IB . S U B J E C T T E R M S iC ontinue on reverse if necessary an d id en tify by block n u m b e r)microwave & millimeter waves; digital circuits; transmis sion lines; characteristic impedance; dielectric losses; conductor losses; finite element method. This paper describes a finite element approach to quasi-TEM analysis of several dif ferent types of isolated and coupled microwave transmission lines. Both the first and higher-order ordinary elements, as well as singular and infinite elements are used to solve for the potential and field distribution in the cross-section of the line. Next, the cross-sectional field distribution is inserted in a variational expression to com-, pute the capacitance per unit length of the line and the effective permittivity and characteristic impedance of the line are obtained from the capacitance value. A perturbational approach is developed for estimating the losses due to conductor and dielec tric dissipation and computing the attenuation constant.Lines treatable by this method may contain an arbitrary number of arbitrarily shaped conductors, including a system of conductors either placed above a single ground plane or between two parallel ground planes, and inhomogeneous dielectric regions that can be approximated locally by a number of homogeneous subregions.(0Ver) DISTHI B U T IO N / Unclassified S E C U R IT Y C LA S S IFIC A TIO N OF TH IS PAGE Unclassified S E C U R IT Y C L A S S IF IC A T IO N O F T H IS P A G E S E C U R IT Y C L A S S IFIC A TIO N OF TH IS PAGE Quasi-TEM A n a ly s is o f M icro w a v e T ra n sm issio n L in es b y th e F in ite E lem en t M eth od

SUMMARYIn this paper the finite element method (FEM) is used to analyse general, multiconductor transmission-line systems of arbitrary cross-section. The per-unit-length matrices of capacitance, inductance, conductance and resistance, which characterize a multiconductor transmission line, are obtained from the FEM analysis. Numerical results are presented and compared both with experimental results and other available data.

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