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BT0046
COMMUNICATION TECHNOLOGY
[1 Mark each]
1) The number of the levels in digital signal is
a) One
b) Two
c) Four
d) Ten
2) Which one can provide a digital signal?
a) Sine Wave
b) Square wave
c) Spikes
d) None
3) The Modulation index will be
a) ec/Ec
b) em/Em
c) Em/Ec
d) Ec/Em
4) The correct sequence of digital communication system at transmitted end
a) Source encoder-->Channel-->Modulator-->LPF
b) Channel-->Encoder-->LPF-->Modulator
c) Encoder-->LPF-->Modulator-->Channel
d) LPF-->Encoder-->Channel-->Modulator
5) Which of the following system is digital?
a) PPM
b) PCM
c) PFM
d) PWM
6) The main advantage of PCM is
a) Lower B.W
b) Lower Power
c) Lower Noise
d) None
7) In pulse transmitter ratio of time on to time off is called___________.(Duty cycle)
8) While demodulating PCM is first converted into__________.(PAM)
9) Quantizing occurs in
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a) FM
b) AM
c) PCM
d) PAM
10) PCM stands for __________________ (Pulse code modulation)
11) In pulse modulation, the number of samples required to ensure no loss of information
is given by
a) Nyquist Theorem
b) Parsevals
c) Thenvin
d) Fonrier Theorem
12) Which one is analog
a) PCM
b) Delta
c) Deferential PCM
d) PAM
13) DSSS stands for ___________ (Direct sequence spread spectrum)
14) FHSS stands for _____________-.(Frequency hopping spread spectrum.)
15) Digital Modulation is one where the base band signal is digital True/ False
16) BPSR requires half the B.W of corresponding QPSR. True / False
17) PAM is a best signal to noise ratio. True / False
18) A byte is a ___________binary digit word length. (8 Binary)
19) The number of binary digit to make a word (8 Bit)
20) The amplitude modulation is better than PCM True / False
21) Short wave AM broadcast transmission is used for both notional and overseas
services. True / False
22) FM broadcast is done in
a) Short wave range
b) VHF and LHF range
c) Microwave range
d) VLF and VHF range
23) Modern AM broadcast transmitters are high power level modulation systems.
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True/ False
24) Volume compressor is always used in a radio broadcast transmitter.
True/ False
25) A volume compressor clips the signal when it reaches a predetermined value.
True / False
26) A peak clippers clips the sly at the specified value. True / False
27) Pre-emphasis boosting up the 1000 frequencies. True / False
28) VODAS is used in all radio broadcast system. True / False
29) SSB transmission needs half the frequency band width per channel as compared to
DSB system. True / False
30) FSK is stands for ___________. (Frequency Shift Keying.)
31) MODEM stands for______________.(Modulator Demodulator)
32) QPSK stands for___________.(Quadrature phone shift keying.)
33) Analog communication is better than digital. True / False
34) Band rate of TI digital system__________.(8000 samples / seconds)
35) The BW requires for N bit PCM is __________.(Nfs)
36) Vocoders are _________________.(Voice Coders)
37) The standard frequency for bell 103 modem are ______& _______.(2225 Hz – 2025
Hz)
38) NRZ stands for ______________. (Non return to zero data format.)
39) Polar NRZ in which________.(Both negative and positive side of wave is used.)
40) AMI stands for_____________.(Alternate mark inversions.)
[2 Marks each]
41) Spread spectrum is used in _________and ___________.
(Military and cellular phones.)
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42) The two logic used in digital communication are _________and _________.
(Positive and negative.)
43) Data formats are ___________and ___________.
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Polar NRZ)
44) Two important types of spread spectrum are ___________and___________.
(FHSS and DSSS.)
45) Data rate of DSSS is lower men FHSS. True / False
46) _____________is the range of frequency occupied bu the signal.
(B.W)
47) The number of sybis / sec is __________and number of bits / sec is__________.
(Band rate , Bit rate)
48) In sampling theorem the Nytuist interval is given by
T = 1 / fm
T = 1 / ∑fm
T = 1 / πfm
T = π / fm
Sampling theorem is associated with
a) PCM
b) FM
c) AM
d) All above
49) Which are statement is True
a) Pulse modulation has power efficiency
b) The PAM system has the best S/N ratio.
c) Blocked grid keying is similar to FSK
d) None
50) Pulse width modulation requires more power than pulse amplitude modulation. True.
51) Quantizing noise occurs in
a) PDM
b) FDM
c) TDM
d) PPM
52) Channels capacity is equal to.
a) B. W of Demand
b) Average frequency
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c) Noise rate
d) Amount of information per second
53) In a communication system, noise is must likely to affect the signal.
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b) At transmitter
c) Channel
d) Information Source
54) Vocoders stands for _______________.
a) Voice encoders
55) Vocoders bits are in _______________ to _____________range.
(1.2 to 2.4 Kb/S)
56) In channel vocoders the speech signal is divided into ______________of
__________B.W. (15 frquency ranges, 200 Hz)
57) Differential PCM encodes _____________and sends _____________ of the samples.
(Difference, difference)
58) Vocoders are ___________, which requires very less___________.
(Voice coders and B.W)
59) Restricting the amplitude of the samples only to predetermined levels is known as
_______.(Quantization.)
60)
[4 Marks each]
61) Layers of digital communication are ____________,
__________,_________and________. (Protocol, coding, format, modulation.)
62) An audio signal consisting of sinosodical term V(t) = 3 Cos3140 t
The signal to quantizing noise ratio when this is quantized using 10 bit is__________.(6N)
63) Compounding is used.
a) To overcome quantizing noise in PCM.
b) To compact the PCM signal.
c) To protect small signals in PCM from quantizing distortion.
d) In PCM receiver to overcome impulse noise.
64) The biggest disadvantage on PCM is
a) Its inability to handler analog signals.
b) The high error rate which its quantizing noise reduces.
c) Its incomparability TDM
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d) The large BW
65) The following terms stand for
a) TDM_____________
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b) FDM_____________
c) PCM_____________
d) FM______________
a) Time division multiplexing
b) Frequency division multiplexing
c) Pulse code modulation
d) Frequency modulation
66) QPSK transmitter consists of
a) Demux and Adder
b) Sub. and Adder
c) Multiplier and Adder
d) None
67) Simple communication Block sequences is
a) Tx channel Rx
b) Rx Tx channel
c) Tx Rx channel
d) None
68) Voice has a band width of ______________and Audio has a BW of
______________and Video has a BW of ________________(3-4 khz, 15 khz , 5 mhz)
69) The Nyquist rate of
70) S(t) =
71) The analog signal has a range 5 khz – 8 khz the Nyquist rate is ___________.(6 khz)
72) Assuming that on analog voice frequency 5 / g which occupies a band of frequency
from 300 hz to 340 hz is to be transmitted over a binary PCM system employing 256
Quantization levels. The minimum sampling frequency is _____________ (6800 Hz)
73) In the above question BW is _______________.(32 kb / sec.)
74) No. of bits required to achieve a signal to Quantization ratio at least 40 db? 7 bits
75) If each S / G is sampled at rate of 8000 Hz the frame of 192 bits occupies a time slat
of _________________.(125 µ sec.)
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