The rapid development of science and technology which is now in this article we explain in depth electromagnetic compatibility and electromagnetic applications darkroom darkroom compatible with the current domestic product compared to other advantages, we want to help everyone.
Electromagnetic compatibility darkroom is also called semi-anechoic darkroom, referred to as EMC darkroom. On the basis of electromagnetic shielding room, electromagnetic wave absorbing material is placed on the inner wall and ceiling, and the ground is an ideal reflecting surface. Thereby simulating the test conditions of the open field. Because there is no reflected wave on the wall, the measurement accuracy is high in the radiation emission and reception test. It is a popular and suitable electromagnetic compatibility test site at home and abroad.Each test item for electromagnetic compatibility requires a specific test site, of which the site requirements are most stringent with radiation emission and radiation immunity tests. The transmission and reception of the 80-1000MHz high-frequency electromagnetic field is based on the theory that the spatial direct wave and the ground reflected wave are superimposed at the receiving point. Unsatisfactory venues will inevitably lead to large test errors. As we all know, the open test site is an important electromagnetic compatibility test site. However, due to the high cost of the open test site and the distance from the urban area, it is inconvenient to use; or it is built in the urban area, and the background noise level is large, which affects the EMC test. Therefore, the electromagnetic shielding semi-anechoic chamber that simulates the open test site has become a common EMC. Test site. US FCC, ANCI C63.6-1992, IEC, CISPR and national military standard GJB152A-97, GJB2926-97 "Electromagnetic Compatibility Test Laboratory Accreditation Requirements" and other standards allow the use of electromagnetic shielding semi-anechoic chambers instead of open test sites for EMC testing .
Electromagnetic shielding semi-anechoic chambers are often used to replace the outdoor open field to test the electromagnetic interference characteristics (EMI) and electromagnetic sensitivity characteristics (EMS) of various electrical and electronic equipment. It is one of the important venues for electromagnetic compatibility certification testing. Outdoor venues are susceptible to interference from ambient electromagnetic noise and climatic conditions, so indoor shielded rooms are often used instead. However, the shielded room is a metal enclosure with a large number of resonant frequencies. Once the radiation frequency and excitation mode of the device under test causes the shielded room to resonate, the measurement error can reach 20 to 30 dB, so it is necessary to surround the wall and top of the shielded room. The absorbing material is installed on the absorbing material, so that the reflection is greatly weakened, that is, only the direct wave and the ground reflected wave are transmitted when the wave propagates, and the structural size is also based on the requirements of the open test field, so that the test of the outdoor open field can be simulated, which is electromagnetic shielding. The absorbing darkroom, also referred to as the EMC darkroom.
The EMC darkroom structure is usually composed of RF shielding room, absorbing material, power supply, antenna, turntable and CCTV monitoring: the RF shielding room ensures that the test is free from external interference; the absorption material ensures the absorption characteristics of the darkroom; the antenna and turntable ensure The measured object is tested according to the conditions and conditions required by the standard; the monitoring and testing of the CCTV monitoring system is carried out normally, and the power supply system guarantees the test power. Auxiliary equipment such as RF screen doors, ventilated waveguide windows, cameras, lights, power boxes, etc. should be designed to be placed outside the main reflection area as much as possible to prevent any metal parts from being exposed to the main reflection area. The floor of the darkroom is the only reflective surface of electromagnetic waves. The requirements for the floor are: continuous flat without bumps. There must be no gaps that exceed 1/10 of the minimum operating wavelength to maintain the conductive continuity of the floor. The dark room grounding wire and power cable should be laid on the wall. Do not traverse the room. The wire should also be worn with metal pipes, and keep the metal pipe and the floor well. In order to avoid radio wave reflections affecting measurement errors, the person and test control equipment should not be in the test site. Therefore, the general EMC darkroom is composed of a test darkroom and a control room. The test antenna and the equipment to be tested are placed in the test darkroom, and the operator and the test control instrument are in the control room. If there is a high-power amplifier device, you should also set up the power amplifier room to place these devices to avoid interference with the surrounding environment. The dark room and the control room should each use an independent power supply system, use different phase power supplies, and pass through their respective filters to avoid interference from the control room through the power line into the dark room.
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