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
View Answer
Explanation: Average energy per bit is given by average energy symbol divided by log2 M.
2. Which FSK has no phase discontinuity?
a) Continuous FSK
b) Discrete FSK
c) Uniform FSK
d) None of the mentioned
View Answer
Explanation: Continuous frequency shift keying has no phase discontinuity between symbols.
3. FSK reception is
a) Phase Coherent
b) Phase non coherent
c) Phase Coherent & non coherent
d) None of the mentioned
View Answer
Explanation: Reception of FSK can be either phase coherent or phase non coherent.
4. FSK reception uses
a) Correlation receiver
b) PLL
c) Correlation receiver & PLL
d) None of the mentioned
View Answer
Explanation: Frequency shift keying uses correlation receiver and phase locked loop.
5. In non coherent reception _____ is measured.
a) Phase
b) Energy
c) Power
d) None of the mentioned
View Answer
Explanation: In non coherent reception of FSK, energy in each frequency is measured.
6. Every frequency has ____ orthogonal functions.
a) One
b) Two
c) Four
d) Six
View Answer
Explanation: Every frequency has two orthogonal functions – sine and cosine.
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
View Answer
Explanation: If we correlate the received signal with only one of the orthogonal function for example sine, the inner product obtained will be zero.
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
View Answer
Explanation: If we correlate the received signal with both the orthogonal function, the two inner products obtained will be in phase and quadrature.
9. Simulation is used to determine
a) Bit error rate
b) Symbol error rate
c) Bit error
d) Symbol error
View Answer
Explanation: A simulation of digital communication system is used to estimate bit error rate.
10. Matched filter is a _____ technique.
a) Modulation
b) Demodulation
c) Modulation & Demodulation
d) None of the mentioned
View Answer
Explanation: Matched filter is a demodulation technique with LTI.
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
View Answer
Explanation: Amplitude shift keying and uni-polar PAM both schemes are called as on off keying.
12. QAM uses ______ as the dimensions.
a) In phase
b) Quadrature
c) In phase & Quadrature
d) None of the mentioned
View Answer
Explanation: QAM uses in phase and quadrature which is cosine and sine respectively as the dimensions.
13. Which has same probability of error?
a) BPSK and QPSK
b) BPSK and ASK
c) BPSK and PAM
d) BPSK and QAM
View Answer
Explanation: BPSK is similar to bipolar PAM and both have same probability of error.
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
View Answer
Explanation: Digital microwave relay, dial up modem and etc uses QAM modulation technique.
Sanfoundry Global Education & Learning Series – Digital Communications.
To practice all areas of Digital Communications, here is complete set of 1000+ Multiple Choice Questions and Answers.
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