CSE3213_07_ShiftKeyingW2012_Part_1

CSE3213_07_ShiftKeyingW2012_Part_1 - can be represented by...

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1 Analog Transmission of Digital Data: ASK, FSK, PSK, QAM CSE 3213, Winter 2012 Instructor: Dusan Stevanovic Required reading: Garcia 3.7
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2 Why Do We Need Digital-to-Analog Conversion?! 1) The medium/channel is band pass, and/or 2) Multiple users need to share the medium.
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3 Modulation of Digital Data Modulation process of converting digital data or a low-pass analog to band-pass (higher-frequency) analog signal Digital-to-analog modulation. Analog-to-analog modulation. Carrier Signal aka carrier freq. or modulated signal - high freq. signal that acts as a basis for the information signal information signal is called modulating signal freq bandpass channel
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4 Modulation of Digital Data (cont.) Digital-to-Analog Modulation process of changing one of the characteristic of an analog signal (typically a sinewave) based on the information in a digital signal sinewave is defined by 3 characteristics (amplitude , frequency , and phase ) digital data
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Unformatted text preview: can be represented by varying any of the three application : transmission of digital data over telephone wire (modem) Types of Digital-to-Analog Modulation 5 Modulation of Digital Data: ASK ASK – strength of carrier signal is varied to represent binary 1 or 0 both frequency & phase remain constant while amplitude changes commonly, one of the amplitudes is zero demodulation : only the presence or absence of a sinusoid in a given time interval needs to be determined advantage : simplicity disadvantage : ASK is very susceptible to noise interference – noise usually (only) affects the amplitude , therefore ASK is the modulation technique most affected by noise application : ASK is used to transmit digital data over optical fiber 1 binary t), f Acos(2 binary 0, 1 binary t), f cos(2 A binary t), f cos(2 A s(t) c c 1 c π π π Is this picture, from the textbook, entirely correct?! +A -A...
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This note was uploaded on 02/14/2012 for the course CSE 3213 taught by Professor A during the Winter '10 term at York University.

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CSE3213_07_ShiftKeyingW2012_Part_1 - can be represented by...

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