A generalization of Van den Berg's integral-square error iterative computational technique for scattering

Van den Berg shows a way of using spectral iteration (SI) within a scheme that shows good convergence. His method can be reinterpreted as a global expansion of the field quantities in terms of a set of basis functions. It is shown here that the orthogonalization of these basis functions can considerably improve convergence rates. This involves extra storage requirements, but only a negligible decrease in speed of computation.