1 / 14

Electrical Communications Systems ECE.09.331 Spring 2010

Electrical Communications Systems ECE.09.331 Spring 2010. Lecture 7a March 2, 2010. Shreekanth Mandayam ECE Department Rowan University http://engineering.rowan.edu/~shreek/spring10/ecomms/. Signals Systems. Modulation Index Efficiency Bandwidth Noise.

kumiko
Télécharger la présentation

Electrical Communications Systems ECE.09.331 Spring 2010

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Electrical Communications SystemsECE.09.331Spring 2010 Lecture 7aMarch 2, 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 • Complex Envelope Representation • Spectrum of a bandpass signal • DSB-SC Modulation • Costas Loop • QAM • SSB

  3. ECOMMS: Topics

  4. 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

  5. Spectrum of a Bandpass Signal

  6. |M(f)| -B 0+B Signals Systems Modulation Index Efficiency Bandwidth Noise Performance Transmitters Receivers Standards Time Domain Complex Envelope Spectrum Power DSB-SC Modulation Message Spectrum Matlab Demo http://engineering.rowan.edu/~shreek/spring10/ecomms/demos/dsbsc.m f DSB-SC Spectrum |S(f)| -fc-B -fc -fc+B 0fc-B fc fc+B f

  7. DSB-SC: Coherent Detector Product Modulator Baseband LPF v(t) s(t) Aocos2pfct Local Oscillator

  8. 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) Synchronous Coherent Detection: Costas PLL I-Channel Q-Channel

  9. 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

  10. |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

  11. 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')

  12. 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

  13. SSB Generation: Weaver’s Method

  14. Summary

More Related