Signal Processing

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Signal Processing Analog to Digital and Digital
to Analog Conversion
Jiang Li
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Outline

• Introduction to Signals
• Definition and Examples
• Analog Signal vs. Digital Signal
• Components of Signals
• Amplitude, Frequency, Phase
• A/D Conversion
• Block Diagram of Data Stream
• Sampling, Quantization, Encoding
• D/A Conversion
• Summing Amplifier and R-2R Network (Ladder)

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Signals Introduction

• Definition
• Signals are the detectable transmitted
  electromagnetic energy that can be used to
  carry information.
• Examples
• Telephone conversation over a telephone line
• Live television news interview from ABC
• Data download over your network line via the
  Internet

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Signals Analog vs. Digital

• Analog signal has a continuous waveform,
  with examples such as music and video.

• Digital signal has a discrete or non-continuous
  waveform, with examples such as 1s and 0s in
  computer systems.

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Signals Analog vs. Digital (contd)

• It is hard to separate noise from an analog
  signal

• Noise in a digital signal. You can still
  discern a high voltage from a low voltage.

• Noise in a digital signal. Too much noise -
  you cannot discern a high voltage from a low
  voltage.

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Signals Components

• The Amplitude (a) of a signal is the height of
  the wave above or below a given reference point.

• The Frequency ( f ) is the number of times a
  signal makes a complete cycle within a given time
  frame.

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Signals Components (contd)

• The Phase ( ) of a signal is the position of
  the waveform relative to a given moment of time
  or relative to time zero.

• A change in phase can be any number of angles
  between 0 and 360 degrees.
• Phase changes often occur on common angles, such
  as 45, 90, 135, 180, etc.

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Motivation of Analog to Digital Conversion
Cassette vs. CD
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Block Diagram of Data Stream
continuous-time, continuous-amplitude
discrete-time, discrete-amplitude
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Sampling
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Sampling (contd)
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Quantization
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Quantization (contd)
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Encoding
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D / A Conversion using Summing Amplifier
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D / A Conversion using R 2R Network (Ladder)
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R 2R Network (Ladder) DAC Details