A study of wave interactions with flanged waveguides and cavities using the on-surface radiation condition method

The scattering of a plane wave from the open end of a flanged, parallel plate waveguide is approximately solved using the On-Surface Radiation Condition method. Simple explicit formulae are given for the field within the waveguide and for the bistatic cross-section. In addition, our theory also gives an approximate solution to the associated open cavity problem, which is formed when the waveguide is terminated by a short circuit positioned a finite distance from the aperture. These problems serve as prototypes for receiving antennae and open resonators respectively. Numerical results are presented which confirm the accuracy of the OSRC method. An interesting byproduct of our analysis is the approximate prediction of the complex eigenfrequencies of the open resonator.