COMPUTATION OF THE RCS OF COATED OBJECTS BY A GENERALIZED PTD APPROACH

We consider the diffraction of an incident plane wave by 3D objects, s uch as missiles. These objects can be either perfectly conducting or c oated with dielectric or magnetic coatings. Their shape, usually descr ibed in CAD format, can be quite complex, with reentrant cavities, win gs, ..., such that multiply reflected, reflected diffracted, and multi ple diffracted rays exists. Morover, as these objects are designed to have a low RCS, these rays can be, for some angles of incidence, the m ain contributions to the RCS. PTD is all efficient technique to comput e the RCS of complex objects, that has the desirable property of provi ding bounded results for any angle of incidence and observation. Howev er, this theory has been mainly applied to perfectly conducting object s, the fringe wave is computed for wedge-like discontinuities, it does not include multiple phenomena. We have generalized PTD in three dire ctions. First, we have extended the fringe wave concept to the case of an edge satisfying an impedance boundary condition. Second, we have c omputed diffraction by rounded edges or by tips by using an hybrid asy mptotic-MoM method. Third, we have included multiply reflected or diff racted rays: We present some examples of Res and comparison with other methods.