Field-to-wire coupling model for the common mode in random bundles of twisted-wire pairs

A multiconductor-transmission-line (MTL) model of field coupling to a random bundle composed of twisted-wire pairs (TWPs) running above ground is proposed for the computation of the induced common-mode (CM) noise. The nonuniform bundle is effectively represented by cascading uniform MTL sections, whose models are derived from a single reference solution through permutations of rows and columns in matrices and vectors. This is achieved by exploiting the concepts of: 1) averaged per-unit-length parameters, 2) reference cross-section, 3) minimum-distance shifts of TWP positions in the reference cross-section. Repeated-run analysis is used to outline the high sensitivity (tens of dBs) of the induced CM noise to random configurations of electrically long bundles, and to derive statistical estimates of CM voltages induced by a plane-wave field at each TWP terminal. Accuracy and computational efficiency of the proposed approach are proved by comparison versus full-wave simulations.