Communication Engineering Set 2

Computer Science Engineering (CSE)

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This set of Communication Engineering Multiple Choice Questions & Answers (MCQs) focuses on Communication Engineering Set 2

Q1 | It is only the reflected color that decided the color of an object.
  • true
  • false
Answer: false
Explaination:
color of any object is decided by the reflected color for opaque object and wavelength transmitted through it for transparent object, while both reflector color and wavelength transmitted are considered for a translucent object.
Q2 | What do you understand by the term “carrier” in modulation?
  • voltage to be transmitted
  • resultant wave
  • voltage for which amplitude, phase or frequency can be varied
  • voltage for which amplitude, phase or frequency remains constant
Answer: voltage for which amplitude, phase or frequency can be varied
Explaination:
carrier wave is the wave with frequency higher than the message signal,
Q3 | Carrier wave in modulation is a resultant wave.
  • true
  • false
Answer: false
Explaination:
carrier wave is the wave with frequency higher than the message signal, whose certain characteristics like amplitude, phase or frequency are varied with respect to the instantaneous amplitude of the message signal. thus forming the modulated wave which is the wave to be transmitted.
Q4 | For a low level AM system, amplifier modulated stage must have                    
  • harmonic devices
  • linear devices
  • non-linear devices
  • class a amplifiers
Answer: linear devices
Explaination:
in low-level modulation, the generation of amplitude modulated signal takes place at low power levels. the generated am signal is then amplified using a chain of linear amplifiers, which are required to avoid waveform distortion. thus, linear devices are used in low level amplitude modulated system.
Q5 | Which is the greatest disadvantage of Pulse Code Modulation?
  • highly prone to noise
  • cannot travel long distances
  • its inability to handle analog signals
  • large bandwidth is required for it
Answer: large bandwidth is required for it
Explaination:
pulse code modulation (pcm) is a digital form of communication. for demodulation of pcm, it is necessary to convert it into pam. quantization noise occurs in pcm only. its greatest disadvantage is its requirement for large bandwidth.
Q6 | Inductance and capacitance of a line is 0.8
  • 158
  • 166
  • 143
  • 127
Answer: 158
Q7 | Quantization noise occurs in                                    
  • frequency division multiplexing
  • time division multiplexing
  • delta modulation
  • amplitude modulation
Answer: amplitude modulation
Explaination:
quantisation is the process
Q8 | What the main advantage of PCM?
  • can travel small distances
  • higher bandwidth
  • lower noise
  • good reception
Answer: lower noise
Explaination:
pulse code modulation is a technique in which the amplitude of an analogue signal is converted to a binary value represented as a series of pulses. it is less prone to noise and can travel through long distances without loss of data.
Q9 | In AM pilot carrier, transmission has
  • carrier and part of one side band
  • two side bands and a carrier
  • two side bands
  • carrier, one side band and part of other side band
Answer: two side bands and a carrier
Explaination:
in amplitude modulated wave, the transmitted wave has two side bands and a carrier. thus it’s bandwidth is twice the maximum modulating frequency.
Q10 | Quantization noise depends upon both sampling rate and number of quantization levels.
  • true
  • false
Answer: false
Explaination:
quantization noise in pulse code modulation (pcm) depends upon only on number of quantization levels.
Q11 | Which of the following frequency is not transmitted in AM transmission?
  • upper side band frequency
  • carrier frequency
  • lower side band frequency
  • audio frequency
Answer: audio frequency
Explaination:
audio frequency is the frequency that is not transmitted in am transmission.
Q12 | Companding is used in PCM transmitters to allow amplitude limiting in the receivers.
  • true
  • false
Answer: false
Explaination:
companding is the process through which the signal to noise ratio of a wave is reduced by compressing and expanding the signal. it decreases the number of bits required to record the strongest signal. companding also improves signal to noise ratio.
Q13 | What is the use of Companding?
  • in pcm transmitters to allow amplitude limiting in the receivers
  • in pcm receiver to overcome impulse noise
  • to overcome quantizing noise in pcm
  • to protect small signals in pcm from quantizing distortion
Answer: to protect small signals in pcm from quantizing distortion
Explaination:
