A coaxial cable (CoaxialCable) is a cable that has two concentric conductors, and the conductors and shield share the same axis. The most common coaxial cable consists of copper wire conductors isolated by insulation material, in the inner layer of insulation material is another layer of ring conductor and its insulator, and then the whole cable by the PVC or Teflon material sheath.

A coaxial cable working principle:

Coaxial cable is divided into four layers from the inside out: the center copper wire (single stranded solid wire or multi-stranded stranded wire), plastic insulator, mesh conductive layer and wire sheath. The center copper wire and mesh conductive layer to form the current loop. Because the center copper wire and mesh conductive layer for coaxial relationship and so named.
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, this wire would be the equivalent of an antenna transmitting a radio outward, an effect that depletes the power of the signal and reduces the strength of the received signal.
Coaxial cables are designed to solve this problem. The radio emitted from the center wire is isolated by a mesh conductive layer that can be grounded to control the emitted radio.
The problem with coaxial cables is that if a section of the cable is crushed or twisted, the distance between the center wire and the mesh is not always the same, which can cause the internal radio waves to be reflected back to the source. This effect reduces the power of the signal that can be received. To overcome this problem, a plastic insulator is added between the center wire and the conductive mesh layer to ensure a consistent distance between them. This also results in a cable that is relatively stiff and not easily bendable.

The way coaxial cables are categorized:

Coaxial cable can be divided into two basic types, baseband coaxial cable and broadband coaxial cable. Currently the baseband is commonly used cable, its shield is made of copper made of mesh, the characteristic impedance of 50 (such as RG-8, RG-58, etc.); broadband coaxial cable commonly used cable shield is usually stamped with aluminum, the characteristic impedance of 75 (such as RG-59, etc.).
Coaxial cable can be divided into: coarse coaxial cable and fine coaxial cable according to its diameter size. Coarse cable is suitable for relatively large local networks, it is a long standard distance, high reliability, because the installation does not need to cut the cable, so you can flexibly adjust the computer into the network location as needed, but the coarse cable network must be installed transceiver cables, the installation is difficult, so the overall cost is high. On the contrary, thin cable installation is relatively simple, low cost, but because of the installation process to cut the cable, the two ends must be installed on the basic network connector (BNC), and then connected to the ends of the T-type connector, so when the joints are more likely to produce bad potential problems, which is currently in operation, one of the most common failures that occur in the Ethernet.
Both thick and thin cables are bus topologies, i.e., multiple machines are connected to a single cable. This topology is suitable for machine-intensive environments, but when a contact fails, the fault will cascade to affect all machines on the entire cable. Failure diagnosis and repair are troublesome, therefore, will gradually be replaced by unshielded twisted pair or fiber optic cable.

Coaxial cable is widely used

1.power system

Power systems using wire and cable products are mainly overhead bare wire, busbar (bus), power cables (plastic cables, oil-paper power cables (basically replaced by plastic power cables), rubber-coated cables, overhead insulated cables), branch cables (instead of part of the bus), electromagnetic wire and electrical equipment for power equipment wire and cable and so on.

2.information transmission

Wire and cable used for information transmission systems are mainly telephone cables, television cables, electronic cables, radio frequency cables, fiber optic cables, data cables, electromagnetic lines, power communication or other composite cables.

3.instrumentation system

This part in addition to overhead bare wire almost all other products are applied, but mainly power cables, electromagnetic lines, data cables, instrumentation cables and so on.
Installation method:
Coaxial cable is generally installed between equipment and equipment. A connector is equipped at each user location to provide an interface for the user. The installation method of the interface is as follows:
(1) Thin cable, cut off the thin cable, install the BNC head at both ends, and then connect it to both ends of the T-type connector.
(2) thick cable, thick cable is generally installed using a clipboard-like Tap device, which uses the Tap on the guide pin to penetrate the cable insulation, directly connected to the conductor. Terminators are provided at both ends of the cable to weaken the reflection of the signal.

Advantages of coaxial cable

1.low Signal Loss

Coaxial cable signal loss rate is low, even if the long distance transmission, but also to maintain the strength and stability of the signal. So it has a great advantage in the cable TV network, long-distance data transmission and other fields, can provide users with stable and reliable signal service.

2.high bandwidth characteristics

Coaxial cable has high bandwidth characteristics, which means that it can quickly and efficiently transmit large amounts of data. Whether it is high-definition video, large file transfer or high-speed network connection, coaxial cable can meet.

3.high interference immunity

The shielding layer of coaxial cable is designed to provide excellent anti-interference capability, which can effectively resist external electromagnetic interference, such as radio wave interference and power line interference. This anti-interference performance makes it in the electromagnetic environment of complex places, such as factories, substations, etc., can still be stable signal transmission, to ensure the reliability of communication.

4.easy installation and durability

Coaxial cable is easy to install, does not require special specialized skills and complex tools, ordinary users can also be installed. Moreover, it has high durability, the outer sheath can protect the internal structure, reduce the damage caused by external forces, environmental factors, etc., and reduce maintenance costs.

The limitations of coaxial cable

1. limited transmission distance

Coaxial cable signal loss is low, but its transmission distance will be limited. As the transmission distance increases, the signal will gradually attenuate, when more than a certain distance, the signal quality will be significantly reduced, can not be used normally. Different types and quality of coaxial cable, its effective transmission distance will be different, in the actual application of the need to choose the appropriate cable according to the specific circumstances.

2.relatively high cost

The manufacturing process of coaxial cable is complicated and requires the use of more materials, especially the metal material of the shielding layer, so the production cost goes up.

3. Less flexible

Coaxial cables are not as flexible as twisted pair cables, and cannot withstand tangling, pressure and severe bending during installation, all of which can damage the cable structure and prevent signal transmission

4.large size

The diameter of the thin cable will be 3/8 inch thick, to take up a lot of space in the cable ducts, which is more of a problem in some of the places with strict space requirements for cabling, such as narrow wireways inside buildings, inside electronic equipment, and so on. Larger sizes not only increase the difficulty of wiring, but may also affect the overall aesthetics of the layout.

With its unique structural design, coaxial cable is widely used in many fields. However, it also has limitations. In the actual application, we have to choose the most suitable cable according to the specific needs and scenarios, based on the advantages and disadvantages of coaxial cable, to ensure the efficient and stable operation of the communication system. With the continuous development of technology, coaxial cable is also improving and innovating, and can play a role in more fields in the future.