This set of Digital Communications Multiple Choice Questions & Answers (MCQs) focuses on “Sources of corruption”.
1. The main sources of corruption are
a) Sampling and quantizing effects
b) Channel effects
c) Sampling, quantizing and channel effects
d) None of the mentioned
View Answer
Explanation: The analog signal obtained from sampling quantization and transmitted pulses will have corruption from several sources in which the two main sources are quantizing and sampling effect and channel effect.
2. The distortion in quantization is called as
a) Round off error
b) Truncation error
c) Round off & Truncation error
d) None of the mentioned
View Answer
Explanation: After sampling and quantization of input signals, the ouput sampled sequence consists of some distortion which can be called as round off error or truncation error.
3. In quantization process, the amount of quantization noise is _______________ to number of levels.
a) Directly proportional
b) Inversely proportional
c) Independent
d) None of the mentioned
View Answer
Explanation: The distortion introduced to approximate the analog signal is called as quantization noise. The amount of this noise is inversely proportional to number of levels employed in quantization process.
4. Saturation noises can be avoided or reduced by
a) Automatic gain control
b) Amplifying
c) Filtering
d) None of the mentioned
View Answer
Explanation: When the difference between input and output signal increases, we say that analog to digital converter is working in saturation. This introduces saturation noise or error. This can be reduced by using automatic gain control.
5. Timing jitter can be reduced by
a) Good power supply isolation
b) Stable clock reference
c) Good power supply isolation & Stable clock reference
d) None of the mentioned
View Answer
Explanation: Jitter occurs when there is a slight position change in the sampled signals. This timing jitter can be controlled by power supply isolation and clock reference.
6. The reasons for the threshold effect are
a) Thermal noise
b) Interference from other users
c) Interference from circuit switching transients
d) All of the mentioned
View Answer
Explanation: The channel noise which is caused by thermal noise interference from other users and circuit switching transients is called as threshold effect.
7. When channel bandwidth is greater than the pulse bandwidth, it causes
a) Intersignal interference
b) Intersymbol interference
c) Bandwidth error
d) None of the mentioned
View Answer
Explanation: When channel bandwidth is greater than pulse bandwidth, the signal widens and expands exceeding the symbol duration which causes intersymbol interference.
8. The _____________ corresponds to average quantization noise power.
a) Mean
b) Variance
c) Probability density function
d) None of the mentioned
View Answer
Explanation: The variance corresponds to average quantization noise power. It is calculated assuming the quantization noise and probability distribution function.
9. Signal to noise ratio increases as ___________ increases.
a) Quantization level
b) Square of quantization level
c) Square root of quantization level
d) None of the mentioned
View Answer
Explanation: On calculating the number of levels, quantization error and power and also signal to noise ration we can find that signal to noise ratio depends directly on square of number of quantization levels.
10. Signal to noise ratio is infinite when
a) Quantization noise is zero
b) Number of levels are infinite
c) Quantization noise is zero & Number of levels are infinite
d) None of the mentioned
View Answer
Explanation: In the limit L tends to infinity and signal to quantization noise ratio tends to infinity when quantization levels are infinite and quantization noise is zero.
11. The ratio of average signal power and quantization noise is
a) 3L2
b) L2/3
c) 2L3
d) L3/2
View Answer
Explanation: On calculating the signal power and the quantization noise, and on taking its ratio it depends on the number of quantization level L and we get as 3L2.
Sanfoundry Global Education & Learning Series – Digital Communications.
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