Electromagnetic compatibility (EMC) refers to the ability of a device or system to operate in its electromagnetic environment and to produce unacceptable electromagnetic interference to any device in its environment. Therefore, EMC includes two requirements: on the one hand, the electromagnetic interference generated by the equipment in the normal operation process cannot exceed a certain limit; on the other hand, the appliance has certain electromagnetic interference in the environment. The degree of immunity, ie electromagnetic sensitivity. Electromagnetic compatibility (EMC) is divided into electromagnetic interference (EMI) and electromagnetic resistance (EMS), and all electronic products must comply with the general requirements of electromagnetic compatibility. Electromagnetic compatibility issues in the electronic, electrical, information, communications and other products continue to use high-tech to promote innovation, in addition to users demand communication quality, but also under the government's active development of relevant regulations to control, more prominent electromagnetic compatibility The importance and urgency of related issues. For example, Europe has stepped up post-market testing of imported products, causing many card closures to occur. The National Bus Quality Supervision and Inspection Center introduced electromagnetic compatibility laboratories from Germany including 3/5 m method semi-anechoic chamber, conduction test shielding room, shielding amplifier room, etc., which was completed in February 2005 and successfully passed the Chinese laboratory. Acceptance of the National Accreditation Board (CNAL). During the planning and construction of the central 3/ 5 m method semi-anechoic darkroom, we have accumulated and summarized some experiences for your reference and reference. 1. Selection and construction of the overall scheme of semi-anechoic darkroom Electromagnetic compatibility semi-anechoic darkroom is mainly used to replace electromagnetic radiation disturbance measurement and electromagnetic radiation sensitivity measurement in an open test field without electromagnetic interference. Since the test environment of the semi-anechoic chamber needs to simulate the electromagnetic wave propagation conditions of the open test site (that is, only the direct wave and the ground reflected wave when the electromagnetic wave propagates), the size of the darkroom should be based on the structural requirements of the open test field, which is generally divided into standard 10 m method, 5 m method and 3 m method. There are many types of semi-anechoic chambers, which vary greatly in terms of function, structure, material selection, and installation form. However, which solution is adopted depends mainly on the type of test required by the user, the space size of the object to be tested, the test level, and the like. First of all, we must clarify the test frequency range, whether it is a military standard test or a civilian standard test, whether it is to carry out internal pre-compliance and diagnostic tests, or to carry out third-party certification test; secondly, to clarify the maximum space that the test object may occupy, test The main application criteria, its own financial situation and possible future expansion and upgrade requirements, etc., select a suitable feasible test site and equipment configuration. There are two basic ways to build a semi-anechoic chamber: assembly and welding. The assembled housing consists of a profiled steel plate (made of two curved plates on four sides) and a bolt-on module. Conductive gaskets are placed between any two adjacent shield modules to ensure excellent RF shielding and electrical continuity. This method is light in structure, easy to assemble, easy to repair and disassemble in the future, and has a short construction period. The welding shield system consists of a large piece of steel plate welded together to form a compact RF seal. The benefits of soldered packages are durability and higher shielding performance due to the elimination of seam leaks, but are not easily disassembled and are suitable for fixed locations. Due to the different types of shielding plates built by darkroom manufacturers in darkrooms, the connection methods and processes between the shielding panels are different. In order to ensure good electrical contact and sealing, the shielding panels and their connection methods should be carefully understood and compared. And combined with the actual construction cycle and other requirements to choose. 2. Maternal building and infrastructure Building an EMC laboratory is a systems engineering that follows a scientific design interface: test equipment → semi-anechoic chambers → maternal building design. For the implementation of specific projects, the order is just the opposite, undergoing the process of maternal construction → semi-anechoic chamber installation → test equipment installation and commissioning. Therefore, the mother building must be built before the construction of the semi-anechoic chamber, including floor space, structural load, space size, power supply, gas supply, air conditioning and waterproofing. The design of the parent building must first consider sufficient ceiling height to accommodate the requirements of the built-in semi-anechoic chamber, conducted test shielded room, shielded amplifier room, and other ancillary facilities. Sufficient space must be reserved between the parent building and the darkroom to facilitate installation, maintenance and ventilation of the darkroom. The floor of the parent building is primarily responsible for the weight and load of all shields and mounting parts, and special care is required. The civil construction ground needs to be carefully laid, requiring the ground waviness to be no more than a few millimeters in the range of several meters, and high moisture requirements. In addition, the turntable in the dark room needs to be installed in a concrete pit of a certain depth, the terrain is low, and it must be waterproofed. Before the installation of the darkroom, there is generally a relatively high residual humidity requirement for the load-bearing ground, and a grounding point with a low grounding resistance is also provided for each test chamber. Due to the many interface problems involved between the darkroom and the parent building, and the domestic construction companies have little experience to learn from them, it is very important to let the civil engineering design units, construction units and darkroom manufacturers communicate and communicate. necessary. 