EMC-performance of balanced (symmetrical) cables

The frequency range of balanced pairs or quads, e.g. for horizontal floor wiring for data communication has increased up to the GHz range. Especially in this field of data transmission a high screening effectiveness and a good EMC behaviour of such cables is required. In order to measure the EMC-behaviour of these cables, new measuring procedures have been developed which are under discussion for international standardisation. The screening effectiveness of screened balanced pairs is the sum of the unbalance attenuation of the pair and the screening attenuation of its screen which is described as the coupling attenuation. With the new triaxial measuring procedure and its measuring tube in accordance to IEC 46A/320/CDV the screening attenuation of the screen and the coupling attenuation of the complete cable can be measured. The difference of the coupling attenuation and the screening attenuation is the unbalance attenuation. In this way the unbalance attenuation of balanced cables may be measured up to the GHz range with baluns without a centre tap