Shielding effect of coaxial cable

    Coaxial cable is a commonly used shielded cable that can suppress electromagnetic leakage of transmitted electrical signals and shield electromagnetic interference in abnormal environments. The level of shielding effectiveness mainly depends on the effectiveness of the outer core shielding layer, the material of the shielding layer and its mesh weave density, and the grounding method of the cable shielding layer, signal source impedance and load matching and other factors. Our common or commonly used metal wire braid is a kind of shielding layer that is easy to use, low quality and low cost. It is widely used, but its shielding effectiveness has no precise calculation formula. It can only be measured or provided by the manufacturer. Its shielding effectiveness It increases with the increase of the mesh density, and decreases with the increase of the transmission signal frequency.

    The shielding effectiveness of a coaxial cable is also related to the degree of bending of the cable during installation, because the actual coverage of the shielding mesh braid varies with the degree of cable bending. When the cable is bent, the density of the shielding net near the inner side increases, while the density of the shielding net near the outer side decreases significantly, which will affect the shielding effect of the coaxial cable. At the same time, excessive bending of the cable will cause the position of the cable core wire to shift and cause the characteristic impedance to change. Therefore, when the cable is installed, the minimum bending radius for indoor use should be greater than 5 times the outer diameter of the cable, and for outdoor use, it should not be less than 10 times the outer diameter of the cable.

(Huiputech)