# Signals

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

1. In the digital communication system, signals in different frequency bands are**a) Orthogonal**

b) Non orthogonal

c) Orthogonal & Non orthogonal

d) None of the mentioned

2. Properties of impulse function are

a) Symmetry

b) Time scaling

c) Shifting**d) All of the mentioned**

3. Properties of Fourier transform are

a) Duality property

b) Time shifting property

c) Modulation property**d) All of the mentioned**

4. A base-band signal can be up-converted using

a) Sine wave**b) Cosine wave**

c) Filtering

d) None of the mentioned

5. A band-pass signal can be down-converted using

a) Sine wave**b) Cosine wave**

c) Time delayed wave

d) None of the mentioned

6. In down-conversion multiplication with cosine wave is followed by**a) Low pass filter**

b) High pass filter

c) Bandpass filter

d) Bandstop filter

7. ADSL has _____ information channels.

a) One**b) Three**

c) Four

d) None of the mentioned

8. Fourier transform of a signal gives the

a) Frequency content

b) Bandwidth**c) Frequency content & Bandwidth**

d) None of the mentioned

9. Random things in a communication system are

a) Timing offset

b) Device frequency

c) Attenuation**d) All of the mentioned**

10. Which can be used for periodic and non periodic?

a) Fourier series**b) Fourier transforms**

c) Fourier series & transforms

d) None of the mentioned

11. A band-pass signal has a Fourier transform equal to

a) One**b) Zero**

c) Infinity

d) Cannot be determined

12. A band-pass signal has

a) DC component**b) No DC component**

c) No side lobes

d) Cannot be determined

13. Which are orthonormal signal representation?

a) Sine and cosine at same frequency

b) Wavelets

c) Complex sinusoids at a different frequency**d) All of the mentioned**

14. Constellation diagram is plotted in

a) Constellation space**b) Signal space**

c) Orthogonal space

d) Boundary space

15. Cumulative distributive function is

a) Non negative

b) Non decreasing**c) Non negative & decreasing**

d) None of the mentioned

16. Which are non negative functions?

a) PDF

b) PMF**c) PDF & PMF**

d) None of the mentioned