1 J.Dąbrowski, Intro to RF Front-End Design 1 Introduction to RF Front-End Design Jerzy Dąbrowski Division of Electronic Devices Department of Electrical Engineering (ISY) Linköping University e-mail: [email protected]J.Dąbrowski, Intro to RF Front-End Design 2 Objectives of the course • Learn principles of wireless digital communication transceivers • Gain knowledge of RF front-end circuits • Learn basic design methods and techniques for RF circuit design in CMOS technology • Understand the related possibilities and limitations
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J.Dąbrowski, Intro to RF Front-End Design1
Introduction to RF Front-End Design
Jerzy DąbrowskiDivision of Electronic Devices
Department of Electrical Engineering (ISY)Linköping University
• Learn principles of wireless digital communication transceivers
• Gain knowledge of RF front-end circuits• Learn basic design methods and techniques
for RF circuit design in CMOS technology• Understand the related possibilities and
limitations
2
J.Dąbrowski, Intro to RF Front-End Design3
Organization of the course
• Lectures 8 x 2h • Laboratory work 3 x 4h (guided by Henrik
Fredriksson and Rashad Ramzan)• Project work (Simulink/Cadence Spectre) • Individual reports• Course books:
– B. Razavi, RF Microelectronics, Prentice-Hall, 1998 – T.H. Lee, The Design of CMOS RF Integrated Circuits,
Cambridge Univ. Press, 1998/2004
J.Dąbrowski, Intro to RF Front-End Design4
Outline of the lecture
• Wireless communication systems today
• Digital communication RF channel
• Digital modulation techniques
• Multiple access techniques
• Digital RF transceiver at glance
• CMOS RF design issues
• Summary
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J.Dąbrowski, Intro to RF Front-End Design5
Wireless Communication Systems Today
WLANBluetooth
DECTPHS
CT1/CT2EDGE, GSM IS-54/IS-95
PDCGPS
Satellite
Paging
10m 100m 1000m 10km 100km 1000km Range
Bit Ratekb/sec
1
10
100
1000
In-door
Cordless
Cellular
4G directionsAlso many other wireless applications and gadgetsUMTS
CDMA2000
Zigbee
10,000
UWB100,000
J.Dąbrowski, Intro to RF Front-End Design6
Overview of PCS Standards
1 W1, 2, 11Mb/s
QPSK25 ppm3000 kHz
2400-2483CDMA802.11b(DSSS)
0.125, 0.25, 0.5, 2W
3840 (max)
QPSK0.1 ppm5000 kHz
1920-1980 (Tx)2110-2170 (Rx)
W-CDMA/ TD-CDMA
WCDMA(UMTS)
1,4,100 mW1000GFSK20 ppm1000 kHz
2400-2483CDMA/ FDMA/FH
Bluetooth
Peak PowerRate(kb/s)
Modulation Technique
FrequencyAccuracy
ChannelSpacing
Frequencyband (MHz)
Access Scheme
Standard
N/A
0.8, 1, 2, 3 W
250 mW
0.8, 2, 5, 8 W
0.8, 2, 5, 8 W
1228
48
1152
270.8
270.8
GMSK90 Hz200 kHz1710-1785 (Tx)1805-1850 (Rx)
TDMA/FDMA/ TDD
DCS-1800
OQPSK
π/4 QPSK
GMSK
GMSK
N/A1250 kHz
824-849 (Tx) 869-894 (Rx)
CDMA/ FDMA
IS-95
200 Hz30 kHz824-849 (Tx) 869-894 (Rx)
TDMA/FDMA
IS-54
50 Hz1728 kHz
1880-1900TDMA/FDMA/ TDD
DECT
90 Hz200 kHz890-915 (Tx)935-960 (Rx)
TDMA/FDMA/ TDD
GSM
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J.Dąbrowski, Intro to RF Front-End Design7
• Tx’s convert BB to RF signals using modulation
• Tx’s must not corrupt one another – division of RF band
• Rx’s select wanted RF signals and retrieve BB by demodulation
• Rx’s must suppress unwanted signals and noise
Tx1BB1
RF1
Tx2BB2
RF2Rx1
BB…
RF1
RF2
RF …
Tx3BB3
RF3
RF communication channel
Rx2BB…
RF1
RF2
RF3
J.Dąbrowski, Intro to RF Front-End Design8
Above 300 GHz< 1 mm
30–300 GHz10 mm – 1 mm11EHFExtremely high frequency
