0.
Question
Marks Co. No. BL
1.
Sampling theorem finds application in
(a) Amplitude modulation
(b) Frequency modulation
(c) PCM
(d) FSK
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2.
If sampling time is greater than the Nyquist interval, then:
(a) Bandwidth increases
(b) Channel capacity increases
(c) Guard time reduces
(d) Overlapping is occurred
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3.
In communication systems, sampling technique leads
to:
(a) High cost
(b) Better efficiency
(c) Higher speed of communication
(d)
simpler operation
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4.
For a bandlimited signal with bandwidth W, Nyquist
sampling frequency fs satisfied the condition:
(a) 𝑓𝑠≥2𝑊
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(b) 𝑓𝑠 ≥ 𝑊
(c) 𝑓 ≤2𝑊
𝑠
(d) 𝑓𝑠 ≤ 𝑊
5.
6.
Flat top sampling of low pass signals produces
(a) Oversampling
(b) Aliasing
(c) Aperture effect
(d) Delay distortion
In PCM, the quantization noise depends on
(a) sampling rate
(b)
number of quantization level
(c) signal power
frequency
(d) signal
7.
Quantizing noise occurs in
(a) Time-division multiplex
(b) Frequency division multiplex
(c) Pulse code modulation
(d) Pulse-width modulation
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8.
PCM generation requires a LPF at the beginning
because:
(a) To eliminate aliasing effect
(b
To eliminate quantization noise
(c) To eliminate decoding noise
(d) To eliminate crosstalk
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9.
The maximum quantization error in PCM , with
number of quantization level ‘q’ is:
(a) 1/q
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To avoid aliasing, what is the Nyquist rate of this
signal x ( t) = 8 cos 200 wt ?
(a) 50 Hz
(b) 100 Hz
(c) 200 Hz
(d) 400 Hz.
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12
In a 7-bit PCM system output signal to quantization
ratio for sinusoidal modulating signal will be
(a) 54.6 dB
(b) 42.5 dB
(c) 43.8 dB
(d) 34.4 dB
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13
If the number of bits per sample in a PCM system is
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(b) 2/q
(c) 2/q
(d) 4/q
10
How many bits would be required to represent a 256
level quantization in PCM?
(a) 6
(b) 8
(c) 5
(d) 7
11.
increased from n to n+1, the improvement in signal to
quantization noise ratio will be.
(a) 3 dB
(b) 6 dB
(c) 2n dB
(d) n dB
14
The standard data rate of a PCM voice channel is
(a) 8 kbps
(b) 8 bps
(c) 16 kbps
(d) 64 kbps
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15
A PAM signal can be detected by using
(a) an ADC
(b) an integrator
(c) a bandpass filter
(d) a highpass filter
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16
Time division multiplex:
(a) Stacks several channels in adjacent
frequency slots
(b) Interleaves pulses belonging to different
transmissions
(c) Combine 5 groups into a single super
group
(d) Can be used with PCM only.
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17
The maximum frequency present in one PCM signal
is fm, then for proper detection the message signal
sampling rate fs should follow the relation
(a) fs =fm
(b) fs>fm
(c) fs ≥ 2fm
(d)fs
=
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Companding is used:
(a) To protect small signals in PCM from
quantizing distortion
(b) To overcome quantized noise in PCM
(c) To overcome impulse noise
(d) To overcome white noise
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19
Which of the following system is digital
modulation?
(a) Pulse-position modulation
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fm/2
(b) Pulse-code modulation
(c) Pulse-width modulation
(d) Pulse-frequency modulation
20
Delta modulator is called:
(a) One-bit DPCM
(b) Two-bit DPCM
(c) Half-bit PCM
(d) One level DPCM
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21
Slope overload occurs in
(a) PCM
(b) DM
(c) ADM
(d) DPCM
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22
ADM involves additional hardware designed to
provide variable step size:
(a) Reducing slope-overload effects
(b) Reducing granular noise
(c) both (a) and (b)
(d) Reducing SNR
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23
In DM slope overload condition is:
a. Maximum DM slope maximum signal slope
b. Maximum DM slope< maximum signal slope
c. Both (a) and (b)
d. None of these
24
In DM granular noise can be avoided by
(a) reducing step size of quantizer
(b) by reducing sampling rate
(c) increasing step size of quantizer
(d) None of these
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25
Which of the following techniques is most suitable for
transmission of speech?
