Analysis And Application Of Remote Transmission Characteristics Of Weak Signal

Soft X-ray（particle flow with wavelength range from 0.1 to 1 nm）Diagnosis System for ITER Project of International Thermonuclear Fusion Reactor,the anti-radiation soft X-ray detection device converts the optical signal produced by nuclear fusion into electrical signal through silicon photodiode,and the electrical signal needs to be transmitted through an interconnection system consisting of twisted pair cable and LEMO connector,the consequent problem of signal integrity needs to be studied and analyzed.To verify and evaluate the feasibility of cable and connector applications,based on theory of electromagnetic field simulation,related transmission line and signal integrity,in this dissertation,the sensitive parameters such as reflection,crosstalk and attenuation of signals are simulated and analyzed and combined with the actual test.The research results can be used as an important basis for the model selection,simulation test and reliability evaluation of cables and connectors.Firstly,this study is mainly aimed at the signal reflection problem in Meter-scale twisted pair cables.In this dissertation modeling and analysis of cable based on HFSS and ADS simulation software.In order to solve the problem that the long-distance cable has high requirements on the hardware resources of the laboratory computer,the S-parameter cascade method is proposed to simulate and analyze,and from the two perspectives of the transmission line circuit model and the electromagnetic simulation three-dimensional model,the reflection problem of the signal in the cable has been studied and analyzed.The simulation results show that the lengths of two kinds of cable are exponentially related to the inherent resonant frequency of the cable.And the insertion loss S₂₁ of the different frequency input signals in the cable has a function relationship with the length of cable.Secondly,in order to select a connector for signal remote transmission in complex electromagnetic radiation environment.In this dissertation,series B LEMO connectors are simulated based on CST simulation software.The attenuation,reflection,transmission delay and magnetic shielding performance of the connector are simulated and analyzed in the working frequency band of the connector,and the influence of the discontinuity of the transmission line caused by the corner of the connector on the signal transmission is mainly studied.And the principle of field-circuit co-simulation is utilized,the crosstalk problem between the differential pairs in the connector is simulated and analyzed.The experimental results show that the insertion loss is not less than-0.5dB and the transmission delay is 0.65ns in the working frequency band of the connector.The insertion loss and return loss corresponding to the corner value of the core have an exponential relationship with the frequency.The connector has a good magnetic shielding effect,and the crosstalk amplitude has a quadratic function relationship with frequency.Finally,the attenuation of cables,interconnected cables and connectors and the crosstalk of connectors are tested and analyzed by using spectrum analyzer and other devices.The simulation results are in good agreement with the test results.