What Are the Functions of the Insulation Layer in a Coaxial Cable?

The insulation layer serves both physical and electrical purposes:

Physical Function:
It maintains a fixed distance between the center conductor and the shielding layer, providing structural support for the overall cable.

Electrical Function:

By maintaining the spacing between the center conductor and the shielding layer, it establishes the cable’s characteristic impedance.

It ensures sufficient dielectric strength to prevent high-voltage breakdown between the center conductor and the shielding layer.

Thus, the insulation layer must be designed to match the conductor’s cross-sectional area and thickness, balancing dielectric strength with cost-effectiveness.

Common Materials:

PVC (Polyvinyl Chloride): Low cost, easy to process, suitable for low-voltage cables; operating temperature generally ≤105°C.

XLPE (Cross-Linked Polyethylene): Higher heat resistance, can withstand >150°C long-term, commonly used in medium- and high-voltage cables.

Fluoroplastics (e.g., F46, PFA, PTFE): Wide temperature range (-60°C to 260°C), excellent chemical resistance, suitable for extreme environments.

Special Materials:

Physically Foamed PE: Used in 4th-generation coaxial cables; foaming reduces dielectric constant, improving signal transmission speed.

PE (Polyethylene): Low-cost traditional insulation material, still used in some coaxial cables.

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