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Electrical measurements MCQ Quiz Hub
Digital Communications MCQs set-3
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1. Modulation channel consists of
Amplifier
Signal processing units
Amplifier & Signal processing units
None of the mentioned
2. Modulation channel does not accept an analog input signal.
True
False
3. If operating frequency bands are higher ______ is available.
Smaller bandwidth
Larger bandwidth
Smaller & Larger bandwidth
Cannot be determined
4. Ground wave communication occurs in
Low frequency band
Medium frequency band
Low & Medium frequency band
None of the mentioned
5. Sampling theorem is used for converting
Continuous time signal to discrete
Discrete to continuous time signal
Continuous time signal to discrete & vice versa
None of the mentioned
6. A signal can be recovered from its sample by using
Low pass filter
High pass filter
Band pass filter
Band stop filter
7. Which is practically realizable?
A train of pulses
Impulse train
All of the mentioned
None of the mentioned
8. In flat top sampling scheme, ______ is kept constant after sampling.
Amplitude
Phase
Frequency
Time period
9. Loop filter is a ______ used to reduce noise.
Low pass filter
High pass filter
Band pass filter
Band reject filter
10. A stationary stochastic process has
Finite energy signal
Infinite zero signal
Zero energy signal
None of the mentioned
11. The power spectral density function of the stochastic process is
Real
Odd
Real & odd
None of the mentioned
12. For a periodic function, the spectral density and auto correlation functions form
Fourier transform pair
Laplace transform pair
Hilbert transform pair
Z transform pair
13. The capacity of a channel is given by
Number of digits used in coding
Volume of information it can take
Maximum rate of information transmitted
Bandwidth requires information
14. In a communication system, a process in which statistical averages and time averages are equal is called as
Stationary
Ergodic
Gaussian
Poisson
15. A rectangular pulse of duration T is applied to a matched filter. The output of the filter is a
Rectangular pulse of duration T
Rectangular pulse of duration 2T
Triangular pulse
Sine function
16. The line code has a zero dc component for pulse transmission of random binary data is
NRZ
RZ
Alternate mark inversion
None of the mentioned
17. The auto-correlation of white noise is
A delta function
A constant
Gaussian
None of the mentioned
18. Ionospheric communication can take place in
High frequency band
Very high frequency band
Ultra high frequency band
Super high frequency band
19. Satellite communication takes place in
Ultra high frequency band
Super high frequency band
Ultra & Super high frequency band
None of the mentioned
20. The weighing matrix is
Positive quantity
Inverse of covariance matrix of the input vector
Positive quantity & Inverse of a covariance matrix of the input vector
None of the mentioned
21. Non uniform tree _____ bit rate.
Increases
Decreases
Does not affect
None of the mentioned
22. Two clock with rates T1 and T2 are incommensurate if its ratio is
Rational
Irrational
Equal
None of the mentioned
23. Possible timing error detection methods are
Early late
Zero crossing
Early late & Zero crossing
None of the mentioned
24. Which has minimum power loss during transmission?
Twisted Copper cable at 1KHz
Optical fiber
Twisted copper cable at 100KHz
Wave guide
25. Voltage generated by lightning is an example for
Energy signal
Power signal
Energy & Power signal
None of the mentioned
26. In the digital communication system, signals in different frequency bands are
Orthogonal
Non orthogonal
Orthogonal & Non orthogonal
None of the mentioned
27. Properties of impulse function are
Symmetry
Time scaling
Shifting
All of the mentioned
28. Properties of Fourier transform are
Duality property
Time shifting property
Modulation property
All of the mentioned
29. A base-band signal can be up-converted using
Sine wave
Cosine wave
Filtering
None of the mentioned
30. A band-pass signal can be down-converted using
Sine wave
Cosine wave
Time delayed wave
None of the mentioned
31. In down-conversion multiplication with cosine wave is followed by
Low pass filter
High pass filter
Bandpass filter
Bandstop filter
32. ADSL has _____ information channels.
One
Three
Four
None of the mentioned
33. Fourier transform of a signal gives the
Frequency content
Bandwidth
Frequency content & Bandwidth
None of the mentioned
34. Random things in a communication system are
Timing offset
Device frequency
Attenuation
All of the mentioned
35. Which can be used for periodic and non periodic?
Fourier series
Fourier transforms
Fourier series & transforms
None of the mentioned
36. A band-pass signal has a Fourier transform equal to
One
Zero
Infinity
Cannot be determined
37. Which are orthonormal signal representation?
Sine and cosine at same frequency
Wavelets
Complex sinusoids at a different frequency
All of the mentioned
38. Constellation diagram is plotted in
Constellation space
Signal space
Orthogonal space
Boundary space
39. Cumulative distributive function is
Non negative
Non decreasing
Non negative & decreasing
None of the mentioned
40. Which are non negative functions?
PDF
PMF
PDF & PMF
None of the mentioned
41. The sampling process includes methods such as
Filtering
Sample and hold
Amplifying
None of the mentioned
42. The output of sampling process are called as ________
Pulse code modulation
Pulse amplitude modulation
Frequency modulation
Amplitude modulation
43. According to Sampling theorem
Ts is greater than 1/2fm
Ts is lesser than 1/2fm
Ts is equal to 1/2fm
Ts is lesser than or equal to 1/2fm
44. The fourier tranform of one impulse train is also another impulse train with a period of the output equal to the
Period of the input
Reciprocal of the period of input signal
Half the period of input
Twice the period of the input
45. The process in which the top of each pulse in the output samples retains the shape of the analog segment is called as ________
Natural sampling
Ideal sampling
Aliasing
None of the mentioned
46. The effects of aliasing are ________
Attenuation of high frequency spectral replicates
Non uniform spectral gain applied to desired baseband spectrum
Attenuation and non uniform spectral gain
None of the mentioned
47. Aliasing can be removed using
Prefiltering
Postfiltering
Prefiltering & Postfiltering
None of the mentioned
48. Which process is more economical?
Undersampling
Oversampling
Aliasing
None of the mentioned
49. Flat top sampling or practical sampling has
Same frequency
Same amplitude
Same time difference
None of the mentioned
50. Multiplication of input signal with pulse train is done in ________ sampling.
Impulse sampling
Natural sampling
Flat top sampling
None of the mentioned
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