Analog and Digital Communication Systems MCQs

1. Which of the following is not a characteristic of analog communication?
A) High noise immunity
B) Infinite resolution
C) Susceptible to noise
D) Continuous signal representation
Answer: A

2. In analog communication, the signal is typically represented by:
A) Discrete values
B) Digital pulses
C) Continuous waveforms
D) Binary digits
Answer: C

3. The process of converting analog signals into digital form is known as:
A) Modulation
B) Demodulation
C) Sampling
D) Quantization
Answer: C

4. The bandwidth of an FM signal:
A) Depends on the frequency deviation and modulation index
B) Is independent of modulation index
C) Is only affected by frequency deviation
D) Is zero for pure sine wave modulation
Answer: A

5. Which modulation technique is used for transmitting digital data over analog channels?
A) Amplitude Modulation (AM)
B) Frequency Modulation (FM)
C) Phase Modulation (PM)
D) Quadrature Amplitude Modulation (QAM)
Answer: D

6. PCM stands for:
A) Pulse Code Modulation
B) Phase Code Modulation
C) Phase Continuous Modulation
D) Pulse Continuous Modulation
Answer: A

7. In PCM, quantization noise can be reduced by:
A) Increasing the sampling rate
B) Decreasing the number of quantization levels
C) Using a larger number of quantization levels
D) Increasing the amplitude of the signal
Answer: C

8. The Nyquist sampling theorem states that:
A) Sampling rate should be less than half the highest frequency component
B) Sampling rate should be more than half the highest frequency component
C) Sampling rate should be equal to the highest frequency component
D) There is no relationship between sampling rate and frequency component
Answer: A

9. Which of the following is an advantage of digital communication over analog communication?
A) Higher bandwidth efficiency
B) Lower security
C) More susceptible to noise
D) Limited dynamic range
Answer: A

10. The process of converting digital signals back into analog form is called:
A) Demodulation
B) Modulation
C) Sampling
D) D/A conversion
Answer: D

11. Which of the following is used to combine baseband signals for transmission over a common medium?
A) Demodulator
B) Modulator
C) Multiplexer
D) Oscillator
Answer: C

12. Which modulation technique is widely used in broadcast radio transmission?
A) QAM
B) AM
C) FM
D) PCM
Answer: B

13. Which of the following is not a type of digital modulation?
A) PSK (Phase Shift Keying)
B) FSK (Frequency Shift Keying)
C) AM (Amplitude Modulation)
D) QAM (Quadrature Amplitude Modulation)
Answer: C

14. In digital communication, FEC (Forward Error Correction) is used to:
A) Detect errors and request retransmission
B) Correct errors without the need for retransmission
C) Prevent errors during transmission
D) Reduce bandwidth requirements
Answer: B

15. A signal is sampled at a rate of 8 kHz. What is the Nyquist frequency for this signal?
A) 4 kHz
B) 8 kHz
C) 16 kHz
D) 32 kHz
Answer: B

16. Which of the following is a disadvantage of analog communication?
A) Higher fidelity
B) More immune to electromagnetic interference
C) Limited repeatability
D) Easier synchronization
Answer: C

17. The process of converting digital data into digital signals is known as:
A) Modulation
B) Demodulation
C) Digital-to-Analog Conversion
D) Analog-to-Digital Conversion
Answer: C

18. In digital communication, what does BER stand for?
A) Bit Error Rate
B) Bandwidth Error Rate
C) Binary Error Rate
D) Burst Error Rate
Answer: A

19. In a PCM system with 8-bit quantization, the number of possible quantization levels is:
A) 256
B) 128
C) 64
D) 512
Answer: A

20. Which of the following is a key characteristic of QAM?
A) It uses multiple carriers
B) It is only used for analog modulation
C) It uses phase modulation
D) It has low spectral efficiency
Answer: A

21. The Shannon-Hartley theorem relates to:
A) Maximum data rate over a channel
B) Minimum signal-to-noise ratio required for error-free communication
C) Minimum bandwidth required for a given data rate
D) Maximum modulation index for a carrier signal
Answer: A

22. Which modulation technique is commonly used in Wi-Fi (IEEE 802.11) systems?
A) AM
B) FM
C) PSK
D) QAM
Answer: D

23. Manchester encoding is a form of:
A) Line coding
B) Block coding
C) Carrier modulation
D) Spread spectrum modulation
Answer: A

24. In frequency modulation (FM), the frequency of the carrier signal varies:
A) Proportional to the instantaneous amplitude of the modulating signal
B) In discrete steps according to the modulating signal
C) Periodically in fixed intervals
D) Based on the phase of the modulating signal
Answer: A

25. In digital communication, what does ASK stand for?
A) Amplitude Shift Keying
B) Angle Shift Keying
C) Amplitude Spectrum Keying
D) Angle Spectrum Keying
Answer: A

