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Digital communication- student version

Digital communication- student version. Dr. Uri Mahlab. General overview. Digital Radio Theory and Implementation -How a Digital Radio Works. Digital Radio Block Diagram. CODER. MOD. UPCONVERTER. DEMOD. DECODER. DOWNCONVERTER. Analog vs. Digital Modulation. AM. FM. PM. DIGITAL.

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Digital communication- student version

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  1. Digital communication- student version Dr. Uri Mahlab ד"ר אורי מחלב

  2. General overview Digital Radio Theory and Implementation -How a Digital Radio Works ד"ר אורי מחלב

  3. Digital Radio Block Diagram CODER MOD UPCONVERTER DEMOD DECODER ד"ר אורי מחלב DOWNCONVERTER

  4. Analog vs. Digital Modulation AM FM PM DIGITAL With digital modulation information is in the phase and amplitude of the signal ד"ר אורי מחלב

  5. The IQ Diagram Q magnitude Vq phase I Vi ד"ר אורי מחלב

  6. Analog Modulation on the IQ diagram Q A FM B I C PM D ד"ר אורי מחלב

  7. BPSK Timing and State Diagram BPSK Constellation Diagram Reference Q State 1 State 0 0 State 1 State I = 0 deg. = 180 deg. t ד"ר אורי מחלב

  8. QPSK Modulation 4 Possible States Q 01 00 Vq I Vi 10 11 ד"ר אורי מחלב

  9. 16 QAM State Diagram Q 0000 0001 0011 0010 0100 0101 0111 0110 I 1100 1101 1111 1110 1000 1001 1011 1010 ד"ר אורי מחלב

  10. Symbol Rate: “The rate at which the carrier moves between points in the constellation” ד"ר אורי מחלב

  11. Example: A 16 QAM radio has 4 bit per state (or symbol). If the radio operates at 16 Mb/s, then the carrier must change states or 4 million times per second (4 MBaud) SYMBOL RATE = 4MHz 16 Mb/s 4 Bits ד"ר אורי מחלב

  12. Some Typical Modulation Formats BPSK QPSK 8PSK 16QAM 64QAM ד"ר אורי מחלב

  13. QPSK Modulator BALANCED MODULATION SYMBOL RATE: fs = fb/2 IN-PHASE DATA STREAM I 0° fb I.F SERIAL TO PARALLEL CONVERTER CARRIER PHASE SHIFT COMBINER BPF BINARY NRZ INPUT SIGNAL 90° fs = fb/2 Q 01 00 QUADRATURE DATA STREAM BALANCED MODULATION 11 10 COMBINED VECTOR STATE DIAGRAM ד"ר אורי מחלב

  14. I, Q, Eye diagram and Constellation +1 I -1 +1 Q -1 EYE Q 5 3 CONSTELLATION : I 2 1,4 ד"ר אורי מחלב

  15. QPSK Demodulator Phase Demodulation LPF. Thresh Comp. I I fb/2 0° IF Input Symbol timing rec.(STR) Parallel to serial converter BPF Power Splitter Car Rec. Phase Splitter 90° fb/2 Q LPF. Thresh Comp. Q Binary NRZ Phase Demodulation fb ד"ר אורי מחלב

  16. 16 QAM Modulator 2-to-4 level convert Premod. LPF I I 0° L.F. 16 QAM Output Data LO Phase split BPF Binary NRZ Data 90° 2-to-4 level convert Premod. LPF Q Q ד"ר אורי מחלב

  17. 16 QAM Demodulator L O G I C 4-Level Signal I LPF 0° Data Out fb BPF STR X2 data con blner CR IF Input Regeneration 90° Q 4-to-2 level converter of Q channel. Same design as I channel. LPF 4-Level Signal ד"ר אורי מחלב

  18. Which waveform requires more bandwidth? A B time ד"ר אורי מחלב

  19. Bandwidth Considerations ד"ר אורי מחלב

  20. Two random data sequence time frequency ד"ר אורי מחלב

  21. Unfiltered Digital Radio Spectrum ד"ר אורי מחלב

  22. An UNFILTERD Radio frequency MOD U/C CODER time Data is easier to recover but signal requires a lot of bandwidth D/C DEMOD DECODER time ד"ר אורי מחלב

  23. A FILTERED Radio frequency MOD U/C CODER time Signal requires less bandwidth but data is filtered D/C DEMOD DECODER ד"ר אורי מחלב time

  24. Intersymbol Interference ד"ר אורי מחלב

  25. Nyquist Filtering Raised Cosine ד"ר אורי מחלב

  26. Filter Coefficient & Determines Required B.W. Amplitude Response Linear Phase (Flat Group Delay) ד"ר אורי מחלב

  27. The Filtering is Distributed in the Radio CODER MOD UPCONVERTER DEMOD DECODER ד"ר אורי מחלב DOWNCONVERTER

  28. SUMMARY As the modulation complexity increases, the radio becomes more spectrally efficient. However, it also become more susceptible to errors caused by noise and distortions. ד"ר אורי מחלב

  29. P(x) THRESHOLD TOTAL PROBABILITY OF NOISE AMPLITUDE EXCEEDING THIS THRESHOLD 0.4 0.3 0.2 0.1 X -30 -20 -10 10 20 30 ד"ר אורי מחלב

  30. How Error Occur VOLTAGE BINARY SIGNAL + AMPLTUDE NOISE FDP NORMAL 1 VALUE 1 1 ERROR DECISION 0 0 ERROR THRESHOLD NORMAL 0 VALUE Received signal with superimposed noise ד"ר אורי מחלב PROB

  31. Gaussian Distribution PROBABILITY DENSITY FUNCTION P(x) 0.4 0.3 0=RMS VALUE AFTER SUBTRACTING DC COMPONENT 0.2 NEVER RECHS ZEBO 0.1 X -30 -20 -10 10 20 30 ד"ר אורי מחלב

  32. Meaning of Eye diagram Threshold ד"ר אורי מחלב

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