Numerical solution of higher order mode cut-off frequencies in symmetric TEM cells using finite element method [EMI measurement applications]

The higher-order-mode cut-off frequencies in symmetric transverse electromagnetic cells are computed with the finite-element method. Transverse electric and transverse magnetic modes are considered. For symmetry, only one-quarter of the cross section is analyzed. Electric and magnetic walls are introduced in the cross section, which includes the effect of the gap between the center conductor and the sidewalls. This arrangement enhances the accuracy of the solution. The results obtained by this method are compared with those of other methods. Discrepancies observed in the results of other methods are explained. The present method is the more powerful one; with this method, mode identification can easily be made using an eigenvector solution