The variational method and the method of moments in the problem of plane wave scattering by a rectangular cavity in an impedance screen

The problem of electromagnetic plane wave diffraction by a rectangular cavity in an impedance screen is solved. The problem is reduced to solution of a Fredholm integral equation for the field function in the aperture. The equation has a symmetric kernel. Expressions for the angular distribution of the scattered far-field are obtained by the method of moments and the variational method. Numerical results are analyzed and compared.