In a high frequency product, the antenna plays an essential role:
- A 1/4 wave antenna without its ground plane will behave almost like a wire, whereas if its ground plane is sufficient, its efficiency will be maximum.
- The antenna must always be placed high and clear of any metallic obstacle.
- The antenna cable is another important element that should not be neglected. Ddepending on the type of cable used, the loss will be more or less important [for lengths over 3m it is recommended to use the CFP10 cable (10mm diameter).]
Propagation of radio waves
Radio waves (RF for Radio Frequency) propagate in a straight line in several directions.
The speed of propagation of waves in a vacuum is 3.108 m/s.
In any other environment, the signal is weakened by
- The reflection
- Refraction
- Diffraction
- The absorption
Absorption of radio waves
When a radio wave encounters an obstacle, part of its energy is absorbed and transformed into energy, part continues to propagate in an attenuated manner and part may eventually be reflected.
Reflection of radio waves
When a radio wave meets an obstacle, all or part of the wave is reflected, with a loss of power. The reflection is such that the angle of incidence is equal to the angle of reflection.
Properties of the media
Materials | Weakening | Examples |
---|---|---|
Air | None | Open space, interior courtyard |
Wood | Low | Door, floor, partition |
Plastic | Low | Partition |
Glass | Low | Non tinted windows |
Tinted glass | Average | Tinted windows |
Water | Average | Aquarium, fountain |
Living beings | Average | Crowds, animals, humans, vegetation |
Bricks | Average | Walls |
Plaster | Average | Partitions |
Ceramic | High | Tile |
Paper | High | Paper rolls |
Concrete | High | Load-bearing walls, floors, pillars |
Armored glass | High | Bulletproof glass |
Metal | Very high | Reinforced concrete, mirrors, metal cabinet, elevator shaft |