Calculation Of Shielding Performance Of Cable Shielded Sheath With Pigtail

With the progress of science and technology,all kinds of electronic equipment and power system have a greater demand,and the structure is more compact.These make the electromagnetic environment more and more complex.The harness will be concentrated in a limited space so that the interference is increasingly severe and the electromagnetic spectrum is even more abundant.The electromagnetic compatibility of electronic equipment systems is becoming increasingly apparent.In order to make the normal operation of electronic equipment,the cable must be shielded by the corresponding shielding measures.The use of shielding sheath is a very effective measure to prevent the crosstalk of cable and the external electromagnetic interference.To a certain extent,it can block the transmission of electromagnetic wave,and avoid the electromagnetic compatibility of the cable in the sheath.In this paper,the crosstalk coupling problem of shielded cable in time and frequency domain is studied in terms of multi conductor transmission line theory,finite-difference time domain method and BLT equation.The main contents include the following four parts:1.In the case of high frequency,the cable is electro-long,and the current and voltage along the line are no longer evenly distributed under the short length.Therefore,the distribution parameters of the multi?conductor transmission line are analyzed.Because of the existence of braided mesh,the electromagnetic field will be transmitted into the sheath.The transfer impedance is deduced as the shielding parameter of the internal loop excitation source,and the self-made double short circuit three coaxial method is used to test and verify.2.The coupling of the single-line to the complete shielded cable is studied based on the theory of the multi-conductor transmission line in the frequency domain.In addition,due to the limitation of the actual situation,the pigtail is used to terminal grounding.Investigate that pigtail grounding ways have effects on the shielding performance of shielding sheath.Furthermore,the influence factors of the crosstalk resonance frequency are analyzed,and the crosstalk resonance frequency of non-parallel beam is studied.3.Combining the multi-conductor transmission line equation and finite difference method of time domain,the difference equation of cable crosstalk is deduced.The crosstalk model of single-wire shielded cable is established,and the time domain characteristic of shielded terminal is analyzed by using different excitation sources.And use CST for simulation verification.4.The field-coupled telegram equation and BLT super-matrix equation of the transmission line network are deduced.The distribution excitation source of the shield under the external field irradiation is obtained by the Green function method,then the terminal response of the inner loop is obtained according to the transfer impedance.For the terminal of using the pigtail,based on the pipeline of BLT cable network,the shielding layer is divided into small segments,which can be used to calculate the current at each point.The relationship between the maximum current and the core terminal response voltage of the complete shielded cable and the cable shield with the pigtail at different frequencies and the time domain response of the core terminal under the pulse excitation are studied.