(a) M-ary pulse modulation waveforms
(b) Line codes
(c) DPCM waveforms
(d) ADPCM waveforms
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26
Which system is effective to reduce cumulative error?
(a) PCM
(b) DPCM
(c) Delta Sigma Modulation
(d) ADM
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27
To avoid slope overload in delta modulation, the
maximum value of signal amplitude will be
(a) ∆fs
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(b) B/s
(c) ∆fs/B
(d) fs/B
Where, ∆ - step size, fs- sampling frequency,
B – signal frequency
28
Split-phase Manchester format represents
(a) Successive 1s are represented by pulses with
alternating polarity
(b) 1s with a positive half-interval pulse followed by a
negative half-interval pulse
(c) Each 1 by an “on” pulse for full bit duration
(d) Each 1 by an “on” pulse for half bit duration
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29
Scrambling is a coding operation applied to the
message at:
(a) The transmitter
(b) The receiver
(c) The channel
(d
The transmitter and receiver both
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30
Source coding in a data communication is done in
order to
(a) Enhance information transmission
rate
(b) Reduce transmission rate
(c) Conserve transmission power
(d) Facilitate clock recovery
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If a voice frequency signal is sampled at a rate of
32,000 samples per second and characterized by peak
value of 2 volts at a delta modulator. Calculate SNR.
Bandwidth is 4 KHz.
a) 19.45
b) 2.57
c) 19.59
d) 1.67
32 A compact disc records audio signals digitally by using PCM.
Assume the audio signal bandwidth to be 15 KHz.
What is Nyquist rate?
a) 30 KHz
b) 35 KHz
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c) 3.57 KHz
d) 18 Khz
If the Nyquist samples are quantized into L=65,536 levels
and then binary coded, determine the number of binary digits
required to encode a sample.
a) 16
b) 9
c) 8
d) 7
Determine the number of binary digits per second required to
encode the audio signal.
(a) 240 K bits/sec
(b) 340 K bits/sec
(c) 17 K bits/sec
(d) 68 K bits/sec.
33 For practical reasons, the signals are sampled at a rate well
above Nyquist rate at 44,100 samples per second. If
L=65,536, determine the number of bits per second required
to encode the signal.
(a) 740 K bits/sec
(b) 340 K bits/sec
(c) 705.6 K bits/sec
(d) 680 K bits/sec.
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34 The maximum quantization error in PCM , with number of
quantization level ‘4’ is:
(a) 1/4
(b) 2
(c) 4
(d) 1
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35 How many bits would be required to represent a 256 level
quantization in PCM?
(a) 6
(b) 8
(c) 5
(d) 7
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36 To avoid aliasing, what is the Nyquist rate of this signal x ( t)
= 8 cos 200 wt ?
(a) 50 Hz
(b) 100 Hz
(c) 200 Hz
(d) 400 Hz.
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37 In a 7-bit PCM system output signal to quantization ratio for
sinusoidal modulating signal will be
(a) 54.6 dB
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(b) 42.5 dB
(c) 43.8 dB
(d) 34.4 dB
38 If the number of bits per sample in a PCM system is
increased from n to n+1, the improvement in signal to
quantization noise ratio will be.
(a) 3 dB
(b) 6 dB
(c) 2n dB
(d) n dB
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39 The length of the PN sequence with 4-stage register is:
(a)10
(b) 15
(c)7
(d) 16
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40 The number of bits per sample in a PCM system is increased
from 8 to 16. The bandwidth of the system will increase
a) 8 times
b) 2 times
c) 6 time
d) 28 times.
