2007/Dec/12web.nchu.edu.tw/~ycchiang/RFIC/RFIC_modulation.pdf · • Mobile RF Communication f1 f1...
Transcript of 2007/Dec/12web.nchu.edu.tw/~ycchiang/RFIC/RFIC_modulation.pdf · • Mobile RF Communication f1 f1...
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2007/Dec/12
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Modulation and Detection
• Why modulation?– Transmission lines and antenna concerns.– Communication spectrum distribution.– Simpler receiving circuits in non-ideal communication channel.
ω ω0 Cω− Cω+0Figure 3.1 (a) Baseband and (b) passband signals.
Modulator Channel DemodulatorBasebandSignal
DetectedSignal
Transmitter Receiver
Figure 3.2 Simple communication system.
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Analog Modulation
• Amplitude Modulation
t
t
t
ω ω0 Cω− Cω+0Figure 3.4 Amplitude modulation in (a) time domain, (b) frequency domain.
ωCω− Cω+0
∗
)(AM tx
tCωcos
LPFinV outV1C 1R
Figure 3.5 AM detectors.
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Analog Modulation
• Phase and Frequency Modulation (PM & FM)
t
t
t
)(txBB
)(txPM
)(txFM
Figure 3.6 Phase- and frequency-modulated waveforms corresponding to a square wave baseband signal.
Figure 3.7 Simple frequency modulator.
)(BB tx )(FM tx
Voltage-Controlled Oscillator
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Analog Modulation
• Phase and Frequency Modulation (PM & FM)
t tinV outV
1C1R
Figure 3.8 Simple frequency demodulator.
ω0 ωCω
)(BB fx )(FM fx
ωCω
)(FM fx
ωmω0mω−
mC ωω +mC ωω −
)(BB fx)a(
)b(
Figure 3.9 Narrowband FM with (a) random and (b) sinusoidal modulation.
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Digital Modulation
• Signal
• ASK
• PSK
• FSK
t
t
t
t
Signal constellations
[ ] ( ) ( )[ ]LL xxtx 2121)( φφαα ⋅=
1α
2α
CA+
CA+
1α0 CA+CA−
1α0 CA+
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Digital Modulation
• Binary and M-ary Signaling
0 1 0 1 1 0 1 0 0 0 1 1 0 0
01 0110 10
00
11
00
t
BinaryData
4-LevelData
Figure 3.13 Four-level digital representation of a binary stream.
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Digital Modulation
• Effect of Noise
• ASK
• FSK
t
Signal constellations
1α0 CA+
t
1α
2α
CA+
CA+DecisionBoundary
1α0 CA+CA−
BPSK 1α
2α2CA
+
2CA
+
2CA
−2CA
−
QPSK QAM
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Digital Modulation
• BPSK
1α0 CA+CA−
tAtp CC 1 cos)( ω+=
tAtp CC 2 cos)( ω−=
BasebandData
)(BPSK tx
)(BPSK tx
tA CC ωcos2
∫bT
0
bT(a)(b)
BasebandData
(c)
Figure 3.29 BPSK (a) modulator, (b) constellation, (c) demodulator.
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Digital Modulation
• QPSK
BinaryBaseband
Data
S/PConverter
tC cosωtC sinω )(tx
A
B
∫bT
0
∫bT
0
P/SConverter
)(QPSK tx tC cosωtC sinω
BasebandData
ST
ST
Figure 3.32 Quadrature modulation.
Figure 3.34 Coherent QPSK detection.
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Multiple Access Techniques
• Mobile RF Communication
1f
1f
1f
1f
1f
1f
1f
2f1f 2f
1f
mobile unit(hand-held unit)
base station
downlink (forward channel)
uplink(reverse channel)
Figure 4.1 (a) Simple cellular system, (b) 7-cell reuse pattern.
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Multiple Access Techniques
1f
1f
1f
1f
1f
Figure 4.2 Cochannel interference.
Cell A
Cell B
MTSO
Figure 4.2 Problem of handoff.
