Prediction Of Electromagnetic Noise In Multiconductor Transmission Lines Based On The Coupling Effect Of Fields-to-Transmission Lines

Cable plays an important role in the connection of complex electrical and electronic systems.The inherent characteristic of long-line causes its vulnerability to electromagnetic interference,which results in degradation of system reliability and even failure.In the early stage of design,the prediction of cable electromagnetic interference(EMI)can make designers solve EMI problems in time and thus reduce the cost of rectification,which as a result attracts a lot of attention.At present,there are many researches on this problem and the research contents are mainly focused on the coupling mechanism.However,as a typical object,the prediction of coupling EMI in cable still needs further researches.In this paper,a series of studies are carried out,which mainly include the following parts:1.The multiconductor transmission line(MTL)model is established to calculate the coupling EMI noise in parallel cables.Considering the similarity transformation method and boundary conditions,the MTL equation is solved.Besides,the electromagnetic parameters are obtained by ANSYS,in which the finite element method(FEM)is adopted.As a comparison,this chapter also introduces the method of moments(MoM)and employs the electromagnetic simulation software,called FEKO,to verify the established model.2.The probability distribution of crosstalk in wire harness is studied.As a kind of attribute,twisted wires and changing positions lead to the uncertainty of crosstalk in wire harness.Assumming that the cross section of harness is fixed,the wires change position only at the junction of two neighboring segments.Therefore,each segement has a same probability distribution.After that,the distribution of mutual parameters of the whole bundle is acquired by convolution and then the distribution of crosstalk is obtained by Monte Carlo method.The experimental results show that the crosstalk distribution of the wire harness is closely related to its twist degree.3.Under the excitation of uniform plane wave,the coupling model of the cable is proposed.To compute the noise of terminal loads,similarity transformation is applied once again.Moreover,this capter gives a way to calculate special solution and undetermined coefficient of the equation.Setting a uniform plane wave as the incident wave,the noise voltage is predicted and simulated under the condition of vertical and horizontal polarization.The simulation indicates that the noise of the cable is related to the direction of the incident field as well as the electromagnetic parameters of the harness.4.A method to deal with non-uniform field is investigated.If taking an inhomogeneous field as the excitation,the special solution would no longer be a simple formula.By sampling the transverse and longitudinal electric field with software FEKO,the equivalent voltage and current source along the transmission line is calculated.To obtain the solution of the equation,the three order spline interpolation method is adopted.Then,the boundary condition is used to aquair the simulated voltage.As a simple proof,an inhomogeneous field generated by an electric dipole is simulated.In addition,an experiment platform is set up with logarithm periodic antenna in an anechoic chamber,in which measurements were operated at 100~220MHz,and the simulation curve are consistent with the experiment curve.