Analog Communication - Electronic Engineering (MCQ) questions & answers

1)   In Pulse Position Modulation, the drawbacks are
- Published on 16 Oct 15

a. Synchronization is required between transmitter and receiver
b. Large bandwidth is required as compared to PAM
c. None of the above
d. Both a and b
Answer  Explanation  Related Ques

ANSWER: Both a and b

Explanation:
In Pulse Position Modulation, the position of the pulse of the carrier is varied with reference to the position of a reference pulse. The position is varied in accordance with the sampled modulating signal. In PPM, synchronization is required between the transmitter and the receiver. Large bandwidth is required in Pulse position Modulation as compared to the Pulse amplitude modulation.


2)   In PWM signal reception, the Schmitt trigger circuit is used
- Published on 16 Oct 15

a. To remove noise
b. To produce ramp signal
c. For synchronization
d. None of the above
Answer  Explanation  Related Ques

ANSWER: To remove noise

Explanation:
In pulse width modulation, the width of the carrier varies with the amplitude of the modulating signal at the time of sampling. In PWM signal reception, the received PWM signal is applied to the Schmitt trigger circuit. The Schmitt trigger circuit is used to remove noise in the PWM waveform. This output is the supplied further for detection of the original information.


3)   In pulse width modulation,
- Published on 16 Oct 15

a. Synchronization is not required between transmitter and receiver
b. Amplitude of the carrier pulse is varied
c. Instantaneous power at the transmitter is constant
d. None of the above
Answer  Explanation  Related Ques

ANSWER: Synchronization is not required between transmitter and receiver

Explanation:
In pulse width modulation, the width of the carrier varies with the amplitude of the modulating signal at the time of sampling. Pulse width modulation is a type of Pulse Time Modulation. As there is no variation in the amplitude of the carrier, the noise may be easily removed at the receiver. It does not require synchronization between the transmitter and the receiver.


4)   In different types of Pulse Width Modulation,
- Published on 16 Oct 15

a. Leading edge of the pulse is kept constant
b. Tail edge of the pulse is kept constant
c. Centre of the pulse is kept constant
d. All of the above
Answer  Explanation  Related Ques

ANSWER: All of the above

Explanation:
There are types of Pulse Width Modulation. In one of the variations, leading edge of the pulse is kept constant and pulse width is measured with respect to leading edge. In second type, tail edge of the pulse is kept constant and pulse width is measured with respect to it. And the third type has a constant centre of the pulse and the pulse width changes on both the sides of the centre of the pulse.


5)   In Pulse time modulation (PTM),
- Published on 16 Oct 15

a. Amplitude of the carrier is constant
b. Position or width of the carrier varies with modulating signal
c. Pulse width modulation and pulse position modulation are the types of PTM
d. All of the above
Answer  Explanation  Related Ques

ANSWER: All of the above

Explanation:
In Pulse time modulation (PTM), amplitude of the carrier is kept constant and the Position or width of the carrier varies with the amplitude of the modulating signal at the time of sampling. Pulse width modulation and pulse position modulation are the types of Pulse Time Modulation.
As there is no variation in the amplitude of the carrier, the noise may be easily removed at the receiver.


6)   Drawback of using PAM method is
- Published on 16 Oct 15

a. Bandwidth is very large as compared to modulating signal
b. Varying amplitude of carrier varies the peak power required for transmission
c. Due to varying amplitude of carrier, it is difficult to remove noise at receiver
d. All of the above
Answer  Explanation  Related Ques

ANSWER: All of the above

Explanation:
In PAM, Bandwidth is very large as compared to modulating signal frequency. In PAM, the amplitude of the rectangular pulse train is varied according to the instantaneous value of the modulating signal. Due to this, the required power for transmission is also varied. Due to varying amplitude of carrier, the interference of noise is very high in PAM. So it is difficult to remove noise at receiver.


7)   Pulse time modulation (PTM) includes
- Published on 16 Oct 15

a. Pulse width modulation
b. Pulse position modulation
c. Pulse amplitude modulation
d. Both a and b
Answer  Explanation  Related Ques

ANSWER: Both a and b

Explanation:
In pulse modulation systems, the carrier is a train of pulses rather than a continuous signal. The parameters of the pulses are varied according to the instantaneous value of the modulating signal. The carrier is a train of pulses rather than a continuous signal. In PTM, the timing of the pulses of the carrier is varied in accordance with modulating signal. PTM includes:
- Pulse width modulation
- Pulse position modulation


8)   In pulse amplitude modulation,
- Published on 16 Oct 15

a. Amplitude of the pulse train is varied
b. Width of the pulse train is varied
c. Frequency of the pulse train is varied
d. None of the above
Answer  Explanation  Related Ques

ANSWER: Amplitude of the pulse train is varied

Explanation:
Pulse amplitude modulation is a type of analog pulse modulation system. In pulse modulation systems, the carrier is a train of pulses rather than a continuous signal. In PAM, the amplitude of the rectangular pulse train is varied according to the instantaneous value of the modulating signal. The pulses in PAM signal may be flat top type or natural type samples.


9)   Types of analog pulse modulation systems are
- Published on 16 Oct 15

a. Pulse amplitude modulation
b. Pulse time modulation
c. Frequency modulation
d. Both a and b
Answer  Explanation  Related Ques

ANSWER: Both a and b

Explanation:
In pulse modulation systems, the carrier is a train of pulses rather than a continuous signal. The parameters of the pulses are varied according to the instantaneous value of the modulating signal. There are two types of pulse modulation systems:
- Pulse amplitude modulation
- Pulse time modulation


10)   The sampling technique having the minimum noise interference is
- Published on 16 Oct 15

a. Instantaneous sampling
b. Natural sampling
c. Flat top sampling
d. All of the above
Answer  Explanation  Related Ques

ANSWER: Natural sampling

Explanation:
The natural sampling is the technique that has the minimum noise interference to the sampled signal. It is obtained by multiplying the input signal with the sampling function. It is a practical method used for sampling of signals. Chopping principle is used to sample the signal in natural sampling and it satisfies the Nyquist criteria for sampling of signals.


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