26. In an analog communication system, which component is used to amplify weak signals?
A) Modulator
B) Demodulator
C) Mixer
D) Amplifier
Answer: D

27. Which of the following is true about the bandwidth of a digital signal?
A) It is always narrower than that of an analog signal
B) It depends on the modulation scheme and data rate
C) It is fixed and cannot be adjusted
D) It is always wider than that of an analog signal
Answer: B

28. The process of converting a continuous signal into a discrete signal is called:
A) Modulation
B) Sampling
C) Demodulation
D) Quantization
Answer: B

29. Which modulation technique is commonly used in satellite communication?
A) AM
B) FM
C) PSK
D) QPSK
Answer: D

30. The quantization noise in PCM systems is primarily due to:
A) Sampling rate
B) Quantization levels
C) Modulation index
D) Carrier frequency
Answer: B

31. The primary advantage of QPSK over BPSK is:
A) Higher data rate
B) Lower bandwidth requirement
C) Improved error performance
D) Simpler implementation
Answer: A

32. Which modulation technique is susceptible to the non-linear effects of the amplifier?
A) AM
B) FM
C) QAM
D) PSK
Answer: A

33. In an analog communication system, if the carrier frequency is 1 MHz, what is the upper sideband frequency for an AM signal with a modulation frequency of 5 kHz?
A) 995 kHz
B) 1.005 MHz
C) 1.0055 MHz
D) 5 kHz
Answer: B

34. In digital communication, Manchester encoding ensures:
A) Low power consumption
B) Long transmission range
C) Synchronization between transmitter and receiver
D) High spectral efficiency
Answer: C

35. Which of the following is a disadvantage of PCM compared to analog communication?
A) Higher signal-to-noise ratio
B) More susceptible to quantization noise
C) Greater bandwidth efficiency
D) Simpler modulation and demodulation
Answer: B

36. In an analog communication system, the bandwidth of an AM signal with modulation index 1 is:
A) Equal to the carrier frequency
B) Twice the sum of carrier and modulating signal frequencies
C) Equal to the sum of carrier and modulating signal frequencies
D) Equal to the modulating signal frequency
Answer: C

37. In digital communication, which technique is used to transmit data at different speeds in the same channel?
A) Multiplexing
B) Demultiplexing
C) Modulation
D) Codec
Answer: A

38. The power efficiency of AM (Amplitude Modulation) is:
A) 100%
B) Less than 100%
C) Greater than 100%
D) 50%
Answer: B

39. Which of the following is not a type of digital modulation?
A) PCM (Pulse Code Modulation)
B) PWM (Pulse Width Modulation)
C) PAM (Pulse Amplitude Modulation)
D) PSK (Phase Shift Keying)
Answer: C

40. In digital communication, what is the purpose of error detection and correction techniques?
A) To avoid modulation and demodulation
B) To increase the transmission power
C) To improve the signal-to-noise ratio
D) To ensure data integrity
Answer: D

41. The channel capacity of a communication system depends on:
A) Signal frequency
B) Signal amplitude
C) Signal bandwidth
D) Signal phase
Answer: C

42. Which of the following is a disadvantage of FDM (Frequency Division Multiplexing)?
A) High bandwidth efficiency
B) Complexity in demodulation
C) Low spectral efficiency
D) Reduced susceptibility to noise
Answer: B

43. Which digital modulation technique has higher spectral efficiency?
A) BPSK (Binary Phase Shift Keying)
B) QPSK (Quadrature Phase Shift Keying)
C) 16-QAM (Quadrature Amplitude Modulation)
D) 64-QAM (Quadrature Amplitude Modulation)
Answer: D

44. In PCM, what is the relationship between the sampling rate and the bandwidth of the signal?
A) Directly proportional
B) Inversely proportional
C) Not related
D) Equal
Answer: A

45. Which modulation technique is robust against phase shifts and amplitude variations in the channel?
A) QAM
B) PSK
C) FSK
D) PCM
Answer: B

46. In digital communication, which error detection technique uses a parity bit?
A) CRC (Cyclic Redundancy Check)
B) Hamming Code
C) Checksum
D) Reed-Solomon Code
Answer: B

47. What is the advantage of differential encoding in digital communication?
A) It reduces the need for synchronization
B) It increases the data rate
C) It decreases the complexity of modulation
D) It improves the error correction capability
Answer: A

48. Which of the following is a common technique for line coding in digital communication?
A) ASK
B) BPSK
C) NRZ
D) QAM
Answer: C

49. In digital communication, which technique is used to improve the efficiency of bandwidth utilization?
A) Synchronization
B) Scrambling
C) Modulation
D) Source coding
Answer: D

50. Which modulation technique is commonly used in fiber optic communication systems?
A) AM
B) FM
C) PSK
D) ASK
Answer: C

Analog and Digital Communication Systems MCQs

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