In recent years, more and more attention has been paid to the problem of EMI (Electromagnetic Interference, EMI). There are two forms of EMI, namely conducted interference and radiated interference. Conducted interference refers to the coupling (interference) of a signal in an electrical network to another electrical network through a conductive medium, and radiation interference refers to the coupling (interference) of a signal in a system to another electrical network or electronic device through space. Therefore, the design of high-speed PCB systems, high-frequency signal lines, IC pins and connectors may all be sources of radiation interference with antenna characteristics, thereby affecting the normal operation of other systems or equipment.
EMI test is a test designed to detect the intensity of radiated interference generated by the equipment under test (EUT and DUT), which is carried out by EMI interference test equipment>. It consists of two parts: RE test and CE test. The RE test is used to detect the radiated energy of the object under test, while the CE test is used to measure the response of the object under test to external signals.
EMI (Electromagnetic Interference) refers to the phenomenon that a signal in one system or electronic device is unintentionally coupled to another system or electronic device through space or a conductive medium, and the arrival of this signal will affect the interfered system performance. In the lighting industry, in addition to meeting the certification standards of different countries, EMI testing has also become a necessary testing operation for lighting equipment. For EMI interference test equipment>, three-loop antennas and EMI receivers are generally used in the world. The three-loop antenna is mainly used to convert low-frequency magnetic field components in the directions of X, Y, and Z axes into radio frequency signals, and then It is transmitted to the EMI receiver through the coaxial cable, and finally it is analyzed and processed by the software and the disturbance level is judged. In addition, in the 9KHz-300MHz frequency band, the CDN (capacitive coupling network) method is also used for EMI detection to realize the isolation, sampling and impedance matching of RF signals, and at the same time provide power for the test products; the CDN terminal voltage method is mainly based on the CISPR-15 standard , for luminaires and luminaire lighting equipmentThe disturbance signal is tested, and finally analyzed, processed and judged by the EMI test software. The test range of this method is from 9KHz-300MHz, which is also aimed at the emerging LED lighting industry. For the LED lighting industry, the scanning frequency from 30MHz to 300MHz is clearly required in CE certification, so the CDN method is more accurate and effective, which is conducive to improving the safety and reliability of lighting equipment.
Quality testing of electronic appliances and lighting equipment also need to be constrained. For example, the FCC certification of the United States and the CE certification of the European Union require LED lighting equipment to meet the EMI interference test equipment> test items. The frequency of conducted interference test is from 0.15MHz to 30MHz, while the frequency of radiated interference test is from 30MHz to 1GHz; for CE certification, the frequency of conducted interference test is from 9KHz to 30MHz, and the frequency of radiated interference test is from 30KHz to 300MHz. In order to test 9KHz-30MHz EMI, antennas and EMI receivers can be used, according to CISPR15, EN55015, GB17743 standards; for low-frequency magnetic fields that may be generated by lighting fixtures, three-loop antennas provided by CISPR116-1-4 can be used to measure radiation disturbances; in addition One is to use the LISN test method, which is also an international general test method. It is mainly composed of EMI inspection machine, artificial power network, LISN and test software; 9KHz-300MHz can be tested by CDN method, which uses EMI receiver, CDN and attenuator The test system composed of it is used to test the conducted interference generated by lamps and lamps and lighting equipment under normal working conditions.
EMI has a great impact on society, therefore, it should avoid electromagnetic wave radiation pollution, which is accurately defined as the task of improving electromagnetic compatibility. The international organization CISPR (COMITÉ INTERNATIONAL SPECIALIRADIO INTRUSION) has defined a number of electromagnetic compatibility standards to ensure and guarantee the safe use of electronic and electrical equipment in society. In Europe, the European Standards Committee has issued standards such as EN55015 and EN55022. These measures and standards are aimed at regulating the electromagnetic compatibility restrictions and other requirements of electronic products in order to reduce social problems caused by electromagnetic interference.
Therefore, for EMI control and management, no matter the scientific and technological team of the government department or the electrical and electronic manufacturer, they should be responsible for electromagnetic pollution, comprehensively grasp and be familiar with the CISRP-16 standard and other related requirements, rationally design and assemble products, and optimize product structure. Corresponding testing methods and EMI interference testing equipment> are used to improve the electromagnetic interference performance of products and ensure the stability of social order and the health of the social environment.