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Edit: ANCI 2021-12-30 79
Electromagnetic Compatibility EMC (Electro Magnetic Compatibility) refers to the ability of a device or system to operate compliantly in its electromagnetic environment without causing intolerable electromagnetic interference to any device in its environment.
Therefore, EMC includes two requirements: On the one hand, it means that the electromagnetic interference generated by the equipment to the environment in which it is in normal operation cannot exceed a certain limit; degree of immunity, ie electromagnetic susceptibility.
The six-step method of EMC rectification is as follows: the first step is to find and confirm the radiation source, the second step is filtering, the third step is absorbing, the fourth step is grounding, the fifth step is shielding, and the sixth step is energy dispersion. The specific ideas are as follows:
Step 1: The methods of finding and confirming the radiation source include the exclusion method, the frequency point search method of the spectrum analyzer, and the natural frequency analysis method of the component. The exclusion method includes wire drawing method, partition work exclusion method, human body touch method with low voltage and small current, and regional shielding exclusion method. The component natural frequency analysis method refers to the analysis and classification method of the fixed frequency of some components and their frequency multiplication frequency, such as the operating frequency of crystal oscillator and DDR components are fixed.
The second step: filtering is generally divided into capacitive filtering, RC filtering and LC filtering;
the third step: the method of absorbing electromagnetic waves includes the circuit series magnetic bead method, the winding through the magnetic ring method and the absorbing material method. Special attention should be paid when using the method of absorbing electromagnetic waves: the frequency of electromagnetic waves radiated exceeding the standard must be within the frequency range of electromagnetic waves absorbed by the absorbing material used, otherwise the absorbing method will fail.
Step 4: The grounding method is generally divided into single-point grounding method and multi-point grounding method.
Step 5: The shielding method generally includes the shielding method of adding a shielding cover, the shielding method of the shell and the shielding method of the PCB trace layout.
Step 6: The energy dispersion method means that the control software of some measured objects can use technologies such as frequency spread and frequency hopping to broaden the frequency bandwidth and hopping frequency of the frequency band where the energy is concentrated to realize the dispersion of the frequency band energy, so that the additional frequency at a single point can be achieved. The energy on the radiator is reduced, that is, it has the effect of reducing the intensity of the electromagnetic wave radiated by the single-point frequency. Therefore, this method has a significant effect on the frequency radiation exceeding the standard of the spike burr-shaped waveform, but has no significant effect on the frequency radiation exceeding the standard of the envelope waveform.
This six-step EMC rectification method is more suitable for the rectification of common electronic equipment. However, the above 6 methods are actually considered to be helpful to improve the EMC radiation rectification efficiency, save the cycle, and quickly pass the EMC test, but they are not a fundamental solution to the EMC problem. The EMC problem is the most ideal. Think about it, instead of using some "encirclement and interception" solutions to emergency after the event.
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