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Free download in PDF Digital Modulation Techniques Multiple Choice Questions and Answers for competitive exams. These short objective type questions with answers are very important for Board exams as well as competitive exams. These short solved questions or quizzes are provided by Gkseries.
(1)
In uniform quantization process
[A]
The step size remains same
[B]
Step size varies according to the values of the input signal
[C]
The quantizer has linear characteristics
[D]
Both a and c are correct
Answer: Both a and c are correct
(2)
Timing jitter is
[A]
Deviation in location of the pulses
[B]
Change in frequency
[C]
Change in amplitude
[D]
All of the above
Answer: Deviation in location of the pulses
(3)
Probability density function defines
[A]
Probability of error
[B]
Amplitudes of random noise
[C]
Density of signal
[D]
All of the above
Answer: Amplitudes of random noise
(4)
Pulse shaping is done
[A]
after line coding and modulation of signal
[B]
by limiting the bandwidth of transmission
[C]
to control Inter Symbol Interference
[D]
All of the above
(5)
For a noise to be white Gaussian noise, the optimum filter is known as
[A]
Matched filter
[B]
Bessel filter
[C]
Base band filter
[D]
Low pass filter
(6)
The time interval over which the received signal may be sampled without error may be explained by
[A]
Height of the eye opening of eye pattern
[B]
Rate of closure of eye of eye pattern
[C]
Width of eye opening of eye pattern
[D]
All of the above
Answer: Width of eye opening of eye pattern
(7)
Eye pattern is
[A]
Resembles the shape of human eye
[B]
May be seen on CRO
[C]
Is used to study ISI
[D]
All of the above
(8)
Advantages of using AMI
[A]
May be used for longer distance
[B]
Prevents build-up of DC
[C]
Needs least power as due to opposite polarity
[D]
All of the above
(9)
In Alternate Mark Inversion (AMI) is
[A]
0 is encoded as no pulse and 1 is encoded as negative pulse
[B]
0 is encoded as negative pulse and 1 is encoded as positive pulse
[C]
0 is encoded as positive pulse and 1 is encoded as negative pulse
[D]
0 is encoded as no pulse and 1 is encoded as positive or negative pulse
Answer: 0 is encoded as no pulse and 1 is encoded as negative pulse
(10)
For M equally likely messages, M>>1, if the rate of information R > C, the probability of error is
[A]
Close to unity
[B]
Unknown
[C]
Arbitrarily small
[D]
Not predictable
(11)
For M equally likely messages, M>>1, if the rate of information R ≤ C, the probability of error is
[A]
Not predictable
[B]
Close to unity
[C]
Arbitrarily small
[D]
Unknown
Answer: Arbitrarily small
(12)
The negative statement for Shannon’s theorem states that
[A]
If R > C, the error probability increases towards Unity
[B]
If R < C, the error probability is very small
[C]
Both a & b
[D]
None of the above
Answer: If R > C, the error probability increases towards Unity
(13)
According to Shannon Hartley theorem,
[A]
The channel capacity becomes infinite with infinite bandwidth
[B]
The channel capacity does not become infinite with infinite bandwidth
[C]
Has a tradeoff between bandwidth and Signal to noise ratio
[D]
Both B and C are correct
Answer: Both B and C are correct
(14)
The channel capacity is
[A]
The maximum information transmitted by one symbol over the channel
[B]
Information contained in a signal
[C]
The amplitude of the modulated signal
[D]
All of the above
Answer: The maximum information transmitted by one symbol over the channel
(15)
For M equally likely messages, the average amount of information H is
[A]
H = log2M
[B]
H = 2log10M
[C]
H = log10M
[D]
H = log10M2
(16)
The capacity of Gaussian channel is
[A]
C = 2B(1+S/N) bits/s
[B]
C = B2(1+S/N) bits/s
[C]
C = B(1+S/N) bits/s
[D]
C = B(1+S/N)2 bits/s
Answer: C = B(1+S/N) bits/s
(17)
The probability density function of a Markov process is
[A]
p(x1,x2,x3…….xn) = p(x1)p(x2/x1)p(x3/x2)…….p(xn/xn-1)
[B]
p(x1,x2,x3……xn) = p(x1)p(x2 * x1)p(x3 * x2)……..p(xn * xn-1)
[C]
p(x1,x2,x3…….xn) = p(x1)p(x1/x2)p(x2/x3)…….p(xn-1/xn)
[D]
p(x1,x2,x3……xn) = p(x1)p(x2)p(x3)…….p(xn)
Answer: p(x1,x2,x3…….xn) = p(x1)p(x2/x1)p(x3/x2)…….p(xn/xn-1)
(18)
Orthogonality of two codes means
[A]
The integrated product of two same code words is zero
[B]
The integrated product of two different code words is zero
[C]
The integrated product of two different code words is one
[D]
None of the above
Answer: The integrated product of two different code words is zero
(19)
The Golay code (23,12) is a codeword of length 23 which may correct
[A]
8 errors
[B]
2 errors
[C]
3 errors
[D]
5 errors
(20)
The prefix code is also known as
[A]
Convolutional code
[B]
Parity bit
[C]
Instantaneous code
[D]
Block code
Answer: Instantaneous code
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