Research on the influence of screw spacing on magnetic shielding effectiveness of a shielding cabin

Large shields are usually formed by splicing small pieces of metal, resulting in gaps that affect the shielding effectiveness of the shield. Affected by the screw fixed spacing, the size of the slits will also be changed. Since it is difficult to deduce the influence of fixed spacing on shielding effectiveness by theoretical formula or software simulation, we built a 2m*2m*2m shielding cabin model and explored the influence of fixed spacing on shielding effectiveness by changing the fixed spacing of screws. During measurement, the selected frequency range was 0.25-1000MHz. In the selected frequency range, for different frequencies, different antennas were used and a total of 22 frequency points were selected for measurement. The results show that the smaller the screw spacing, the greater the shielding effectiveness. When the screw spacing is reduced by half, the shielding effectiveness increases by about 6-8dB, especially at low frequency. When screw spacing is 0.25m, the maximum shielding effectiveness is about 44dB, the minimum is about 25dB, and the average shielding effectiveness is about 35dB. In addition, the polarization mode and antenna position have little influence on the results. So it can be used as a guide and reference for the design of large shielding body in the future.