How Coaxial Cables Work

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

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

If a high-frequency current is transmitted using a normal wire, the wire acts as an antenna that emits radio outwards, an effect that dissipates 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 a mesh conductive layer, which can be grounded to control the transmitted radio.

There is also a problem with coaxial cables, that is, if a certain section of the cable is squeezed or twisted to a large extent, the distance between the center wire and the mesh conductive layer is not consistent, which will cause the internal radio waves to be reflected back to the signal source. This effect reduces the power of the signal that can be received. To overcome this problem, a plastic insulator is added between the central wire and the mesh conductive layer to ensure that the distance between them is always the same. This also results in the fact that the cable is relatively stiff and does not bend easily.

In essence, the shielding material of coaxial cable is mainly to improve the outer conductor, from the initial tubular outer conductor to a single-layer braided 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 the single layer braiding is the worst, and the transfer impedance of the double layer braiding is reduced by 3 times compared with the first layer of the braid, which shows that the shielding effect of the double layer braiding is greatly improved compared with the single layer. Major coaxial cable manufacturers are constantly improving the outer conductor structure of the cable to maintain its performance.