Pulse Code Modulation (PCM) MCQ
Pulse Code Modulation (PCM) MCQ, MCQ on Pulse Code Modulation, MCQ on PCM, Objective questions on PCM, Objectives on Pulse Code Modulation, Pulse Code Modulation MCQ with Answer, Multiple Choice Question on PCM, Pulse Code Modulation Objectives with answers, MCQ on PWM, MCQ on PAM, Engineering MCQ
Multiple-Choice Questions
Q.1. In PCM, the quantization noise depends on
- sampling rate
- number of quantization levels
- signal power
- none of the above
Answer: number of quantization levels
Q.2. Which of the following modulation is digital in nature
- PAM
- PPM
- DM
- none of the above
Answer: DM
Q.3. Which of the following modulation is analog in nature
- PCM
- DPCM
- DM
- none of the above
Answer: none of the above
Q.4. In PCM, if the number of quantization levels is increased from 4 to 64, then the bandwidth requirement will approximately be
- 3 times
- 4 times
- 8 times
- 16 times
Answer: 3 times
Q.5. Quantization noise occurs in
- PAM
- PWM
- DM
- none of the above
Answer: DM
Q.6. Companding is used in PCM to
- reduce bandwidth
- reduce power
- increase S/N ratio
- get almost uniform S/N ratio
Answer: get almost uniform S/N ratio
Q.7. Pulse stuffing is used in
- synchronous TDM
- asynchronous TDM
- any TDM
- none of the above
Answer: asynchronous TDM
Q.8. The main advantage of PCM is
- less bandwidth
- less power
- better performance in presence of noise
- possibility of multiplexing
Answer: better performance in presence of noise
Q.9. The main disadvantage of PCM is
- large bandwidth
- large power
- complex circuitry
- quantization noise
Answer: large bandwidth
Q.10. The main advantage of DM over PCM is
- less bandwidth
- less power
- better S/N ratio
- simple circuitry
Answer: simple circuitry
Q.11. In a DM system, the granular noise occurs when modulating signal
- increases rapidly
- decreases rapidly
- changes within the step size
- has high frequency component
Answer: changes within the step size
Q.12. Pick the odd man out
- URZ
- BRZ
- Manchester code
- differential code
Answer: Manchester code
Q.13. The number of bits per sample in a PCM system is increased from 8 to 16. The bandwidth of the system will increase
- 8 times
- 2 times
- 1/2 times
- 28 times
Answer: 2 times
Q.14. The standard data rate of a PCM voice channel is
- 8 kbps
- 8 bps
- 16 bps
- 64 kbps
Answer: 64 kbps
Q.15. The signal-to-quantization noise ratio for a sinusoidal signal quantized using 10 bit PCM is:
- 62 dB
- 10 dB
- 60 dB
- 32 dB
Answer: 62 dB
Q.16. The output SNR in a DM system for a 1 kHz sinusoid sampled at 32 kHz without slope overload and followed by a 4 kHz post-reconstruction filter is given as
- 30.6 dB
- 8 dB
- 24.9 dB
- 20 dB
Answer: 24.9 dB
Q.17. The line code that has zero d.c. component for pulse transmission of random binary data is
- UP-NRZ
- UP-RZ
- BPRZ-AMI
- BPNRZ
Answer: BPRZ-AMI
Q.18. The number of bits per sample in a PCM system with sinusoidal input is increased from n to n +1. The improvement in signal to quantization noise ratio will be
- 3 dB
- 6 dB
- 2n dB
- n dB
Answer: 6 dB
Q.19. The word length of a 64 quantization level PCM for S = 2 is
- 3
- 4
- 5
- 6
Answer: 6
Q.20. The word length of a 64 quantization level PCM for S = 4 is
- 3
- 4
- 5
- 6
Answer: 3
Q.21. In a PCM system, the number of quantization levels is 32 and the maximum signal frequency is 4 kHz. The bit transmission rate is
- 8 kbps
- 16 kbps
- 32 kbps
- 40 kbps
Answer: 40 kbps
Q.22. For a PCM system with 256 quantization levels, the sampling frequency is 10 kHz. The BW is
- 20 kHz
- 40 kHz
- 80 kHz
- 10 kHz
Answer: 40 kHz
Q.23. The bandwidth required for transmission of high quality speech is
- 10 kHz
- 15 kHz
- 4 kHz
Answer: 15 kHz
Q.24. Consider the following statements comparing delta modulation with PCM systems: DM requires
- a lower sampling rate
- a higher sampling rate
- a large bandwidth
- simpler hardware
Which of these statements are correct?
- 1, 2 and 4
- 1, 2 and 3
- 1, 3 and 4
- 2, 3 and 4
Answer: 2, 3 and 4
Q.25. The ramp signal m(t) = at is applied to a delta modulator with sampling period Ts, and step size δ. Slope overload distortion would occur if
- δ< a
- δ> a
- δ < aTs
- δ> aTs
Answer: δ < aTs
Q.26. In asynchronous TDM, for n signal sources, each frame contains m slots, where m is usually
- less than n
- 2n
- n
- greater than 2n
Answer: n
Q.27. A sinusoidal signal with peak-to-peak amplitude of 1.536 V is quantized in 128 levels using a mid-rise uniform quantizer. The quantization noise power is
- 0.768 V
- 48 x 10-6 V2
- 12 x 10-6 V2
- 3.072 V
Answer: 12 x 10-6 V2
Q.28. In a PCM system, if the code-word length is increased from 6 to 8 bits, the signal-to-quantization noise ratio improves by the factor
- 8/6
- 12
- 16
- 8
Answer: 16
Q.29. In the output of a DM speech encoder, the consecutive pulses are of opposite polarity during time interval t1 < t < t2. This indicates that during this internal
- the input to the modulator is essentially constant
- the modulator is going through slope overload
- the accumulator is in saturation
- the speech signal is being sampled at the Nyquist rate
Answer: the input to the modulator is essentially constant
Q.30. The minimum step-size required for a delta-modulator operating at 32 K samples/second to track the signal [u(t) being the unit step function]
x(t)=125t[u_{t}-u_{t-1}]+(250-125t)[u_{t-1}-u_{t-2}]so that slope-overload is avoided, would be
- 2^{-10}
- 2^{-8}
- 2^{-6}
- 2^{-4}
Answer: 2^{-8}
Q.31. In delta modulation, the slope overload distortion can be reduced by
- decreasing the step size
- decreasing the granular noise
- decreasing the sampling rate
- increasing the step size
Answer: increasing the step size
Q.32. Which is the most important sub-system for recovering and reconstructing signals in a TDM system?
- Envelope detector followed by a low pass filter
- Synchronization circuit for proper timing
- Bandpass filters to segregate channels
- Coherent detector to ensure frequency and phase correction
Answer: Coherent detector to ensure frequency and phase correction
Q.33. Which one of the following is correct?
In a TDM system, each signal is allotted in a frame a unique and fixed
- frequency slot
- time slot
- amplitude slot
- phase slot
Answer: time slot
Q.34. A speech signal band limited to 4 kHz and peak-to-peak voltage varying between +5 V and -5 V, is sampled at the Nyquist rate. Each sample is quantized and represented by 8 bits. The number of quantization levels required to reduce the quantization noise by a factor of 4 would be
- 1024
- 512
- 256
- 64
Answer: 512