Simultaneous computation of higher eigenmodes in loss-free waveguides and cavities

In some applications (e.g. gyrotrons, particle accelerators) the higher modes of waveguides and resonant structures are of interest. The computation is difficult since most of the methods calculate either extremal eigenvalues or the inversion of the system matrix is necessary. The presented method extends the subspace iteration with polynomial acceleration to non extremal eigenvalues by using special polynomials. This enables the simultaneous iteration of a group of eigenvalues inside an arbitrary frequency range during one computation run.