Upload
duongkhuong
View
219
Download
4
Embed Size (px)
Citation preview
1
Teknologioita adaptiivisiin RF-moduleihinMarkku Ylilammi
VTT Mikro- ja nanotekniikka
Teknologioita adaptiivisiin RF-moduleihin
Markku YlilammiVTT Mikro- ja nanoelektroniikka
Kännykän antennin säteilyimpedanssi vaihtelee voimakkaasti eri käyttötilanteissa. Myös laaja toimintataajuusalue ja saman antennin käyttö eri taajuusalueilla aiheuttaa impedanssi-epäsovitusta RF-elektroniikan ja antennin välillä. Säädettävän sovituspiirin avulla voidaan saavuttaa merkittävä parannus seisovan aallon suhteeseen. Tämä helpottaa tehovahvistimen vaatimuksia ja alentaa tehonkulutusta. Vastaanottopuolella adaptiivinen piiri kasvattaa LN-vahvistimeen siirtyvää signaalia. Adaptiivisia RF-moduleita voidaan valmistaa useilla tekniikoilla. Esityksessä tarkastellaan ferrosähköisten ohutkalvojen kehitystä säädettäviksi kondensaattoreiksi ja BAW-tekniikkaa, joka on korvaamassa SAW-suodattimia.
Application Example: Compensation of Handset Antenna Proximity Effects
A cellular phone next to a human body
A cellular phone on a metal table
Contact: [email protected]
Conventional and Reconfigurable Multi-Band Rx/Txsystem
• By using tunable and reconfigurable components and circuits• Number of components can be lowered • Performance and functionality can be increased
Contact: [email protected]
Analog switch
Some MEMS Components from DC to 220 GHz
• Varactors
• Switches
• Phase shifters
• Capacitor banks
• Filters
• Impedance tuners
• Matching networks
• Antennas
• Power sensors
Contact: [email protected]
Roadmap of passive RF components (c) WTC Arrro
Adaptiivinen RF moduli
• Integroitu RF-piiri• Sähköisesti säädettävä reaktiivinen elementti • Miniatyroisoitu RF-suodatin (BAW, SAW)• Ohjauselektroniikka
Reconfigurable Matching Networks for Power Amplifiers in Adaptive Radio Links
Multi-band matching of a 10 Ω load to 50 Ω
Matching network for 20-50 GHz applications
Contact: [email protected]
Electrically controlled variable capacitor (Varactor)
Adaptive antenna (impedance matching in variable environment)
Steerable antenna (adjustable phase delay lines)
Tunable filter (the pass band of a wide band filter tuned by varactors)
RF-switch (based on tunable resonance circuits)
Ferroelectric mixer (utilizes the nonlinearity of a ferroelectric material)
Tunable microwave disk (cavity) resonator
Ferroelectric thin films
The electric permittivity of a ferroelectric insulator depends on the electric field. A capacitor with this insulator can be controlled by a DC voltage.
Exemplary materials: BaSrTiO3, SrTiO3
Voltage or field
permittivity or capacitance
Q value
Temperature
Typical characteristics
Capacitance ratio 1.5 - 2.5 (STO)
Q-value at 10 GHz 100 - 200
(single crystals 1000 (STO))
Curie temp. 40 - 400 K (BSTO)
Permittivity of ferroelectric thin filmsPbMgNbO (200 nm) / LSCO / MgO heterostructure
Courtesy of University of Oulu
Perm
ittiv
ity
Bias voltage0 2 4 6
500
1000
1500ε'
UB (V)
Sähköisesti säädettävä kondensaattori voidaan tehdä käyttämällä ferrosähköistä materiaalia
GoodPoorExcellentGoodTemperature drift
2000199519901970Known since
~300°C + 750°C post-processannealing
~700°CLowNot relevantSputterTemperature
LowModerateHighHighCost
SiSapphire/SiSiGaAsSubstrate
???HermeticPackaging
ModerateModerateExcellentPoorPower handling
ModerateModerateExcellentVery poorLinearity
?µsecmsecnsecTuning Speed
<50V<30V<100V<10VDC-Bias
~200~70~200~60Q
2:13:11.5:14:1Tunability
BiZnNbOBaSrTiOMEMSGaAs
Säädettävien kondensaattoreiden kilpailevat teknologiat @ 2GHz
Source: Prof. Susanne Stemmer, UCSB, Tutorial Talk at IMS, 2005
Varactors based on ferroelectric materials
Tunable RF-circuits based on ferroelectric thin films (e.g. BaxSr1-xTiO3) offer large potential, but the technology requires development.
