Signal Classification

Digital Communications Systems

This set of Digital Communications Multiple Choice Questions & Answers (MCQs) focuses on “Classification of Signals”.

1. What is the period of a signal x(t)?
a) T
b) 2T
c) T/2
d) None of the mentioned

2. Which of the given signals are periodic?
a) x(t) = 4 cos(5πt)
b) x(t) = u(t) – 1/2
c) x(t) = 4u(t) + 2sin(3t)
d) x[n] = 2sin(3n)

3. Check whether the signal is periodic or not?
x(t) = cos(4t) + 2sin(8t)
a) Periodic with period π/2
b) Periodic with period 2
c) Periodic with period 2/π
d) Not periodic

4. Find the periodicity of the following signal. x(t)=cos((2π/7)t)sin((3π/5)t)
a) 30
b) 7
c) 35
d) 5/3

5. Find the fundamental period of 1+sin^2 (3π/5)n.
a) 10/3
b) 5
c) 3π/5
d) None of the mentioned

6. Which signal is called as energy signal?
a) Finite energy and zero power
b) Finite energy and non-zero power
c) Infinite energy and zero power
d) Infinite energy and non-zero power

7. Which signal is said to be power signal?
a) Infinite power and zero energy
b) Infinite power and non-zero energy
c) Finite power and infinite energy
d) Finite power and zero energy

8. Determine the periodicity and also find whether it is a power or energy signal?
e(-at)u(t)
a) Periodic and energy signal
b) Non periodic and energy signal
c) Periodic and power signal
d) Periodic and energy signal

9. Continuous Impulse signal is a power or energy signal?
a) Power signal
b) Energy signal
c) Both power and energy
d) Neither power nor energy signal

10. Discrete impulse signal is a power or energy signal?
a) Power signal
b) Energy signal
c) Both power and energy signal
d) Neither power or energy signal

11. A unit impulse function has?
a) Large amplitude
b) Zero pulse width
c) Unity weight
d) All of the mentioned

12. Which of the following is done to convert a continuous time signal into discrete time signal?
a) Modulating
b) Sampling
c) Differentiating
d) Integrating

13. The deflection voltage of an oscilloscope is a ‘deterministic’ signal.
a) True
b) False

14. The even part of a signal x(t) is?
a) x(t)+x(-t)
b) x(t)-x(-t)
c) (1/2)*(x(t)+x(-t))
d) (1/2)*(x(t)-x(-t))

15. Which of the following is the odd component of the signal x(t)=e(jt)?
a) cost
b) j*sint
c) j*cost
d) sint

16. For a continuous time signal x(t) to be periodic with a period T, then x(t+mT) should be equal to ___________
a) x(-t)
b) x(mT)
c) x(mt)
d) x(t)

17. Let x1(t) and x2(t) be periodic signals with fundamental periods T1 and T2 respectively. Which of the following must be a rational number for x(t)=x1(t)+x2(t) to be periodic?
a) T1+T2
b) T1-T2
c) T1/T2
d) T1*T2

18. Let x1(t) and x2(t) be periodic signals with fundamental periods T1 and T2 respectively. Then the fundamental period of x(t)=x1(t)+x2(t) is?
a) LCM of T1 and T2
b) HCF of T1and T2
c) Product of T1 and T2
d) Ratio of T1 to T2

19. All energy signals will have an average power of ___________
a) Infinite
b) Zero
c) Positive
d) Cannot be calculated

20. x(t) or x(n) is defined to be an energy signal, if and only if the total energy content of the signal is a ___________
a) Finite quantity
b) Infinite
c) Zero
d) None of the mentioned

20. What is the period of cos2t+sin3t?
a) pi
b) 2*pi
c) 3*pi
d) 4*pi

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