The three laws of EMC (Electromagnetic Compatibility) rectification

Rule 1: The cost-effectiveness relationship of EMC. The earlier you consider and solve the EMC issues, the lower the cost and the better the effect.

     Carrying out EMC design during the new product development stage can significantly reduce costs and improve efficiency compared to making improvements only after the product fails the EMC test. On the contrary, efficiency will be greatly reduced and costs will increase significantly.

Experience has shown that conducting EMC design concurrently with functional design, and performing EMC tests after the completion of samples and prototypes, is the most time-efficient and cost-effective approach. On the contrary, if EMC is not taken into account during the product development stage and only improvements are made after the product is put into production and it is found to be non-compliant with EMC standards, it not only brings significant technical difficulties but also inevitably leads to a huge waste of time and costs. Moreover, due to the defects in structural design and PCB design, it is impossible to implement improvement measures, resulting in the product being unable to be launched.

Rule 2: The larger the area of the high-frequency current loop, the more severe the electromagnetic interference radiation will be.

The minimum path for high-frequency signal current to flow through an inductor is as follows: when the frequency is high, the inductance of the conductor is greater than its resistance, and the high-frequency signal of the conductor becomes an inductor. When inductors are connected in series, radiation is generated. Electromagnetic radiation is mainly produced by the high-frequency current loop of the tested EUT equipment. The worst case is an open-circuit antenna. The corresponding solution is to reduce and shorten the wiring, reduce the area of the high-frequency current loop, and try to eliminate any antennas required for abnormal operation, such as discontinuous wiring or components with antenna effects, such as long pins.

How to reduce the area of the high-frequency current loop is one of the important tasks for reducing radio frequency radiation interference or enhancing the anti-interference ability of radio frequency radiation.

Rule 3: The higher the frequency of the loop current, the more severe the electromagnetic interference radiation will be. The increase in the electromagnetic radiation field intensity is proportional to the square of the current frequency f.

The second most important way to reduce radiation interference or enhance the anti-interference ability of radio frequency radiation is to find ways to decrease the frequency f of the high-frequency current of the interference source, that is, to reduce the frequency f of the interfering electromagnetic wave.

The following content of this article applies the above three rules to advocate considering the EMC issue as soon as possible and introduces EMC design and improvement of EMC problems.

Improve EMC issues, such as treating diseases. If the product fails the EMC test, we can only know from the measurement results which frequency points are "exceeding the standard". Where the electromagnetic interference from these frequencies comes from is often the most difficult problem for engineers to discover and solve. EMC issues of the product are difficult to talk about, but once mentioned, they are easy to understand. Improving EMC issues, first of all, based on the path and mechanism generated by EMI, that is, the elements of EMC problems, target (test samples, first make some judgments, such as the cause of the EMC problem, whether it is the source of interference for equipment and AV audio and video devices or internal interference).

Then, based on the test diagrams of the test items, we should look at the essence from the phenomena and analyze the reasons for the out-of-tolerance results - identify the sources of interference, thoroughly discover the ways of interference, and thus have a clear goal. To analyze the reasons for the out-of-tolerance results, a high-frequency oscilloscope or spectrum analyzer along with on-site probes can be used to verify and analyze the results. From the frequency domain to the time domain, and then from the frequency domain to the time domain, analyze and identify the corresponding circuits and components that cause the EMC problem.