In the data and signal transmission it is important to ensure electromagnetic compatibility. The number of systems being used for the acquisition, processing and distribution of data is continuously growing. Microelectronics are spreading into new fields of application (e.g. automotive electronics). The growing popularity of xDSL with its high transmission rates and worldwide networks has led to new EMC problems.
Until recently the use of shielded cables was the main way of preventing data transmission from being disturbed by RF interference fields. A more economical solution is the use of symmetrical transmission line systems. In these, twisted pair lines are used in conjunction with data line chokes. The chokes used here have extremely good symmetry characteristics.
The main advantages are the low space requirements even for high inductance values used to suppress common-mode interference. This is achieved by using bifilar windings, which are more favorable for producing chokes with excellent symmetry characteristics than other winding designs. This results in very low stray inductance, a characteristic that is highly desirable for achieving the lowest possible attenuation of the differential-mode data signal.