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Digital Communications MCQs set-4
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Digital Communications MCQs set-4
1
The main sources of corruption are
A
Sampling and quantizing effects
B
Channel effects
C
Sampling, quantizing and channel effects
D
None of the mentioned
2
The distortion in quantization is called as
A
Round off error
B
Truncation error
C
Round off & Truncation error
D
None of the mentioned
3
In quantization process, the amount of quantization noise is _______________ to number of levels.
A
Directly proportional
B
Inversely proportional
C
Independent
D
None of the mentioned
4
Saturation noises can be avoided or reduced by
A
Automatic gain control
B
Amplifying
C
Filtering
D
None of the mentioned
5
Timing jitter can be reduced by
A
Good power supply isolation
B
Stable clock reference
C
Good power supply isolation & Stable clock reference
D
None of the mentioned
6
The reasons for the threshold effect are
A
Thermal noise
B
Interference from other users
C
Interference from circuit switching transients
D
All of the mentioned
7
When channel bandwidth is greater than the pulse bandwidth, it causes
A
Intersignal interference
B
Intersymbol interference
C
Bandwidth error
D
None of the mentioned
8
The _____________ corresponds to average quantization noise power.
A
Mean
B
Variance
C
Probability density function
D
None of the mentioned
9
Signal to noise ratio increases as ___________ increases.
A
Quantization level
B
Square of quantization level
C
Square root of quantization level
D
None of the mentioned
10
Signal to noise ratio is infinite when
A
Quantization noise is zero
B
Number of levels are infinite
C
Quantization noise is zero & Number of levels are infinite
D
None of the mentioned
11
The length of the code-word obtained by encoding quantized sample is equal to
A
l=log(to the base 2)L
B
l=log(to the base 10)L
C
l=2log(to the base 2)L
D
l=log(to the base 2)L/2
12
Quantization noise can be reduced by ________ the number of levels.
A
Decreasing
B
Increasing
C
Doubling
D
Squaring
13
In PCM encoding, quantization level varies as a function of ________
A
Frequency
B
Amplitude
C
Square of frequency
D
Square of amplitude
14
What is bit depth?
A
Number of quantization level
B
Interval between two quantization levels
C
Number of possible digital values to represent each sample
D
None of the mentioned
15
Choosing a discrete value that is near but not exactly at the analog signal level leads to
A
PCM error
B
Quantization error
C
PAM error
D
Sampling error
16
In PCM the samples are dependent on ________
A
Time
B
Frequency
C
Quanization leavel
D
Interval between quantization level
17
DPCM encodes the PCM values based on
A
Quantization level
B
Difference between the current and predicted value
C
Interval between levels
D
None of the mentioned
18
Delta modulation uses _____ bits per sample.
A
One
B
Two
C
Four
D
Eight
19
Sample resolution for LPCM ____ bits per sample.
A
8
B
16
C
24
D
All of the mentioned
20
Adaptive DPCM is used to
A
Increase bandwidth
B
Decrease bandwidth
C
Increase SNR
D
None of the mentioned
21
The size of the quantile interval is called as
A
Inter level
B
Step size
C
Quantile size
D
Level width
22
Uniform quantization provides better quantization for
A
Weak signals
B
Strong signals
C
Weak & Strong signals
D
None of the mentioned
23
Non uniform quantization provides better quantization for
A
Weak signals
B
Coarse signals
C
Weak & Coarse signals
D
None of the mentioned
24
In non uniform quantization, the quantization noise is _______ to signal size.
A
Inversely proportional
B
Directly proportional
C
Equal
D
Double
25
The output SNR can be made independent of input signal level by using
A
Uniform quantizer
B
Non uniform quantizer
C
Uniform & Non uniform quantizer
D
None of the mentioned
26
Companding is the process of
A
Compression
B
Expansion
C
Compression & Expansion
D
None of the mentioned
27
Which value of μ corresponds to linear amplification?
A
μ=0
B
μ=1
C
μ>0
D
μ<0
28
What is the standard value of μ in μ-law ?
A
128
B
255
C
256
D
0
29
The standard value of A in A-law is
A
87
B
88
C
86.7
D
87.6
30
Which type of quantization is most preferable for audio signals for a human ear?
A
Uniform quantization
B
Non uniform quantization
C
Uniform & Non uniform quantization
D
None of the mentioned
31
Which waveforms are also called as line codes?
A
PCM
B
PAM
C
FM
D
AM
32
When pulse code modulation is applied to non binary symbols we obtain waveform called as
A
PCM
B
PAM
C
M-ary
D
line codes
33
Examples of PCM waveforms are
A
Non return to zero
B
Phase encoded
C
Multilevel binary
D
All of the mentioned
34
Which type is used and preferred in digital logic circuits?
A
NRZ-L
B
NRZ-M
C
NRZ-S
D
None of the mentioned
35
Which method is called as differential encoding?
A
NRZ-L
B
NRZ-M
C
NRZ-S
D
None of the mentioned
36
Which method is preferred in magnetic tape recording?
A
NRZ-L
B
NRZ-M
C
NRZ-S
D
None of the mentioned
37
NRZ-S is complement of _______
A
NRZ-L
B
NRZ-M
C
NRZ-L & NRZ-M
D
None of the mentioned
38
The return to zero waveform consists of
A
Unipolar RZ
B
Bipolar RZ
C
RZ-AMI
D
All of the mentioned
39
Phase encoded group consists of
A
Manchester coding
B
Bi-phase-mark
C
Miller coding
D
All of the mentioned
40
In which waveform logic 1 is represented by half bit wide pulse and logic 0 is represented by absence of pulse?
A
Unipolar RZ
B
Bipolar RZ
C
RZ-AMI
D
Manchester coding
41
In which waveform logic 1 and logic 0 are represented by opposite one half bit wide pulses?
A
Unipolar RZ
B
Bipolar RZ
C
RZ-AMI
D
Manchester coding
42
In which waveform logic 1 is represented by equal amplitude alternating pulses?
A
Unipolar RZ
B
Bipolar RZ
C
RZ-AMI
D
Manchester coding
43
Application of phase encoded binary signals are
A
Optical communication
B
Magnetic recording
C
Satellite telemetry
D
All of the mentioned
44
In which waveform one is represented by half bit wide pulse positioned during the first half and zero is represented by half bit wide pulse positioned in the second half?
A
Bi-p-L
B
Bi-p-M
C
Bi-p-S
D
Delay modulation
45
Which binary waveform uses three levels?
A
Bipolar RZ
B
RZ-AMI
C
Bipolar RZ & RZ-AMI
D
None of the mentioned
46
Which waveform type has the feature of clocking?
A
Manchester coding
B
Bbi-p-M
C
Delay modulation
D
NRZ-L
47
Which waveform has the feature of error detection?
A
NRZ-L
B
RZ-AMI
C
Manchester coding
D
Duobinary
48
Which waveform scheme introduces bandwidth compression?
A
Duobinary
B
Manchester coding
C
Phase encoded waveform
D
Multilevel codes
49
Which waveform type has better noise immunity?
A
NRZ
B
RZ
C
Phase encoded
D
Multilevel codes
50
In pulse modulation, reciprocal of T(time) is
A
Bandwidth
B
Symbol rate
C
Signal voltage
D
None of the mentioned
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