What is coaxial cable?

Coaxial cable is the primary medium for wired transmission of radio frequency signals. It is composed of a core wire and a shielding mesh tube made up of two conductors. Because the axes of these two conductors are coincident, it is referred to as a coaxial cable or coaxial line.

Structure of coaxial cable

RF coaxial cable consists of a copper conductor, insulator, braid (outer conductor), and protective plastic layer of 4 parts.

Coaxial-cable-structure
Coaxial-cable-structure

Copper conductor

The inner conductor is usually composed of a solid conductor. It uses a high-frequency signal skin effect and can be made of either empty copper tubes or copper-plated aluminium rods. It does not require the use of steel-clad wire for user network power, but for power distribution networks or backbone lines, it is recommended to use copper-clad aluminium wire to ensure optimal transmission performance and to meet the electrical and mechanical requirements of the cable. This reduces the weight and cost of the cable.

Insulator

The insulator can be made of polyethene, polypropylene, polyvinyl chloride (PVC and fluoroplastics, etc.), and the commonly used insulating medium is polyethene, which has low loss and good process performance.

Braided mesh (outer conductor)

A braided network is both a transmission circuit of a wire and also has a shielding effect, the outer conductor through the outer conductor of the coaxial cable has a dual role, there are often three kinds of structure.

1, Metal tubular: this structure uses copper or aluminium tape longitudinal package welding, or seamless copper tube extrusion package stretch and become, this form of structural shielding performance is the best, but the flexibility is poor, commonly used in trunk cables.

2, Aluminium-plastic composite tape longitudinal package lap: this structure has a better shielding effect, and low manufacturing costs, but because the outer conductor is a round tube with longitudinal seams, electromagnetic waves will be leaked from the gap through the leakage and should be used with caution.

3, Woven mesh and aluminium-plastic composite tape longitudinal package combination: this is from a single woven mesh structure developed, it has good flexibility and lightweight and reliable joints and other characteristics, experiments have proved that the use of reasonable composite structure, the shielding performance of a great deal of improvement in the current form of this structure is used in large quantities.

Protective plastic layer

Outdoor cables should be used with black polyethene with excellent weather characteristics, for indoor user cables from aesthetic considerations, it is appropriate to use light-coloured polyethene.

Coaxial cable structure characteristics

Coaxial cables consist of an inner conductor surrounded by an insulating layer, a metal shield outside the insulating layer, and an outermost sheath. The metal shielding mesh of this structure can prevent the centre conductor from radiating electromagnetic fields to the outside and can also prevent external electromagnetic fields from interfering with the signal of the centre conductor.

The specific classification of coaxial cable

Coaxial cable is a type of cable that is commonly used for transmitting high-frequency signals with low signal loss and anti-interference capability. Depending on their characteristics and uses, coaxial cables can be classified into several categories.

1, commonly used coaxial cable

Commonly used coaxial cable refers to the most widely used coaxial cable in communication, broadcasting, television, etc., consisting of an inner conductor, insulation, an outer conductor, and an outer sheath. Commonly used coaxial cable has the advantages of high transmission bandwidth, stable signal transmission, strong anti-jamming ability, etc., widely used in cable TV, radio television, and other fields.

2, RG series coaxial cable

RG series coaxial cable is a standardized coaxial cable specification, commonly used in video signal transmission and computer network connection.RG series coaxial cable is characterized by stable impedance, and transmission distance is far and is suitable for long-distance video surveillance and network transmission. Common RG series coaxial cable has RG59, RG6, RG11, and other specifications, of which RG59 is suitable for short-distance video transmission, RG6 is suitable for medium and long-distance video transmission, and RG11 is suitable for long-distance video transmission.

3, Low-loss coaxial cable

Low-loss coaxial cable is a special coaxial cable used for high-frequency signal transmission. It adopts low-loss insulation and high-quality conductor materials, with low signal loss and high signal transmission efficiency. Low-loss coaxial cable is widely used in wireless communication, satellite communication, and other fields, and can effectively improve signal transmission quality and distance.

4, High-temperature coaxial cable

High-temperature coaxial cable is a kind of coaxial cable that can work normally in a high-temperature environment. It is made of high-temperature resistant materials, which can withstand high working temperatures and ensure the stability and reliability of signal transmission. High-temperature coaxial cable is widely used in aerospace, military equipment, and other fields, to meet the needs of high-temperature signal transmission in special environments.

5, lightning protection coaxial cable

A lightning protection coaxial cable is a coaxial cable with lightning protection. It adopts special lightning protection materials and structural design, which can effectively prevent lightning on the signal transmission of the interference and damage to the lightning-proof coaxial cable is widely used in radar, communication base stations, and other places that need lightning protection to ensure the stability and reliability of signal transmission.

6, Underwater coaxial cable

Underwater coaxial cable is a kind of coaxial cable specially used for underwater communication. It adopts a special waterproof material and sealed structure design, which can transmit signals normally underwater. Underwater coaxial cable is widely used in submarine fiber optic cable, ocean observation, and other fields, and can meet the needs of underwater communication.

Working Principle

Coaxial cables conduct alternating current (AC) rather than direct current (DC), which means that the direction of the current will be reversed several times per second. If a normal wire is used to transmit high-frequency currents, the wire is equivalent to an antenna that transmits 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 centre 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 centre wire and the mesh is not always the same, which can cause the internal radio waves to be reflected in 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 centre 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.

Advantages

1, Strong anti-interference ability: coaxial cable shielding layer can effectively reduce the external interference on the signal, so the coaxial cable in the long-distance transmission of signals, the signal quality is more stable
2, Long transmission distance: coaxial cable can be transmitted over a longer distance than the average cable, and usually can be transmitted over a distance of a few hundred meters
3, Suitable for high-frequency transmission: coaxial cable internal conductor and shielding layer between the distance is close so coaxial cable is suitable for high-frequency transmission, such as television signals and network transmission
4, High durability: coaxial cable’s external insulation is usually made of high-temperature-resistant, anti-ageing materials, so the coaxial cable’s life is long

Disadvantages

1, Higher cost: Coaxial cables are more expensive to manufacture and therefore more expensive.
2, Difficult to install: Coaxial cables are difficult to install and require specialized technicians to install.
3, Larger size: Coaxial cable is larger and is not suitable for some places where space is limited.
4, Heavyweight: The Coaxial cable is heavy, need to consider the weight capacity of the installation.

Need help with your customized coaxial cables or consulting solutions?

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If you need to know more about RF connectors, please click to view: RF Connector Basics