In this post we shall learn about the importance of Polarisation of Electro Magnetic waves. In our earlier lesson, we had understood about the Electro Magnetic Spectrum.
ELECTRICAL – MAGNETIC COMPONENTS
We are aware that the electrical and magnetic components of EM Waves are perpendicular to each other. The electrical component is the one which carries the message. Therefore, polarisation is named after the electrical component of the wave.
Polarisation of a wave is the plane of the electrical component of the wave. If the electrical component is horizontal to the earth’s surface, it is called as a horizontally polarised wave. Similarly, if the electrical component is vertical to the earth’s surface, it is called as a vertically polarised wave.
HORIZONTAL – VERTICAL – CIRCULAR POLARISATION
Vertical and horizontal ariels transmit vertically and horizontal polarised waves respectively. Similarly, vertically polarised wave can be received only by a vertical ariel and horizontally polarised wave can be received only by a horizontal ariel. Circularly polarised waves are created by a Helical antenna which has the benefit of being received by both vertical as well as horizontal types of antennae.
Circular polarisation is used if the polarisation is likely to change during ionospheric transmission. Circular polarisation has the additional benefit of reducing rain clutter. Therefore, Radars use circularly polarised waves to reduce rain clutter. Global Positioning System (GPS) also use circularly polarised waves. Although circular polarisation has distinct advantages, generating circularly polarised waves require high power transmitters.
In this lesson, we have understood the term called polarisation and its importance in transmission of Radio Waves. In our next lesson, we shall learn about the basics of Sinusoidal or Sine waveform. We need to understand Sinusoidal Waveform, since radio waves travel in the form of a Sine Wave.