microwave devices, mobile phones3–30 GHz100 mm – 10 mm10SHFSuper high frequency
television broadcasts, wireless LAN300–3000 MHz1 m – 100 mm9UHFUltra high frequency
FM and television broadcasts30–300 MHz10 m – 1 m8VHFVery high frequency
Shortwave broadcasts and amateur radio3–30 MHz100 m – 10 m7HFHigh frequency
AM broadcasts300–3000 kHz1 km – 100 m6MFMedium frequency
Navigation, time signals, AM longwavebroadcasting
30–300 kHz10 km – 1 km5LFLow frequency
Military communication3–30 kHz100 km – 10 km4VLFVery low frequency
300–3000 Hz1000 km – 100 km3ULFUltra low frequency
30–300 Hz10,000 km – 1000 km2SLFSuper low frequency
3–30 Hz100,000 km – 10,000 km1ELFExtremely low frequency
< 3 Hz> 100,000 km
Example usesFrequencyWavelengthITU bandAbbrBand name
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J.Dąbrowski, Intro to RF Front-End Design9
Propagation Effects
• Path loss, interferers and external noise
• Multi-path and fading
( ) [ ]( ) [ ]dBm
dBλ/π4log20
RxAntPTxAntTxRx
P
GLGPP
RL
+−+=
=
RTx Rxλ
Power loss in open area
Received power incl. gain of the antennas
Direct path
Tx Rx
Reflective path
Moving objects or Rx/Txresult in signal fluctuations, (different varying paths)
Immobile or mobile object
Wanted signal is corrupted by interferers and noise
intsignoisesig PPSIRPPSNR ==
J.Dąbrowski, Intro to RF Front-End Design10
Digital Tx & Rx
Analog BB
inputADC DSP DAC RF
Front-End
RF part (analog)
RFFront-End
ADC DSP DAC
Analog BB
output
RF part (analog)
BB part (digital)
BB part (digital)
Coding, Interleaving,
Shaping, Modulation
Demodulation, Deinterleaving, Decoding
Upconversion,gain, filtering
Downconversion,gain, filtering
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J.Dąbrowski, Intro to RF Front-End Design11
BB data rate
t
x(t)
t
y(t)Sampling
1/fSNyquist limit
fS > 2Bx
Number of bits per sample: NSampled BB data rate: R = fS N bits/sec
Example: For voice coding B = 3.4 kHz fS = 8 kHz and N = 8 → R = 64 kb/sec.Next, compression with vocoders is used so R = 2.4 .. 9.6 kb/secbut the transmitted data rate would be much higher for system arrangements and extra data needed, e.g. GSM – 270 kb/s, IS-95 (CDMA) – 1.23Mb/s
QuantizationN bits
J.Dąbrowski, Intro to RF Front-End Design12
Shannon limitsInformation capacity: C = 2B log2M [bits/sec]
Channel bandwidth
Number of signal levels transmitted
Bandwidth efficiency: C/B = 2 log2M [bits/sec/Hz]
For 2-levels: C/B = 2, maximum possible to achieve,
1 10 01 1
0 0
Tb2Tb
Low pass channel
Bmin = 1/2Tb
In Rx at least the first harmonic is needed
M = 2
Period = 2Tb
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J.Dąbrowski, Intro to RF Front-End Design13
Shannon limit due to noise
C = 2B log2M [bits/sec]
Information capacity if B or M 000001
010
100101
011
The more levels the more noise harmful
C = B log2(1 + SNR) [bits/sec]
Channel noise limits C, but M is not specified here.
In practice bit rate must be R < C to support transmission with an acceptable error rate
M-ary system
J.Dąbrowski, Intro to RF Front-End Design14
RF systems vs channel capacity
×+=
=
BC
NE
BC
BNRESNR
b
b
02
0
1log
Bit rate R < C for any system
e.g. for GSM: R/B = 270kbps/200kHz = 1.35 @ SNR = 9dB for BER < 10-3
for DECT:R/B = 1152kbps/1728kHz = 0.67@ SNR = 10.3dB for BER < 10-3
This IEEE 802.11a (in 5 GHz band) transceiver employs a direct-conversion architecture and includes an internal synthesizer. This is Intel's first RFIC used in a WLAN product.