Analysis of Multiconductor Transmission Lines, 2nd Edition

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THE PER-UNIT-LENGTH PARAMETERS FOR TWO-CONDUCTOR LINES

The per-unit-length parameters of inductance, capacitance, resistance, and conductance are essential ingredients in the determination of the transmission-line voltages and currents from the solution of the transmission-line equations. All of the cross-sectional dimension information about the specific line being investigated is contained in these parameters and nowhere else. Hence, without a determination of these for the transmission line under consideration, solution of the transmission-line equations cannot be completed as the per-unit-length parameters in them are unknown. It is important to recall that, under the fundamental transverse electromagnetic (TEM) field structure assumption, the per-unit-length parameters of inductance, capacitance, and conductance are determined as a static (dc) solution to Laplace's equation, for example, ²(x, y) = 0, in the two-dimensional cross-sectional (x, y) plane of the line. Therefore, the per-unit-length inductance (external), capacitance, and conductance are governed by the fields external to the line conductors and are determined as static field solutions in the transverse plane for perfect conductors that have conductivities of σ = ∞. The per-unit-length resistances and internal inductances ...