| Reasonable analysis of the electromagnetic susceptibility(EMS)of the receiving system can effectively characterize the response of the receiving system to interference signals and describe the working status of the receiving system in the interference environment,and provide a theoretical reference for the electromagnetic protection of the system.Taking the civil aviation wireless receiving system as the research object,the theoretical research of the system-level EMS has been carried out.The research results can comprehensively evaluate the EMS characteristics of the receiving system under external interference.First,discuss the components and performance indicators of the superheterodyne structure receiving system,classify the components of the receiving system according to linear and non-linear operating characteristics,analyze the transmission characteristics of different types of modules,and conduct signal transmission simulation and module characteristics analysis in modules At the same time,the non-linear characteristics of the module were analyzed,which laid a theoretical foundation for the establishment of the subsequent comprehensive evaluation model.Then,a comprehensive evaluation model of system-level EMS is proposed.The model includes three descriptive parameters,namely error threshold,system failure probability and system alarm time,and establishes a mathematical model of each parameter.First,three performance indicators of error threshold are proposed,namely gain,susceptibility and anti-interference margin;for modules with different operating characteristics,an error threshold model based on performance indicators is established,and the system-level error threshold solution process is designed according to the logical relationship between the module and the system,Obtain the most sensitive indicator and EMS threshold curve in the frequency band by comparing the interference signal thresholds corresponding to the three performance indicators.Then,a method combining Fault Tree Analysis(FTA)and Weibull distribution is proposed to estimate the failure probability of the system.Finally,the Markov process is used to establish the relationship between the expected value of the system warning time and the system failure probability.Finally,according to the non-ideal filtering characteristics of the filter,the error threshold model is modified and optimized,and the selectivity curve of non-ideal filtering is expressed by the broken line approximation method,and the response model of in-band and adjacent-band is obtained.The state of the receiving system when the high-power interference signal invades is analyzed,and the conclusion is that it may lead to system saturation and function failure.And for the most serious image frequency interference of the receiving system,effective suppression measures are proposed.Taking a certain multi-point positioning receiving system as the experimental object,the comprehensive evaluation model and the classic Volterra behavioral model were used to solve the problem.Finally,the actual measurement was carried out to verify the effectiveness of the proposed model.And use the random data generated by Weibull distribution to get the system failure probability and alarm time. |
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