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41 In a PCM system, the number of quantization levels is 16 and
the maximum signal frequency is 4 kHz, the bit transmission
rate is
(a) 64 kbps
(b) 32 kbps
(c) 16 kbps
(d) 8 kbps
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42 A delta modulation system is designed to operate at 3 times
the Nyquist rate for a signal with a 3 kHz bandwidth. The
quantization step size is 250 mv. Find the maximum
amplitude of a 1 kHz input sinusoid for which the delta
modulator does not show slope overload.
(a) 0.5 volt
(b) 0.1 volt
(c) 0.2 volt
(d) 0.71 volt
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43 A delta modulation system is designed to operate at 3 times
the Nyquist rate for a signal with a 3 kHz bandwidth. The
quantization step size is 250 mV. Find the SNR for a 1 kHz
input sinusoid for which the delta modulator does not show
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slope overload.
(a) 24.5 dB
(b) 21.5 dB
(c) 22.5 dB
(d) 23.5 dB
44 A binary channel with rb=36,000 bits/sec is available for
PCM voice transmission. Find appropriate values of number
of bits per quantization level (ν) assuming W= 3.2 kHz.
a) 3
b) 2
c) 7
d) 5
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47 A television signal having a BW of 4.2 MHz is transmitted
using a binary PCM system. Number of quantization
levels used is 512. Determine Codeword length
a) 2
b) 5
c) 6
d) 9
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48 A television signal having a BW of 4.2 MHz is transmitted
using a binary PCM system. Number of quantization
levels used is 512. Determine Transmission bandwidth
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45 A binary channel with rb=36,000 bits/sec is available for
PCM voice transmission. Find appropriate values of
quantization level (q) assuming W= 3.2 kHz.
a) 32
b) 25
c) 26 d) 64
46 A binary channel with rb = 36,000 bits/sec is available for
PCM voice transmission. Find appropriate values of sampling
frequency (fs) assuming W= 3.2 kHz.
a) 7.6 KHz
b) 7.8 KHz
c) 6.2 Khz
d) 7.2 KHz
a) 27.8 MHz
b) 37 MHz
c) 34.8 MHz
d) 37.8 MHz
49 A television signal having a BW of 4.2 MHz is transmitted
using a binary PCM system. Number of quantization
levels used is 512. Determine Output signal to
quantization ratio
a) 12·45 dB
b) 26·5 dB
c) 2·6 dB
d) 58.8 dB
50 A television signal having a BW of 4.2 MHz is transmitted
using a binary PCM system. Number of quantization
levels used is 512. Determine final bit rate
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51 A communication channel of bandwidth 75 KHz is required
to transmit binary data at the rate of 0.1 Mbps using
Raised cosine pulse. Determine the corresponding
roll-off factor.
a) 5.4
b) 0.22
c) 4.1
d) 0.5
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52
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54 A voice frequency signal band limited to 3 KHz is
transmitted with the use of the DM system. The pulse
repetition frequency is 30000 pulses per second, and the step
size is 40 mV. Determine the maximum permissible speech
signal amplitude to avoid a slope overload.
a) 63.69 mV
b) 53.59 mV
c) 26.69 mV
d) 56.89 mV
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55 The analog voltage waveform has a BW of 4 KHz and an
amplitude range of – 3.8 to + 3.8 volts. It has the average
power of 30 mili Watt and the required SNR is 20 dB. Find
the number of bits in each PCM word required.
a) 6
b) 7
c) 2
d) 5
56 The SNR for 16 quantization levels is 20 dB; find the SNR in
normal scale.
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a) 75.6 Mbits/s
c) 75.9 Mbits/s
b) 78.6 Mbits/s
d) 65.6 Mbits/s
Consider an audio signal𝑒𝑚(𝑡) = 2𝑐𝑜𝑠(100π𝑡).Find the
signal-to-quantization noise ratio when the signal is
quantized using 8-bit PCM.
a) 49.8 dB
b) 42·5 dB
c) 52·6 dB
d) 32·7 dB
53
Consider an audio signal𝑒𝑚(𝑡) = 2𝑐𝑜𝑠(100π𝑡). How
many bits of quantization are needed to achieve a
signal-to-quantization noise ratio of at-least 30 dB?