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Multiple Access Techniques
• Diversity– Space diversity– Frequency diversity– Time diversity
Direct Path
Reflective Path)log(loss
d
41
Figure 4.4 Indirect signal propagation and resulting loss profile.
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Multiple Access Techniques
Figure 4.8 Time-division of duplexing.
Figure 4.9 Frequency-division of duplexing.
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Multiple Access Techniques
• Frequency-Division Multiple Access
• Time-Division Multiple Access
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Multiple Access Techniques
• Code-Division Multiple Access– Direct-Sequence CDMA
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Multiple Access Techniques
• Code-Division Multiple Access– Direct-Sequence CDMA
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Multiple Access Techniques
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Multiple Access Techniques
• Frequency-Hopping CDMA
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Wireless Standards
• Advanced Mobile Phone Service (1G Cellular Systems)– Frequency-Division Multiple Access– Analog FM
Figure 4.17 (a) AMPS air interface, (b) duplexer characteristics.
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Wireless Standards
• North American Digital Standard (NADC; 2G Cellular system)
Figure 4.18 NADC (a) air interface, (b) frame structure, (c) TX and RX time slots.
− Digital modulation− TDMA / FDM− IS-54 / IS-136 digital standard
1850−1910 MHz
1930−1990 MHz
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Wireless Standards
• Global System for Mobile Communication (2G Cellular system)– Digital modulation– TDMA / FDM
Figure 4.19 GSM (a) air interface and (b) frame structure.
DCS-1800: 1710−1785 MHzPCS-1900: 1850−1910 MHz
DCS−1800: 1805-1880 MHzPCS−1900: 1930-1990 MHz
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Wireless Standards
• Qualcomm CDMA (2G)– Digital modulation– CDMA / FDM
2110−2170 MHz (Asia)1930−1990 MHz
1920−1980 MHz (Asia)1850−1910 MHz
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Wireless Standards
• Digital European Cordless Telephone (2G Cellular system)– Digital modulation– TDMA / FDM
Figure 4.22 DECT (a) air interface and (b) frame structure.
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Wireless Standards
• 2G → 3G (144 kb/s in-vehicle, 384 kb/s for pedestrians)• 2.5G: General Packet Radio Service
Enhanced Data rate for Global Evolution
• Non-cellular Wireless Applications– IEEE 802.11 (WiFi)– Bluetooth– WPAN– Ultra-Wide Band (normalized bandwidth > 25%)– Multiple-Input Multiple-Output
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Wireless Standards
• Summary of IEEE 802.11b/g and 802.11a
Mb/s 545.5 MS/s; 12
Mb/s 54for QAM-64 :OFDMTDD
CSMA/CAgoverlappin-non 12
MHz 20 :OFDMMHz 58255725MHz 53505150
802.11a
gfor Mb/s 54bfor Mb/s 11or 2 ,1
OFDM) :(802.11g0.5 GFSK, :FHSS
TDDCSMA/CA
goverlappin-non 3MHz 25 :DSSS / 1MHz :FHSS
MHz 5.24832400802.11b/g
rate symbolor Bit
ModulationmethodDuplex Access Multiple
channels ofNumber spacing Channel
range Frequency Parameter
−
−−
=
−
BT
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Wireless Standards
• Summary of Bluetooth
MS/s 1GFSK
active) (7 200TDD
Hopping Frequency 79
MHz 1MHz 24802402
Europe ofmost America,North
rate SymbolModulation
channelper UsersmethodDuplex Access Multiple
channels ofNumber spacing Channel
range Frequency Parameter
−
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Wireless Standards
• Wireless Personal Area Network• Summary of IEEE 802.15.4 (“ZigBee”)
kb/s 2500.5 GFSK,
255FDD
TDMAMHz 5
MHz 24722412Europe
kb/s 400.5 OQPSK,
255FDD
CSMA/CAMHz 5
MHz 928902AmericaNorth
kb/s 2500.5 OQPSK,
255FDD
CSMA/CAMHz 5
MHz 24802402AmericaNorth
rate SymbolModulation
channelper UsersmethodDuplex Access Multiplespacing Channel
range Frequency Parameter
=
−
=
−
=
−
BTBTBT