汽车点火系统EMI产生机理及其抑制方法

点火系统是汽车内最主要的电磁干扰源，其产生的电磁辐射会对周围电磁环境造成较大的影响。因此，有必要对点火系统的电磁干扰产生机理、传播路径以及抑制措施进行研究。首先系统地分析了汽车点火系统产生电磁干扰的机理，并结合线束电磁干扰排查测试，得出火花塞电极间的火花放电是点火系统中的主要电磁干扰源。其次研究了传导干扰的传播路径和辐射发射的原因。最后设计并制作了两种电源线滤波器，实验结果表明电源线混合滤波器能在宽频带范围内有效降低电源线上的干扰信号，从而降低电源线辐射发射的能力，使整车的辐射骚扰测试能满足相关的电磁兼容国家标准。

The study on EMI principle and suppression method of vehicle ignition system

Vehicle ignition system is the main electromagnetic interference source. Electromagnetic radiation produced by ignition system will produce the interference to electromagnetic environment around. It is necessary to study the electromagnetic interference (EMI) principle, noise paths and suppression method. We analyze the electromagnetic interference principle of ignition system, and harness trouble-shooting related to electromagnetic interference is also tested. Results show that the spark discharge between spark plug electrodes is the main interference source in ignition system. Then, the paths of conducted interference and the reason of radiated emission are discussed in detail. Finally, two kinds of power supply cord EMI filters are designed and implemented on the basis of analysis results. Experimental results indicate that the filter can reduce the noise of power-wire in broadband range. Simultaneously, the radiation emission performance from power wire is also reduced observably. The proposed mixing filter has been demonstrated in this paper to perform satisfactorily with excellent effectiveness in suppression of conducted EMI from 10 MHz to 110 MHz, and the object car can also pass the EMC standard tests.