The electromagnetic shielding box is a metal body made of a conductive body or a magnetically permeable material, and the electromagnetic body is limited to a certain space, and the metal body for suppressing radiation interference is used. The conduction and radiation are processed to provide a device that provides a non-interfering test environment to the device under test.
• Isolate external base station signals and external interference signals.
• Isolate interference from adjacent test equipment.
• Absorb RF signals inside the box to reduce interference.
• Reduce the impact of personnel and test more accurately.
• Save operating time and increase work efficiency.
Many people don't understand the principle of electromagnetic shielding. They think that if they use metal as a box and then ground the box, they can act as electromagnetic shielding. The result under this conceptual guidance is failure. Because the electromagnetic shielding is not related to the grounding of the shield. There are only two factors that really affect the shielding effectiveness of the shield: one is that the entire shield surface must be electrically conductive and the other is a conductor that does not directly penetrate the shield. There are many conductive discontinuities on the shield. The most important one is the non-conductive gap formed by the joints of different parts of the shield. These non-conductive gaps create an electromagnetic leak as if the fluid would leak from the gap in the container. One way to address this leakage is to fill the gap with a conductive elastomer to eliminate non-conducting points. This is like the principle of filling rubber in the gap of a fluid container. This elastic conductive filling material is an electromagnetic sealing gasket. In many literatures, the electromagnetic shield is likened to a liquid-tight container, and it seems that electromagnetic wave leakage can be prevented only when the gap is sealed with a conductive elastic material to the extent that the drip does not leak. In fact this is not exact. Whether the gap or hole leaks electromagnetic waves depends on the size of the slit or hole relative to the wavelength of the electromagnetic wave. When the wavelength is much larger than the opening size, no significant leakage will occur.
Shielding concept: When the analog interference source is placed outside the shielding box, the ratio of electric field strength, magnetic field strength or power at a certain point in the space before and after the shielding box is placed is taken as the logarithm (lgp1/p2), expressed in dB.
When the electromagnetic wave reaches the surface of the shield, the reflection of the incident wave is caused by the discontinuity of the impedance at the interface between the air and the metal. This reflection does not require that the shielding material must have a certain thickness, only the discontinuity at the interface is required; b. The energy that is not reflected off the surface and enters the shielding body is attenuated by the shielding material during the forward propagation in the body. . The so-called absorption; c, the remaining energy that has not been attenuated in the shielding body, when passed to the other surface of the material, encounters a discontinuous interface of the metal-air impedance, which will form a re-reflection and return to the shielding body. This reflection may have multiple reflections at the interface of the two metals. In summary, the electromagnetic shield's attenuation of electromagnetic energy is mainly based on the reflection of electromagnetic waves and the absorption of electromagnetic waves.
Shielding performance can be expressed in terms of shielding factor or shielding attenuation. In the space protection zone, the ratio of the field strength (E0 or H0) in the presence of the shield to the field strength (E or H) in the absence of the shield, that is, E0/H0 or H0/H is called the shielding coefficient. The smaller the shielding factor, the better the shielding effect.
The shielding effect can also be represented by the shielding attenuation, which represents the attenuation value of the interference field strength through the shield. The shielding attenuation can be obtained in units of decibels (dB) by the following formula. The larger the attenuation value, the better the shielding effect.
1, application wireless communication test
2, EMC test
3, coupling test
4, RF function test
5, receiver sensitivity test
6, transmitter radiation power test
7, Bluetooth, DAB/DMB
8, mobile phone, Bluetooth, wireless router and other equipment, the whole machine or chip test
There are many types of electromagnetic shielding boxes on the market. For example, the OI-ES series electromagnetic shielding box of marine instruments is an excellent product.
This series of electromagnetic shielding box is welded with 3mm thick aluminum plate, which is lighter and more beautiful than the traditional electromagnetic shielding box. The load-bearing ribs and the universal wheel at the bottom of the box can effectively improve the load-bearing level of the box and can be easily moved at the test site. The shielding box can achieve 100dB shielding performance in the frequency range of 10MHz to 18GHz, and has obvious advantages in similar products.
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