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 x_{1}(t) and x_{2}(t) be periodic signals with fundamental periods T1 and T2 respectively. Which of the following must be a rational number for x(t)=x_{1}(t)+x_{2}(t) to be periodic?

a) T_{1}+T_{2}

b) T_{1}-T_{2}**c) T _{1}/T_{2}**

d) T

_{1}*T

_{2}

18. Let x_{1}(t) and x_{2}(t) be periodic signals with fundamental periods T_{1} and T_{2} respectively. Then the fundamental period of x(t)=x_{1}(t)+x_{2}(t) is?**a) LCM of T _{1} and T_{2}**

b) HCF of T

_{1}and T

_{2}

c) Product of T

_{1}and T

_{2}

d) Ratio of T

_{1}to T

_{2}

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