Transmission medium

A transmission medium is any material substance which can propagate waves or energy.

A transmission medium can be classified as a:

  • Linear medium, if different waves at any particular point in the medium can be added;
  • Bounded medium, if it is finite in extent, otherwise unbounded medium;
  • Uniform medium, if its physical properties are unchanged at different points;
  • Isotropic medium, if its physical properties are the same in different directions.
Image:RG-59.jpg
Coaxial Cable, one example of a transmission medium

Electromagnetic radiation is transmitted through media such as optical fiber, twisted pair wires, coaxial cable, dielectric-slab waveguides. They may also pass through any physical material which is transparent to the specific wavelength, such as water,air, glass, or concrete. Electromagnetic waves can also travel through free space, because it does not require physical matter.

Sound is by definition the vibration of matter, and so does require a physical medium for transmission, as does heat energy.

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Telecommunications

For telecommunications purposes in the United States, Federal Standard 1037C, transmission media are classified as one of the following:

  • Guided (or bounded) - Waves are guided along a solid medium such as a transmission line.
  • Wireless (or unguided) - Transmissions and receptions are achieved by means of an antenna.
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See also