Detailed computation of the effects on the performance of open resonators caused by imperfections in the resonator geometry

The problem of computation of field distributions existing within microwave open resonators is addressed. The approach which is studied involves the evaluation of fields existing at the mirrors after each of a series of field transits with a view to determining an eventual field distribution which is constant from one transit to another. Of particular interest are the cases of concave mirrors and where the mirrors are misaligned or imperfect in geometry. The effect of an included lossy perturbing object is studied. The relative merits and difficulties of using computations based on Huygens´ method and one based on a Fourier transform approach are investigated. The former method is adopted and applied to a large open resonator for the cases listed above, the evaluations necessary for the three-dimensional geometries demanding extensive computer time. The field behaviour and the consequences of the results are discussed, as is their relevance to open resonator design and scattering measurements