Question

Question about wave propagation

1. Explain what is: line of sight propagation, tropospheric propagation and ionospheric propagation.
2. What is fading? Why is diversity needed?
3. State the cause of ionospheric propagation.

Answer 1

Answer )
A ) Line-of-sight propagation is a characteristic of electromagnetic radiation or acoustic wave propagation which means waves travel in a direct path from the source to the receiver. Electromagnetic transmission includes light emissions traveling in a straight line.

Tropospheric propagation describes electromagnetic propagation in relation to the troposphere. The service area from a VHF or UHF radio transmitter extends to just beyond the optical horizon, at which point signals start to rapidly reduce in strength

Ionospheric Propagation. The ionosphere exists between about 90 and 1000 km above the earth's surface. Radiation from the sun ionizes atoms and molecules here, liberating electrons from molecules and creating a space of free electron and ions.

B) In wireless communications, fading is variation of the attenuation of a signal with various variables. These variables include time, geographical position, and radio frequency. Fading is often modeled as a random process. A fading channel is a communication channel that experiences fading.
Fading is a major impairment in transmitting the signal in wireless communication. Thus, it becomes very necessary to nullify its effect to transmit the signal successfully and so the diversity technique along with its different types is being employed to combat the effect of fading.

C ) Ultraviolet light from the sun collides with atoms in this region knocking electrons loose. This creates ions, or atoms with missing electrons. This is what gives the Ionosphere its name and it is the free electrons that cause the reflection and absorption of radio waves.