In this thesis, a high frequency method is shown which combines the uniform geometrical theory of diffraction(UTD) and aperture integration(AI) to analyze electromagnetic plane wave scattering by a perfectly-conducting, semi-infinite parallel plate waveguide with a uniform layer of absorbing material on its inner wall, and with a graded planar termination inside. In this method, first, the field of an arbitrary point in the parallel plate waveguide is computed by UTD. Second, the electromagnetic scattering is computed by equivalent current, which can be obtaind from the field of aperture at the waveguide, and by AI.
