Signals

Digital Communications Systems

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

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