Computation of the Impedance Matrix of Multiconductor Transmission Lines Using High-Order Surface Impedance Boundary Conditions

High-order surface impedance boundary conditions (SIBCs) are coupled to the boundary element method to produce a new integral formulation technique for the computation of the impedance matrix of multiconductor transmission lines (MTLs). The method extends the use of the Leontovich SIBC into lower frequencies and does so quickly and efficiently in that the solution of the integral equations need only be computed once, whereas the solution may be obtained over the whole applicable frequency domain. The current formulation is theoretically rigorous and applies to arbitrarily smooth curved surfaces. The method is applied to the calculation of per-unit-length (p.u.l.) parameters in lossy MTLs of arbitrary cross sections, without taking into account the earth return path or the surrounding media resistivity.