Adaptive RF-circuits are very advantageous for wireless applications: E.g. tunable antenna (compensation for antenna mistuning):
- improved performance: better SNR (high data rate channels), lower power consumption- reduction of parallel hardware in multiband systems- reduction of development costs (basic design adapted to several models)
Advantages of FE thin film materials:- fast (tunability up to THz-range)- low losses at high frequencies, especially above 10 GHz - high relative permittivity (typically εr > 100 …500) <=> compact devices- thin films allow low tuning voltages, also compact structures
Current disadvantages / limitations: - small tuning range ε (0)/ε (Umax) ~ 2 due to low breakdown fields - large temperature-coefficient. T-compensation by adaptive tuning restricted due to small available tuning range.- nonlinear effects- hysteresis, thin-film nonidealities
Ferroelectric varactors vs. competing technologies:-diode varactors: larger tunabilities available Cmax/Cmin = 5 .. 10, but losses and tunability worsen above 10 GHz.- MEMS varactors: typically excellent performance, but plagued by size, integration issues, price.
Design of an integrated adaptive matching circuit with adjustable BST-capacitors, a coil with thick Cu metal, bias resistors. (c) Tomi Mattila, VTT
top view
ACin
ACout
GND
GND
side view inductor Cu
BSTPt
Pb/Sn
SiO2
R
GND ACin ACoutDC1
R
GNDDC2L
DC1
DC2
LQ_L
C2Q_C2
C1Q_C1
Z_a = R_a + j X_a
Zin
Design parameters:f0 = 1 GHz, Za = 20 ... 100 + j -100 ... 100 OhmL = 5 nH, QL = 50 QC1 = QC2 = 50
Optimization strategy (preliminary):Adjust C1 and C2 to minimize|Γ|2 at f0, f0 - ∆f, f0 +∆f, ∆f = 10 MHz
0.620.600.380.00300.4644.98.812.7100100
0.890.720.110.00090.2947.18.710.50100
0.620.620.380.00300.4144.87.112.8-100100
0.500.560.500.00410.5444.09.013.410050
1.000.800.000.00020.1748.79.48.5050
0.500.590.500.00410.4444.06.413.7-10050
0.270.410.730.00980.7541.08.716.010020
0.820.900.180.00000.0449.87.15.7020
0.270.450.730.00970.641.05.616.6-10020
Pout no ΠPout|Γ|^2 no Π|Γ|^2Xin (Ω)Rin (Ω)C2 (pF)C1 (pF)X_a (Ω)R_a (Ω)
• sacrifice 1dB power at Za=50Ω <=> significant reduction in |Γ|2
Tunable π-network
AntennaMatching net Zin Pout
2.20.41.80.7
-1.00.50.0
-0.9-0.1
dB
Physical Properties of Ferroelectric Materials
TcT
εr
FERROelectric• spontaneous
polarization• piezo• hysteresis
(high RF-losses)
PARAelectric
• tunable, low-loss materialfor RF-applications
21)0(
)(E
E r
r αε
ε+
≈
!!))0((:Note 3rεαα =
E
εr
electric field
BaxSr1-xTiO3
O.G. Vendik, E.K. Hollmann, A.B. Kozyrev , and A. M. Prudan,"Ferroelectric tuning of planar and bulk microwave devices ",
J. Supercond. 12, 325 (1999).
Q
1000
100
10
Nonlinearity
-20.000 -10.000 0.000 10.000 20.000-60.00
-35.00
-10.00
15.00
40.00APLAC 7.90 User: VTT Microsensing Nov 29 2005
DCbiasf1 2f13f1 4f15f1
-20.000 -10.000 0.000 10.000 20.00030.00
37.50
45.00
52.50
60.00APLAC 7.90 User: VTT Microsensing Nov 29 2005
DCbiasPIIP3
DCbias
Udc = 0..20 V
PIIP
3[d
Bm
]
[V]
[V]
GSM spec.
ω
3ω
Pω = +33 dBm
P3ω = -22 dBm
Goal: ∆f/f = 5% for 1 GHz Q=10 antenna
Application analysis: Antenna tuning
U1/2 = 20 VAntenna eq. circuit
Q = 10
50
Ohm
spec. 65 dBm
Utilize inversely biased varactors topology:- no even-order nonlinearities- convenient DC-blocking
-20.000 -10.000 0.000 10.000 20.0002.80
3.80
4.80
5.80
6.80APLAC 7.90 User: VTT Microsensing Nov 28 2005
DCbiasC
C [p
F]
DC
RFin RFout
APLAC-model forFE capacitor
FE non-idealities: history effects
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
-5 0 5 10 15 20
Udc (V)
C(U
dc)
/ C
(0)
4.7pF series
7.5pF series
5 min
10 min
1 sec
1 sec
=> typical offset ∆C/C0 ~ 10 % after 1 sec!!!
