1 / 21

Electrical Communications Systems ECE.09.331 Spring 2009

Electrical Communications Systems ECE.09.331 Spring 2009. Lecture 12b April 15, 2009. Shreekanth Mandayam ECE Department Rowan University http://engineering.rowan.edu/~shreek/spring09/ecomms/. Plan. Digital Bandpass Communications Why digital modulation?

amity
Download Presentation

Electrical Communications Systems ECE.09.331 Spring 2009

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 2009 Lecture 12bApril 15, 2009 Shreekanth Mandayam ECE Department Rowan University http://engineering.rowan.edu/~shreek/spring09/ecomms/

  2. Plan • Digital Bandpass Communications • Why digital modulation? • Digital Modulation: Introduction (ASK, FSK, PSK) • Binary Phase Shift Keying (BPSK) • Quadrature Phase Shift Keying (QPSK) • M-ary PSK and M-ary QAM • Observing Digital Bandpass Signals • Constellation diagrams • Eye Diagrams

  3. ECOMMS: Topics

  4. Digital Communications Transceiver Anti- aliasing Filter Error Control Encoder Data Encryption Encoder Channel/ Line Encoder Source Encoder Sampling Quantization Modulator MUX ADC Analog i/p CODEC MODEM Multiple access channel Analog o/p Error Control Decoder Data Encryption Decoder Source Decoder Audio Amp Reconstruction/ DAC Equalization / Decision Circuits Demod-ulator DEMUX

  5. Digital Bandpass Communications • Why digital modulation? Reproduced from: http://www.tm.agilent.com/tmo/Notes/pdf/5965-7160E.pdf

  6. Industry Trends Reproduced from: http://www.tm.agilent.com/tmo/Notes/pdf/5965-7160E.pdf

  7. Applications Reproduced from: http://www.tm.agilent.com/tmo/Notes/pdf/5965-7160E.pdf

  8. Digital Modulation Carrier signal: Ac cos (2pfct + f) Modulation: m(t) Modulated signal: Ac (t) cos (2pfc(t) t + f(t))  m(t); discrete Vary Vary Vary amplitude frequency phase Variations are discrete!!!!!

  9. Recall: Dig Comm Principle Digital message 1 1 1 0 1 0……… 0 0 Digital code Analog message modulate 1 0 1 0 Sinusoidal carrier AM FM PM AM & PM

  10. Signal Vector Representation s(t) = Ac(t) cos (2pfct + f(t)) fixed!!! Q S Magnitude Phase 0 degrees I I-Q Plane

  11. Phase Change Magnitude Change S2 Q Q S1 S1 S2 I I Magnitude & Phase Change Q S1 S2 I Signal Changes:Representation in the IQ Plane I-Q Diagrams or Constellations Frequency Change ???

  12. Binary Phase Shift Keying (BPSK) s(t) = Ac cos(2pfct + f(t)) IQ Diagram Q p radians f(t) 1 0 0 radians t I

  13. Quadrature Phase Shift Keying(QPSK) IQ Diagram s(t) = Ac cos(2pfct + f(t)) Q 3p/4 01 11 10 f(t) p/4 00 p/4 t I 10 -p/4 11 01 00 -3p/4

  14. M-ary Phase Shift Keying(M-ary PSK) Q I Octophase I-Q Constellation

  15. M-ary Quadrature Amplitude Modulation(M-ary-QAM) Q I 16 QAM I-Q Constellation

  16. Different ways of looking at a digitally modulated signal

  17. Time & Frequency Domain View Reproduced from: http://www.tm.agilent.com/tmo/Notes/pdf/5965-7160E.pdf

  18. Frequency & Power View Reproduced from: http://www.tm.agilent.com/tmo/Notes/pdf/5965-7160E.pdf

  19. I-Q Constellation Diagram Matlab Demo: qpsk.m Reproduced from: http://www.tm.agilent.com/tmo/Notes/pdf/5965-7160E.pdf

  20. Eye Diagram Matlab: >>eyediagram Reproduced from: http://www.tm.agilent.com/tmo/Notes/pdf/5965-7160E.pdf

  21. Summary

More Related