Several aspects of suppressing electromagnetic radiation need to be paid attention to in PCB board design

by:A-TECH      2021-03-13
PCB is the source of electromagnetic interference (EMI), so PCB design is directly related to the electromagnetic compatibility (EMC) of electronic products. If emphasizing EMC/EMI in high-speed PCB design, it will help shorten the product development cycle and speed up the time to market. Therefore, many engineers are very concerned about the problem of suppressing electromagnetic interference in this forum. For example, Shu Jian of Wuxi Xiangsheng Medical Imaging Co., Ltd. said that the harmonics of the clock signal were found to be very serious in the EMC test. Is it necessary to perform special treatment on the power supply pins of the IC that uses the clock signal? Connect a decoupling capacitor to the power supply pin. In the PCB board design, what other aspects should be paid attention to to suppress electromagnetic radiation? The relevant person pointed out that the three elements of EMC are radiation source, transmission route and victim. The propagation path is divided into space radiation propagation and cable conduction. So to suppress harmonics, first look at the way it spreads. Power decoupling is to solve the propagation of conduction mode. In addition, necessary matching and shielding are also required. At the same time, filtering is a good way to solve EMC radiation through conduction. In addition, it can also be considered from the aspects of interference sources and victims. In terms of interference source, try to use an oscilloscope to check whether the signal rising edge is too fast, there is reflection or overshoot, undershoot or ringing. If so, you can consider matching; in addition, try to avoid making 50% duty cycle signals, because this kind of signal has no even There are more sub-harmonics and more high-frequency components. For victims, measures such as land coverage can be considered.
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