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chapter 3

1. Data and Signals . Data ??? ????????????????????????????????????????? ???? ????????????????? ?????????? CDSignals ??? ????????????????? ???????????????????????????? ?????????????????????? ????????????????? 2 ?????? ??? Analog signals , Digital signal. 2. ?????????? Data to Signal. 3. ????????????????? (Analog Data).

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chapter 3

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    1. Chapter 3??????????????????? 1

    2. Data ??? ????????????????????????????????????????? ???? ????????????????? ?????????? CD Signals ??? ????????????????? ???????????????????????? ???? ?????????????????????? ????????????????? 2 ?????? ??? Analog signals , Digital signal 2

    3. ?????????? Data to Signal 3

    4. ????????????????? (Analog Data) ????????????????????????? (continuous signal) ??????????????????????????????????????????? (frequency) ???????????????? (oscillation) ???? ?????????????? sine wave ?????????????????????? ???????????????????????????????????????? ???????????????????????????????????? ????????????????????????????????????????????? ????-????? sine wave ???????????????????? 4

    5. ???????? ?????? sine , cosine wave 5

    6. ??????????????????????????? Analog 6

    7. ??????? (Digital Signal) ???????????????????????????????????????? ???? (1 ???? 0) ???????????????????????????????????? ????????????????????????????????????????????(channel) ?????????????? ??? ??? ?????? (bit per second) ???? ?????? ??????????????????????? 56 Kbit / sec. (56 * 1000 bps) ?????? 0, 1 ?????????? ?????????????????????????????????????????? 0 ???? low voltage, 1 ??????? high voltage = 0101101 7

    8. 8

    9. ???????????????? ??????? (Digital Terms) Bit: ????? Binary Digit ??? ????????????????? 1 ?????? 1 ??????????????? 10 ?????? 2 ??????????????? 10011001 ?????? 153 ??????????????? Byte ?????????? 8 ??? 9

    10. ???????? ????????????????????????? 1010

    11. ?????????????????????????? 1111

    12. Periodic ??? Aperiodic signal Periodic signal ????????????????????????????????????????????????????????????????? Aperiodic signal ?????????????????????????? ????????? random ?????? ?????????? analog ??? digital ?????????????? Periodic ??? Aperiodic 12

    13. ???????????????? Analog 1313

    14. ???????????????? Analogue ????????? (Amplitude): ???????????????????? ??????????? (volt) ??????? (Frequency): ??????????????????????? ??????????? ??????? (Hz) ??? (Period): ??????????????????????????????????????? ??????????? ?????? , T=1/f ??? (Phase): ?????????????????????????????????? ??????????? ????, ??????? 1414

    15. Phase ????????? 1515

    16. ???????????????????????? ????? sine ??? 1 ???? 6 ???????????????????????,??? radian ??? = 360 x 1 / 6 = 60 ???? = 2x60 /360 rad 1616

    17. 17

    18. 18

    19. Composite signal ????? sine wave ??????????????????? ????????????????????????????????? ????????????????????????????? wave ??????????????? ???? sine wave ???????????????????????? ????????? Fourier Analysis 1919

    20. Composite signal 2020

    21. Time ??? Frequency domain ?????????????????? time-domain ???????????? plot ???? frequency-domain ??? 2121

    22. Spectrum & Bandwidth Spectrum ??? ??????????????????? Bandwidth ??? ???????????????????????????????????????????? ???????????????????? BW = fmax fmin 2222

    23. ????????????????????? sine wave ??????? 100 ,300 , 500 , 700 ,900 Hz ???? bandwidth ?????? frequency spectrum ???????????????? = 10 V ??? 2323

    24. ???????? bandwidth,spectrum ????????????? bandwidth ?????? 300-3100 Hz ??????? 2800 Hz Electronic spectrum 2424

    25. ?????????????????????????????????????? (Channel Capacity) ??????????????????????????????????????? ??????????????????????????????????? ??????????????????????????????? Data rate ??????????????????? ??????????? ???????????? (bps) Bandwidth ????????????????????????????????? ??????????????????????????? ???????????????????????? ??????????? Hertz Noise ???????????????? Error rate ?????????????????????????????? 2525

    26. ???????? Channel Capacity ??????? bps ???????????????????? (Noise) ???????????? Nyquist ??? B ??? bandwidth, M ????????????????? element 2626

    27. ???????????????????? Noise ????????????????????????????????????????? Signal-to-noise ratio ?????????????????????? S=?????????????? (watts) , N=????? noise (watts) SNR ???????????????????????????????? noise SNR ????????????????? SNR ???????????????????? Data rate ??????????? noise ????????? shannon 2727

    28. Example: ????????????? Bandwidth 3000 HZ (300 Hz to 3300 Hz), SNR = 3162 (35 dB) ?????????????????? ????????????? = 3000 log2 (3163) = 3000 * 11.62 = 34,860 bps 2828

    29. Attenuation ???????????????????? ???????????????????????? (Amplitude ????) ??????????? Amplifier Distortion ???????????????????? ????????????????????? ?????????????????????????????????????????? Noise ??????????? Impedence Mismatch ????????????????????????????? ????????????????? cable ???????????????????????????????????????????????? ??????? echo canceller ???? 2929

    30. Attenuation 3030

    31. Distortion 3131

    32. ???????????????????? Thermal: white noise ???????????????????????????? ??????????????????????? ?????????????????????????????????????? ?????????????????????????? Induced Noise ????????????????????????????????????????????????????? ???? ??????? Crosstalk ??????????????? ?????????????????????????????????????????????? Impulse noise ????????????????????????????????????????????????????????????????? ???? ??????, ??????????????????? Intermodulational ????????????????????????????????? ??????????????????? 3232

    33. Line Noise ???????????????????????????????????????????????????? noise ????????????????????????? ???? line noise level ???????????????????????????? noise 3333

    34. Propagation ??? Transmission velocity Propagation delay (Tp) ???????????????????????????? Transmission delay (Tx) ???????????????????????????????????????? ??????????????????? = Tp + Tx Round trip (a) = Tp / Tx 3434

    35. ???? 3535

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