a) 6
b) 7
c) 2
d) 5
a) 69
b) 97
c) 100
d) 115
57 Given the signal m(t)=10 Cos(400πt). Cos (100πt), find the
minimum sampling rate based on the band pass
sampling theorem.
a) 450 Hz
b) 600 Hz
c) 400 Hz
d) 500 Hz
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58 A television signal has a bandwidth of 4.5 MHz. This signal
is sampled and converted into a PCM signal. Determine the
sampling rate if the signal is to be sampled at a rate 20%
above the Nyquist rate.
a) 10.8 MHz
b) 8.8 MHz
c)
8.9
MHz
d) 7.8 MHz
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59 A television signal has a bandwidth of 4.5 MHz. This signal
is sampled and converted into a PCM signal. The signal is to
be sampled at a rate 20% above the Nyquist rate. If the
samples are quantized into 1024 levels, determine the number
of binary pulses required to encode each sample.
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60 A television signal has a bandwidth of 4.5 MHz. This signal
is sampled and converted into a PCM signal. The signal is to
be sampled at a rate 20% above the Nyquist rate. If the
samples are quantized into 1024 levels, calculate system bit
rate.
a) 18 MHz
b) 108 MHz
c) 88 MHz
d) 10.8 MHz
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61 A binary PCM system uses a uniform quantizer and 7-bit
binary encoder. If the bit rate is 50 Mb/s, what is the
maximum bandwidth for which the system will operate
satisfactorily?
a) 1.8 MHz
b) 35 MHz
c) 3.57 MHz
d) 18 MHz
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a) 10
b) 9
c) 8
d) 7
62 29. If a voice frequency signal is sampled at a rate of 32,000
samples per second and characterized by a peak value of 2
volts, determine the value of step size to avoid slope overload
problem. Bandwidth is 4 KHz.
a) 1.57 Volt
c) 1.5 Volt
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b) 2.57 Volt
d) 1.67 Volt
63 30. If a voice frequency signal is sampled at a rate of 32,000
samples per second and characterized by a peak value of 2
volts at a delta modulator. Calculate quantization noise
power. Bandwidth is 4 KHz.
a) 0.822 W
b) 0.722 W
c) 0.882 W
d) 0.832 W
64.
2
What do you mean by PDF, conditional PDF and explains
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65 What is mean or average and importance of Gaussian
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distribution?
66 Prove that P(Ā)=1-P(A)
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67 Explain the relationship between random variables and
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random process.
68 The PDF of a random variable is given as
5
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A certain computer becomes inoperable if two 5
3
3
their significance?
ƒ𝑋(𝑥) = 𝐾e−𝑏𝑥
=0
ƒo𝑟 𝑥 ≥ 0
ƒo𝑟 𝑥 < 0
𝑎𝑛𝑑 𝐾, 𝑏 > 0
1. Find the value of K in terms of b.
2. Find mx and 𝜎2.
69
𝑥
components A and B both fail. The probability that
A fails is 0.01 and the probability that B fails is
0.005. However, the probability that B fails
increases by a factor of 3 if A has failed.
a. Calculate
the
probability
that
computer becomes inoperable.
Find the probability that A will fail if B has failed.
the
70
Consider a random sinusoidal signal 𝑥(𝑡) =
5
3
3
sin(𝜔O𝑡 + 𝜑), where a random variable ′𝜑′ is
𝜋
uniformly distributed in the range ± 2. Find the
71
mean value of x(t).
Find the autocorrelation function of a real
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3
2
72
valued time signal.
The autocorrelation function 𝑅𝑥(𝑟)satisfy the
5
3
5
73
property 𝑅𝑥(𝑟) = 𝑅𝑥(−𝑟). Prove it.
Find the autocorrelation function 𝑅𝑥(𝑟) of the
5
3
3
74
signal 𝑥(𝑡) = Vsin(𝜔𝑡)
A binary source generates 1 and 0 randomly with 5
3
3
3
3
3
3
3
3
probabilities 0.6 and 0.4, respectively. What is the
probability that at least three 1’s will
occur in a five digit sequence?