3. Several aspects involved in the construction of semi-anechoic darkroom 1. The size of the anechoic chamber. You should be aware that the darkroom you are building is a standard 10 m method semi-anechoic chamber or a standard 3 m method semi-anechoic chamber or a anechoic chamber of custom size according to your site requirements; whether the anechoic chamber is to be equipped with a shielded control room and amplifier room What are their respective lengths, widths, and heights, and which direction they are built in the darkroom. 2. The type, size and number of screen doors. The screen door is divided into single, double and triple knives, and is available in electric, pneumatic and manual. You should choose them according to your future equipment and personnel accessibility and the shielding performance, durability, reliability, ease of maintenance and other aspects of the screen. 3. Type and connection method of the shielding plate. Because of the different types of shields used by darkroom manufacturers to build darkrooms, the connections and processes between shields are different. In order to ensure good contact tightness and electrical continuity, attention should be paid to understanding and comparing the connection between the shielding plates and shielding plates they choose. 4. Shielding room shielding performance. The darkroom manufacturer should be provided with specific shielding performance indicators (given specific values) that can be achieved by its electromagnetic shielding room, which should include shielding performance of magnetic fields, electric fields, plane waves, and microwaves in different frequency segments (from low frequency band to high frequency band). index. 5. Absorbing materials. Pay attention to the manufacturer and model of absorbing materials used by darkroom manufacturers (including ferrite absorbing materials and sharp absorbing materials); pay attention to the composition of absorbing materials and its high temperature resistance, high humidity performance and flame retardant Performance; to understand whether its long-term use is easy to deform and the absorbing properties of various absorbing materials in different frequency bands, to understand how they are laid in the darkroom and where they are laid. 6. Power line and signal line filters. Consider whether the type of power source and their maximum power to be used in the darkroom, such as test equipment, test equipment and auxiliary equipment, and lighting systems, whether to use 380V, 220V, 110V AC voltage, whether there is a need for DC power supply testing and testing Equipment, their number, special test equipment and auxiliary equipment require special filters, etc., all need to be considered, so that suppliers can prepare these power lines and signal line filters in advance. 7. Letter guide and waveguide ventilation window. The dark room needs to be installed with a waveguide venting window to connect with the exhaust fan or air conditioning system. Pay attention to the frequency band design of the waveguide ventilating window, and its shielding performance should meet the shielding performance of the shielding room. The signal guides are used to mount terminals or signal interfaces that cannot be installed directly through the shielded wall; the number and location of the guides and the number and type of terminals on them should be discussed with the test equipment supplier. 8. Fire alarm device and lighting facilities. Be careful to select lighting fixtures that do not cause any radio interference; the installation of fire alarms should not affect the performance of the darkroom. 9. Automation in the darkroom. Automation in the darkroom includes an antenna lift tower, turntable and monitoring system and a controller that can control them. The choice of antenna lifting tower should consider the manufacturer, model and whether there is an adapter for installing the antenna, whether it is supported by the test equipment (that is, whether the test software of the test equipment connected to it has a driver supporting it); the turntable should also be subject to Test equipment support and determine the size and carrying capacity of the turntable according to the size of the equipment under test, and consider the rotation angle and positioning accuracy of the turntable; the monitoring system includes a camera installed in the dark room and a monitor placed in the control room, Select the number of cameras and monitors according to actual usage. The camera should select a model that can work normally in a wide frequency range and high field strength without generating RF interference signals, and install it in no meals. Shooting area. 10. Performance testing and warranty training for darkrooms. Since the darkroom is not only suitable for EMI testing in EMC, it can also be used for radiated immunity testing in EMS. Therefore, the performance test of the darkroom should include the shielding performance test after the darkroom shield is built and the site attenuation test and the field uniformity test after the darkroom is fully constructed. These tests are to be carried out in accordance with the contractual requirements and the relevant standards for international darkroom construction acceptance. Choose a well-known and accredited testing organization. The darkroom warranty and associated equipment, parts warranty and training should be included in the contract. 4. Features and functions of this electromagnetic compatibility laboratory The electromagnetic compatibility laboratory of the National Bus Quality Supervision and Inspection Center is mainly composed of a semi-anechoic chamber, a conduction test shielding room, a shielding amplifier room and a shielding control room. The shield of the darkroom has a length of 17.6 m, a width of 13.5 m and a height of 9.5 m. The dark room is equipped with a turret with a bearing capacity of 8000 kg, a diameter of 5 m, an automatic lifting antenna system of 0.8 to 4 m, and an exhaust gas discharge system. The operating frequency of the darkroom is 9 kHz~40 GHz, and the test area in the dark area above the turntable is 4m high and 2m high. Pneumatic fixtures and cooling fans are also available inside the darkroom. It can complete the radiation and conduction emission test, radiation and conduction immunity test of the whole vehicle and its electronic components, motorcycle complete vehicles and their electronic components, as well as the vehicle static discharge test. Conduction test shielding room size is 8.0 m long, 4.0 m wide and 3.0 m high. In addition to testing the transient emission, conduction immunity and electrostatic discharge of automotive parts, it can also complete household appliances and electric Testing of items such as conducted disturbance voltage, absorbed power, and disturbing magnetic fields of tools and electrical lighting equipment. All the projects in the laboratory have passed the test of foreign third parties, and all the indicators are greatly better than the requirements of relevant international standards. 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