digital communication one mark objective questions and answers
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1. Define modulation?
Modulation is a process by which some characteristics of high frequency carrier signal is varied in accordance with the instantaneous value of the modulating signal.
2.What are the types of analog modulation?
Amplitude modulation.
Angle Modulation
Frequency modulation
3.Define depth of modulation.
It is defined as the ratio between message amplitude to that of carrier amplitude.
m=Em/Ec
4. What are the degrees of modulation?
Under modulation. m<1 font="font">
Critical modulation m=1
Over modulation m>1
5. Define Amplitude Modulation
It is the process by which the amplitude of the carrier wave is changed in accordance with the instantaneous value of the message signal.
7. Define modulation index for AM
It is defined as the ratio of the maximum modulating voltage to the maximum carrier voltage. It is also called as ‘Depth of modulation’.
m = Vm / Vc
8. What is the relation between total power and carrier power?
Pt = Pc (1 + m )
Pt : Total power
Pc : Carrier power
m :Modulation index
9.What is the need for modulation?
Ease of transmission
Multiplexing
Reduced noise
Narrow bandwidth
Frequency assignment
Reduce the equipments limitations.
10.What are the types of AM modulators?
There are two types of AM modulators. They are
Linear modulators
Non-linear modulators
Linear modulators are classified as follows
Transistor modulator
There are three types of transistor modulator.
Collector modulator
Emitter modulator
Base modulator
Switching modulators
Non-linear modulators are classified as follows
Square law modulator
Product modulator
Balanced modulator