Digital Modulation Techniques Quiz | Digital Modulation Techniques Multiple Choice Questions and Answers

Questions
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

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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

Answer: 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

Answer: Matched 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

Answer: 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

Answer: 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

Answer: Close to unity
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

Answer: H = log2M
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

Answer: 3 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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