(a) Define the term \"modulation\" and explain how this can be achieved. Briefly
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Question
(a) Define the term "modulation" and explain how this can be achieved. Briefly explain why this is important in communications. [6 marks] (b) What is meant by multiplexing and explain why is it necessary in most telecommunication systems? Also explain how multiplexing achieved in frequency division multiplexing (FDM) and in time division multiplexing (TDM) [6 marks] (c) Plot the 2-sided spectrum of the DSB-SC commercial speech (300 Hz to 3.4 kHz) signal modulated on a 5 MHz carrier, assuming that the speech signal has the same amplitude of 5 V over the whole baseband. How many speech signals could be transmitted in the 800-900 MHz band, using FDMExplanation / Answer
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Modulation is the process of superimposition of a high frequency carrier signal on the modulating signal which is the message signal/ information bearing signal.Modulation is achieved by varying any parameter of the carrier signal like amplitude, frequency or phase in accordance with the instantaneous value of the modulating signal.
Modulation is very important in communication because
- it ensures secure transmission of the message signal as at higher frequencies signal is less effected by noise and distortion .
-When a message has to be travelled along a long distance , it cannot be sent alone due to chances of huge information loss due to attenuation and propagaton.Modulation of a message signal with a carrier signal will enable the message to be transmitted to long distances without any significant loss
-When the signal is modulated the partical antenna height need not be longer as wavelength is inversely proportional to frequency.
- if the message signal is modulated it will have greater radiation efficiency and signal can travel longer distances.
- operating range of the signal will be higher if the signal is modulated
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