Non-uniform rotation rate estimation for ISAR in case of slant range migration induced by angular motion

Target rotation is the desired motion to obtain descriptive inverse synthetic aperture radar images. However, it can generate blurring effects: the migration through resolution cells. This blurring is more severe when the rotation rate is non-uniform. A method to estimate the non-uniform rotation rate (second-order model) for non-cooperative targets is addressed here. The technique considers the possibility of existence of slant range migration induced by angular motion, unlike other approaches. It needs a previous estimation of the range and radial velocity of two prominent points at two instants and minimises a function in order to estimate the motion parameters, which are used to polar format the radar data. The method is compared with the moving target imaging algorithm of Werness et al. and a time-frequency based technique. Simulated data are used to verify the approach and make the comparisons.