Electromagnetic Interference Characterristics Of Non-Parallel Transmission Lines

Transmission line is an important part of the connection between electrical and electronic equipment, to transmit information and energy between different systems. In the actual interconnect cables or wiring, the transmission lines frequently emerge in mixed, unequal and non-parallel structures. When the transmission line through a current or induced current by external electromagnetic, then it will have some cable crosstalk leading to electromagnetic interference in transmission line connection circuits. Therefore, this article will regard the electromagnetic interference of non-parallel transmission lines as a research target, it’s significant to ensure normal operation in electromagnetic equipment and EMC forecast..First, the article describes the derivation of the transmission line equation and solve electromagnetic interference by settle transmission line transient response. Use FDTD method for multi-conductor transmission line in the time domain differential equations discretization based on Multi-conductor transmission line model to get iterative formula for solving the transmission line transient response.Secondly, calculating and analyzing the crosstalk characteristics of non-parallel transmission line, Consider non-parallel transmission line structure, it will be seen as a cascade of a plurality of small pieces of parallel transmission lines. Based on the theory of parallel transmission, obtaining the iterative formula of transient response and distributed parameters in each node of non-parallel transmission lines by FDTD method. Comparing the results of simulation software with FDTD calculation program results to verify the correctness of the algorithm. Using non-parallel transmission line model to analysis the change of crosstalk voltage affected by distribution parameters such as the angle β between two lines, ground clearance h, line length l in disturbed line at beginning and end.At last, having studied on the coupling characteristics of non-parallel transmission lines. Considering the irradiation of external electromagnetic, and it is equivalent to a distribution source of non-parallel transmission line. Establishing the transmission line model which is not parallel to the ground and deriving the FDTD iteration formula containing distributed sources to get induced current response on non-parallel transmission lines. The results contrast with the simulation software verifies the correctness of the algorithm, and then analyzed the coupling characteristics of non-parallel transmission line in the environment of free space and shield cavity. Analyzing the change of induced current and voltage at the RL-side affected by the change of distribution parameters such as perigee height h, line length l, radius r, angle β, ground conductivity σg, load impedance of RL in non-parallel transmission lines and electromagnetic wave polarization angle a in the space. The results show that the change of coupled regularity caused by the change of distribution parameter in free space is same as in shielding chamber.