On the edge condition with the method of lines in planar waveguides

The accuracy of 'method of lines' -solutions for the dispersion characteristics of planar waveguides is investigated, when the structure considered contains perfectly conducting edges. In consequence of the discretisation, the width of the metallic strip is undetermined. An effective width is defined such that the discretized field satisfies the edge condition approximately. Thus, the discretisation error can be reduced considerably without increase of computing time.