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Electrical Communications Systems ECE.09.331 Spring 2010

Electrical Communications Systems ECE.09.331 Spring 2010. Lecture 7b March 3, 2010. Shreekanth Mandayam ECE Department Rowan University http://engineering.rowan.edu/~shreek/spring10/ecomms/. Signals Systems. Modulation Index Efficiency Bandwidth Noise.

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Electrical Communications Systems ECE.09.331 Spring 2010

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  1. Electrical Communications SystemsECE.09.331Spring 2010 Lecture 7bMarch 3, 2010 Shreekanth Mandayam ECE Department Rowan University http://engineering.rowan.edu/~shreek/spring10/ecomms/

  2. Signals Systems Modulation Index Efficiency Bandwidth Noise Performance Transmitters Receivers Standards Time Domain Complex Envelope Spectrum Power Plan • Recall: Costas Loop • QAM • Complex Envelope • SSB Modulation • Angle Modulation Systems • Definitions - Phase and Frequency Modulation • Complex Envelope • Time Domain • Analyzing FM Signals - Battle Plan!!!!

  3. ECOMMS: Topics

  4. v1(t) Product Modulator Baseband LPF v3(t) v4(t) VCO LPF X s(t) -90o Phase Shift Phase Discriminator Product Modulator Baseband LPF v2(t) Recall: Costas PLL I-Channel Q-Channel

  5. Product Modulator S s(t) m1(t) LPF Product Modulator Local Oscillator Local Oscillator -90o Phase Shift -90o Phase Shift Product Modulator LPF m2(t) Product Modulator Quadrature Amplitude Modulation (QAM) Rx Tx I-Channel Q-Channel

  6. message: m(t) carrier: c(t) Modulator s(t): radio signal Complex Envelope Representation • We want a common mathematical representation for • information transfer from baseband to bandpass • any bandpass signal • any time of modulation • signal/noise and signal+noise

  7. Spectrum of a Bandpass Signal

  8. |S(f)| -fc-B -fc -fc+B 0fc-B fc fc+B f Single Sideband (SSB) Modulation • Recall: DSB-SC Spectrum • USSB - Signal with zero-valued spectrum for |f| < fc • LSSB - Signal with zero-valued spectrum for |f| > fc

  9. 1.5 1 0.5 0 -0.5 -1 0 1 2 3 4 5 6 7 time, t in sec The Hilbert Transform » t=0:0.1:2*pi; » w=sin(t); » plot(t,w) » hold Current plot held » H=hilbert(w); » plot(t,imag(H),'r'); » xlabel('time, t in sec')

  10. Product Modulator S s(t) m(t) Product Modulator -90o Phase Shift Sideband Filter Product Modulator m(t) s(t) Carrier -90o Phase Shift Carrier SSB Generation Phasing Method Filter Method

  11. SSB Generation: Weaver’s Method

  12. ECOMMS: Topics

  13. Angle Modulation Systems • Signal Representation • Complex Envelope • Time Domain Representation • Terminology • Phase Sensitivity • Frequency Deviation • Instantaneous Frequency • Phase & Frequency Modulation Indices Phase Modulation (PM) Frequency Modulation(FM) Instrument Demo Matlab Demo: anglemod.m

  14. Angle Modulation Systems • Signal Representation • Complex Envelope • Time Domain Representation • Terminology • Phase Sensitivity • Frequency Deviation • Instantaneous Frequency • Phase & Frequency Modulation Indices Phase Modulation (PM) Frequency Modulation(FM) Instrument Demo Matlab Demo: anglemod.m

  15. Signals Systems • Time Domain • Complex Envelope • Spectrum • Single-tone FM • Narrowband FM • Wideband FM • Bessel Functions • Power Performance Transmitters Receivers Standards Modulation Index Efficiency Bandwidth Noise Analyzing FM Signals - Battle Plan!!! Instrument Demo

  16. Summary

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