Hamid Rategh Wireless LAN Receiver Injection-Locked...
Transcript of Hamid Rategh Wireless LAN Receiver Injection-Locked...
A CMOS Frequency Synthesizer with anInjection-Locked Frequency Divider for a 5 GHz
Wireless LAN Receiver
Hamid Rategh
Center for Integrated SystemsStanford University
OUTLINE
� Motivation
� Introduction to wireless LAN
� Synthesizer architecture
� Synthesizer building blocks
� Summary and conclusion
MOTIVATION
� Large demand for wideband wireless LAN systems
– 20+ Mb/s data rate
– Low cost
– Low power
� New released frequency band
– Unlicensed national information infrastructure (U–NII) band
GOAL
� Design a 5 GHz frequency synthesizer for a U–NII bandwireless–LAN receiver (HIPERLAN compatible).
� Implement in CMOS.
� Minimize power consumption.
FREQUENCY OF OPERATION
23.5 MHz
5.15 5.30 5.35 5.8255.725
HIPERLAN U-NII
5.15 GHz
GHz
5.35
HIPERLAN/1 STANDARD
Class A Class B Class C
Transmitter power +10 dBm +20 dBm +30 dBm
Receiver sensitivity -50 dBm -60 dBm -70 dBm
Maximum signal level -25 dBm
Modulation GMSK (BT=0.3)
Data rate 20 Mb/s
Topology multihop ad hoc
Carrier switching time � 1 ms
Channel bandwidth 23.5 MHz
HIPERLAN MULTIHOP ad hoc topology
Forwarder
RECEIVER ARCHITECTURE
rfLO1=f x
Σ
Σ
16
17 16
1LO2=LO1x
rff =5.15-5.35 GHz
Q
I+
-
+
+
LNA
SynthesizerFrequency
� Weaver architecture.
� Requires quadrature LO’s to reject the image signal.
TYPICAL PLL–BASED FREQUENCY SYNTHESIZER
VCO
M
PFD
Loop Filter
Channel Selection
foutref f =Mfref
� Reference is a crystal oscillator.
� fout = M� fref
� Multiple LO frequencies are generated by changing M.
� Frequency dividers are power hungry.
– Their power consumption increases with frequency.
PROPOSED PLL ARCHITECTURE
f
Charge PumpPFD
M
ModulusChannelSelect Control
Loop Filter VCO
f
PrescalerProgram &
CountersPulse Swallow
outref
Tracking ILFD
12
N/N+1
� fref=11 MHz
� fo=4.840–4.994 GHz
� 8 channels
� M=220–227
� N=8
INJECTION LOCKING
� By impressing an oscillator with an external (incident) signal,frequency locking can be achieved.
– First-harmonic injection locked oscillators ( fifo= 1).
– Subharmonic injection locked oscillators ( fifo= 1N
).
– Superharmonic injection locked oscillators ( fifo= N ).
Injection–locked frequency dividers (ILFDs).
ILFD SIMPLIFIED PICTURE
f(e) = e2
iω iω2
iωi2
ωi2
ω
i2
ωi Η(ω)e uω
2,
,
3@
� Intermodulation of the input and output is the base of frequencydivision in an ILFD.
� An ILFD is an oscillator with perturbed oscillation.
– Oscillation conditions should be satisfied in the presence ofthe incident signal.
SPECIAL CASE (DIVIDE–BY–TWO)
f(e) = a0 + a1e+ a2e2 + a3e3
� Condition 1:
j�!!rj < jH0a2Vi
2Q
j ;
H0Q
=LQ!r
Q
= L!r
� Condition 2:
H0(a1 +3
2a3V2
i + a2Vi cos(�)) < 1
TRACKING ILFD
Tracking ILFD
12
Vc
VVi o
VCO
� Locking range extension
DIFFERENTIAL TRACKING ILFD
Vx
Vin
Vout
Vc
M1M2
M3M4 R1R2
Ibias
Vdd
- - ++
� 0.24 �m CMOS
� Vdd=1.5 V
� Ibias=300 �A
� fo=2.45 GHz
� fi=4.9 GHz
INDUCTOR DESIGN (ILFD)
� Maximum locking range) maximize L
� Minimum power consumption) maximize LQ
INDUCTOR DESIGN
Cp1 Cp2
RsiCsiRsi Csi
