Coaxial Cables

Coaxial Cables


Coaxial cables are a type of electrical cables, which consist of a round conducting wire that is surrounded by an insulating spacer, and which is again surrounded by a cylindrical conducting sheath. All these layers are surrounded by a final insulating layer. Coaxial cable is used as a high-frequency transmission line for carrying a high-frequency or broadband signal.




The coaxial cable was invented in the year 1929 and was first used commercially in the year 1941.

The coaxial cable is popularly called coaxial because it has one physical channel (the copper core), which carries the signal surrounded by another concentric physical channel (a metallic foil or braid), and an outer sheath or cover, all running along the same axis. The outer channel acts as a shield (or ground).

Coaxial cables are available as both rigid and flexible. Rigid coaxial cable has a solid sheath, while flexible coaxial cable has a braided sheath, usually of thin copper wire.



Coaxial Cable Variations
Triaxial cable or Triax is a form of coaxial cable that makes use of a single center conductor with two shields. This composition helps in a greater transmission distance with less loss due to interference from outside electrical signals. These special cables consist of three - conductor cables.


Twinaxial cable or Twinax is two coaxial systems packaged within a single cable.
Coaxial Cable and Triaxial Cable Dielectric Include:
Polyethylene
Fluorinated ethylene propylene
Foamed polyethylene
Foamed fluorinated ethylene propylene





Important Parameters of Coaxial Cables
Impedance: It is measured in ohms (O) and can becalculated from the ratio of the inner and outer diameters and the dielectric constant.


Capacitance: It is measured in farads per metre.


Resistance: It is measured in ohms per metre.


Attenuation or loss: It is measured in decibels per metre.


Outside diameter: It dictates which connector must be used for terminating the cable.



Cutoff frequency: It is the boundary at which energy entering the cable begins to be reflected instead of being transmitted.
Applications
Coaxial cables are used in diverse fields and applications. These include:
Short coaxial cables: Home video equipment, measurement electronics.

Long distance coaxial cable: Used for connecting radio networks and television networks.
Micro coaxial cables: Used in various consumers devices, military equipment, and in ultra-sound equipment.