Coaxial Cable Construction

What is a coaxial cable? What are the different layers of a coaxial cable?

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Editorial Team - everything RF

Apr 4, 2019

The coaxial cable was invented by Oliver Heaviside in 1880. It was developed for transmitting RF and Microwave signals from one point to another with minimal signal loss.

A typical microwave coaxial cable consists of inner and outer conductors separated by a polymer dielectric. These three layers are then encapsulated by a polymer jacket as shown in the Figure below. The outer jacket protects the cable and the signal within it from any external interference.

The inner and the outer diameter of a coaxial cable share the same geometrical axis.

The dimensions of the inner conductor, the outer conductor and the space in between is kept uniform along the length of cable.

The dielectric separates the inner conductor from the outer conductor. The type of dielectric used determines the electrical characteristics of the cable i.e the level of attenuation, propagation velocity and the frequency up to which it can operate. Higher the dielectric constant of the dielectric, higher the frequency it can carry and higher the distance.

Common Dielectric materials usually used for cable fabrication are:

  • PTFE - Poly-Tetrafluoro-Ethylene
  • FPE - Foamed Polyethylene
  • PEF - Polyethylene Foam
  • ASP - Air Space Polyethylene
  • FEP - Fluorinated Ethylene Propylene
  • PE - Propylene