Digital communication

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    31-Dec-2015
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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 - PowerPoint PPT Presentation

Transcript of Digital communication

  • Digital communication

    H V KUMARASWAMY

  • Topics to be covered in this sessionI Minimum shift keyingII M-ary FSKIII M-ary PSK

  • Minimum shift keyingProper utilization of phase during detection, for improving noise performanceComplexity increasesCPFSK (Continuous-phase frequency-shift keying). (0) denotes the value of the phase at time t=0

  • An angle-modulated wave(t) is the phase of s(t), continuous function of time.Carrier frequencyPhase Deviation ratioMeasured with respect to bit rate 1/Tb

  • At time t=Tb Phase Tree

  • Phase Trellis, for sequence 1101000

  • In terms of In phase and Quadrature Component+ Sign corresponds to symbol 1- Sign corresponds to symbol 0

    h=1/2

  • For the interval of Half cosine pulseIn phase components+ Sign corresponds to (0) =0- Sign corresponds to (0) =

  • Quadrature components+ Sign corresponds to (Tb) =/2- Sign corresponds to (Tb) = -/2

    Half sine pulse

  • Four possibilities

  • Basic functions

  • coefficients

  • Signal Space Characterization of MSK

  • MSK receiver Q-channel

  • Sketch the waveform of the MSK signal for the sequence for the 101101.Assume that the carrier frequency a) 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/TbAlso 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

  • conclusion