Multiply-screened coaxial cable has distributed inter-screen impedance - forming lumped series chain with lumped transfer imped as parallel branches

摘要

The multiply-screened coaxial cable has a central line (C) for signal transmission and n outer screening sleeves (Bn). The characteristic impedance (Z12) between the first (B1) and the second screen (B2) is effectively in series with the characteristic impedances between other adjacent screens (Z23 to Z(n-1)n). These series impedances are coupled to parallel transfer impedance ZTn representing in lumped form the cable's distributed transfer impedance (i.e. a function of length). Each screening sleeve is constructed from two layers connected together electrically by an intermediate layer of a magnetic metal having a high SIGMA. MU. f. product, where SIGMA is the conductivity MU the permeability and f the frequency.