75
Given the PDF of a random variable X is:
ƒ(𝑥) = {
𝑘, 𝑎 ≤ 𝑥 ≤ 𝑏
5
, where k is a constant.
0, o𝑡ℎe𝑟wi𝑠e
76.
Determine the value of k
77. If a= -1 and b=2, then for c=1/2, find
𝑃(|𝑥| ≤ 𝑐)
78 The input X to the Binary Symmetric Channel (BSC) 5
shown in the figure is ‘1’ with probability 0.8. The
crossover probability is 1/7. If the received bit Y = 0,
determine the conditional probability that ‘1’ was
transmitted.
79 The PDF of a Gaussian random variable X is given by
Find the probability of the event {X=4}
5
80 X(t) is a WSS process with zero mean.
5
3
3
5
3
3
5
3
3
83 For a random variable ‘X’ following the probability density 5
function, p(x), shown in figure, the mean and the variance
are, respectively
3
3
84 A maze has eight areas as shown below.
3
3
Y(t)=∑2
k=O
X(𝑡 + 𝑘). PSD of X(t) is given as
2
SX(ω)=1+𝜔2 . Find Variance of Y(t).
81 Consider a Random Process , X(t) = 3V(t) -8, where V(t) is
a zero mean stationary process with
autocorrelation RX (τ) = 4. e−5|𝑐|. Determine the power of
X(t).
82 . An output of a communication channel is a random
variable v with the probability density function as shown in
the figure. Find the mean square value of v.
The rat moves through the areas in the maze at random.
That is, if an area has exits to areas, the rat moves to
each of these areas with probability
. Let
be the
area the mouse is located in after the
th move.
Then find transition probability matrix.ofMarkov chain
5
85 Given that
5
3
4
5
3
4
5
3
4
Determine the following conditional probabilities:
∙
∙
∙
86 Consider a Markov chain with the following transition
probability matrix.
Suppose that initially the Markov chain is in state 0 50%
of the time, in state 1 30% of the time and in state 2 20%
of the time. Calculate the
probability
87 When a binary digit, 0 or 1, is transmitted through a
communication system, it passes through several stages. At
each stage, there is a probability that the digit is
transmitted in error. Let
be the digit that is the output
at the
the stage. Then
is a two- state
Markov chain with the following transition probability
matrix.
Determine the following:
●
If the digit to be sent is 0, determine the
probability that no error occurs up to the
second stage.
●
If the digit to be sent is 0, determine
the probability that a correct message is
received at stage 2 through stage 4.
88 Derive Chapman-Kolmogorov equations for -step
transition probability
5
3
2
5
3
2
5
3
3
5
6
2
5
6
1
5
6
1
decision rule.
94 . Define orthogonal signal space and orthogonal vector 5
6
2
89 Consider a Markov chain with the following transition
probability matrix.
Determine
and
90 Consider a Markov chain with the following transition
probability matrix.
Suppose that initially the process is equally likely to be in
state 0 or state 1. Determine
and
91.
.
Mention the importance of signal
space representations.
92 Write a short note
on
Gram-
Schmidt
orthogonalization procedure.
93 Write a short note on maximum likelihood
space. Bring out clearly its applications in representing a
signal and vector respectively.
95 Explain how functions can be approximated using
4
6
4
2+5
6
2
4+4
6
3
4
6
2
2+1
6
2
100. Discuss the orthogonality in complex signals.
5
6
2
101. State and explain sampling theorem for band
5
1
1
5
1
2
5
1
2
5
1
2
5
1
3
orthogonal functions.
96 Define the error function while approximating signals
and hence derive the expression for
condition for orthogonality between two
waveforms f1(t) and f2(t)
97.
(a)
98.
(a)
Using the Gram-Schmidt orthogonalization,
find an orthonormal basis for s1(t) to s4(t).
(b)
Determine the signal vectors for this
orthonormal basis.
Why and When is the representation of a signal
space in a vector space useful?