companding is the process through which the signal to noise ratio of a wave is reduced by compressing and expanding the signal. it decreases the number of bits required to record the strongest signal. companding also improves signal to noise ratio. it is mainly used to protect small signals in pcm from quantizing distortion.
Q14 | 5 PSD MODULATORS AND DEMODULATORS
  • true
  • false
Answer: false
Explaination:
modern mobile communication systems use digital modulation techniques.
Q15 | Which of the following is not an advantage of digital modulation?
  • greater noise immunity
  • greater security
  • easier multiplexing
  • less bandwidth requirement
Answer: less bandwidth requirement
Explaination:
digital modulation offer many advantages over analog modulation. some advantages include greater noise immunity and robustness. they provide easier multiplexing of various forms of information and greater security.
Q16 | The performance of modulation scheme is not measured in terms of                      
  • power efficiency
  • bandwidth efficiency
  • cost and complexity
  • transmitted power
Answer: transmitted power
Explaination:
the performance of modulation scheme is often measured in terms of its power efficiency and bandwidth efficiency.
Q17 | In digital communication system, in order to increase noise immunity, it is necessary to increase                    
  • signal power
  • signal amplitude
  • signal frequency
  • signal magnitude
Answer: signal power
Explaination:
in digital communication system, in order to increase noise immunity, it is necessary to increase signal power.
Q18 | Which of the following is the ratio of signal energy per bit to noise power spectral density?
  • bandwidth efficiency
  • spectral density
  • power efficiency
  • power density
Answer: power efficiency
Explaination:
power efficiency is often expressed as the ratio of signal energy per bit to noise power spectral density required at the receiver input for a certain probability of error. power efficiency is a measure of how favourably the trade-off between fidelity and signal power is made.
Q19 | Increasing the data rate implies the increase in pulse width of digital symbol.
  • true
  • false
Answer: false
Explaination:
there is an unavoidable relationship between data rate and bandwidth occupancy. increasing the data rate implies decreasing the pulse width of a digital symbol, which increases the bandwidth of the signal.
Q20 | Which of the following is the ratio of the throughput data rate per Hertz?
  • bandwidth efficiency
  • spectral density
  • power efficiency
  • power density
Answer: bandwidth efficiency
Explaination:
bandwidth efficiency reflects how efficiently the allocated bandwidth is utilized. it is defined as the ratio of throughput data rate per hertz in a given bandwidth. it describes the ability of a modulation scheme to accommodate data within a limited bandwidth.
Q21 | Which of the following is defined as the range of frequencies over which the signal has a non zero power spectral density?
  • null to null bandwidth
  • half power bandwidth
  • 3 db bandwidth
  • absolute bandwidth
Answer: absolute bandwidth
Explaination:
the absolute bandwidth is defined as the range of frequencies over which the signal has a non-zero power spectral density. for symbols represented as rectangular baseband pulses, the psd profile extends over an infinite range of frequencies, and has an absolute bandwidth of infinity.
Q22 |                is equal to width of main spectral lobe.
  • null to null bandwidth
  • half power bandwidth
  • 3 db bandwidth
  • absolute bandwidth
Answer: null to null bandwidth
Explaination:
null to null bandwidth is a simpler and more widely accepted measure of bandwidth. it is equal to the width of main spectral lobe.
Q23 | Half power bandwidth is also called
  • absolute bandwidth
  • null to null bandwidth
  • 3 db bandwidth
  • zero db bandwidth
Answer: 3 db bandwidth
Explaination:
half power bandwidth is also called the 3 db bandwidth. it is defined as the interval between frequencies at which the psd has dropped to half power, or 3 db below the peak value.
Q24 | FM is a part of general class of modulation known as              
  • angle modulation
  • phase modulation
  • amplitude modulation
  • frequency modulation
Answer: angle modulation
Explaination:
fm is a part of general class of modulation known as angle modulation.
Q25 | Frequency modulated signal is regarded as the phase modulated signal in which the modulating wave is differentiated before modulation.
  • true
  • false
Answer: false
Explaination:
frequency modulated signal is regarded as the phase modulated signal in which the modulating wave is integrated before modulation. this means that an fm signal can be generated by first integrating the message signal and then using the result as an input to a phase modulator.
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