Global range alignment for ISAR

A new technique is developed for range alignment in inverse synthetic aperture radar (ISAR) imaging. The shifts made to the echoes are modeled as a polynomial, and the coefficients of this polynomial are chosen to optimize a global quality measure of range alignment. This technique is robust against noise and target scintillation, and avoids error accumulation. In addition, the shift in the time domain is implemented by introducing a phase ramp in the frequency domain, which removes the limitation of integer steps.