Lect15_Digital Modulation (III)

Lect15_Digital Modulation (III) - ECE 620 Introduction to...

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ECE 620 Introduction to RF Integrated Circuits Prof. Waleed Khalil Lecture Digital Modulation (III) 15 1
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Outline Digital Modulation Types QPSK MSK GMSK BER 2
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Quadrature Phase Shift Keying (QPSK) QPSK output signal is sum of modulated +/- cos (I-channel) and +/- sin (Q-channel) 2x the BW efficiency of BPSK Large envelope variation during phase transitions Example: amplitude goes to zero when transition from 1,1 to -1,-1 state Require linear amplification 3 I Q 1,1 1,-1 -1,-1 n=2, m=4 -1,1   t f c 2 sin +   t f c 2 cos Even Bits (b 0 , b 2 , . .. ) Polar NRZ Odd Bits(b 1 , b 3 , . .. ) Polar NRZ QPSK Q-channel I-channel Phase of carrier: 45 º , 135 º , -135 º , -45 º b 0 ,b 1
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Types of QPSK QPSK Allow transitions though “zero” (π phase shift transitions) Large envelope variations Used in WCDMA O-QPSK Minimize envelope variations by eliminating transitions though “zero”
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Lect15_Digital Modulation (III) - ECE 620 Introduction to...

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