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Digital Communications MCQs set-11
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1. In finite state machines, output is predicted using
Past output
Present input
Past output & Present input
None of the mentioned
2. In TCM the signals are decoded using
Soft decision decoders
Hard decision decoders
Soft & Hard decision decoders
None of the mentioned
3. Trellis coded modulation scheme
Has memory
Is memory-less
Needs more bandwidth
None of the mentioned
4. In TCM channel capacity can be increased.
True
False
5. Transmission bandwidth depends on
Rate of signalling
Density of signal points
Reduced distance
None of the mentioned
6. Which determines the error performance in TCM?
Reduced distance
Free distance
Bandwidth
None of the mentioned
7. The TCM decoder uses
Minimum likelihood detector
Maximum likelihood detector
Does not use redundant bits
None of the mentioned
8. Flat top sampling of low pass signals
Gives rise to aperture effect
Implies over sampling
Leads to aliasing
Introduces delay distortion
9. In a delta modulation system, granular noise occurs when the
Modulating signal increases rapidly
Pulse rate decreases
Pulse amplitude decreases
Modulating signal remains constant
10. A PAM signal can be detected using
Low pass filter
High pass filter
Band pass filter
All pass filter
11. Coherent demodulation of FSK signal can be performed using
Matched filter
BPF and envelope detectors
Discriminator
None of the mentioned
12. The use of non uniform quantization leads to
Reduction in transmission bandwidth
Increase in maximum SNR
Increase in SNR for low level signals
Simplification of quantization process
13. Which of the following requires a synchronizing signal?
Single channel PPM system
PAM
DM
All of the mentioned
14. A PWM signal can be generated by
An astable multi vibrator
A monostable multi vibrator
Integrating a PPM signal
Differentiating a PPM signal
15. TDM is less immune to cross-talk in channel than FDM.
True
False
16. In an ideal TDM system, the cross correlation between two users of the system is
1
0
Infinity
-1
17. TDM requires
Constant data transmission
Transmission of data samples
Transmission of data at random
Transmission of data of only one measured
18. In M-ary FSK, as M increases error
Increases
Decreases
Does not get effected
Cannot be determined
19. In M-ary FSK as M tends to infinity, probability of error tends to
Infinity
Unity
Zero
None of the mentioned
20. For non coherent reception of PSK _____ is used.
Differential encoding
Decoding
Differential encoding & Decoding
None of the mentioned
21. Which modulation technique have the same bit and symbol error probability?
BPSK
DPSK
OOK
All of the mentioned
22. An amplifier uses ______ to take input signal.
DC power
AC power
DC & AC power
None of the mentioned
23. Which has 50% maximum power efficiency?
Class A
Class B
Class AB
None of the mentioned
24. Which generates high distortion?
Class A
Class B
Class C
Class AB
25. Class B linear amplifiers have maximum power efficiency of
50%
75%
78.5%
None of the mentioned
26. Which has the maximum power efficiency?
Class A
Class B
Class C
Class AB
27. Free space in idealization which consists
Transmitter
Receiver
Transmitter & Receiver
None of the mentioned
28. Properties used to determine stream’s fidelity
Sampling rate
Bit depth
Sampling rate & Bit depth
None of the mentioned
29. In bipolar codes, pulses can be
Positive
Negative
Absent
All of the mentioned
30. Delta modulation is ______ conversion.
Analog to digital
Digital to analog
Analog to digital and digital to analog
None of the mentioned
31. To achieve high signal to noise ratio, delta modulation must use
Under sampling
Over sampling
Aliasing
None of the mentioned
32. The demodulator in delta modulation technique is
Differentiator
Integrator
Quantizer
None of the mentioned
33. Source of noise in delta modulation is
Granularity
Slope overload
Granularity & Slope overload
None of the mentioned
34. When probability of receiving a symbol is 1 then how much information will be obtained?
Little information
Much information
No information
None of the mentioned
35. In channel encoding procedure
Redundancy bits are added
Errors are corrected
Redundancy bits are added & Errors are corrected
None of the mentioned
36. Modulation process includes
Analog to digital conversion
Digital to analog conversion
All of the mentioned
None of the mentioned
37. Switching exists in
Point to point communication
Broadcast communication
Point to point & Broadcast communication
None of the mentioned
38. Space division has dedicated
Paths
Time slots
Paths & Time slots
None of the mentioned
39. In time division system, the actual switch is called as
Speech memory
Cross point
Connecting point
None of the mentioned
40. In time division, connection is established using
Data exchange
Galvanic connection
Data exchange & Galvanic connection
None of the mentioned
41. Analogue switches provides
Good bandwidth
Low distortion
Low cost
All of the mentioned
42. Operations performed by switching system
Path establishment
Information exchange
Tariff computation
All of the mentioned
43. PCM includes the process of
Amplitude discretization
Time discretization
Amplitude & Time discretization
None of the mentioned
44. For which quantization process is used?
Amplitude discretization
Time discretization
Amplitude & Time discretization
None of the mentioned
45. Modulation process corresponds to ______ the amplitude, frequency or phase.
Switching
Keying
Switching or keying
None of the mentioned
46. Which has same probability of error?
ASK and FSK
ASK and PSK
PSK and FSK
None of the mentioned
47. Which has higher error probability performance?
Uni-polar base-band signalling
Bipolar base-band signalling
ASK
FSK
48. Time division multiplexing uses
High pass filter
Commutator
High pass filter & Commutator
None of the mentioned
49. In TDM, at the receiver end, ____ filter is used.
Low pass
High pass
Band pass
Band stop
50. Which provides more secure communication?
CDMA
FDMA
TDMA
None of the mentioned
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