Research On EMI Prediction Method Of Vehicular Communication System

With the development of Electronic Science and technology,more and more electronic and electrical equipment are equipped in modern vehicular communication system,which forms a complex electromagnetic environment inside the vehicle.And in the actual battlefield environment,the vehicular communication system will not only be interfered by the enemy equipment intentionally,but also be interfered by the friendly equipment unintentionally,which leads to the electromagnetic interference problem of the vehicular communication system.The topic of this paper comes from the project of "##### electromagnetic environment effect test and evaluation system".Based on the hierarchical screening method,this paper proposes a novel EMI prediction method for vehicular communication system to quantitatively describe the interference margin and interference condition of vehicular receiver,which is verified by an example.The main research work of this paper is as follows:1.Based on the three elements of electromagnetic interference,the principle of electromagnetic interference between systems is analyzed,and the calculation model of interference margin is given.Then the transmitter model,receiver model,antenna coupling degree model and propagation loss model are introduced.2.Based on the traditional hierarchical screening method,a novel EMI prediction method for vehicular communication system is proposed.The vehicular receiver is regarded as the main body of the evaluation in this method,the ambient noise of the receiver is equivalent to an interference source,the effective interference amount of multiple interference sources acting on the receiver is superimposed at the same time,the interference margin of the receiver is calculated through the total interference amount,and then the interference margin is converted into the performance change of the receiver to realize the performance evaluation of the vehicular communication system.3.The relationship between the key performance index of communication system and the interference margin is studied,communication distance,speech intelligibility and bit error rate are selected to evaluate the performance of vehicular communication system after being disturbed.Firstly,according to the influence of different types of interference sources on the sensitivity of receiver,the calculation models of narrowband and broadband interference power and the sensitivity of ultrashort wave receiver are established,and compared with the measured data,the results show that the error between the predicted value of more than 60%frequency points and the measured data is within 3dB.Based on the analysis of receiver desensitization,the influence of desensitization on the actual communication distance is discussed,Secondly,according to the definition index model,the quantitative relationship between interference margin and speech intelligibility of analog communication system under different signal to noise ratio is simulated and analyzed.Then,the relationship between bit error rate and interference margin of digital communication system under different modulation types,different coding methods and different channel models is obtained by Simulink simulation,and the performance differences between them are compared.Finally,the effectiveness and feasibility of the proposed method are verified by an evaluation example.