Electromagnetic scattering from an inhomogeneous object by ray tracing

A 'shooting and bouncing ray' (SBR) formulation is presented for treating the electromagnetic scattering from electrically large, inhomogeneous objects. A dense grid of rays representing the incident plane wave is shot toward the inhomogeneous object. At the scatterer boundary, reflected rays and refracted rays are generated due to discontinuity of the medium parameters. The trajectory, amplitude, phase and polarization of the rays inside the inhomogeneous object are traced based on geometrical optics. Whenever the rays cross the scatterer surface, additional reflected/refracted rays are generated and are tracked. This process is repeated until the intensities of the refracted/reflected rays become negligible. The contributions of the exiting rays to the total scattered field are calculated by using the equivalence principle in conjunction with a ray-tube integration scheme. The ray formulation is applied to calculate the backscattering from cylinders and spheres and good agreement with the exact series solutions is observed in the high frequency range. In addition, the backscattering mechanisms in penetrable objects are interpreted in terms of simple ray pictures.