Table 2 lists the two types of high initial permeability permalloy rolled strip in four frequency magnetic properties. The specified frequency (frequency condition is extremely important), we can easily choose the best grades and shielding strip thickness. In many cases, people not only requires good shielding material properties, but also lightweight, which promoted the new materials and new varieties are emerging. The recent emergence of high-permeability material CO-NETIC AA and NETIC S3-6 made of foil shielding and shielding tape. CO-NETIC material has high permeability: r = 4.5 105, the effective attenuation of low frequency magnetic interference can achieve very high magnetic shielding; materials have excellent resistance to magnetic saturation capacity, can produce a certain magnetic field decay. Cell phone connects with the base station through the radio wave to complete the transmission of data and voice with the specific baud rate and modulation mode and cell phone jammer will work according to this communication principle. Both materials have excellent workability, its magnetic properties are very stable, in line with the U.S.
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military standard MIL-N-14411 "high permeability iron-nickel alloy sheet, strip, holding materials, profiles and wire." Its made of foil and tape (the product specifications shown in Table 3), can effectively handle the many complex magnetic shielding. Of course, due to price factors, the complex requirements of the product should be considered in the selection. (Applications: radar, transformers, motors magnetic shield, chassis wall stickers cover, improved leakage magnetic field lines and cables need to wrap sensitive low-frequency magnetic field of the protection of electronic equipment.) Shielding for the magnetic field, can be double shield the structure.cell phone jammer will scan at a specific speed, which will form the messy code interference. For shielded from external magnetic field, the shielding layer in vitro is not easy to use magnetic saturation materials such as silicon steel, etc.; while shielding layer can be used easily in vivo saturation of the high-magnetic materials such as permalloy, etc., as shown in Figure 1a.
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On the contrary, for the internal magnetic field shielding, then the material to reverse the order, as shown in Figure 1b, inside and outside the two should be noted that magnetic insulation. When no grounding requirements, insulating materials can be used as a support body; from the shield should be able to both prevent the purpose of starting the electric field sensor, generally used in non-ferromagnetic materials (such as copper, aluminum) pieces of ground for its support. 2. Non-metallic non-metallic magnetic materials, magnetic materials that ferrite magnetic material is a metal oxide with ferromagnetic properties. cell phone jammer uses the DC-DC converter input voltage. At high frequencies with high permeability, higher electrical resistivity and high dielectric properties, are widely used in high-frequency weak areas, such as radar, computers, audio-visual, ultrasonic, etc.
One is mainly used for 1kHz-300MHz high frequency and ultra high frequency soft magnetic materials (Mn-Zn ferrite and nickel zinc ferrite) made of magnetic units, magnetic tube (EMI absorption part), set in the signal cables, light cables, switch to connect online, and the pin shielded high-frequency components such as signal channel, in order to avoid electromagnetic interference. Second, a good conductor material a good conductor material for high frequency electromagnetic fields, low frequency electric field and electrostatic field shielding. As the iron magnetic permeability decreases as the frequency increases, and greater resistance itself, so that the shielding performance deteriorated, while the magnetic losses increase, so the high frequencies do not apply. 3gcell phonejammer uses output voltage of 5V.
According to electromagnetic theory, in the high-frequency electromagnetic fields, the main role is to absorb losses, shielding material, the smaller the resistance (ohms into heat dissipation), the resulting eddy current increases, the greater the anti-magnetic field, the better the shielding effect ; the same time, a good conductor and the return loss of greater low-frequency electric field.