Study On Electromagnetic Radiation Calculation Of Non-uniform Transmission Lines

In modern industry,cables are responsible for connecting various electronic devices in the system to make them function,and they are an indispensable part of the system.However,a large number of studies have shown that most of the electromagnetic interference or non-compliance with the radiation emission test standards of the system equipment is caused by the cable.The cable will act as an efficient transmitting antenna and radiate the interference of the electronic equipment connected to the system.Other equipment in the system or in the adjacent system,the sensitive equipment in the system cannot work normally or even be damaged after being subjected to electromagnetic interference.Therefore,for the EMC design of electronic and electrical systems,considering the signal integrity and anti-interference of the system,the research on electromagnetic radiation of cables is essential.For the electromagnetic radiation of the cable treatment methods,roughly divided into two methods.The first method is the analytical calculation method based on the traveling wave theory.The result is very accurate,but it takes a long time.Compared with the Hertz dipole approximation method,the calculation efficiency is greatly improved under the premise of ensuring the accuracy.The current research on electromagnetic radiation of cables mainly focuses on uniform transmission lines,while the research on non-uniform transmission lines in actual engineering is relatively rare.Moreover,in different situations,such as acceleration and deceleration,vibration,turbulence,etc.,parameters such as height from the ground and distance between cables will have certain randomness.To solve these problems,a new method combining iterative adaptive perturbation method,Hertz dipole approximation method and chaotic polynomial expansion method is proposed to calculate and analyze the electromagnetic radiation of non-uniform transmission lines under different conditions.The main contents and contributions of the paper are listed as follows:(1)Based on the theory of transmission line,a mathematical model of the iterative adaptive perturbation of non-uniform transmission line is established.Based on the lossless double conductor transmission line equation,the value of the mean term and the perturbation term are solved by using the iterative technique and boundary conditions.The mean term and the perturbation term are superimposed together to form the current and voltage of the transmission line.Then,two typical non-uniform cable models,tilt and bend,were designed.CST software simulation and cascading method were used to calculate the near end current and the far end current of the cable,respectively.The accuracy of the iterative adaptive perturbation method was verified.(2)A new method combining iterative adaptive perturbation method and Hertz dipole approximation method is proposed for the electromagnetic radiation of non-uniform transmission lines with fixed position.Using the theory of dipole antenna,the radiation fields of each dipole in the three-dimensional space at the observation point in three directions are calculated.The radiation fields in the three directions are superimposed together to be the total radiation fields of the transmission line at the observation point.In order to verify the accuracy and effectiveness of the proposed method,two typical non-uniform cable models of arc cable and sinusoidal cable were designed,and the effects of non-uniform transmission line bending degree,cable radius,cable length and cable height on the electromagnetic radiation of the transmission line were discussed.(3)A new method,which combines chaotic polynomial expansion method,iterative adaptive perturbation method and Hertz dipole approximation method,is proposed to deal with the electromagnetic radiation of non-uniform transmission lines with random parameters.According to the theory of polynomial chaos,the non-uniform transmission lines to make use of orthogonal polynomial chaos multinomial,and by using boundary conditions to solve the transmission line current,and then can be divided into a number of electric dipole radiation field for solving three directions,superimposed together is the non-uniform transmission lines total chaos polynomial expansion expression of the radiation field.By calculating the mean value,standard deviation and probability density function of two typical random non-uniform transmission line models,which are inclined and curved,the accuracy and effectiveness of the proposed method are verified by comparing with the traditional Monte Carlo-cascade-Hertz dipole approximation method,and this method is applied to practical engineering.