Research On Calculation Of Crosstalk And Field-to-wire Coupling On Aircraft

Nowadays,Twisted wire pairs(TWPs)are widely used in transmission systems,due to its low cost and anti-interference ability,especially in aircrafts as the Bus.The anti-interference ability of the TWPs relys on the twist structure.However,some machining errors or some demands in use may course lead to nonuniformity of the structure,and decrease the anti-interference ability.Cables nearby and external fields are the two major types of interference sources.This paper improve a new model of crosstalk between single wire and the TWPs,and a new model of field-to-TWPs coupling,both based on the multiconductor transmission line theory(MTL).These models can predict the response on nonuniform TWPs’ terminal,in the situation of crosstalk or field-to-wire coupling.The nonuniformity of the TWPs includes the nonuniformity of its twist pitchs and the distance between two wires,and the incomplete twists in its termination.These types of nonuniformity are also analyzed in the models in this paper.The twist pitches are gained by random process based on the statistical characteristic of TWP samples.The process of solving TWP models includes locating the points on the TWP in coordinate system,calculating the equivalent voltage source and current source produced by interferences,calculating electric parameter matrixes and chain-parameter matrixes,and calculating the terminal response of the multiconductor systems.Calculating the electric parameter matrixes is the first thing to do to solve the MTL equation.In this paper,analytic method is used to calculate the per-unit-length inductance matrix,and the method of moments(MoM)are also used to calculate the per-unit-length capacitance matrix.The model of crosstalk between single wire and nonuniform TWPs is made in the 2D coordinate system based on the cascaded transmission line theory,and can be calculated in Matlab.Then the crosstalk experiment is used to verify the model.It shows that the model can be used to analyze the nonuniformity’s influence on the terminal response of the TWPs under the interference of crosstalk.The field-to-wire coupling model is made in the 3D coordinate system,which is based on the Agrawal field-to-wire coupling model.The numerical method is used to calculate the equivalent voltage source produced by external electrical field.Then the terminal response can be calculated by the cascaded transmission line theory.GTEM cell method is used to verify the model.Finally,the model is used to analyze the nonuniformity’s influence on the terminal response of the TWPs exposed in electrical field.The TWP models mentioned in this paper can be used to predict the nonuniformity’s influence on TWPs’anti-interference ability and provide a reference to choose TWPs in practical use and define the degree of damage in the twist structure.