Velocity Factor
CommentsCreated Saturday 08 May 2021
The Velocity Factor (VF) is a property of transmission lines, specifically used with coaxial cables. Since any dielectric permittivity greater than 1 (air/vacuum) will have the effect of slowing the phase velocity of a wave, the VF is given as a percentage representing that reduced phase velocity.
The velocity factor is simply the inverse of the square root of the relative permittivity. Some common phase velocities are given below.
| Coax Type | Dielectric Material | VF | εr | Z0 |
|---|---|---|---|---|
| RG316 | PTFE | 69% | 2 | 50 ohm |
| T10 Drop Cable | Foam/HDPE | 85% | 1.38 | 75 ohm |
| RG8/U | Foam/HDPE | 78% | 1.64 | 50 ohm |
Backlinks:
High Speed Design Wiki:Glossary
High Speed Design Wiki:Glossary:Velocity Factor
High Speed Design Wiki:Signal Integrity:Transmission Lines:Wavelength, Physical Length and Relative Permittivity
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