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Analog and Digital Signals

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Analog-to- Digital Conversion ... Table of sampled waveform values. Quantization. Properties of A-D Converter. Quantization : ... analog conversion. Anti ... – PowerPoint PPT presentation

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Title: Analog and Digital Signals


1
Analog and Digital Signals
2
Terminology
  • Analog signal an analog signal is continuous in
    time and amplitude.
  • Digital signal a digital signal exists only at
    discrete, equally spaced moments of time.
  • Analog-to- digital converter hardware used to
    convert a continuous signal into a discrete
    digital signal.

3
Analog-to- Digital Conversion
From Rosen and Howell,
Signals and Systems for Speech and Hearing.
4
Analog Sine Wave
5
Properties of A-D Converter
  • Sampling rate the number of times the analog
    signal is sampled per second, e.g., if the signal
    is sampled 20,000 times per second the sampling
    rate is 20kHz. The amplitude value of the
    waveform is sampled 20,000 times in a second.

6
Sampled sine wave
7
Nyquist Theorem
  • The sampling rate must be greater than twice the
    highest frequency of interest.
  • If the sampling rate is not high enough, a higher
    frequency may appear as a different, lower
    frequencies when sampled. This is an alias.

8
Example of aliasing
9
Table of sampled waveform values
10
Quantization
11
Properties of A-D Converter
  • Quantization
  • Process of assigning a value to the sample.
  • Which bin (quantizing step) does a sample belong
    in?
  • The accuracy depends on the number of bits
    available.
  • Quantizing error the amount by which the
    quantized value is smaller or larger than the
    sampled value.

12
Quantization step size
13
Quantization Error
14
Sampled sine wave
15
Digital to analog conversion
16
Anti-imaging filter
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