Techniques appropriate for low and high frequency numerical evaluation of the scattered fields from complex shapes are discussed. Object size in terms of wavelengths dictates the type of solution to be used. For targets in and just above resonance, the method of moments (MM) is used. The limitation in this case is that the scatterer cannot be too large in terms of the wavelength. For radar targets in the microwave band, the uniform geometrical theory of diffraction (UTD) and modifications thereof form the basis for the computation. This has the basic limitation that the scattering mechanisms need to be known and included in the model. Examples are given for both frequency regimes.>

An overview is presented of a hybrid technique for solving electromagnetic radiation and scattering problems by combining the method of moments (MM) with a special Green's function. The method, referred to as an MM/Green's function solution, combines the ability of MM solutions to treat geometrically complex bodies with the accuracy and computational efficiency of Green's function solutions. Compared to a standard MM solution, the MM/Green's function solution reduces the number of unknowns and thus the computer storage requirements. In most cases the CPU time for the MM/Green's function solution is considerably less than that for a standard MM solution. An example problem of TM scattering by a semicircular strip in the presence of a circular cylinder is solved by the MM, and by the MM/Green's function technique with a matrix, exact eigenfunction, and high-frequency Green's function.>