of deterministic components of ISAR trajectory signals with stepped frequency modulation is suggested. 3D ISAR geometry is described by means of analytical geometry. The geometry and kinematics of the object and ISAR observation system are described in separate 3D Cartesian coordinate system. The object space, moving rectilinearly, is presented as a 3D regular grid of isotropic point scatterers. The analytical expressions for computing the range distance to point scatterers of the object space are derived. The complex ISAR signal, reflected from the 3D target is obtained by four receivers, placed on the axes and origin of the coordinate system of observation. Four 2D ISAR signals, registered by receivers appear to be four 2D projections of the 3D ISAR signal. The 3D image is considered as a set of 2D images retrieved from the 2D ISAR signal projections. The image reconstruction procedure includes both range and azimuth compression. Fast Fourier transforms are applied to each 2D ISAR signal projection to realize range compression and azimuth compression. A synchronized range alignment and an autofocusing technique are applied to each received ISAR signal projection. To illustrate the capability of the 3D ISAR signal model numerical experiment is accomplished.