99. How can you determine if two signals are orthogonal?
What is the angle between orthogonal
signals?
limited signals.
are the different
102. What
kinds of sampling
operations and explain them with suitable circuits?
103. Explain the cause of the aliasing problem and how this
problem can be overcome?
104. What are the different kinds of pulse modulations
and explain them with suitable waveforms?
105. Show that the transmission BW requirement for PAM
signal is much higher than the modulating
signal.
106. Describe the generation of PAM signal with
5
1
1
5
1
3
5
1
2
109. A binary channel with rb=36,000 bits/sec is available for 5
1
3
5
1
3
(c) Output signal to quantization ratio
(a)
Explain the need for non-uniform quantization. 5
1
3
5
1
2
5
1
2
5
1
2
5
1
2
suitable circuit diagram.
107. For PAM transmission of a voice signal having fm=3 KHz,
calculate the required transmission
BW. Given that fS=8 KHz and width of carrier pulse
=0.1TS.
108. Explain operation of a uniform quantizer and
mention its drawbacks.
PCM voice transmission. Find appropriate values of ν, q,
and fs assuming W= 3.2
kHz.
110.
A television signal having a BW of 4.2 MHz is
transmitted using a binary PCM system. Number of
quantization levels used is 512. Determine
(a) Codeword length
(b) Transmission bandwidth
111.
What are the laws associated with it?
(b)
For an n-bit PCM system prove that signal to
quantization noise ratio in dB is given by (S/N) = 1.76
+6.02n for a full scale sinusoidal
modulating signal with amplitude v volts.
112.
Explain the need and operation of companding
technique.
113. Explain the operation of a linear predictor block in
114.
DPCM system
How SNR performance is improved in DPCM
system compared to the PCM system?
115. What is the basic difference between DM and DPCM?
Explain that the performance of a DM
system is superior to a DPCM system.
116. Explain that the performance of an ADM system is
5
1
2
117. What are the desirable properties of line codes?
5
2
1
118. For the given data stream 1110010100,
5
2
2
5
2
2
5
2
2
5
1
2
5
1
3
A communication channel of bandwidth 50 KHz is 5
2
3
1
3
superior to a DM system.
Sketch the transmitted sequence of rectangular
pulses for each of the following line codes:
a.
Unipolar NRZ
b.
Unipolar RZ
c.
Polar RZ
d.
Polar NRZ
e.
Manchester
the implication
119. Explain
of
“Intersymbol
Interference” in digital communication.
120. What do you mean by eye pattern?
What
information do we get from it? How can it be
generated using CRO?
121. Write the statement of the sampling theorem and derive the
expression
of
the
interpolation
formula
regarding
reconstruction from sampled signal.
122. A TV signal has a bandwidth of 4.5 MHz.Thesignal is
sampled and converted into PCM signal. Determine the
sampling rate if the signal is to be sampled at a rate of 20%
above
Nyquist rate.
123.
required to transmit binary data at the rate of 500
kbps using Raised cosine pulse. Determine the
corresponding roll-off factor.
124.
(a)
State
sampling theorem. What
is the Nyquist rate of sampling?
(b) Explain with suitable block diagram
how an analog signal is converted into a digital
signal using a PCM system.
(c) A television signal has a bandwidth of
4.5
MHz. This signal is sampled and converted
15
into a PCM signal.
(i) Determine the sampling rate if the signal is to
be sampled at a rate 20% above the Nyquist rate.
125.
If the samples are quantized into 1024 levels,
determine the number of binary pulses required to
encode each sample.
(a)
Discuss the generation of time division 15
multiplexed
PAM
signal
and
calculate
1
3
1
3
the
transmission B.W requirement for PAM/TDM
system.
(b)
Write the advantages and disadvantages of
TDM over FDM.
(c)
24 voice signals are multiplexed and
transmitted using the PAM/TDM system. The
sampling operation uses flat top samples with 1µs
duration and there is a provision of synchronization
by adding an extra pulse of duration 1 µs. The
highest frequency component of voice signal is 3.4
KHz. Assuming fS=8 KHz calculate spacing
between pulses of multiplexed signal and
required transmission B.W.
