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ECE Objective Questions { Discrete Time Signals and Systems }



22. The auto eorelation function of white noise is
A. a delta function
B. a constant
C. Gaussian
D. exp (? I t ) with usual notation

23. The spectral density of white noise is
A. exponential
B. uniform
C. Poisson
D. Gaussian

24. The probability density function of the envelope of narrow band noise is
A. Uniform
B. Gaussian
C. Rayleigh
D. Rician

25. The Fourier transform of a Gaussian time pulse is 1 z2 ? z
A. Uniform
B. a pair of impulses
C. Gaussian
D. Rayleigh

26. The z-transform of a system is H(z)= z- 0.2 If the ROC is VI < 0.2, then impulse response of the system is
A. (0.2) u[n]
B. (0.2) u[-n -1]
C. -(0.2)" u(n)
D. ?(O.2)n u(-n -I)

27. A causal LTI system is described by the difference equation 2yin] = ay[n -21- 2x[nl + 13x In -II The system is stable only if
A.a= 2 PI < 2
B. lal = 2 IRI > 2
C. u = 2, any value of 13
D. al = 2, any value of a

28. The region of convergence of the z-transform of a unit step function is
A. IZI > 1
B. Z <1
C. (Real part of z) > 0
D. (Real part of z) < 0

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