Geometric approach for determining stationary phase points in radar imaging

This paper proposes a geometric approach to find out the stationary phase points in radar imaging, namely the coordinates of the transmitting and the receiving antennas that have the greatest contribution to a specified point in the wavenumber spectrum of the scattered field. The foundation of the proposed approach is that, the Green’s function can be approximated by a locally plane wave when the distance between the individual antennas and the object is much larger than the wavelength. In this way, the stationary phase points can be easily found through geometric calculations, much more convenient than the prevailing algebraic approach of letting the first derivative of the phase term to be zero. Six examples for different propagation backgrounds and antenna setups are provided in this paper. It is demonstrated that, the proposed method is beneficial in eliminating extraneous roots of the stationary phase points, which could be generated by letting the first derivative of the phase term to be zero in the stationary phase method.