Pulse Code Modulation

Question 1
Marks : +2 | -2
Pass Ratio : 50%
Choosing a discrete value that is near but not exactly at the analog signal level leads to
PCM error
Quantization error
PAM error
Sampling error
Explanation:
One of the limitations of PCM is quantization error which occurs when we choose a discrete value at some near by value and not at the analog signal level.
Question 2
Marks : +2 | -2
Pass Ratio : 50%
Delta modulation uses _____ bits per sample.
One
Two
Four
Eight
Explanation:
Delta modulation is used for analog to digital conversion and vice versa. It is a simple form of DPCM. Its uses 1 bit per sample. It also depends on the difference between the current and previous sample values.
Question 3
Marks : +2 | -2
Pass Ratio : 50%
The signals which are obtained by encoding each quantized signal into a digital word is called as
PAM signal
PCM signal
FM signal
Sampling and quantization
Explanation:
Pulse code modulation is the name for the class of signals which are obtained by encoding the quantized signals into a digital word.
Question 4
Marks : +2 | -2
Pass Ratio : 50%
The length of the code-word obtained by encoding quantized sample is equal to
l=log(to the base 2)L
l=log(to the base 10)L
l=2log(to the base 2)L
l=log(to the base 2)L/2
Explanation:
The quantized sample which are digitally encoded into l bit value code-word. The length l can be calculated as l=log(to the base 2)L.
Question 5
Marks : +2 | -2
Pass Ratio : 50%
What is bit depth?
Number of quantization level
Interval between two quantization levels
Number of possible digital values to represent each sample
None of the mentioned
Explanation:
One of the properties of PCM signal which determines its stream fidelity is bit depth which is the number of possible digital values that can be used to represent each sample.
Question 6
Marks : +2 | -2
Pass Ratio : 50%
Quantization noise can be reduced by ________ the number of levels.
Decreasing
Increasing
Doubling
Squaring
Explanation:
The process of quantization replaces the true signal with the approximation(quantization noise). By increasing the number of quantization level the quantization noise can be reduced.
Question 7
Marks : +2 | -2
Pass Ratio : 50%
DPCM encodes the PCM values based on
Quantization level
Difference between the current and predicted value
Interval between levels
None of the mentioned
Explanation:
Differential PCM encodes the PCM value based on the difference between the previous sample and the present sample value.
Question 8
Marks : +2 | -2
Pass Ratio : 50%
In PCM encoding, quantization level varies as a function of ________
Frequency
Amplitude
Square of frequency
Square of amplitude
Explanation:
In linear PCM the quantization levels are uniform. But in normal PCM encoding the quantization level vary according to the amplitude, based of A-law of Myu-law.
Question 9
Marks : +2 | -2
Pass Ratio : 50%
Sample resolution for LPCM ____ bits per sample.
8
16
24
All of the mentioned
Explanation:
Common sampling resolution for LPCM are 8, 16, 20, 24 bits per sample.
Question 10
Marks : +2 | -2
Pass Ratio : 50%
In PCM the samples are dependent on ________
Time
Frequency
Quanization leavel
Interval between quantization level
Explanation:
The samples depend on time,an accurate clock is required for accurate reproduction.