What Is Coaxial Cable

Coaxial cable is a kind of electric wire and signal transmission line, which is generally made of four layers of materials: the innermost is a conductive copper wire, the outer surface of the wire is surrounded by a layer of plastic (used as an insulator and a dielectric), and the insulator is surrounded by a layer of plastic. There is a thin layer of mesh conductor (usually copper or alloy), and then the outermost layer of insulating material is used as the outer skin.

Coaxial cable can be used for the transmission of analog and digital signals, and is suitable for a variety of applications, the most important of which are television broadcasting, long-distance telephone transmission, short-distance connections between computer systems, and local area networks. Coaxial cable has developed rapidly as a means of spreading television signals to thousands of households, which is cable television. A cable TV system can load dozens or even hundreds of TV channels, and its transmission range can reach tens of kilometers. Coaxial cables have long been an important part of long-distance telephone networks. Today, it faces increasing competition from fiber optics, terrestrial microwave, and satellite

Coaxial cable is divided into four layers from the inside to the outside: the central copper wire (single-strand solid wire or stranded wire), plastic insulator, mesh conductive layer and wire sheath. The central copper wire and the mesh-like conductive layer form a current loop. It is named because the central copper wire and the mesh conductive layer are in a coaxial relationship.

Coaxial cables conduct alternating current rather than direct current, which means that the direction of the current is reversed several times per second

If a normal wire is used to transmit high-frequency currents, the wire acts as an antenna that emits radio outward, an effect that loses the power of the signal and reduces the strength of the received signal.

Coaxial cables are designed to solve this problem. The radio emitted by the central wire is isolated by the mesh conductive layer, which can control the emitted radio by grounding.

There is also a problem with coaxial cables, that is, if a certain section of the cable is squeezed or twisted, the distance between the center wire and the mesh conductive layer is not consistent, which will cause the internal radio waves to be blocked. reflected back to the source of the signal. This effect reduces the acceptable signal power. To overcome this problem, a plastic insulator is added between the center wire and the mesh conductive layer to ensure a consistent distance between them. This also causes the cable to be relatively stiff and not easy to bend.

In essence, the shielding material of coaxial cable is mainly to improve the outer conductor, from the initial tubular outer conductor to single-layer braid and double-layer metal. Although the tubular outer conductor has very good shielding performance, it is not easy to bend and is inconvenient to use. The shielding efficiency of single-layer braiding is the worst, and the transfer impedance of double-layer braiding is 3 times lower than that of one-layer braiding. It can be seen that the shielding effect of double-layer braiding is greatly improved than that of single-layer braiding. Major coaxial cable manufacturers are constantly improving the outer conductor structure of the cable to maintain its performance.