Digital Communications Multiple Choice Questions on “M-ary modulation and amplifiers”.
1. In M-ary FSK, as M increases error
A. Increases
B. Decreases
C. Does not get effected
D. Cannot be determined
Answer: B
Clarification: In M-ary FSK as M increases error decreases.
2. In M-ary FSK as M tends to infinity, probability of error tends to
A. Infinity
B. Unity
C. Zero
D. None of the mentioned
Answer: C
Clarification: In M-ary FSK as M tends to infinity, probability of error becomes zero.
3. For non coherent reception of PSK _____ is used.
A. Differential encoding
B. Decoding
C. Differential encoding & Decoding
D. None of the mentioned
Answer: C
Clarification: For non coherent reception of PSK, differential encoding is used at the transmitter and decoding is used at the receiver.
4. Which modulation technique have the same bit and symbol error probability?
A. BPSK
B. DPSK
C. OOK
D. All of the mentioned
Answer: D
Clarification: BPSK, DPSK, OOK and non coherent FSK have same bit and symbol error probability.
5. An amplifier uses ______ to take input signal.
A. DC power
B. AC power
C. DC & AC power
D. None of the mentioned
Answer: A
Clarification: An amplifier uses DC power to take an input signal and increase its amplitude at the output.
6. Which has 50% maximum power efficiency?
A. Class A
B. Class B
C. Class AB
D. None of the mentioned
Answer: A
Clarification: Class A amplifiers have 50% maximum power efficiency.
7. Which generates high distortion?
A. Class A
B. Class B
C. Class C
D. Class AB
Answer: C
Clarification: Class C amplifiers generate high distortion and it is closer to switch than an amplifier.
8. Class B linear amplifiers have maximum power efficiency of
A. 50%
B. 75%
C. 78.5%
D. None of the mentioned
Answer: C
Clarification: Class B linear amplifiers have maximum power efficiency of 78.5%.
9. Which has the maximum power efficiency?
A. Class A
B. Class B
C. Class C
D. Class AB
Answer: C
Clarification: Class C has the maximum power efficiency when compared to the other linear amplifiers.
10. Free space in idealization which consists
A. Transmitter
B. Receiver
C. Transmitter & Receiver
D. None of the mentioned
Answer: C
Clarification: Free space is an idealization that consists of only transmitter and receiver.
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