T. Rother, General aspects of solving Helmholtz's equation underlying eigenvalue and scattering problems in electromagnetic wave theory, J ELECTROM, 13(7), 1999, pp. 867-888
This paper considers conceptual aspects of different numerical methods for
solving eigenvalue and scattering problems in electrodynamics. We will focu
s on the separation of variables method, the method of lines as a special f
inite-difference technique, and surface integral equation methods. It will
be shown that there are interrelations between these different methods, and
that it is possible to derive a general mathematical description based pn
the separation of variables method. The method of lines is used as a starti
ng point. Its concept is developed up to the Green's function belonging to
the homogeneous Helmholtz equation with inhomogeneous boundary conditions p
rescribed on surfaces which doesn't coincide with a constant coordinate lin
e in one of the coordinate systems in which the Helmholtz equation becomes
separable. With this Green's function we are able to derive a corresponding
surface integral equation. Finally, the limiting behavior of the method of
lines for an infinite number of discretization lines is considered. This r
esults in a generalization of the separation of variables method.