126.
(a)
“Pulse modulation system is not digital; 15
whereas, pulse-code modulation is.”- justify.
(b) Discuss why PCM is more noiseresistant than the other forms of pulse modulation.
(c)
Derive the expression of noise power and
PCM system with uniform quantizer.
(d)
A binary PCM system uses a uniform quantiz
bit rate is 100 Mb/s, what is the maximum band
operate satisfactorily? Determine the output signal
full load sinusoidal modulating wave
of frequency 1MHz is applied to the input.
127.
(a)
Why is companding used? Describe μ- law
15
1
3
(ii) How many bits of quantization are
needed to achieve a signal-to-quantization noise
ratio of at-least 30 dB?
(a)
Describe A/D conversion using delta 15
1
3
1
3
2
2
and A-law companding.
(b)
(c)
Describe the operation of a DPCM system.
Consider
an
audio
signal
em (t) = 2 cos(100πt) .
(i) Find the signal-to-quantization noise ratio
when the signal is quantized using 8- bit PCM.
128.
modulator. Mention the limitations of the DM
system and explain the overcome procedure.
(b)
What is the dynamic range of a Delta
modulator? Establish its relationship with step size
∆.
(c) A voice frequency signal band limited
to 3 KHz is transmitted with the use of the DM
system. The pulse repetition frequency is 30000
pulses per second, and the step size is 40 mV.
Determine the maximum permissible speech signal
amplitude to
avoid a slope overload.
129.
(a)
What will be the practical difficulties if 15
fS=2fm?
(b)
Explain how adaptive delta modulation
improves the system's tolerance to slope overload?
(c)
The spectral range of a band pass signal
extends from 10.0 MHz to 10.4 MHz. Find
the minimum sampling rate.
130.
(a) Consider the unipolar binary RZ signal with
p(t)=Π(2rbt). Determine an expression of the power
spectrum of a unipolar RZ signal. (b)Consider
the
unipolar
binary NRZ signal
with p(t)=Π(rbt). Show that the only impulse in
15
Gx(f) is at f=0.
(c) Write a short note on Regenerative repeater.
131.
(a)
Explain the Nyquist criterion for zero 15
4
3
15
4
2
15
1
2
15
1
3
intersymbol interference (ISI) in respect to time and
frequency domain?
(b)
What are the limitations of an ideal solution
and how can it be solved with the help of Raised
Cosine Function?
(c)
A communication channel of bandwidth 75
KHz is required to transmit binary data at a rate of
0.1 Mbps using raised cosine
pulses. Determine the roll of factor α.
132.
(a) What do you mean by matched filter for
digital reception?
(b)
Derive an expression for error
probability of a matched filter.
(c)
State and explain Nyquist criterion for
zero ISI.
133.
(d) What is the role of an equalizer?
(a)
With a neat block diagram, explain the
generation and reception of delta modulation.
(b)
What are the limitations of DM?
How can these be solved?
(c)
For a sinusoidal signal (A coswt), find
the condition for no slope overload if step size
is and sampling period is T.
134.
(a)Draw a practical Linear Delta Modulator (LDM)
circuit and explain its operation.
b) Explain the limitations of LDM.
c)
How are limitations of LDM overcome in
ADM?
d)
Determine the output SNR of a LDM
system for 2 kHz sinusoidal input signal sampled
at 64 kHz. Slope overload distortion is not present
and reconstruction
filter has a bandwidth of 4 kHz.
135.
a)
A PCM system uses a uniform quantizer
15
1
3
15
1
1
5x6
1
2
5
2
followed by an n bit encoder. Show that if the input
to the system is a sinusoidal signal then SNR IS
approximately given by (1·8 + 6 n) dB.
b)
Explain the role of companding in pulse
code modulation.
c) The information in an analog signal
waveform is to be transmitted over a PCM system
with an accuracy of ± 0·1% (full scale). The analog
voltage waveform has a BW of 100 Hz and an
amplitude range of - 10 to + 10 volts. Find the
number of bits in each PCM word. Also find the
minimum bit rate in the PCM signal and minimum
transmission bandwidth required.