Agilent 4294A LCR-bridgefac ~ 5 MHz, Vac ~ 50 mV
Bulk Acoustic Wave FiltersBulk Acoustic Wave Filters
EGSM (Enhanced Global System for Mobiles) Widely spread standard
Receiver Rx band 925-960 MHz (3.71%)Transmitter Tx band 880-915 MHz (3.90%)PCN band around 2 GHz
Very demanding application from filter design &Very demanding application from filter design &manufacturing point of view!manufacturing point of view!
Coils have very low Q value in this frequency range LC filters are not feasible.
Electromagnetic resonators' size about wavelength (30 cm).Traditional solution is SAW (Surface Acoustic Wave) filter:- requires single crystal piezoelectric substrate LiTaO3- lithography too expensive above 2 GHz- very low maximum power;
not suitable for Tx
Infineon CDMA RF front end
Operation principle of BAW
Piezolayer
Sound velocity 10000 m/s
Top metal electrode
Bottom metal electrode
Acoustic wave (stress distribution)
Electric field generates an acoustic wave inside the piezolayer. This wave resonates between the air interfaces.
Resonance frequency = ½ velocity of sound / thickness.
The sound wave may be either longitudinal or shear.
RF
BAW Approaches
Air
Piezolayer
Air
AirSupportElectrode
Electrode
Substrate
Substrate
Electrode
Piezolayer
Electrode
Low-Z
High-Z
Low-Z
High-Z
λ/4
BRIDGE FBAR MIRROR SMR SEM cross section image
Cross-section of a complete resonator, 3 Mo / SiO2 layer pairs in the mirror
Piezo
Bottom contact
Frequency tuning layer
In a mirror resonator there is an acoustic interference mirror which reflects sound back to the piezolayer. The structure is also called SMR Solidly Mounted Resonator
Infineon, Epcos (Ger.), NXP (formerly Philips, Netherl.)
BAW Mirror Resonator
One segement of a ladder filter
0
5
10
15
20
25
30900 950 1000 1050Frequency (MHz)
Tra
nsm
issi
on (d
B)
Serial resonance frequencyof the shunt (L) resonator
Parallel resonance frequencyof the series (H) resonator
Pass band
H
L
The width of the pass band is limited by the coupling keff.
One segment of a ladder filter
2eff
center
kfBW
<
BAW filters on a test waferH resonators
L resonators
Test resonators1 mm
Example of a commercial product on market
Courtesy Infineon AG
Size 2 x 1.6 x 0.6 mm
2W#69 D4G6o11 b
0
5
10
15
20
25
30800 850 900 950 1000 1050
Frequency (MHz)
Ref
lect
ion
S11,
Ins
ertio
n lo
ss S
21 (d
B)
S21
S11EGSM
VSWR
S21925 MHz 2.95 dB960 MHz 2.33 dB3.5 dB BW 38.2 MHzILmin 1.26 dBRipple 1.69 dBVSWR 2.17Stopband 23.38 dB
Ladder filter with six resonators.
Properties of resonator D41o11:fs 944.7 MHz, fp 971.6 MHzQs 460, Qp 890, Radius 0.943keff 0.234, FoM 48.5Nonc. 0.37 %, RL 53 kOhmCo 3.70 pF Cm 213.7 fF Lm 132.8 nHRm 0.91 Ohm Rx 0.82 Ohm
VTT Measured EGSM ladder filter with three segments or six resonators
Potential of BAW technology in RF filters
Performance estimates expected in commercial devices:
• Operating frequency 1 - 10 GHz, probably higher
• Q-value 2000 at 2 GHz, higher in more distant future
• Coupling coefficient 0.24 (6.5%, AlN), decreases with frequency
• Power handling capacity in filter 4 W, probably higher
• New filter structures (SCR, CRF) in near future
Industrial playersInfineon AG, GermanyAvago, USA, (Agilent)Epcos AG, GermanySkyworks, USA, (Agere)Triquint, USA, (TFR
Technologies)Fujitsu, JapanNXP, Netherland (Philips)STM, FranceLG, KoreaSamsung, Korea
Main products FiltersDuplexersDevelopment goalsHigher frequencies (above 2 GHz)Lower temperature coefficient (< 20 ppm/K)Higher power (several watts)Integration of BAW in IC chipsNew device structures
Markets
Main competitor still SAW filters.
Fierce competition in prices.
New manufacturers enter production.
In mass production
In development phase
Entering the market
Infineon AG, Munich, is the largest manufacturer and technically the most advanced.
BAW filters
• Resonators: coupling K2 up to 10.4% (keff = 0.282, ZnO), quality factor Q > 1200• Theory developed sufficiently to predict measurements
• Filters meeting EGSM specifications can be made without any external components
• No need for hermetic package (unpacked wirebonded VTT filter worked years in a Nokia mobile phone)
• Technology is compatible with integration on silicon chips
• Future:
• Filters for mobile phones have been commercialized
⇒ R&D directed to improve performance
and to create new device structures.
BAW ladder filters on 100 mm glass wafer (VTT)