Analog andDigital Communicationonline bits2
- 1. DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING II B.Tech, II Semester –Quiz-I Course Name: ANALOG & DIGITAL COMMUNICATIONS 1. The costas receiver is used for a) FM signal b) DSB-SC signal c) PCM signal d) DM signal 2. Vestigial side band signals are detected by a) Filters b) Synchronous detection c) Balanced modulator d) None of the above 3. Limitations of Frequency discrimination method are: a) Cannot be used for video signals b) Designing of band pass filter is difficult c) Both a and b d) None of the above 4. Generation of SSB SC signal is done by a) balanced modulator b) Frequency discrimination method c) Product modulator d) Both a and b
- 2. 5. Noise power at the resistor is affected by the value of the resistor as a) Directly proportional to the value of the resistor b) Inversely proportional to the value of the resistor c) Unaffected by the value of the resistor d) Becomes half as the resistance value is doubled 6. Low frequency noise is a) Transit time noise b) Flicker noise c) Shot noise d) None of the above 7. Hilbert transform may be used in a) Generation of SSB signals b) Representation of band pass signals c) Designing of minimum phase type filters d) All of the above 8. For over modulation, the value of modulation index m is a) m<1 b) m = 1 c) m > 1 d) Not predetermined 9. Bandwidth required in SSB-SC signal is (fm is modulating fr Bandwidth required in SSB- SC signal is (fm is modulating frequency): a) 2fm b) < 2fm c) > 2fm d) fm 10. What is the need of doing Pre emphasis?
- 3. a) For boosting of modulating signal voltage b) For boosting of modulating signal frequency c) For removing amplitude variations due to noise d) For removing frequency variations 11. A distorted signal of frequency fm is recovered from a sampled signal if the sampling frequency fs is a) fs > 2fm b) fs < 2fm c) fs = 2fm d) fs ≥ 2fm 12. What is used to generate a DSB signal? a) Balanced modulator b) Carrier suppressor c) Antimodulator d) Sideband suppressor 13. Which of the following is an advantage of SSB over DSB? a) No change in spectrum space b) Reduce in spectrum space c) Carrier is suppressed d) Power is not wasted on the carrie 14. Why is no carrier signal transmitted when the amplitude of the modulating signal is 0 in an SSB transmission? a) Attenuation b) Undermodulation c) No sideband is generated d) All the sideband is suppressed 15. Which one of the following is not true with respect to SSB signal?
- 4. a) Hard to demodulate b) Less power c) Carrier is suppressed d) Very low range 16. The low power carrier transmitted with SSB signal is called as? a) SSB carrier b) Dummy carrier c) Fake carrier d) Pilot carrier 17. The value of a change in frequency of the carrier wave by the modulating signal is called as? a) Maximum modulation frequency b) Maximum carrier frequency c) Maximum carrier frequency d) Modulating frequency deviation 18. What is the ratio of frequency deviation to the modulating frequency is known as? a) Frequency index b) Frequency ratio c) Modulation index d) Modulation ratio 19. In NBFM, the modulation index is close to __________ a) 1 b) greater than 1 c) 10 d) infinite 20. Quantization noise occurs in ________
- 5. a) Frequency Division Multiplexing b) Time Division Multiplexing c) Delta Modulation d) Amplitude Modulation 21. When bandwidth is the major consideration a narrow and wide band FM can be approximated to? a) DSB-SC b) SSB c) VSB d) AM 22. What is the expected modulation index in case of narrow band FM? a) less than or equal to 1 b) infinite c) 1.5 d) more than 1 23. Envelope detector consists of a) Rectifier and high pass filter b) Rectifier and low pass filter c) Amplifier and low pass filter d) Amplifier and high pass filter 24. The minimum tone separation corresponds to a) T b) 1/T c) 2T d) T/2 25. Costa’s receiver is used for ________ a) coherent detection of AM-SC signal
- 6. b) asynchronous detection of AM-SC signal c) amplification of signal d) frequency mixing of signal 26. FM signal is better than AM signal because a) Less immune to noise b) Less adjacent channel interference c) Amplitude limiters are used to avoid amplitude variations d) All of the above 27. Wide band FM has the characteristics a) The frequency sensitivity kf is large b) Bandwidth is wide c) Both a and b d) None of the above 28. Guard bands are provided in FM signal to a) Prevent interference from adjacent channels b) To increase the noise c) To increase bandwidth d) None of the above 29. Maximum frequency deviation and the maximum bandwidth allowed for commercial FM broadcast is a) 80KHz, 160Khz b) 75KHz, 200Khz c) 60KHz, 170Khz d) 75KHz, 250Khz
- 7. 30. After passing the FM signal through mixer, what is the change in the frequency deviation Δ when the modulating frequency is doubled? a) Becomes 2 Δ b) Becomes Δ /2 c) Becomes Δ2 d) Remains unchanged ----------Key---------- 1. (b) 2. (b) 3. (c) 4. (d) 5. (c) 6. (b) 7. (d) 8. (c) 9. (d) 10. (a) 11. (b) 12. (a) 13. (b) 14. (c) 15. (a) 16. (d) 17. (c) 18. (b) 19. (a)
- 8. 20. (d) 21. (d) 22. (a) 23. (b) 24. (b) 25. (a) 26. (d) 27. (c) 28. (a) 29. (b) 30. (d)