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Digital communication

Digital communication. H V KUMARASWAMY. Topics to be covered in this session. I Minimum shift keying II M-ary FSK III M-ary PSK. Minimum shift keying. Proper utilization of phase during detection, for improving noise performance Complexity increases

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Digital communication

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  1. Digital communication • H V KUMARASWAMY

  2. Topics to be covered in this session • IMinimum shift keying • II M-ary FSK • III M-ary PSK

  3. Minimum shift keying Proper utilization of phase during detection,for improving noise performance Complexity increases CPFSK (Continuous-phase frequency-shift keying) • . θ(0) denotes the value of the phase at time t=0

  4. An angle-modulated wave θ(t) is the phase of s(t), continuous function of time. Carrier frequency Phase Deviation ratio Measured with respect to bit rate 1/Tb

  5. At time t=Tb Phase Tree

  6. Phase Trellis, for sequence 1101000

  7. In terms of In phase and Quadrature Component h=1/2 + Sign corresponds to symbol 1 - Sign corresponds to symbol 0

  8. In phase components For the interval of Half cosine pulse + Sign corresponds to θ(0) =0 - Sign corresponds to θ(0) = п

  9. Quadrature components + Sign corresponds to θ(Tb) =п/2 - Sign corresponds to θ(Tb) = -п/2 Half sine pulse

  10. Four possibilities

  11. Basic functions

  12. coefficients

  13. Signal Space Characterization of MSK

  14. MSK receiver Q-channel

  15. Sketch the waveform of the MSK signal for the sequence for the 101101.Assume that the carrier frequencya) Is 1.25 times the bit rate. b) Equal to the bit Solution (a) fc =(f1+f2)/2=1.25/ Tb OR f1+f2=2.5/Tb Also f1-f2=1/(2Tb) Solving f1=1.5/Tb f2=1/Tb (b) fc=1/Tb f1+f2=2/Tb f1-f2=1/(2Tb)\ Solving f1=1.25/Tb f2=0.75/Tb

  16. conclusion

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