TABLE OF CONTENTS The geometrical theory of diffraction (GTD) and its uniform versions present some drawbacks for the calculation of the radar cross-section of a complex target, the most important of which are:
They do not allow us to calculate in general, the field on the caustics of the reflected rays.
They need sophisticated ray searching techniques which are very sensitive to the defects of the geometrical description when the surface is defined by computer aided geometrical design tools (B-splines etc.).
The success of the physical optics (PO) and the physical theory of diffraction (PTD) is mainly due to the abovementioned drawbacks of GTD.
The method of asymptotic currents is a natural extension of PO and PTD, which are founded on the radiation of the geometrical optics (GO) currents on the illuminated part of a target augmented by the radiation of the fringe currents close to the edges. Compared to PO, the asymptotic current method takes into account the currents on the shadow side of the target by introducing the creeping waves on convex surfaces and the whispering gallery modes on concave surfaces. Furthermore, in the illuminated part, close to the shadow boundary, the PO currents are replaced by more accurate transition zone solutions. Another difference is that the radiation of the fringe current is not calculated by introducing a diffraction coefficient referred to as Ufimtsev s coefficient D u given by
or by the radiation of an equivalent line source, but by using approximate expressions for the fringe currents in...
