Modulation Techniques

Digital Communications Systems

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

1. Average energy per bit is given by
a) average energy symbol/log2 M
b) average energy symbol * log2 M
c) log2 M/ Average energy symbol
d) none of the mentioned

2. Which FSK has no phase discontinuity?
a) Continuous FSK
b) Discrete FSK
c) Uniform FSK
d) None of the mentioned

3. FSK reception is
a) Phase Coherent
b) Phase non coherent
c) Phase Coherent & non coherent
d) None of the mentioned

4. FSK reception uses
a) Correlation receiver
b) PLL
c) Correlation receiver & PLL
d) None of the mentioned

5. In non coherent reception _____ is measured.
a) Phase
b) Energy
c) Power
d) None of the mentioned

6. Every frequency has ____ orthogonal functions.
a) One
b) Two
c) Four
d) Six

7. If we correlate the received signal with any one of the two orthogonal function, the obtained inner product will be
a) In phase
b) Quadrature
c) Zero
d) Cannot be determined

8. If we correlate the received signal with both orthogonal function the inner product will be
a) In phase
b) Quadrature
c) In phase and quadrature
d) Unity

9. Simulation is used to determine
a) Bit error rate
b) Symbol error rate
c) Bit error
d) Symbol error

10. Matched filter is a _____ technique.
a) Modulation
b) Demodulation
c) Modulation & Demodulation
d) None of the mentioned
.

11. Which is called as on-off keying?
a) Amplitude shift keying
b) Uni-polar PAM
c) Amplitude shift keying & Uni-polar PAM
d) None of the mentioned

12. QAM uses ______ as the dimensions.
a) In phase
b) Quadrature
c) In phase & Quadrature
d) None of the mentioned

13. Which has same probability of error?
a) BPSK and QPSK
b) BPSK and ASK
c) BPSK and PAM
d) BPSK and QAM

14. Which system uses QAM?
a) Digital microwave relay
b) Dial up modem
c) Digital microwave relay & Dial up modem
d) None of the mentioned

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