Electromagnetic Interference Analysis Of Wireless Communication Devices

With the development of wireless communication technology, wireless communication device has been widely used in various fields. As wireless communication device serves in these fields, it also has a variety of electromagnetic interference from the inside and outside, which seriously affects the stability and reliability of wireless communication devices. It is a serious security threat to the relevant fields, therefore, it has important significance to research the electromagnetic interference of wireless communication device.To analyze and evaluate the effect of EMI on wireless communication device, further to optimize the protection ability against EMI of wireless communication device, we propose EMI evaluation methods for wireless communication device, based on the performance of communication command vehicle-mounted antenna radiation emission and quantitative EMI evaluation model of digital spread spectrum communication. First the model is established based on Mom software, according to the problem that many communication antennas are equipped on the top of vehicle. The model is used to study the effect of conductive surface size, material, vehicle body and antenna position to vehicle-mounted antenna pattern. According to field and road transformation theory, using of circuit-port network model for simulation to calculate the vehicle-antenna coupling between different communication bands, which ultimately reflected the distortion of vehicle-antenna pattern and the decrease of the value. Compared with the ideal monopole antenna, antenna directivity decreased nearly half. On the basis, the communication distance as indicator to evaluate the radiation performance of vehicle-mounted antenna based on the ground wave propagation mode, the results show a decrease in performance of vehicle-antenna, which the theory communication distance is14km, but the actual communication distance is only8km.Second, the quantitative evaluation model against EMI of spread spectrum digital communication is established. Then taking pulse and broadband suppressing EMI for example, we establish a forecasting simulation model of direct sequence spread spectrum communication system by using MATLAB software. The typical electromagnetic interference is added to the channel, and the electromagnetic immunity of communication vehicle is analyzed quantitatively by the index of bit error rate. Results show that DS system has a certain immunity of electromagnetic interference, depending on the strength of the signal to interference ratio, the signal to noise ratio and process gain. On the other hand, the research of electromagnetic interference defense is studied by filter.Finally, technology of verification is applied in electromagnetic interference analysis for wireless communication device, by comparison with the theoretical value, electromagnetic emission model and immunity model of wireless communication devices are respectively checked to verify the validity of the model. The reliability of electromagnetic immunity simulation for communication device is verified by plotting the corresponding theory and simulation error rate curves of electromagnetic interference. By using8960tester, the experimental platform is set up to make the verification of experiment. The results show that the content of research has a reference value for electromagnetic interference analysis of wireless communication devices.