A system is defined by its impulse response h(n) = 2n u(n - 2). The system is
A. Stable and causal
B. Causal but not stable
C. Stable but not causal
D. Unstable and noncausal
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A discrete time linear shift-invariant system has an impulse response h[n] with h[0] = 1, h[1] = -1, h[2] = 2, and zero otherwise. The system is given an input sequence x[n] with x[0] = x[2] = 1 and zero otherwise. The number of nonzero samples in the output sequence y[n], and the value of y[2] are, respectively
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If the impulse response of a discrete-time system is h[n] = -5n u[- n - 1], then the system function H(z) is equal to
A. z − 5 − z and the system is stable
B. z − 5 z and the system is stable
C. z − 5 − z and the system is unstable
D. z − 5 z and the system is unstable
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For an N-point FFT algorithm with N = 2m , which one of the following statements is TRUE?
A. It is not possible to construct a signal flow graph with both input and output in normal order
B. The number of butterflies in the mn state is m N
C. In-place computation requires storage of only 2N node data
D. Computation of a butterfly requires only one complex multiplication
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A discrete-time signal x [n] = sin(π2 n), n being an integer, is
A. Periodic with period π
B. Periodic with period π2
C. Periodic with period 2 π
D. Not periodic
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Which one of the following is an eigen function of the class of all continuous-time, linear, time-invariant systems (u(t) denotes the unit-step function)?
A. ejω0 t u(t)
B. cos(ω0 t)
C. ejω0 t
D. sin(ω0 t)
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The Fourier Transform of a function x(t) is X(f). The Fourier transform of d t d x ( t ) will be
A. d t d x ( t )
B. j 2 π f X ( f )
C. j f X ( f )
D. j f X ( f )
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The magnitude and phase of the complex Fourier series coefficient a
k of a periodic signal x(t) are shown in the figure. Choose the correct statement from the four choices given. Notation: C is the set of complex number, R is the set of purely real numbers, and P is the set of purely imaginary numbers.
A. x ( t ) ∈ R
B. x ( t ) ∈ P
C. x ( t ) ∈ ( C − R )
D. The information given is not sufficient to draw any conclusion about x(t)
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Let the signal i(t) = 0 outside the interval [T1 , T2 ], where T1 and T2 are finite. Furthermore, |f(t)| < ∞. The region of convergence (ROC) of the signal's bilateral Laplace transform F(s) is
A. A parallel strip containing the j Ω axis
B. A parallel strip not containing the j Ω axis
C. The entire s-plane
D. A half plane containing the j Ω axis
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The z-transform F(z) of the function f(nT) = anT is
A. z − a T z
B. z + a T z
C. z − a − T z
D. z + a − T z
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The function x(t) is shown in the figure. Even and odd parts of a unit-step function u(t) are respectively,
A. 2 1 , 2 1 x ( t )
B. − 2 1 , 2 1 x ( t )
C. 2 1 , − 2 1 x ( t )
D. − 2 1 , − 2 1 x ( t )
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For the discrete-time system shown in the figure, the poles of the system transfer function are located at
A. 2, 3
B. 2 1 , 3
C. 2 1 , 3 1
D. 2 , 3 1
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Let x [ n ] = ( − 9 1 ) n u ( n ) − ( − 3 1 ) n u ( − n − 1 ) .
The Region of Convergence (ROC) of the z-transform of x[n]
A. Is ∣ z ∣ > 9 1
B. Is ∣ z ∣ < 3 1
C. Is 3 1 > ∣ z ∣ > 9 1
D. Does not exist
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An LTI system having transfer function s 2 + 2 s + 1 s 2 + 1 and input x(t) = sin(t + 1) is in steady state. The output is sampled at a rate ωs rad/s to obtain the final output {y(k)}. Which of the following is true?
A. y is zero for all sampling frequencies ωs
B. y is nonzero for all sampling frequencies ωs
C. y is nonzero for ωs > 2 but zero for ωs < 2
D. y is zero for ωs > 2 but nonzero for ωs < 2
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Let x[n] = x[-n]. Let X(z) be the z-transform of x[n]. If 0.5 + j0.25 is a zero of X(z), which one of the following must also be a zero of X(z).
A. 0.5 - j0.25
B. ( 0.5 + j 0.25 ) 1
C. ( 0.5 − j 0.25 ) 1
D. 2 + j4
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If G(f) represents the Fourier transform of a signal g(t) which is real and odd symmetric in time, then
A. G(f) is complex
B. G(f) is imaginary
C. G(f) is real
D. G(f) is real and non-negative
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Consider the sequence
x[n] = {-4 - j5, 1 + j2, 4}
The conjugate antisymmetric part of the sequence is
A. {-4 - j2.5, j2, 4 - j2.5}
B. {-j2.5, 1, j2.5}
C. {-j5, j2, 0}
D. {-4, 1, 4}
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If the region of convergence of x1 [n] + x2 [n] is 3 1 < ∣ z ∣ < 3 2 , then the region of convergence of x1 [n] - x2 [n] includes
A. 3 1 < ∣ z ∣ < 3
B. 3 2 < ∣ z ∣ < 3
C. 2 3 < ∣ z ∣ < 3
D. 3 1 < ∣ z ∣ < 3 2
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The Fourier series of an odd periodic function, contains only
A. Odd harmonics
B. Even harmonics
C. Cosine terms
D. Sine terms
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Increased pulse-width in the flat-top sampling, leads to
A. Attenuation of high frequencies in reproduction
B. Attenuation of low frequencies in reproduction
C. Greater aliasing errors in reproduction
D. No harmful effects in reproduction
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