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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 presentation, we introduce a simplified communication blocks with which we can understand a modern system.
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Introduction to Communication
System
Electronic Circuit Electronic Circuit DesignDesign
CHO, Yong HeuiCHO, Yong Heui
Electronic Circuits Electronic Circuits DesignDesign
EM Wave LabEM Wave Lab2
1. Communication
Transmission
Information- Channel bandwidth- Base band- Inefficient wave radiation
Modulation – center frequency
Time domain Frequency domain
출처 : RFDH.com
Electronic Circuits Electronic Circuits DesignDesign
EM Wave LabEM Wave Lab3
Why do we need modulation?
Transmission efficiency- Multiplexing- Antenna length: wavelength- Wave radiation: comparison with DC
Battery: DCAntenna: AC
1. Communication
Electronic Circuits Electronic Circuits DesignDesign
EM Wave LabEM Wave Lab4
Communication transmitter (Tx)
Up-conversion: frequency
)cos()cos(2
1)cos()cos( yxyxyx
BBf BBLO ff BBLO ff
출처 : RFDH.com
1. Communication
Electronic Circuits Electronic Circuits DesignDesign
EM Wave LabEM Wave Lab5
Communication receiver (Rx)
Down-conversion: frequency
)cos()cos(2
1)cos()cos( yxyxyx
BBfBBIF ff BBLO ff
IFLO fff IFff
출처 : RFDH.com
1. Communication
Electronic Circuits Electronic Circuits DesignDesign
EM Wave LabEM Wave Lab6
Communication transceiver
Duplexer: bandpass filter or switch- Loss, tx suppression, channel selection
IF: superheterodyneNo IF: direct conversion
출처 : RFDH.com
1. Communication
Electronic Circuits Electronic Circuits DesignDesign
EM Wave LabEM Wave Lab7
FDMA (FDM Access)
Resource: frequency Guard band Simple transceiver Interference
1. Communication
Electronic Circuits Electronic Circuits DesignDesign
EM Wave LabEM Wave Lab8
TDMA (TDM Access)
Resource: time Guard time Complicated transceiver
1. Communication
Electronic Circuits Electronic Circuits DesignDesign
EM Wave LabEM Wave Lab9
Synchronization of TDMA
Guard time: imperfect sync
1. Communication
Electronic Circuits Electronic Circuits DesignDesign
EM Wave LabEM Wave Lab10
GSM TDMA
Global System for Mobile Communication TDMA within FDMA Carrier separation: 200 kHz
1. Communication
Electronic Circuits Electronic Circuits DesignDesign
EM Wave LabEM Wave Lab11
FH(Frequency Hopping)-CDMA
Resource: code Precise clock Very complicated transceiver Bluetooth, military applications
1. Communication
Electronic Circuits Electronic Circuits DesignDesign
EM Wave LabEM Wave Lab12
DS(Direct Sequence)-CDMA
QPSK: Quadrature Phase Shift Keying
1. Communication
Electronic Circuits Electronic Circuits DesignDesign
EM Wave LabEM Wave Lab13
Block diagram of cellular phone
LNA (Low Noise Amplifier), PA (Power Amplifier), Mixer, VCO, switch
Filter, duplexer
2. System
Electronic Circuits Electronic Circuits DesignDesign
EM Wave LabEM Wave Lab14
Digital RF system
Transmitter and receiver
2. System
Electronic Circuits Electronic Circuits DesignDesign
EM Wave LabEM Wave Lab15
AM receiver
Envelope detector
Antenna + BPF + diode + capacitor + speaker
2. System
Electronic Circuits Electronic Circuits DesignDesign
EM Wave LabEM Wave Lab16
AM receiver with amplifier
2. System
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