Calculation of transfer functions of three-dimensional indented objects by the physical optics approximation combined with the method of stationary space

Transient scattering by variously shaped objects is obtained from the transfer functions and the spectrum of the incident pulse by using the Fourier synthesis technique. In order to evaluate the transfer functions of indented three-dimensional smooth objects, an effective method based on the physical optics approximation combined with the method of stationary phase is presented. It is shown that for indented three-dimensional objects, there exist several stationary phase points, including the complex ones. It is confirmed from the numerical results that an accurate solution can be obtained by taking into account the complex stationary points. Also, for a complete solution, the creeping wave term should be included