Aperture coupling in the bodies possessing a finite symmetry group

A numerical method for predicting the field penetrating an arbitrary opening in a symmetric body is considered. The method is based on the usage of coordinate functions of irreducible representations of the group {τ_N} of symmetries of the cavity. It enables one to reduce the calculation time by the factor ~N² and to construct numerically an inverse operator for an arbitrary excitation function. The required machine memory is also reduced by the factor N