Dielectric
The dielectric layer, also known simply as the dielectric, is the insulating layer between the inner conductor and the shielding of a coaxial cable. This layer plays a decisive role in the characteristic impedance and attenuation of the cable. Therefore, different materials are used for the dielectric, depending on the intended use of the cable. Below is a table of some common dielectric materials and their properties:
| Material | Properties |
|---|---|
| Polyethylene (PE) | Low attenuation, good dielectric constant value |
| Polytetrafluoroethylene (PTFE) | Low attenuation, high dielectric constant, thermally stable |
| Polyvinyl chloride (PVC) | Inexpensive, medium to high damping, mechanically flexible |
| Foam PE | Low attenuation, lightweight, high dielectric constant |
The choice of dielectric material depends on various factors such as the signal transmission requirements, the environment in which the cable will be used and the cost. Each material has its own advantages and disadvantages that must be taken into account when making a selection.
Further information: Cable structure