What is a coaxial cable
working principle
The coaxial cable is divided into four layers from the inside to the outside: the center copper wire (single stranded solid wire or stranded wires), the plastic insulator, the mesh conductive layer and the wire sheath. The center copper wire and the mesh conductive layer form a current loop. Because the center copper wire and mesh conductive layer is named after the coaxial relationship.
The coaxial cable conducts alternating current instead of direct current, which means that the current direction will be reversed several times per second.
If a general wire is used to transmit high-frequency currents, this wire will be equivalent to an antenna that transmits radios to the outside. This effect will degrade the power of the signal and reduce the received signal strength.
Coaxial cable is designed to solve this problem. The radios emitted by the center wires are isolated by a meshed conductive layer, which can control the transmitted radios by grounding.
The coaxial cable also has a problem. If a certain part of the cable is crushed or distorted, the distance between the center wire and the meshed conductive layer is not consistent. This will cause the internal radio waves to be affected. 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 was added between the center wire and the mesh conductive layer to ensure that the distance between them was consistent. This also causes the cable to be stiff and not bendable.
Advantages and disadvantages
The advantage of coaxial cable is that it can support high-bandwidth communications over relatively long repeater-less lines, and its disadvantages are also obvious: First, the bulky, thin cable diameter is 3/8 inch thick, and it takes up cable There is a lot of space in the pipeline; the second is that it cannot withstand tangles, stress and severe bending, which can damage the cable structure and prevent the transmission of signals. Finally, the cost is high, and all these drawbacks are exactly what the twisted pair can overcome. So now The LAN environment has basically been replaced by the twisted-pair Ethernet physical layer specification.
Coaxial cable wire and the video monitoring application <br> <br> wire coaxial cable transmission line is a high quality, low loss it can transmit electrical signals, which is particularly suitable for transmission over a wide frequency band Video image signal. Coaxial cable is the most widely used video transmission medium and is generally used for transmission of short and medium distance video signals. The electrical characteristics of the coaxial cable make it ideal for transmitting full video signals from the camera to the monitor (CCTV video signals are composed of widely distributed low frequency signals and high frequency signals). When transmitting low-frequency signals (20 Hz to several thousand Hz), almost any kind of wire can be used. However, if you want to transmit video signals in the frequency range of 20Hz to 6MHz, and you do not want any attenuation, you need to use a special coaxial cable. Therefore, coaxial cable is a high-quality video signal transmission line commonly used in video surveillance system engineering. The structure and characteristics of the coaxial cable transmit multiple video signals and high-definition video signals, so that the original uncompressed high-definition video signals can be transmitted to the terminal, and the simulation can be upgraded to the network at a much faster cost. It facilitates HD-level IP cameras to run on the existing CCTV coaxial infrastructure.
The role of coaxial cable is so prominent that it has contributed to the provision of high-definition quality pictures. Its extensive use has greatly promoted the upgrading of China's video transmission capabilities, and its technology has been more perfect development. Continuing to transmit data, transmit signals, reduce loss and attenuation for video, play a longer and more prominent role.
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