Question

The most commonly employed analog modulation technique in satellite communication is the
A. amplitude modulation
B. frequency modulation
C. phase modulation
D. amplitude and phase modulation

Answer 1

Hint: In this question we have been asked to state which analog modulation technique is used in the satellite communication systems. Therefore, to answer this question, we shall first briefly discuss the process of modulation. We shall also discuss the need for modulation in satellite communications. While doing so, we shall also list the benefits of modulation and determine which among the given options is most useful and suitable as modulation techniques in satellite communications.

Complete answer:
Modulation is the process of varying the carrier signal, with a modulating signal that usually contains information that is to be sent or transmitted. When the carriers signals are modulated, they allow us to send a signal over bypass frequency range. We can transmit multiple signals simultaneously over a single channel, if the every signal is given its own frequency. Modulated signal can be received by smaller antennas. Therefore, it is one of the reasons to modulate the carrier signals.
Among the types of modulated signals, the amplitude modulated signals are more susceptible to the noise interference. Frequency modulation has a very low tolerance for noise interruption. The Frequency modulated signals are mostly used in satellite communications because FM signals allow the power amplifiers to operate at saturation, therefore making maximum use of available power. As the receiver antennas of frequency modulated signals are smaller, the frequency modulated signals can be transmitted and received at low cost.
Therefore, frequency modulation is the most commonly employed analog modulation technique in satellite communication systems.

Therefore, the correct answer is option B.

Note:
When the instantaneous frequency of the carrier wave is encoded with the information to be transmitted, it is known as frequency modulation. In analog frequency modulation, the instantaneous frequency deviation, the difference between carrier and centre frequency is proportional to the modulating signal.