Study Of Electromagnetic Interference Characteristics Of Shielded Cables Based On Time-Domain Blt Equations

As the key factor of connecting the electronic and electrical equipments and systems, cables are used to transfer information and energy between different systems effectively. With the rapid development of electronic and electrical equipments, electromagnetic environment is becoming more and more complex. When a current flows through a cable, the crosstalk will be generated in other cables nearby, and when a cable is radiated by external electromagnetic field, induced current will be generated on the surface of the cable, so that electromagnetic interference will be produced in the terminal equipments and circuits linked by the cable. In order to ensure the normal operation of electrical and electronic equipments and systems, studying the electromagnetic interference (EMI) characteristics of cables has become one of the most important issues need to be solved urgently in engineering electromagnetic compatibility (EMC). Electromagnetic interference calculation is an important aspect in EMC prediction technology, therefore the study of electromagnetic interference of shielded cables has practical value.This paper first introduces the basic principles of the FDTD method and transmission line theory based on time-domain BLT equations, and the theory analysis and equations of the crosstalk of multi-conductor lines are studied.Secondly, the crosstalk model of the single wire and unshielded twisted-pair has been established, the model has been analyzed in theory. The time-domain crosstalk response of the unshielded twisted-pair is obtained by using transmission line theory based on time-domain BLT equations, the nodes of the twisted-pair are corrected by using twisted-wire pair two-line hybrid iterative method to improve the accuracy. It is found that the simulation results obtained in this paper agree very well with the results of commercial simulation software, the method is verified to be corrected.Thirdly, the crosstalk model of the single wire and shielded cable has been established, the model has been analyzed in theory. The time-domain voltage and current response of single wire and shielded cable are obtained through the numerical simulation, the time-domain voltage and current response of the single wire and shielded cable are studied while the distance from the ground and the length of cables change.Finally, the coupling model of shielded twisted-pair has been established, the voltage and current response of the shield layer of shielded twisted-pair are obtained by applying the thin conductor FDTD method, the core wire voltage and current response are received by using transmission line theory based on time-domain BLT equations. The coupling problem from the external electromagnetic field to shielded twisted-pair are numerically simulated, the simulation results show that the shielded twisted-pair has good resistance to electromagnetic field. The shield layer current response, voltage response of the shield layer and core wire terminals are studied while the angle of the external incident electromagnetic field, the length of shielded twisted-pair and the distance from the ground change.