A hybrid approach for calculating the scattering from obstacles within large, open cavities

A hybrid method to analyze the high-frequency scattering from an obstacle within a large, open cavity is developed by using a generalized reciprocity integral and utilizing a plane wave expansion (PWE). The PWE is used because it is efficient, straightforward to implement, and can be used for relatively general geometries. In the hybrid method, the cavity´s front section is analyzed independently from the termination section containing the obstacle. The termination section is accurately characterized by a PWE scattering matrix which may be stored and used in conjuction with different front-section geometries. The accuracy of the hybrid method is confirmed by comparing the radar cross section patterns of some simple cavity and obstacle geometries where each pattern is computed using the hybrid method and a more accurate reference method (such as the method of moments or waveguide modes)