The electromagnetic properties of microwave transmission lines can be described using Maxwell's equations in the frequency domain. Applying a finite-volume scheme this results in an algebraic eigenmode problem. In this paper, an improved numerical computation of the eigenmodes is presented. (orig.)SIGLEAvailable from TIB Hannover: RR 5549(308)+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman