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ECE Objective Questions { Discrete Time Signals and Systems }



8. The difference equation for this system relating any input x[n] and the corresponding output yin] is
A. 3y[n] - 2y[n - 1] = 2x[n]
B. 3y[n] - 2y(n - 1) = 2x[n - 1]
C. 3y[n] - 2y[n + 1] = 2x[n + 1]
D. 3y[n] - 2[y + 1] = 2x[n]

9.  Which one of the following is the region of convergence (ROC) for the sequence In] = b" u(n) + b-n u(-n-1); Ibl < 1?
A. Region 14 < 1
B. Annular strip in the region b> zi> 1
C. Region izi > 1
D. Annular strip in the region b < Izi < 1

10. The system described by the difference equation y(n)-2y (n-1)+y(n-2)= x(n)-x(n-1) has y(n)= 0 and n<0. If x(n) = 8(n), then y(2) will be
A.2
B.1
C. zero
D.-1

11. Given that F(z) and G(z) are the one-sided Z transforms of discrete time functions f(nT) and g(nT), the Z transform of Ef(kT) g(nT - kT) is given by
A. Ef(nT) g(nT)z-n
B. Ef(nT)z "Eg(nT)z-s"
C. Ef(kT) g(nT - kT)z-n
D. Ef(nT - kT) g(nT)z-n

12. Which one of the following represents the impulse response of a system defined by H(z) = z-1"?
A. u[n-m]
B. 6[n-m]
C. S[m]
D. km-n]

13. If the function I-11(z) = (1 + 1.5 z-l-z-2) and H2(Z) = Z2 + 1.5 z-I, then
A. the poles and zeros of the functions will be the same
B. the poles of the functions will be identical but not zeros
C. the zeros of the functions will be identical but not the poles
D. neither the poles nor the zeros of the two functions will be identical

14. Consider the following statements regarding a linear discrete-time system Z2 +H(z) -(z + 0.5)(z - 0.5) 1. The system is stable. 2. The initial value h(0) of the impulse response is -4. 3. The steady-state output is zero for a sinusoidal discrete-time input of frequency equal to one-fourth the sampling frequency? Which of the statements are correct?
A. 1, 2 and 3
B. 1 and 2
C. 1 and 3
D. 2 and 3

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