Establishment Of Cable Transmission Line Model Based On Test Extraction Parameters

The vast majority of equipment emc problems are caused by interference coupling of cables.At present,numerical method is usually used to construct distribution capacitance matrix for non-uniform multi-conductor transmission lines with insulating layers around them.Although this method has high solving accuracy,it is difficult to be applied to practical engineering problems because of the complexity of calculation and the need to know parameters such as insulation layer thickness,dielectric constant and cable structure size.In addition,the traditional multi-conductor transmission line model needs to be improved and optimized due to the large amount of calculation and complexity of calculation.In this paper,the cable with insulation layer is taken as the research object,and the non-uniform multi-conductor transmission line model is established.The accuracy of the transmission line model is verified by evaluating the terminal response voltage of the transmission line,and the transmission line model is applied in relevant fields.The main research contents are as follows:1.Under unknown for insulation dielectric constant capacitance matrix to solve the problem of distributed capacitance is derived based on S parameter matrix is put forward.The terminal response of single cable,double cable and twisted-pair cable models on the ideal ground plane is obtained by combining terminal constraints.The accuracy of distributed capacitance matrix is verified by comparing theory,simulation and measurement.2.In order to solve the problem of large computation and complex operation of multi-conductor transmission line model with multiple signal transmission pairs,the solution of terminal response of one wire pair is divided into its own transmission response and the superposition of crosstalk coupling response generated by other wire pairs based on the mixed mode S parameter theory.The validity of the transmission line model is verified by the comparison of theory,simulation and measurement with shielded four-core cable and shielded six-core cable.3.Construct time domain model of non-uniform transmission line.Combined with the distribution parameters derived earlier,FDTD method was used to solve the terminal time-domain response of the three-conductor transmission line model,and Inverse Fourier transform was used to solve the time-domain response of the crosstalk coupling between wire pairs.The theoretical models of parallel twisted-pair wires and shielded four-core wires placed on the ideal ground plane are constructed,and the time-domain model is verified by comparing the simulation with the actual measurement.4.The field-line coupling and crosstalk coupling of cable transmission line model are studied.The BLT equation was used to solve the terminal coupling response of a single cable under the irradiation of the external field.The field line coupling model was verified by comparing the theoretical calculation results,simulation results and measured results,and the influencing factors of the cable height from the ground and cable terminal impedance were analyzed.The single-single and single-twisted crosstalk models were constructed,and the load plate with the function of balance/unbalance transformation was designed.The influence factors of the distance between two cables and the height between two cables on crosstalk coupling were analyzed.