Finite element analysis of propagating, evanescent, and complex modes in finlines

The finite element method is employed to analyse the characteristics of propagating, evanescent, and complex modes in finlines. The recently developed mixed-interpolation-type triangular elements are used, where no spurious solutions appear and consistency with the published results is obtained. The existence of the complex mode for both the even mode and the odd mode in finlines is found for particular structural parameters and at a certain frequency range. In addition, a new formulation is made for the determination of the characteristic impedance by the finite element method. The possible electric field distributions of the dominant and higher order modes including the evanescent and complex modes are also presented