RCS of waveguide cavities: a hybrid boundary-integral/modal approach

A hybrid technique combining the flexibility of the boundary-integral method and the efficiency of the modal approach is presented. The technique is used for analyzing the electromagnetic scattering from open waveguide cavities. The generalized scattering matrices of the arbitrary waveguide discontinuity regions are determined using a boundary-integral equation formulation. The scattering matrix of the composite structure is found by cascading the scattering matrices of individual sections. The radar cross section of the open cavity is then calculated by a reciprocity formulation in conjunction with the Kirchoff´s approximation. Excellent agreements with the standard method of moments solution and with experimental data for offset bend structures are found. Examples of cavities with arbitrarily shaped and absorber-coated terminations are also presented