Signals And Systems I

20 Questions | Total Attempts: 173

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Signals And Systems I

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Questions and Answers
  • 1. 
    A half – wave rectified sinusoidal waveform has a peak voltage of 10 V. Its average value and the peak value of the fundamental component are respectively given by:
    • A. 

      6.366,7.07

    • B. 

      3.183,7.07

    • C. 

      3.183,5

    • D. 

      6.366,5

  • 2. 
    Which of the following signals is not periodic?
    • A. 

      S(t) = cos 2t + cos 3t + cos 5t

    • B. 

      S(t) = exp(j8πt)

    • C. 

      Exp(-7t)sin 10πt

    • D. 

      S(t) = cos 2t cos 4t

  • 3. 
    The Laplace Transforms of the functions t u(t) and u(t) sin(t) are respectively:
    • A. 

      1/s^2 , s/( s^2+1)

    • B. 

      1/s , 1/( s^2+1)

    • C. 

      1/s^2 , 1/( s^2+1)

    • D. 

      S , s/( s^2+1)`

  • 4. 
    A system with an input x(t) and output y(t) is described by the relation: y(t)=t x(t).This system is
    • A. 

      linear and time-invariant (b) linear and time varying (c) non-linear and time-invariant

    • B. 

      linear and time varying

    • C. 

      Non-linear and time-varying

    • D. 

      non-linear and time-invariant

  • 5. 
    If a signal f(t) has energy E, the energy of the signal f(2t) is equal to  
    • A. 

      E

    • B. 

      E/2

    • C. 

      2E

    • D. 

      4E

  • 6. 
    Let x(t) be the input to a linear, time-invariant system. The required output is 4x(t-2). The transfer function of the system should be:
    • A. 

      4exp(j4*pi*f)

    • B. 

      2exp(-j8*pi*f)

    • C. 

      4exp(-j4*pi*f)

    • D. 

      2exp(j8*pi*f)

  • 7. 
    The impulse response h[n] of a linear time-invariant system is given by h[n]=u[n+3] + u[n+2] – 2 u[n-7] where u[n] is the unit step response sequence. The above system is:
    • A. 

      (a) Stable but not causal

    • B. 

      (b) Stable and causal

    • C. 

      (c) Causal but unstable

    • D. 

      (d) Unstable and not causal

  • 8. 
    If the Laplace transform of a signal y(t) is Y(s)= 1/(s(s-1)), then its final value is
    • A. 

      -1

    • B. 

      0

    • C. 

      1

    • D. 

      Unbounded

  • 9. 
    The input and output of a continuous time system are respectively denoted by x(t) and y(t). Which of the following descriptions is corresponds to a causal system? 
    • A. 

      Y(t) = x(t-2) + x(t+4)

    • B. 

      (b) y(t) = (t-4) x(t+1)

    • C. 

      (c) y(t) = (t+4) x(t-1)

    • D. 

      (d) y(t) = (t+5) x(t+5)

  • 10. 
    The output of this system, to the sinusoidal input x(t)=2cos(2t) for all the time t, is
    • A. 

      (a) 0

    • B. 

      (b) 2^(0.25) cos(2t-0.125*pi)

    • C. 

      (c) 2^(0.5) cos(2t-0.125*pi)

    • D. 

      (d) 2^(0.5) cos(2t-0.25*pi)

  • 11. 
    The trigonometric Fourier series of an even function does not even have the
    • A. 

      Dc term

    • B. 

      (b) Cosine terms

    • C. 

      (c) Sine terms

    • D. 

      (d) Odd terms `

  • 12. 
    A system with input x[n] and output y[n] is given as y[n]= (sin(5/6)*pi*n) x(n) .The system is (sin(5/6)*pi*n) x(n) .
    • A. 

      (a) linear, stable

    • B. 

      (b) non-linear, stable

    • C. 

      (c) linear, stable

    • D. 

      (d) linear, unstable

  • 13. 
    A 1kHz sinusoidal signal is ideally sampled at 1500 samples/sec and the sampled signal is passed through an ideal low pass filter with cut-off frequency 800 Hz. The output signal has the frequency  
    • A. 

      Zero Hz

    • B. 

      0.75 Hz

    • C. 

      0.5 Hz

    • D. 

      0.25 Hz

  • 14. 
    The covolution of an even and odd function yields
    • A. 

      Always an even function

    • B. 

      Always an odd function

    • C. 

      Both even and odd funtion

    • D. 

      Depends on the originals functions

  • 15. 
    The colvolution of two similar width rectangular functions yields
    • A. 

      Ramp

    • B. 

      Step

    • C. 

      Trapezoid

    • D. 

      Triangle

  • 16. 
    System linearity refers to which property?
    • A. 

      Additive

    • B. 

      Scaling

    • C. 

      Both additive and scaling

    • D. 

      Homogeneity

  • 17. 
    To  draw a signal which is both time scaled and time shifted,what is the order of operation?
    • A. 

      First scaling then shifting

    • B. 

      First shifting then scaling

    • C. 

      Order is immaterial

    • D. 

      None

  • 18. 
    In what range should Re(s) remain so that the L.T. of the function e(a+2)t+5  exists?
    • A. 

      Re(s) > a+2

    • B. 

      . Re(s) > a+7

    • C. 

      Re(s)

    • D. 

      Re(s) > a+5

  • 19. 
    Convolution of a step function with itself produces
    • A. 

      Step

    • B. 

      Ramp

    • C. 

      Parabolic

    • D. 

      Impulse

  • 20. 
    On expanding a time limited signal,its
    • A. 

      Energy remains unchanged

    • B. 

      Energy decreases

    • C. 

      Energy increases

    • D. 

      Not possible to comment

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