Solutions for PCB Electromagnetic Compatibility Problems

Dated:2018-01-03      Popularity:1037

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Printed circuit board is the most important part of electronic equipment. With the development of integrated circuit technology, a variety of electromagnetic interference problems have emerged which lead to the economic losses, thus electromagnetic compatibility has become more and more important now. 

In this article, we’d like to analyze the causes of PCB electromagnetic interference and find solutions to electromagnetic interference factors.

PCB interference factors

One is from the PCB interior, which is mainly caused by the parasitic coupling between adjacent circuits and the field coupling of internal components that signal crosstalk along the transmission path, such as capacitors on PCBs, especially those used in high frequency applications. 

Another kind of electromagnetic interference comes from the outside of PCB, it is divided into two kinds of issues of radiation interference and sensitive element. Radiation mainly comes from the harmonic sources of clocks and other periodic signals, and some electronic devices or instruments generate second harmonics due to voltage and power transitions.

To avoid PCB electromagnetic interference, you can follow from the above tips:

1.Reasonable design schematic
When designing a printed circuit board, design a schematic diagram is the first thing. Altium Designer software is generally used to design a schematic diagram, all devices can be used from the schematic library, if the schematic library does not have your ideal components, you can draw them by yourself. Automatic detection is necessary after the schematic diagram is done, it can check whether there exist any obvious errors.
Printed circuit board design can be done after schematic drawing is completed. The result of automatic routing is always unsatisfactory, thus manual layout and wiring are required. While designing the printed circuit board, the issue of electromagnetic compatibility has become an important technical requirement for consideration. Reasonable layout printed circuit board components and wiring layout can effectively reduce the electromagnetic interference problem.

2.Select the equivalent inductance and resistance of smaller capacitors
The issue of crosstalk should also be taken seriously, and crosstalk is where energy is coupled from one line to another. Faraday’s electromagnetic induction phenomenon shows that when a wire through the current, the magnetic field will be generated around the wire. Crosstalk occurs due to different wires’ magnetic fields are interacted. Mutual inductance is one of the mechanisms that produces crosstalk, and its size is proportional to the current in the wire.

3.Limit the periodic signal to a small area
Mutual capacitance is another mechanism to produce crosstalk, which is generated by the two electrodes through the coupled electric field. The solution is to limit the periodic signal in a region as small as possible and block the path of parasitic coupling with the outside world, when necessary, the filters can be used to filter. External sensitive factors are mainly radio frequency interference and electrostatic discharge, etc. To solve this problem, shielding, good grounding and filtering methods are recommended.

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