Investigations of complex modes in a generalized bilateral finline with mounting grooves and finite conductor thickness

A generalized bilateral finline with mounting grooves and finite conductor thickness is analyzed by the full-wave mode-matching method. The final nonstandard eigenvalue equation is derived from unknown coefficients in two slot regions. Both relative and absolute convergence analyses of complex modes are performed. The field patterns along the metallized strips are investigated for relative convergence studies. Once the optimal ratios of the numbers of expansion terms among different regions are decided, an absolute convergence study is initiated to obtain the minimal number of total modal expansion terms to save computer time. The validity of this approach is confirmed by checking the available complex mode data. Finally, the dispersion characteristics of fundamental, higher-order, evanescent, and complex modes are presented for an asymmetric bilateral finline. It is noted that the convergence studies presented provide a guideline to determine the numbers of modal expansion terms used in a millimeter-wave CAD (computer-aided design) program.<>