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When designing high-speed PCB, should the designer consider the rules of EMC and EMI from those aspe

  • Author:o-leading.com
  • Source:o-leading.com
  • Release on:2017-10-11
General EMI/EMC design needs to consider both radiation and conduction (radiated) (conducted) two aspects. The former belongs to the high frequency part (>30MHz) which is the lower part (<30MHz). So we can not only pay attention to high frequency and ignore the low-frequency part. A EMI /EMC good design must start layout we must take into account the location of the device, the PCB stack arrangement, important online travel, the choice of devices, if these are not better than the prior arrangement, after the solution will be less effective, increase the cost. 

For example, the position of the clock generator are advised not to close external high-speed signal connector, try to walk and pay attention to inner impedance matching characteristics of continuous and reference layer to reduce the reflection device push signal slope (slew rate) as small as possible to reduce the high frequency components, choose to pay attention to the coupling (decoupling/bypass) meets the demand for lower frequency response the power supply noise layer capacitance. 

In addition, pay attention to the high frequency signal current return path to make the loop area as small as possible (i.e. loop impedance loop impedance as small as possible) to reduce the radiation range. Can also be used to control the formation of segmentation noise. Finally, ground appropriate choice of PCB and shell (chassis ground).