Cs
L Rs
Sub
w
s
OD
� Design parameters:
– w: metal width
– s: metal spacing
– OD: outer dimension
– n: number of turns
INDUCTOR DESIGN (ILFD)
� In planar spiral inductors maximizing L does not maximize LQ
+
maximize L for a given LQ
ILFD FREE–RUNNING OSCILLATION
0.5 1 1.5 2 2.52380
2400
2420
2440
2460
2480
2500
Control voltage (V)
Out
put f
requ
ency
(M
Hz)
� 0.24 �m CMOS
� Vdd=1.5 V
� Ibias=300 �A
� �f=110 MHz (5%)
� �Vc=2 V
ILFD LOCKING RANGE/POWER CONSUMPTION
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.60
500
1000
Inpu
t ref
erre
d lo
ckin
g ra
nge
(MH
z)
Vc=1.5VVc=2.0V
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
0.5
1
Pow
er (
mW
)
Incident amplitude (V)
� 0.24 �m CMOS
� Vdd=1.5 V
� fo=2.45 GHz
� fi=4.9 GHz
� �f=1 GHz@ 1 V (� 20%)
� Power=0.75 mW@ 1 V
PHASE NOISE MEASUREMENT TEST SETUP
HP8563E50
On chip
Vi
50
50
Vdd
Ext. Amp.DILFD
ILFD PHASE NOISE
100
101
102
103
104
−130
−120
−110
−100
−90
−80
−70
Offset frequency (kHz)
Pha
se n
oise
(dB
c/H
z)
HP83732B Free running Middle freqeuncyEdge frequency � 0.24 �m CMOS
� Vdd=1.5 V
� fo=2.45 GHz
� fi=4.9 GHz
ILFD SUMMARY
Frequency of operation 5 GHz
Output frequency tuning 110 MHz� 5%
Input–referred locking range 600 MHz� 12% @ 0.55 mW
1000 MHz� 20% @ 0.8 mW
Technology 0.24 �m CMOS
Die area 0.225 mm2
Flipflop based divider (for comparison)
0.24 �m CMOS (simulation) 5 mW @ 5 GHz
0.1 �m CMOS [1] 2.6 mW @ 5 GHz
[1] Razavi et al., JSSC Vol. 30, No.2, pp 101–109, Feb. 1995
PROGRAMMABLE FREQUENCY DIVIDER
N/N+1fin
S
M
P
Program Counter
Reset
Swallow Counter
fout
ModulusControl
Channel Selection
Prescaler
� One output cycle =
(N+ 1)S+ (P� S)N = PN+ S input cycles.
� M = PN+ S
� N = 8;P = 26; S = 12:::19;M = 220:::227
PRESCALER (� 8/9)
FF2 FF1MC
Clk
O1
Q
Q 2ClkMC
QQClk 2Clk2/3In
MC
Out
ClkQ
D Q
ClkQ
D Q
NOR/FLIPFLOP IMPLEMENTATION
B
AB B
A
Ibias
Clk
Vdd
RR
Vdd
RR
Q Q
A
Clk
PROGRAM AND PULSE SWALLOW COUNTERS
S=1,2,...,24Swallow Counter (S=1,2,...,24)
MC
FF1
Reset
Reset
Program Counter (P=26)
FF2
OutT-FF
ClkQ
R QT-FF
R
ClkQR
D Q
Clk
D
Q
Q
Q
Ch3Ch2Ch1 Ch4 Ch5
QClk
T-FFR Q
QClk
T-FFR Q
QClk
T-FFR Q
QClk
clk
clk clk
PHASE/FREQUENCY DETECTOR
iU
FF1
FF2
Reset
Reset
V
R
Q
Q
D
Clk
QD
Q
D
Clk i
Output stage
U
U
D
D
CHARGE PUMP AND LOOP–FILTER
Wp
DownI
M6
M7
Vr
Wp
Wn 2Wn Wn
Loop filter
Charge pumpReplica bias Feedback network
WpI
M8
Up
M5
pO
C1C2
R3
C3
R1
Vddvco
Vc1On
UUM4M3
DDM1 M2
CHARGE PUMP CURRENT MATCHING
0 0.5 1 1.5 2−10
−8
−6
−4
−2
0
2
4
6
8
10
Vo (V)
(Id−
Iu)/
Id*1
00
� �II
<0.05%0.25 V� VO � 1.75 V
� �II
<2%0.1 V� VO � 1.8 V
LOOP FILTER
PLL order
2nd order 3rd order 4th order
# Poles 2 3 4
Independent designvariables:
1) Phase marginp p p
2) Loop bandwidthp p p
3) Spur attenuation
p
LOOP FILTER DESIGN (4th ORDER PLL)
104
105
106
107
108
109
−150
−100
−50
0
50
100
Mag
nitu
de (
dB)
open loop transfer function
104
105
106
107
108
109
−300
−250
−200
−150
−100
Frequency (Hz)
Pha
se (
degr
ee)
OutIn
C1
R1
C2 C3
R3
� R3C3 � R1(C2 + C3)
� b = C1
C2+C3
� PM � tan�1(p
1 + b)� tan�1( 1p1+b)
� Wc �p
1+b
R1C1
� ts = f2(PM)
Wc
� R3C3 sets the spur attenuation.
