Wave scattering from finite metal strip gratings

Numerical methods for the problem of scattering from periodic metal gratings has mostly been limited to the case of infinite extent. To solve the finite problem, the authors have proposed a microwave equivalent network approach that connects a finite number of locally homogeneous building blocks of a structure in tandem. To overcome the problem of introducing a radiation wave with a continuous spectrum into an equivalent network expressed only by the discrete terminal ports, the authors recompose the continuous radiation wave into a discrete set of so-called spectral composite modes by applying a complete set of orthonormal function in the spectral domain. As a result, they know the mode amplitude of all of the ports at the input terminal plane, if the incident wave illuminating a structure is expanded into spectral composite modes, providing completely the wave behavior along the structure. An analysis is presented for metal grating of zero thickness (t=0) illuminated by Gaussian beam waves incident in phase from both upper and lower sides with a slant angle of 15 degrees .<>