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Electronics Engineering Objective Questions { Digital Communication System }

239. Noise with uniform power spectral density of No W/Hz is passed through a filter H(o))= 2 exp (--joAd) followed by an ideal low pass filter of bandwidth B Hz. The output noise power in Watts is
A. 2 NoB
B. 4 NoB
C. 8 NoB
D. 16 NoB
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240. A low-pass filter having. a frequency response H (jot)) = A (co) ellKw) does not produce any phase distortion, if
A. A(co) = Cw2, q(.o) = kw3
B.A(w) = Cco2, 0(co) = kw
C.A(co) = Co), 40) = ko32
D. AO)) = C, 4(o) = koC1
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241. The minimum sampling frequency (in samples/sec) required to reconstruct the following signal from its samples without distortion
A.2 x 103
B. 4 x 103
C.6 x 103
D. 8 x 103
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242. A zero- mean white Gaussian noise is passed through an ideal lowpass filter of bandwidth 10 kHz. The output is the uniformly sampled with sampling period ts = 0.03 msec. The samples so obtained would be
A. correlated
B. statistically independent
C. uncorrelated
D. orthogonal
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243. A message signal with bandwidth 10 kHz is Lower-Side Band SSB modulated with carrier frequency fci = 106 Hz. The resulting signal is then passed through a Narrow-Band Frequency Modulator with carrier frequency f2 =109Hz.The bandwidth of the output would be
A. 4 x 10 Hz
B. 2 x 106 Hz
C. 2 x 109Hz
D.2 x 101?Hz
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244. The following two questions refer wide sense stationary stochastic processesI. It is desired to generate a stochastic process (as voltage process) with power spectral density.by driving a Linear-Time-Invariant system by zero mean white noise (as voltage process) with power spectral density being constant equal to I. The system which can perform the desired task could be
A. first order lowpass R-L filter
B. first order highpass R-C filter
C. tuned L-C filter
D. series R-L filter
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245. The parameters of the system obtained in above question would be
A. first order R-L lowpass filter would have R= 412, L= 4H
B.first order R-C highpass filter would have R = 4S-1, C = 0.25 F
C. tuned L-C filter would have L = 4H, C = 4F
D. series R-L-C lowpass filter would have R = 10, L= 4H, C 4F
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