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Published byEdmund Stevenson Modified over 9 years ago
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Session 2
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Objectives: By the end of this session, the student will be able to: Distinguish between data and signals. Cite the advantages of digital data and signals over analog data and signals Identify the 3 basic components of a signal Discuss the bandwidth of a signal & how it relates to data transfer speed Identify signal strength and attenuation, and how they are related Outline the basic characteristics of transmitting analog data with analog signals, digital data with digital signals, digital data with analog signals and analog data with digital signals List and draw diagrams of the basic digital encoding techniques, and explain the advantages and disadvantages of each Identify the different shift keying (modulation) techniques and describe their advantages, disadvantages, and uses Identify the two most common digitization techniques and describe their advantages and disadvantages Discuss the characteristics and importance of spread spectrum encoding techniques Identify the different data codes and how they are used in communication systems
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Analog Waveform 3
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Analog Waveform – with Noise 4
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Digital Waveform 5
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Digital Waveform - Noise 6
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Digital Waveform – More Noise 7
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Analog Signals 8 Amplitude Frequency Spectrum? Bandwidth? Effective bandwidth?
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Analog Signals 9 Spectrum Bandwidth = Y – X Effective Bandwidth = B - A Y XA B Human Voice Spectrum: 300Hz – 3400Hz Bandwidth: 3100Hz
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Waveforms - Phase 10
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Attenuation / Amplification 11 dB = 10log 10 (P 2 / P 1 ) P 1 – power level at transmitter P 2 – power level at receiver A loss of 50% power is -3dB. Whether the loss is from 1000W to 500W or from 10W to 5W.
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Analog Data / Analog Signals 12
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Digital Encoding Schemes 13
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Digital Encoding Schemes 14 NRZ-L (Non-Return to Zero Level) Binary 0 – represented by presence of voltage Binary 1 – represented by absence (or low) voltage
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Digital Encoding Schemes 15 NRZ-I (Non-Return to Zero Inverted) Binary 0 – represented by no voltage change at the time mark Binary 1 – represented by a change in voltage at the time mark What happens to NRZ-I and NRZ-L encoding when transmitting a long series of binary zeros?
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Digital Encoding Schemes 16 Manchester Binary 0 – represented by change from high to low in the middle of the time mark Binary 1 – represented by a change from low to high in the middle of the time mark
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Digital Encoding Schemes 17 Differential Manchester Binary 0 – represented by change at the beginning of the time mark Binary 1 – represented by no change at the beginning of the time mark What happens to Manchester and Differential Manchester encoding when transmitting a long series of binary zeros? Self-clocking
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Bipolar-AMI Bipolar-AMI Digital Encoding 3 voltage levels: binary 0 = zero voltage binary 1 = positive or negative voltage sent depending on last binary 1 sent (negative voltage last sent -> positive voltage sent this time) 18
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4B/5B Digital Encoding Scheme 19
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Amplitude Key Shifting 20
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Amplitude Key Shifting 21
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Frequency Key Shifting 22
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Phase Key Shifting 23
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Quadrature Phase Key Shifting 24
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Quadrature Amplitude Key Shifting 25
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Pulse Code Modulation 26
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Pulse Code Modulation 27
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Pulse Code Modulation Twice the sample rate 28
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Delta Modulation 29
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Frequency Hopping Spread Spectrum 30
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Direct Sequence Spread Spectrum 31
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EBCDIC 32
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ASCII 33
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Review NRZ-L NRZ-I Manchester DiffManchester Bipolar-AMI 4B/5B Encoding 34 0V
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