Abstract : The interactions of an electromagnetic wave and a complex 3D object lead to numerous investigations of modelisation, as much for military than for civil applications. When the objects present a complex geometry and large dimensions compared to the wavelenght, the evaluation of the radiated fields become costly in computation time. To overcome this problem, we use a formulation based on gaussian beams, which are a paraxial solution of the Helmoltz equation. Gaussian Beams do not suffer from caustic problems and may lead to smaller computation time than conventionnal ray techniques. However, some situations such as the diffraction of gaussian beams by metallic edges or the interactions between gaussian beams and heavy curved surface remained unsolved.
The gaussian beam diffraction is modelised using the Spectral Theory of DIffraction in two dimension and the Physical Optic approximation for finite rectangular conducting surfaces in three dimensions. In order to deal with heavy curved surface, we have expressed the plane wave spectrum of a Conformal Gaussian Beam, a Gaussian Beam adapted to curved surface.
We made some measurements into an anechoid chamber to confirm the fact that a known electromatic field can be expand into gaussian beams, before being propagated using analytical expressions. Finally, we use a gaussian beam tracking method in order to evaluate the propagation of electromagnetic waves on large distances.