Microwave Propagation

What are electromagnetic waves? How do they work?

Electromagnetic waves are waves that can travel through space without relying on any support for their movement. Mechanical waves, for instance, require the assistance of a material system to propagate from one area to another. Mechanical and electromagnetic waves are represented by sound and light waves, respectively.

Radio waves, microwaves, X-rays, and gamma rays are all examples of electromagnetic (EM) radiation. 

Definition of microwaves

Microwaves are electromagnetic waves (EM waves) with extremely short wavelengths. Antennas can focus microwave signals.. Signals are sent straight from a transmitter to a destination. The range of a good transmitting antenna does not extend much beyond the visible range in microwave propagations.

What is microwave propagations?

Microwave propagations are EM waves that travel in direct lines from sending antenna to the one receiving, with very few variations. Microwave propagations sometimes face delayed transmissions or multipath fading that occurs because of events in the atmosphere, the same effect as observed in mirages.

Microwave signals bend slightly while travelling oblique between levels of varying air pressure. When a microwave transmission cannot reach a receiver on the summit of a hill, the signal may become weaker as the immobility of waves and changes in temperature have an effect on it. A microwave signal follows the curve of the Earth and travels far beyond the spectrum, thanks to tropospheric ducting. 

Microwave propagations have short wavelengths and because of it, these EM waves have the ability of bending in accordance with the items that come in their path. These EM waves have the ability to identify flying objects and the speed at which they are travelling, which makes it a suitable fit in radar technologies.

The waves have frequencies 1-300 Gigahertz.

Features of microwaves

• Like in space wave propagation, microwave propagation also happens on line of sight systems. 

• The antenna sending the signals and the one receiving are placed in the same concept.

• As the surface of the Earth is curved, the sending and receiving antenna should be placed keeping that in mind, so that efficient transmission can happen.

• As the microwave transmission happens in a single direction, broadcasting to a wider range of receptors happens without much of an issue.

• Transmission, generated through microwave propagations, works with the outdoor receptors only.

• The concept of multipath fading applies to microwaves. This happens because reflection from atmospheric pressure delays the timeline of transmissions, which eventually can cause multipath fading.

• Because their transmission is unidirectional, microwaves require specific antennas, these are:

  • Parabolic: A parabolic shaped antenna, which is specifically designed to focus the power on a tiny beam, which helps in making the signal strong that has optimal signal-to-noise ratio.

  • Horn: An antenna with a long stem and a bend on its head. These are positioned near the signal transmission point, when placed at sending stations, and the waves transmitted by this antenna are disseminated in a series. When these antennas are used as receptors, the signal is collected by the antenna’s head, which is then transported to the stem.

Advantages of microwaves

• Ability to transmit a larger amount of information.

• Ability to focus the signal strength through the antenna.

• Greater bandwidth.

• Lower size of transmitter and receptor, with increase in transmissions.

• Requires a lesser amount of power.

• Lesser attenuation.

• Efficient radar mechanism.

• Smaller size transmission instruments can be devised at lower costs.

Disadvantages of microwaves

• Higher installation expenses.

• Requires greater amount of space.

• Chances of multipath fading.

• Dependence on electric power brings along the inefficiencies of the electric system.

Applications of microwaves

• Telephones

• Mobile phones

• TV broadcasting

• Satellite networks

• WLANs

Key takeaways

• Microwaves are electromagnetic waves with shorter wavelengths that emit electromagnetic radiations.

• The ionised layer of atmosphere does not refract microwaves.

• Microwaves follow a straight path and are reflected by objects that have the ability to conduct.

• Within shorter distances, microwaves are frequently deflected.

• A thin coating of a cable can carry microwave emissions.

• Microwave propagation, like space wave propagation, occurs on a line of sight system.

• Because the Earth’s surface is curved, the sending and receiving antennas should be positioned accordingly to ensure efficient transmission.

• Microwaves are prone to multipath fading. 

• Either a parabolic or a horn antenna is employed.

• Microwaves form efficient communication systems and are widely used in television broadcasting, radar technologies, telephonic networking, etc.

Conclusion

Microwaves are regarded as highly reliable and hence used in the majority of communications systems, even in radar technologies that form one of the most important components of defence mechanisms for countries. The reliability comes from negligible fading of the transmission. Even when there are chances of fading, the transmissions are rerouted through different frequencies that are automated through highly efficient computerised controls.