A Model for Predicting the Surface Transfer Impedance of Braided Cable

Abstract

A model for predicting the surface transfer impedance of non-optimized braided cables has been developed. This model is based on theory and is supported by extensive measurements. The transfer impedance of a braided cable is modeled as the sum of a transfer resistance and a transfer mutual inductance. The latter gives rise to a frequency dependent term. The transfer resistance is inversely proportional to cable diameter. The transfer mutual inductance is best modeled as being independent of diameter. A worst case cable overbraid model accounts for multiple layers of braid. Thus, the surface transfer impedance can be repre­ sented as the sum of a transfer resistance R, and a mutual inductance M-jg• To a first approximation, the transfer resist­ ance is determined by the amount of metal in the braid. This can be calculated using Equation 3