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Introduction to Communication System

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A communication system is for transmitting and receiving the information that users want to exchange. To make up a communication system, we can adopt the FDMA, TDMA, CDMA, and so on. In this …

A communication system is for transmitting and receiving the information that users want to exchange. To make up a communication system, we can adopt the FDMA, TDMA, CDMA, and so on. In this presentation, we introduce a simplified communication blocks with which we can understand a modern system.

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  • 1. Electronic Circuit Design CHO, Yong Heui Introduction to Communication System
  • 2. 1. Communication Transmission 
    • Information
      • Channel bandwidth
      • Base band
      • Inefficient wave radiation
    • Modulation – center frequency
    Time domain Frequency domain 출처 : RFDH.com
  • 3. Why do we need modulation? 
    • Transmission efficiency
      • Multiplexing
      • Antenna length: wavelength
      • Wave radiation: comparison with DC
    Battery: DC Antenna: AC 1. Communication
  • 4. Communication transmitter (Tx) 
    • Up-conversion: frequency
     출처 : RFDH.com 1. Communication
  • 5. Communication receiver (Rx) 
    • Down-conversion: frequency
     출처 : RFDH.com 1. Communication
  • 6. Communication transceiver 
    • Duplexer: bandpass filter or switch
      • Loss, tx suppression, channel selection
    IF: superheterodyne No IF: direct conversion 출처 : RFDH.com 1. Communication
  • 7. FDMA (FDM Access) 
    • Resource: frequency
    • Guard band
    • Simple transceiver
    • Interference
    1. Communication
  • 8. TDMA (TDM Access) 
    • Resource: time
    • Guard time
    • Complicated transceiver
    1. Communication
  • 9. Synchronization of TDMA 
    • Guard time: imperfect sync
    1. Communication
  • 10. GSM TDMA 
    • Global System for Mobile Communication
    • TDMA within FDMA
    • Carrier separation: 200 kHz
    1. Communication
  • 11. FH(Frequency Hopping)-CDMA 
    • Resource: code
    • Precise clock
    • Very complicated transceiver
    • Bluetooth, military applications
    1. Communication
  • 12. DS(Direct Sequence)-CDMA QPSK: Quadrature Phase Shift Keying 1. Communication
  • 13. Block diagram of cellular phone
    • LNA (Low Noise Amplifier), PA (Power Amplifier), Mixer, VCO, switch
    • Filter, duplexer
     2. System
  • 14. Digital RF system Transmitter and receiver  2. System
  • 15. AM receiver 
    • Envelope detector
    Antenna + BPF + diode + capacitor + speaker 2. System
  • 16. AM receiver with amplifier  2. System