Building electromagnetic shielding is a building technical measure taken for buildings (more often, some spaces in such buildings) that need to isolate electromagnetic wave interference and prevent electromagnetic wave leakage.
Introduction: Building electromagnetic shielding is a technical measure taken in building design to isolate electromagnetic wave interference and prevent electromagnetic wave leakage. Electromagnetic shielding technology was developed in the 1940s and became increasingly perfect in the 1950s. Its functions are to prevent external electromagnetic wave interference and to prevent indoor electromagnetic wave leakage. Electromagnetic waves are divided into three categories according to the characteristics of interference: electrostatic induction, magnetic lines of force, and electromagnetic wave interference. According to their characteristics, corresponding structural measures are taken in the building space to combine various forms of shells or mesh covers made of high-conductivity metal materials with the external protective structure to make them have the performance of isolating electromagnetic waves. According to the form of space, it is divided into fixed type, movable room type, assembled cage type, hanging type (i.e. hanging metal plates on the indoor surface), and jacket shielding layer room type. The metal shell can be constructed by using metal flat plates, perforated metal plates, single-layer or double-layer metal wire mesh, metal plate and metal wire mesh composite layers, and honeycomb metal mesh.
Since the 1950s, electromagnetic shielding technology and building shielding design have become increasingly perfect. Currently being studied and applied are metal powder spray coatings, metal film paving layers, and high-efficiency shielding rooms with shielding equipment and automatic control power supplies.
Scope of application: Building electromagnetic shielding is used in two aspects:
First, to prevent external electromagnetic wave interference, to ensure the accuracy of scientific experiments and the quality of industrial products, such as television receiver measurement, precision electronic component testing, electron microscope operation, etc..
Second, to prevent indoor electromagnetic waves from leaking out and being intercepted, and causing confidentiality loss. Microwave radar operation, optical communication testing, ultra-large-scale integrated circuit development, missile guidance system debugging, and early warning system measurement, etc., all need to prevent electromagnetic waves from leaking out.
Characteristics and classification. According to the characteristics of interference, electromagnetic waves are divided into three categories: electrostatic induction, magnetic lines of force, and electromagnetic wave interference. Building electromagnetic shielding involves taking structural measures in the building space according to the characteristics of electromagnetic waves, and combining high-conductivity metal materials into various forms of shells or mesh covers with the external protective structure to make the building space have the performance of electromagnetic shielding. Its forms are divided into fixed room type, movable room type, assembled cage type, hanging type (i.e. hanging metal plates on the indoor surface) and outer shielding layer room type according to the composition of the space; according to the metal shell and structure, it is divided into metal flat plate, perforated metal shell plate, single-layer or double-layer metal wire mesh shell, metal plate and metal wire mesh composite shell and honeycomb metal mesh shell shielding room.
Shielding room design The selection of shielding materials, structures, structures, and space forms of the shielding room should be based on the requirements and structures of electromagnetic shielding in the operation, and the conductivity, magnetic permeability, and electromagnetic interference wave attenuation values should be calculated, and various requirements such as material source, cost, construction, and use and maintenance should be considered to determine. Generally, a small space that is easy to shield is used, with no windows or few windows, the number and area of pipeline crossing holes are minimized, and alloy mesh shells and composite layer structures are used instead of expensive metals to reduce the construction cost.
Materials and structures Shielded rooms with different spectrums should use different shielding materials and structures. The method of pre-burying metal plates in the outer protective structure layer has better shielding performance, but the metal consumption is large, and the cost is high. The method of using metal perforated plates for finishing has a better modeling effect, can reduce deadweight and save metal consumption, but the cost is also high. The method of spreading metal wire mesh in the indoor paint layer uses less metal and is convenient for construction, but the effect of preventing electromagnetic wave penetration is poor. The method of spraying metal powder on the indoor surface to form a shielding shell is a new technology with less metal consumption, fast and convenient construction, but with poor density and durability.
Gap treatment is an important part of shielding room design. To plug the loopholes that may penetrate electromagnetic waves, additional shielding measures need to be taken for the gaps where different walls meet, door and window holes and their overlap with the wall, holes where air conditioners and power supply pipelines pass through the wall, and metal plate (net) welding points, such as adding metal plates (nets), foam plastic pressure seam strips filled with metal wire cloth, solder, lead grounding, comb-shaped spring sheets, honeycomb waveguides, power filters, etc. The figure shows an intermediate frequency shielding room, where 0.4 mm-thick No. 28 galvanized iron sheets are laid on the indoor ceiling, wall, and ground structure layers, and door and window sashes. To prevent the formation of pores for electromagnetic wave penetration, foam plastic pressure seam strips wrapped with copper wire cloth are set at all pipeline openings, door and window frames, and door and window sash overlaps to block electromagnetic waves. At the pipe opening entering the room, a power filter is added, which does not affect the passage of the pipe and can prevent electromagnetic waves from entering and exiting.
