The coaxial cable is divided into four layers from the inside to the outside: a central copper wire (single-stranded solid wire or multiple stranded wires), a plastic insulator, a mesh-shaped 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.
The coaxial cable conducts alternating current instead of direct current, which means that the current direction is reversed several times per second.
If a general wire is used to transmit a high frequency current, the wire would be equivalent to an antenna that emits radio to the outside. This effect depletes the power of the signal and reduces the received signal strength.
The coaxial cable is designed to solve this problem. The radio emitted by the center wire is isolated by a mesh conductive layer, and the mesh conductive layer can control the emitted radio by grounding.
A problem with coaxial cable is that if a certain section of the cable is subjected to relatively large extrusion or distortion, the distance between the center wire and the mesh conductive layer is not uniform, which causes the internal radio waves to be Reflected back to the signal source. This effect reduces the signal power that can be received. To overcome this problem, a layer of plastic insulator is added between the center wire and the mesh conductive layer to ensure that the distance between them is consistent. This also causes the cable to be stiff and not easily bent.
The shielding material of the coaxial cable is mainly an improvement of the outer conductor, and the single tubular outer conductor is sequentially developed into a single layer braided, 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 single-layer weaving has the worst shielding efficiency, and the double-layer weaving has a three-fold reduction in the transfer impedance of one layer of weaving. It can be seen that the double-layer weaving has a much better shielding effect than the single layer. Major coaxial cable manufacturers are continually improving the outer conductor structure of the cable to maintain its performance.