R4RIN
MCQS
Electrical measurements MCQ Quiz Hub
Digital Communications MCQs set-6
Choose a topic to test your knowledge and improve your Electrical measurements skills
1. Which value of r (roll off factor) is considered as Nyquist minimum bandwidth case?
0
1
Infinity
None of the mentioned
2. A pulse shaping filter should satisfy two requirements. They are
Should be realizable
Should have proper roll off factor
Should be realizable & have proper roll off factor
None of the mentioned
3. Examples of double side band signals are
ASK
PSK
ASK & PSK
None of the mentioned
4. Channel’s phase response must be a linear function of
Time
Frequency
Time & Frequency
None of the mentioned
5. Amplitude distortion occurs when
Impulse response is not constant
Impulse response is constant
Frequency transfer function is constant
Frequency transfer function is not constant
6. Phase distortion occurs when
Phase response is function of frequency
Phase response is not a function of frequency
All of the mentioned
None of the mentioned
7. Equalization process includes
Maximum likelihood sequence estimation
Equalization with filters
Maximum likelihood sequence estimation & Equalization with filters
None of the mentioned
8. The maximum likelihood sequence estimator adjusts _______ according to _____ environment.
Receiver, transmitter
Transmitter, receiver
Receiver, receiver
None of the mentioned
9. The filters used with the equalizer is of ______ types.
Feed forward
Feed backward
Feed forward and feedback
None of the mentioned
10. Transversal equalizers are ________ and decision feedback equalizers are ______
Feed forward, feed back
Feed back, feed forward
Feed forward, feed forward
Feedback, feedback
11. Symbol spaced has ____ sample per symbol and fractionally spaced has ___ samples per symbol.
One, many
Many, one
One, one
Many, many
12. The _______ of the opening of eye pattern indicates the time over which the sampling for detection might be performed.
Length
Width
X-axis value
Y-axis value
13. Range of time difference of the zero crossing gives the value of
Width
Distortion
Timing jitter
Noise margin
14. The range of amplitude difference gives the value of
Width
Distortion
Timing jitter
Noise margin
15. As the eye opens, ISI _______
Increases
Decreases
Remains the same
None of the mentioned
16. Pseudo noise signal has _______ and _______ SNR for the same peak transmitted power.
Larger, smaller
Smaller, larger
Larger, larger
Smaller, smaller
17. The index value n, in transversal filter can be used as.
Time offset
Filter coefficient identifier
Time offset & Filter coefficient identifier
None of the mentioned
18. The over-determined set of equations can be solved using
Zero forcing
Minimum mean square error
Zero forcing & Minimum mean square error
None of the mentioned
19. If the filter’s tap weight remains fixed during transmission of data, then the equalization is called as
Preset equalization
Adaptive equalization
Fixed equalization
None of the mentioned
20. Equalization method which is done by tracking a slowly time varying channel response is
Preset equalization
Adaptive equalization
Variable equalization
None of the mentioned
21. Preamble is used for
Detect start of transmission
To set automatic gain control
To align internal clocks
All of the mentioned
22. The disadvantage of preset equalizer is that
It doesnot requires initial training pulse
Time varying channel degrades the performance of the system
All of the mentioned
None of the mentioned
23. For AWGN, the noise variance is
N0
N0/2
2N0
N0/4
24. Performance of BFSK signal is ________ than BPSK.
3db worse
3db better
6db worse
6db better
25. A Gaussian distribution into the non linear envelope detector yields
Rayleigh distribution
Normal distribution
Poisson distribution
Binary distribution
26. The non coherent FSK needs ________ Eb/N0 than coherent FSK.
1db more
1db less
3db more
3db less
27. The DPSK needs ________ Eb/N0 than BPSK.
1db more
1db less
3db more
3db less
28. Coherent PSK and non coherent orthogonal FSK have a difference of ______ in PB.
1db
3db
4db
6db
29. Which is easier to implement and is preferred?
Coherent system
Non coherent system
Coherent & Non coherent system
None of the mentioned
30. Which is the main system consideration?
Probability of error
System complexity
Random fading channel
All of the mentioned
31. Wavelength and antenna size are related as
λ/2
λ/4
2λ
4λ
32. The detection method where carrier’s phase is given importance is called as
Coherent detection
Non coherent detection
Coherent detection & Non coherent detection
None of the mentioned
33. The coherent modulation techniques are
PSK
FSK
ASK
All of the mentioned
34. The real part of a sinusoid carrier wave is called as
Inphase
Quadrature
Inphase & Quadrature
None of the mentioned
35. Antipodal signal sets are those vectors that can be illustrated as
Two 180 opposing vector
Two 90 opposing vector
Two 360 opposing vector
None of the mentioned
36. The FSK signal which has a gentle shift from one frequency level to another is called as
Differential PSK
Continuous PSK
Differential & Continuous PSK
None of the mentioned
37. Which modulation scheme is also called as on-off keying method?
ASK
FSK
PSK
GMSK
38. In amplitude phase keying each phase vector is separated by
90
0
45
180
39. The transformation of the waveform into a single point in signal space is called as
Vector point
Predetection point
Preamplification point
Transformation point
40. The correlating detector is also known as
Maximum likelihood detector
Minimum likelihood detector
Maximum & Minimum likelihood detector
None of the mentioned
41. The minimum nyquist sampling rate is given as, fs =
1/T
T
2/T
2T
42. Phase-locked loop circuitry is used for
Carrier wave recovery
Phase estimation
Carrier wave recovery & Phase estimation
None of the mentioned
43. In differential PSK the date is
Encoded differentially
Decoded differentially
Encoded & Decoded differentially
None of the mentioned
44. Envelope detector consists of
Rectifier and high pass filter
Rectifier and low pass filter
Amplifier and low pass filter
Amplifier and high pass filter
45. The minimum required spacing is the difference between the
Center of the spectral main lobe and first zero crossing
First and second zero crossing
First and last zero crossing
None of the mentioned
46. The minimum tone separation corresponds to
T
1/T
2T
T/2
47. Matched filter is used for
Coherent detection
Non coherent detection
Coherent & Non coherent detection
None of the mentioned
48. In differential encoding the _________ different between two wave forms is measured.
Magnitude
Frequency
Phase
Time period
49. The error probability of DPSK is ________ worse than PSK.
Twice
3 db
Twice (3db)
None of the mentioned
50. The limit which represents the threshold Eb/N0 value below which reliable communication cannot be maintained is called as
Probability limit
Error limit
Shannon limit
Communication limit
Submit