Calculation of far-scattered fields by the method of stationary phase

The scattering problems for a nonconvex body can be analyzed by the physical-optics approximation. The method of stationary phase is a technique for evaluating the diffraction integral in the short-wavelength region. In case of the nonconvex body there exist several stationary points including the complex ones in the reduced phase integral. The radar cross section of the nonconvex body varies with frequency as a result of the interference of the scattered waves from each stationary point. For a moderately high frequency the solutions by the method of stationary phase agree with those obtained using the mode-matching method.