lect8b_Ross_09spg

lect8b_Ross_09spg - Selected topics on digital...

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Elec 300u Selected topics on digital communications Lecture 8b Digital I/Q modulation Constellation diagram Complex mixing Multipath interference Some content taken with permission from material developed for the course EECS6.02 by C. Sodini, M. Perrot and H. Balakrishnan
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Digital I/Q Modulation send symbol from set {-3,-1,1,3} on both I (in-phase) and Q (quadrature) channels each symbol period At receiver, sample I/Q waveforms every symbol period Associate each sampled I/Q value with symbols from a set {-3,-1,1,3} on both I and Q channels
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Constructing Constellation Diagram I -3 -1 1 3 Q -3 -1 1 3 Slicing levels Slicing levels
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Constellation Diagram Associate the 16 combinations with 4 bits e.g. (I,Q) = (1,1) =1101, (I, Q) = (3, -3) = 1010
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Eye Diagram vs. Constellation Diagram • Eye diagram – Shows transition behavior between symbols • Constellation diagram – Shows aggregate placement of sampled I/Q values
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Tools for ISI examination • Eye diagram – ISI causes closing of eye • Constellation diagram – ISI causes spreading of symbol points
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lect8b_Ross_09spg - Selected topics on digital...

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