Digital Communications Questions and Answers – Formatting Analog Information

This set of Digital Communications Multiple Choice Questions & Answers (MCQs) focuses on “Formatting analog information”.

1. The sampling process includes methods such as
a) Filtering
b) Sample and hold
c) Amplifying
d) None of the mentioned
View Answer

Answer: b
Explanation: The analog data is converted to digital data through sampling. Sampling is done using sample and hold mechanism which uses transistor, capacitor or shutter etc.

2. The output of sampling process are called as ________
a) Pulse code modulation
b) Pulse amplitude modulation
c) Frequency modulation
d) Amplitude modulation
View Answer

Answer: b
Explanation: In sampling process, input data is split up into samples whose output samples are called as pulse amplitude modulation as the amplitude of the samples is derived from the input waveform.

3. According to Sampling theorem
a) Ts is greater than 1/2fm
b) Ts is lesser than 1/2fm
c) Ts is equal to 1/2fm
d) Ts is lesser than or equal to 1/2fm
View Answer

Answer: d
Explanation: By sampling theorem the input can be derived from the output samples if Ts is lesser than or equal to 1/2fm.
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4. The fourier tranform of one impulse train is also another impulse train with a period of the output equal to the
a) Period of the input
b) Reciprocal of the period of input signal
c) Half the period of input
d) Twice the period of the input
View Answer

Answer: b
Explanation: When we perform fourier tranform on one impulse train we will get another impulse train with its period reciprocally related to each other.

5. The process in which the top of each pulse in the output samples retains the shape of the analog segment is called as ________
a) Natural sampling
b) Ideal sampling
c) Aliasing
d) None of the mentioned
View Answer

Answer: a
Explanation: In the method of natural sampling, the top of each pulse in the sampled sequence retains the same shape of the analog input signal.
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6. The effects of aliasing are ________
a) Attenuation of high frequency spectral replicates
b) Non uniform spectral gain applied to desired baseband spectrum
c) Attenuation and non uniform spectral gain
d) None of the mentioned
View Answer

Answer: c
Explanation: Aliasing is due to undersampling and its effects are attenuation and non uniform spectral gain.

7. Aliasing can be removed using
a) Prefiltering
b) Postfiltering
c) Prefiltering & Postfiltering
d) None of the mentioned
View Answer

Answer: c
Explanation: Aliasing can be removed using both prefiltering and postfiltering but prefiltering is most effective and preferred.
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8. Which process is more economical?
a) Undersampling
b) Oversampling
c) Aliasing
d) None of the mentioned
View Answer

Answer: b
Explanation: Oversampling is most economic way of sampling or for converting analog information to digital as performing signal processing using digital system is less costlier than doing it with high performace analog system.

9. Flat top sampling or practical sampling has
a) Same frequency
b) Same amplitude
c) Same time difference
d) None of the mentioned
View Answer

Answer: b
Explanation: In flat top sampling the top of the pulses are flat which in turn means that they have the same amplitude.
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10. Multiplication of input signal with pulse train is done in ________ sampling.
a) Impulse sampling
b) Natural sampling
c) Flat top sampling
d) None of the mentioned
View Answer

Answer:b
Explanation: In impulse sampling the input signal is multiplied with impulse train and in natural sampling it is multiplied with pulse train.

Sanfoundry Global Education & Learning Series – Digital Communications.

To practice all areas of Digital Communications, here is complete set of 1000+ Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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