Precautions during construction of shielded machine room

Construction precautions:

1. every seam and discontinuity between the bottom plate and the casing shall be overlapped as well as possible. The degree of overlap plays a decisive role in the shielding effectiveness of the shell; When the requirements for shielding, ventilation and strength are high but the quality is not harsh, the honeycomb plate shall be used to shield the vent, and the wire connection shall be maintained by welding to prevent leakage.

2. where possible, joints shall be welded. In case of limited conditions, it can be fixed by spot welding, riveting with small spacing and screws. When lapping with screws or rivets, it shall be lapped in the middle of the seam first, and then gradually extended to both ends to prevent bending of the metal surface. When no conductive pad is added, the screw spacing shall generally be less than 1% of the maximum working frequency and at least not more than 1/20 wavelength;

3. pay attention to the reduction of overall shielding effectiveness due to the cable passing through the housing. When the typical unfiltered conductor passes through the shield, the shielding efficiency is reduced by more than 30dB; When the power line enters the housing, it shall all pass through the filter box. The input end of the filter should be able to pass out of the shielding shell; If the filter structure is not suitable to pass through the housing, a compartment shall be set for the filter at the place where the power line enters the housing; When the signal line and control line enter / exit the housing, they shall pass through appropriate filters. The multi-core connector with filter pin is suitable for this occasion;

4. the metal control shaft passing through the shield shall be grounded with metal contact, grounding nut or RF pad. It can also be connected with other shafts instead of grounded metal shafts. Generally, a circular tube with a waveguide cut-off frequency higher than the working frequency is used as the control shaft; It must be noted that the shielding effectiveness will be seriously reduced when the metal shaft or wire is penetrated through the cut-off waveguide hole;

5. conductive pads or finger spring materials with high conductivity and good elasticity must be used at places with uneven joints or movable panels; Ensure that the fastening method has sufficient pressure to maintain surface contact in case of deformation, stress, impact and vibration;

Electronic shielding technology is not only a means of confidentiality for the government and enterprises, but also plays a vital role in the important security fields of the country, such as electronic countermeasures in military war, the security of avionics technology, etc. in the future, with the development of wireless technology and the improvement of signal separation, filtering technology and encryption means, shielding technology will also get greater development.