LOOP PARAMETERSParameter Value
Kvco 360 MHz/V (Average)
500 MHz/V (Max)
Ip 3 �A
C1 42 pF
C2 3.5 pF
C3 2.2 pF
R1 170 k
R3 64.5 k
PM 49Æ
Wc 60 kHz
jH(j2�f)j@ fref -45 dB
ts < 35 �s
OutIn
C1
R1
C2 C3
R3
LOOP–FILTER NOISE
100
102
104
106
108
−250
−200
−150
−100
−50
Offset frequency (Hz)
Pha
se n
oise
(dB
c/H
z)
noise of R1noise of R3total noise
� L=-149 dBc/Hz@ 22 MHz
VOLTAGE–CONTROLLED OSCILLATOR
I2m
I1mI1p
I2p
Vo1
M7 M8M4
M6M2M1
M3
M5
Vo2
Vo1
I1=I1p-I1mVo2
-Vo2 I2=I2p-I2m
biasI
biasI
+ +- -
Vdd
Vc+ +- -
Vdd
Vc� 0.24 �m CMOS
� Vdd=1.5 V
� Ibias=4.0 mA
� fo=4.9 GHz
INDUCTOR DESIGN (VCO)
� Maximum Q) minimum inductor noise
� If inductors are not the main source of noise, maximum LQ)
– Maximum oscillation amplitude for a given bias current.
– Minimum phase noise due to active devices.
VCO FREQUENCY TUNING
0 0.5 1 1.5 24.7
4.8
4.9
5
5.1
5.2
5.3
Control voltage (V)
Fre
quen
cy (
GH
z)
� 0.24 �m CMOS
� Vdd=1.5 V
� Ibias=4.0 mA
� �f =550 MHz (11%)
� ( dfdv)max=500 MHz/V
PLL PHASE NOISE
104
105
106
107
108
−150
−140
−130
−120
−110
−100
−90
−80
−70
−60
Offset frequency (Hz)
Pha
se n
oise
(dB
c/H
z)
� L=-134 dBc/Hz@ 22 MHz
SPECTRUM OF THE SYNTHESIZED OUTPUT
4.9 4.92 4.94 4.96 4.98 5−80
−70
−60
−50
−40
−30
−20
−10
0
Frequency (GHz)
Pow
er (
dBm
)
SYNTHESIZER CHIP MICROGRAPH
VCO
ILFDTracking
Prescaler
Counters
BiasLoop Filter
PFD
ChargePump
� 0.24 �m CMOS
� area=1.45 mm2
(1� 1.45 mm2)
SUMMARYSynthesized frequencies 4:840–4:994 GHz
Reference frequency 11 MHz
Spurs < �70 dBc
Phase noise �134 dBc=Hz @ 22MHz
Loop bandwidth 60 kHz
Settling time < 35 �s
Power dissipation
VCO 12 mW
ILFD 1 mW
Prescaler 6:6 mW
Digital+Bias Circuits 2 mWTotal 21:6 mWSupply voltage 1:5 V (analog)
2:0 V (digital)
Implementation
Die area 1:45 mm2
Technology 0:24 �m CMOS
COMPARISON
Ref. f (GHz) P (mW) L (�m) FM PN (dBc/Hz) PNn Spur
[1] 1.6 90 0.6 10.7 -114 @ 600kHz -135.4 -80 dBc
[2] 1.8 51 0.4 14.1 -134 @ 3MHz -142.4
[3] 1.6 36 0.5 22.2 -140 @ 35MHz -126 -45 dBc
[4] 5.0 47 0.4 42.5 -100 @ 5.2MHz -112.5 -50 dBc
This work 5.0 21.6 0.24 55.5 -134 @ 22MHz -134 -70 dBc
� FM = f�LP
� PNn = PN+ 20 log�
�ff
5GHz
22MHz�
[1] J. Parker et al. “A 1.6GHz CMOS PLL with On–chip loop filter” JSSC Vol 33 Mar 98.
[2] J. Craninckx et al. “A Fully Integrated CMOS DCS–1800 Synthesizer” JSSC Vol 33 Dec 98.
[3] A. Shahani et al. “Low Power Dividerless Frequency Synthesis ...” JSSC Vol 33, Dec 98.
[4] C. Lam et al. “A 2.6GHz/5.2GHz Frequency Synthesizer in a 0.4�m CMOS Technology”, VLSI 99.
CONCLUSION
� A 5GHz frequency synthesizer is fully integrated in 0.24�m CMOS.
� Power consumption is reduced significantly by:
– employing a tracking ILFD.
– optimizing spiral inductors for the VCO and ILFD.
– current sharing in the prescaler.
� Loop–filter noise is kept small by using reasonably small resistors.
� A spurious free output is achieved by:
– using a semi–differential charge pump with well matched currents.
– minimizing the skew of the PFD complementary outputs.
– designing a fourth–order loop.
CONTRIBUTIONS
� Developing a general theory for injection–locked oscillators.
� Developing design techniques for very low power ILFD’s with awide locking range.
� Introducing the tracking ILFD.
� Designing a very low power and fully integrated CMOSfrequency synthesizer at 5 GHz.
� Developing a very simple loop filter design recipe for third andfourth order PLL’s.
� Demonstrating the operation of analog CMOS circuits with asub 2 V supply.
ACKNOWLEDGMENTS
National Semiconductor
Stanford Graduate Fellowship Program
Tektronix
Conexant