The Finite Integration Technique - FIT is used in combination with a ray tracing technique in order to solve general radiation and scattering problems. The FIT is very well suited for the analysis of complex structures containing inhomogeneous and anisotropic materials. This method however becomes inefficient when the dimensions of the solution domain are large comparing to the smallest wavelength of the spectrum. Ray tracing techniques on the other hand have been successfully used for the solution of problems where the dimensions of the objects are large comparing to the wavelength. According to these techniques, the scattering from the objects can be approximated by a number of reflected and diffracted rays. Their main limitation is that for small objects the accuracy of the solution is poor. A hybrid method which combines the FIT with a ray tracing technique allows the treatment of a great variety of structures containing both small and large objects. The solution domain is divided into two subdomains: a first one which encloses the small objects and the inhomogenities of the material (if there are some) and a second, an open one, which contains the large scatterers. The internal problem is solved using the FIT with application of an absorbing boundary condition. The resulting field distribution on the boundary is then considered as an equivalent source for the external problem, according to the Equivalence Principle. For the solution of the external problem a ray tracing algorithm is used where diffraction effects are taken into account by applying the UTD formulations. Examples will be given for validation of the method.

* Scholarship from the Foundation of National Grants "IKY" of Greece