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GATE EC : Communications Champion Quiz 1

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Question 1

The power spectral density of a real process X(t) for positive frequencies is shown below. The values of E[X2(t)] and |E[X(t)]|, respectively, are

Question 2

The force on a point charge + q kept at a distance d from the surface of an infinite grounded metal plate in a medium of permittivity is

Question 3

X(t) is a stationary random process with autocorrelation function . This process is passed through the system shown below. The power spectral density of the output process Y(t) is

Question 4

A low-pass filter having a frequency response H(jω) = A(ω) jφ(ω) does not produce any phase distortion if

Question 5

The signal cos Description: Description: D:\GradeStack Courses\GATE Tests (Sent by Ravi)\GATE EC 10-Mar\GATE-ECE-2015-Paper-2_files\image070.png is ideally sampled at a sampling frequency of 15 Hz. The sampled signal is passed through a filter with impulse response Description: Description: D:\GradeStack Courses\GATE Tests (Sent by Ravi)\GATE EC 10-Mar\GATE-ECE-2015-Paper-2_files\image071.png. The filter output is

Question 6

A zero mean white Gaussian noise having power spectral densityDescription: Description: D:\GradeStack Courses\GATE Tests (Sent by Ravi)\GATE EC 10-Mar\GATE-ECE-2015-Paper-2_files\image216.png is passed through an LTI filter whose impulse response h(t) is shown in the figure. The variance of the filtered noise at t = 4 is
Description: Description: D:\GradeStack Courses\GATE Tests (Sent by Ravi)\GATE EC 10-Mar\GATE-ECE-2015-Paper-2_files\image217.jpg

Question 7

The efficiency of Huffman code is linearly proportional to

Question 8

Noise with double-sided power spectral density of K over all frequencies is passed through a RC low pass filter with 3dB cut-off frequency of fc. The noise power at the filter output is

Question 9

A random binary wave y(t) is given by
Description: D:\GradeStack Courses\GATE Tests (Sent by Ravi)\GATE EC 10-Mar\GATE-ECE-2015-Paper-3_files\image236.png
Where p(t) = u(t) – u(t –T), u(t) is the unit function and f is an independent random variable with uniform distribution in [0, T]. The sequence {Xn} consists of independent and identically distributed binary valued random variables with P{Xn = +1} = P{Xn = –1} = 0.5 for each n.
The value of autocorrelation Description: D:\GradeStack Courses\GATE Tests (Sent by Ravi)\GATE EC 10-Mar\GATE-ECE-2015-Paper-3_files\image237.pngequals______.

Question 10

A zero-mean white Gaussian noise is passed through an ideal low-pass filter of bandwidth 10 kHz. The output is then uniformly sampled with sampling period ts = 0.03 m sec. the samples so obtained would be
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Jun 2ESE & GATE EC