Computationally-effective worst-case estimation of currents in transmission lines for EMC diagnostics of big systems

A technique for calculation of currents in transmission lines in a wide frequency range is proposed. The technique is based on a generalization of the lumped-circuit calculation methods to the case of long transmission lines by the introduction of refinement functions. A worst-case model for the amplitude-frequency characteristics of currents in the transmission line is developed on the basis of the proposed technique. The model is intended for diagnostics (express analysis) of electromagnetic compatibility in complexes of radio and electronic equipment. Worst-case nature of the model is provided by construction of the envelope of the current's maxima (observed at resonances) for the high-frequency band. The validity of the model is checked by comparison with the results of numerical simulation of single wire above ground plane, twowire, coaxial, and triaxial transmission lines in a wide range of parameter values: the frequency is varied from 10 kHz to 8 GHz, the length of the line is from 20 cm to 5 m, height of the line above the ground surface is from 2 mm to 100 mm, the ratio of the load capacitance (inductance) to the line capacitance (inductance) is from 10−40 to 104. Straight and piecewise-straight lines (both parallel and non-parallel to the ground plane) are considered during the validation.