Law 1. The law of EMC cost-benefit ratio: the sooner EMC problems are considered and solved, the lower the cost and the better the effect.
EMC design in the research and development stage of new products can greatly save costs and improve efficiency compared with improvement after the EMC test of products is unqualified; On the contrary, the efficiency will be greatly reduced and the cost will be greatly increased.
Experience tells us that it is the most time-saving and cost-effective to conduct EMC design at the same time of functional design and pass EMC test when the sample and prototype are completed. On the contrary, EMC is not considered in the product research and development stage, and the improvement is carried out only after EMC is found to be unqualified after it is put into production. Not only does it bring great difficulties in technology, but also rework will inevitably bring a great waste of cost and time, and even because of the defects related to structural design and PCB design, the improvement measures cannot be implemented, resulting in the product not being put on the market.
Rule 2. The larger the high-frequency current loop area s, the more serious EMI radiation.
High frequency signal current flows through the minimum path of inductance. When the frequency is high, the wiring reactance is generally greater than the resistance, and the connection is the inductance to the high-frequency signal, and the series inductance causes radiation. Electromagnetic radiation is mostly generated by the high-frequency current loop on the EUT tested equipment, and the worst case is the open circuit antenna form. The corresponding treatment method is to reduce and shorten the wiring, reduce the area of high-frequency current loop, and eliminate any antenna that is not required for normal operation, such as discontinuous wiring or long pins of components with antenna effect.
One of the most important tasks to reduce radiation disturbance or improve the anti-interference ability of RF radiation is to find ways to reduce the high-frequency current loop area s.
Rule 3. The higher the loop current frequency f, the more serious the EMI radiation caused, and the electromagnetic radiation field intensity increases in direct proportion to the square of the current frequency f.
The second most important way to reduce radiation disturbance or improve the anti-interference ability of RF radiation is to find ways to reduce the high-frequency current frequency f of disturbance source, that is, to reduce the frequency of disturbance electromagnetic wave.
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