Return loss in twisted pair cables

Modeling of twisted pair cable (TPC) and simulating return loss (RL) is discussed and verified experimentally. A graphical user interface allows entering cable design data including materials, plating, stranding, twisting, and wire naming. A realistic 3D model of a twisted pair cable is calculated. The resulting model is subsequently analyzed numerically using a combination of finite element and boundary element methods. Extracted, frequency dependent unit parameters of the cable are used to build a chain parameter model. Conditions for chain parameter segmentation are discussed. A 50 meter long four TPC was used to verify simulation results against RL measurement. The measurements were carried out with a vector network analyzer. Both ends of the cable were connected to special fixtures, which were designed to eliminate reflections. Simulation and measurement are plotted in the frequency range of 100 kHz to 1 GHz. Good agreement between simulation and measurement of RL is reported.