Reproducing Field-to-Wire Coupling Effects in Twisted-Wire Pairs by Crosstalk

This paper proposes an alternative test procedure for testing the radiated immunity of units and subsystems interconnected through unshielded twisted-wire pairs (TWPs). The procedure makes use of an additional wire placed in close proximity and parallel to the TWP axis to generate the interference, which is then transferred to the TWP under test through crosstalk coupling. Equivalence with field-to-wire coupling is enforced in terms of equal common mode (CM) currents induced at the TWP terminals, by resorting to the introduction of an equivalent CM straight wire to replace the original twisted line. The proposed equivalence scheme, derived by resorting to transmission-line modeling and full-wave numerical simulation, is eventually validated by measurements in the frequency interval from 1 MHz up to 1 GHz. The experiments prove the accuracy of the proposed procedure in reproducing both the CM and the differential noise induced by field-to-wire coupling in the terminations of the twisted lines.