Prediction of radiated fields from cable bundles based on current distribution measurements

In automotive EMC ALSE method, specified in CISPR 25, is commonly used for emission measurements. Components or modules are required to be connected with a test cable bundle for evaluating radiated emissions. The radiation is often mainly dominated by the common mode current along the cable bundle. In order to predict radiated emissions from setups according to ALSE method, without using a large anechoic chamber, this paper presents an alternative and innovative method. The presented approach determines radiated fields from a cable bundle without phase information. It is only based on the amplitude of common mode current from phaseless measurements using a RF current probe. Firstly, radiation model of a cable bundle is simplified to a single equivalent transmission line (TL) according to the mode analysis of multiconductor transmission line (MTL) theory. Then an optimization procedure based on trust-region-reflective (TRR) method and multi-start point algorithm is used to determine the common mode parameters of the equivalent TL by fitting to the measured current amplitude. The phase of common mode current, therefore, is retrieved through optimized TL parameters. Finally, the radiated fields are straightforwardly evaluated by elementary dipoles approximation of the cable bundle. The proposed approach is verified by numerical analysis of different cable bundle models and measurements. The stability and feasibility to evaluate radiated emissions from a cable bundle could be shown.