Digital Communications

Classification of Signals

Question 1
Marks : +2 | -2
Pass Ratio : 100%
What is the period of a signal x(t)?
T
2T
T/2
None of the mentioned
Explanation:
A signal is said to be periodic if the duration of one complete cycle is T and it repeats itself after this duration.
Question 2
Marks : +2 | -2
Pass Ratio : 100%
Determine the periodicity and also find whether it is a power or energy signal?
Periodic and energy signal
Non periodic and energy signal
Periodic and power signal
Periodic and energy signal
Explanation:
This is non periodic as it does not repeat itself after any period. And on calculating we will get energy as 1/2a which is finite. Thus it is an energy signal.
Question 3
Marks : +2 | -2
Pass Ratio : 100%
Continuous Impulse signal is a power or energy signal?
Power signal
Energy signal
Both power and energy
Neither power nor energy signal
Explanation:
On calculating using the power and energy calculation formula we will arrive at it is neither power nor energy signal.
Question 4
Marks : +2 | -2
Pass Ratio : 100%
Find the fundamental period of 1+sin^2 (3Ï€/5)n.
10/3
5
3Ï€/5
None of the mentioned
Explanation:
sin2(3Ï€/5)n = (1-cos(6Ï€/5)n)/2 = 1/2-1/2cos(6Ï€/5)n ; period = 6Ï€/(5*2Ï€) = k/N = 3/5 ; N=5.
Question 5
Marks : +2 | -2
Pass Ratio : 100%
Discrete impulse signal is a power or energy signal?
Power signal
Energy signal
Both power and energy signal
Neither power or energy signal
Explanation:
On calculating using energy formula we will get the energy of this signal as 1 which is a finite value. Thus it is a energy signal.
Question 6
Marks : +2 | -2
Pass Ratio : 100%
Find the periodicity of the following signal. x(t)=cos((2Ï€/7)t)sin((3Ï€/5)t)
30
7
35
5/3
Explanation:
T1=2Ï€/2Ï€/7 = 7, T2=2Ï€/3Ï€/5=5/3, T1/T2=5/21, T=21T1 or 5T2, T=35.
Question 7
Marks : +2 | -2
Pass Ratio : 100%
Which signal is said to be power signal?
Infinite power and zero energy
Infinite power and non-zero energy
Finite power and infinite energy
Finite power and zero energy
Explanation:
A signal is said to be power signal if it has finite power and infinite energy.
Question 8
Marks : +2 | -2
Pass Ratio : 100%
Which signal is called as energy signal?
Finite energy and zero power
Finite energy and non-zero power
Infinite energy and zero power
Infinite energy and non-zero power
Explanation:
A signal is said to be an energy signal if it has finite energy and zero average power.
Question 9
Marks : +2 | -2
Pass Ratio : 100%
Check whether the signal is periodic or not?
Periodic with period π/2
Periodic with period 2
Periodic with period 2/Ï€
Not periodic
Explanation:
T1=2Ï€ /4 T2=2Ï€ /8, T1/T2 = 2 T=T1 or 2T2, T=Ï€ /2.
Question 10
Marks : +2 | -2
Pass Ratio : 100%
Which of the given signals are periodic?
x(t) = 4 cos(5Ï€t)
x(t) = u(t) – 1/2
x(t) = 4u(t) + 2sin(3t)
x[n] = 2sin(3n)
Explanation:
T=2Ï€ / 5Ï€ = 2/5, periodic with period 2/5.