A novel design is presented to defend against electromagnetic interference (EMI) in a high speed data acquisition system. Problems that affect signal integrity (SI) in high speed image acquisition systems, such as reflection, crosstalk and ground bounce, are deeply analyzed in a manner consistent with transmission line theory. The results can theoretically inform EMI design of important networks, including system power, ground, clocks, high speed wires and decoupling capacitors. Experiments simulating print circuit board(PCB) reflection and EMI on high speed signal wires between DM642 and SDRAM are conducted. The power and ground should be placed separately in different layers. The clock lines passing through holes should be as few as possible. The signal lines should be as close to the same length as possible. The results show that amplitude of the signal overshoot is less than 0.7 V and the EMI amplitude is within the federal communications commission(FCC) standard.


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针对高速数据采集电路中的电磁干扰问题,提出一种有效的抗干扰设计方案。利用信号传输线理论,对高速图像采集系统中影响信号完整性的反射、串扰和地弹等问题进行了理论分析,对系统电源、地、时钟、高速信号线等重点网络的电磁干扰设计进行理论指导和设计,并且对DM642与SDRAM间的高速信号线进行PCB(print circuit board)的反射、电磁干扰等仿真分析。设计中电源和地独立分层布线,尽量减少时钟线过孔,信号布线尽量等长。结果显示系统信号传输的过冲幅度小于0.7V,电磁干扰强度在FCC标准控制范围之内。