136.
a)
Define line coding. Write the properties of
line coding.(1+4)
b) What is Companding? Why is it needed in digital
communication? (2+3)c)What is meant by A-law and
µ law and where are they used? (5)
137.
Short Notes :
(a) Differential encoding
(b) Linear prediction coder
(c) Regenerative repeater.
(d) Zero forcing equalizer
(e) Inter symbol Interference
138.
(f) Adaptive Delta Modulation
For a given binary sequence 00111001 draw the ASK,
BPSK, BFSK
and
QPSK
modulated
5
waveform.
139.
What are the merits and demerits of DPSK over BPSK ?
5
5
2
140.
Compare the performances of BPSK, QPSK and
5
5
4
141.
OQPSK system.
Compare the performances of MSK and GMSK
5
5
4
system.
State advantages and disadvantages of M-ary PSK.
5
5
2
With a neat block diagram, explain the
5
5
2
142.
143.
modulation and demodulation of BPSK.
144.
State advantages and disadvantages of M-ary
5
5
2
145.
PSK
Why is the DPSK scheme of carrier modulation
5
5
4
5
5
4
5
4
5
2
5
2
used? Compare the bandwidth and probability of
error of QPSK, BPSK and
BFSK.
146.
Compare QPSK and OQPSK systems with respect
to the following factors:
i) Timing Diagram
ii) I - Q Diagram
147.
iii)iii) Non-linearity handling capability
a) With the help of a simplified diagram explain the 15
working of ASK modulator.
(b)
Sketch the binary ASK, FSK & PSK
waveform
for
the
following
bit
sequence
0110101001
(c) Derive the relation for error probability
148.
of binary ASK.
(a)
Explain the working of the coherent ASK 15
receiver and obtain the expression for probability
of error.
149.
(b) Why are non-coherent ASK receivers simpler
than coherent ASK receivers?
(c) (c) Why is FSK preferred over ASK? Give
reasons.
(a)
Explain the working principle of PSK, and 15
draw the modulator and demodulator block
diagram.
(b) Draw the signal space
representation and obtain the expression for
probability of error for BPSK.
150.
(a)
Mention the drawbacks of coherent
15
5
2
Draw the block diagram for generation 15
5
2
5
2
5
2
5
2
detection of BPSK signals.
(b)
Generate the differentially encoded
sequence fori/p binary sequence 10110110
(b) Draw the block diagram of a DPSK
transmitter and receiver and explain the
generation and detection of DPSK signals.
151.
(a)
and detection of the BFSK signal and explain
clearly its operation.
(b)
Draw the signal space representation and
find the distance between symbols.
(c) Obtain the expression for probability of
152.
error for BFSK.
(a) Draw the block diagram of a QPSK transmitter 15
and receiver and explain the generation and
detection of QPSK signals. Show its signal space
representation and the QPSK modulated
waveform for i/p sequence 01110010.
(b)
Compare QPSK with BPSK in terms of their error
probability.
(c) List the advantages and disadvantages
of DPSK modulation techniques.
a) Draw the block diagram for generation and 15
153.
detection of the BFSK signal and explain its
operation clearly.
(b)
Draw the signal space representation and
find the distance between symbols.
(c) What is the difference between MSK
154.
a)
and QPSK?
Draw the block diagram for generation and
15
noncoherent detection of BFSK signals and explain
the principle.
b)
In a communication system a QPSK
transmitter is used to transmit the data generated
by a DM system which takes 10 kHz sinusoidal
input and samples it at a rate 4 times greater than
theNyquist rate. Determine the bit rate of the DM
system and baud rate of output QPSK symbol.
c)
What is the difference between MSK and
QPSK?
155.
Short Note :
Gaussian Minimum Shift Keying (GMSK)
Orthogonal Frequency Division Multiplexing
Matched Filter
Minimum Shift Keying (MSK)
15
5
2