Lecture 17 Noise in Modulation Systems (I)

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Lecture 17Noise in Modulation Systems (I)

• Fall 2008
• NCTU EE
• Tzu-Hsien Sang

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Outline

• Signal-to-Noise Ratios
• Noise and Phase Errors in Coherent Systems
• Noise in Angle Modulation
• Threshold Phenomenon
• Noise in Pulse Code Modulation

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Signal-to-Noise Ratios

• SNR is one of the most important parameters in
  communications (the other is bandwidth).
• Usually assume Additive White Gaussian Noise
  (AWGN). Compare different receivers (modulations)
  by calculating the SNR at point B.

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White noise
Bandpass noise
Bandpass filtering
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Random attenuation, the message is lost!
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