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Questions and Answers
What does quantisation error represent in digital data conversion?
What does quantisation error represent in digital data conversion?
In pulse code modulation, which aspect is most dependent on the sampling rate?
In pulse code modulation, which aspect is most dependent on the sampling rate?
Which statement best describes the Nyquist Theorem?
Which statement best describes the Nyquist Theorem?
Increasing quantisation levels in a digital system will primarily result in what?
Increasing quantisation levels in a digital system will primarily result in what?
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Which of the following best describes the function of an ADC in a microprocessor system?
Which of the following best describes the function of an ADC in a microprocessor system?
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What is the primary consequence of insufficient sample rates according to the Nyquist theorem?
What is the primary consequence of insufficient sample rates according to the Nyquist theorem?
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Which of the following best describes Pulse Code Modulation (PCM)?
Which of the following best describes Pulse Code Modulation (PCM)?
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Which statement accurately reflects the concept of quantisation in digital signal processing?
Which statement accurately reflects the concept of quantisation in digital signal processing?
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According to the Nyquist theorem, what is the minimum sampling rate required if the maximum frequency (Fmax) of a signal is 20 kHz?
According to the Nyquist theorem, what is the minimum sampling rate required if the maximum frequency (Fmax) of a signal is 20 kHz?
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What is the impact of a high quantisation level on a signal's quality?
What is the impact of a high quantisation level on a signal's quality?
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How does the sample rate of 44.1 kHz for CD-quality audio correspond to potential signal frequencies?
How does the sample rate of 44.1 kHz for CD-quality audio correspond to potential signal frequencies?
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What defines an optimal sampling frequency for a given signal?
What defines an optimal sampling frequency for a given signal?
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Which sampling rate is most appropriate for capturing telephone speech effectively?
Which sampling rate is most appropriate for capturing telephone speech effectively?
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What is the relationship between the number of bits (N) in an analogue-to-digital converter (ADC) and the number of quantisation levels?
What is the relationship between the number of bits (N) in an analogue-to-digital converter (ADC) and the number of quantisation levels?
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How is the resolution (R) of an ADC defined?
How is the resolution (R) of an ADC defined?
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What is the maximum quantisation error in a 3-bit ADC?
What is the maximum quantisation error in a 3-bit ADC?
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Which equation represents the dynamic range (DR) of an N-bit ADC?
Which equation represents the dynamic range (DR) of an N-bit ADC?
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In terms of quantisation levels, what happens when an ADC has non-uniform quantisation?
In terms of quantisation levels, what happens when an ADC has non-uniform quantisation?
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Which of the following best describes Pulse Code Modulation (PCM)?
Which of the following best describes Pulse Code Modulation (PCM)?
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According to Nyquist Theorem, what is the minimum sampling rate required to avoid aliasing?
According to Nyquist Theorem, what is the minimum sampling rate required to avoid aliasing?
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What does an increase in the number of bits (N) in an ADC primarily affect?
What does an increase in the number of bits (N) in an ADC primarily affect?
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Study Notes
Quantisation
- Defines how a value is stored in binary
- CD-quality audio: 16-bits
- Recorded speech: 8- or 12-bits
- Quantisation is necessary for single values too
- Quantisation error: difference between the stored value and the original value
Microprocessor Applications
- Most applications start with analogue data
- Convert analogue data to digital domain using ADC (Analogue to Digital Converter)
- Process data using a microprocessor
- Convert digital data back to analogue using DAC (Digital to Analogue Converter)
- Some applications might lack either an input or output but not both
Transducers
- Transducers convert signals from one form to another
-
Sound:
- Microphone
- Loudspeaker
- Buzzer
- Ultrasonic transducer
-
Vision:
- LED
- LDR (Light Dependent Resistor)
- Photodiode
- Camera sensor
-
Others:
- Temperature
- Pressure
- CO2
- Magnetometer
Analogue-to-Digital Conversion (ADC)
- In an N-bit ADC, the input voltage is divided into 2N levels
-
Resolution (R): the step between levels
- R = VREF / 2N
-
Two main processes in an ADC:
- Sample the input voltage
- Quantise the sample into binary
- Provide the digital sample to the CPU when asked
- Dynamic range: DR = 6.02N + 1.76 dB
Non-Uniform Quantisation
- In non-uniform quantisation, the quantisation levels are not evenly spaced
- Uniform quantisation is assumed in most cases
Sampling
- Sampling is defined by sample rate
-
Examples of sample rate:
- Telephone speech: 8kHz
- CD-quality music: 44.1kHz
- Two-hourly measurement: 0.00014 Hz
- Sample rate must be frequent enough to capture variations in the signal
- Sampling too frequently wastes power, CPU cycles, and memory space
Nyquist Theorem
- States that a continuous signal can be perfectly reconstructed from its samples if the sample rate is at least twice the highest frequency component in the signal
- Fs (Sample Rate) ≥ 2Fmax (Highest Frequency)
Pulse Code Modulation (PCM)
- Continuous sampling of a signal at rate Fs
- Each sample is stored as a signed two's complement integer
- Combines sampling and quantisation to represent analogue signals digitally
Key Terms
- ADC (Analogue to Digital Converter): Converts analogue data to digital data
- DAC (Digital to Analogue Converter): Converts digital data to analogue data
- Quantisation: Process of representing a continuous range of values using a finite set of discrete levels
- Sample Rate: Number of samples taken per second
- Nyquist Theorem: Theoretical minimum sample rate required to accurately reconstruct a signal
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Description
Explore the fundamental concepts of quantisation, microprocessor applications, and transducers in this quiz. Learn about how analogue data is converted to digital and the importance of quantisation in signal processing. Test your knowledge on the devices that aid in these conversions and their applications.
