c. t.-c. nguyen, “towards mems-based receivers,” bwrc winter retreat, 1/(8-9)/06 the future of...
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C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
The Future of RF Microelectromechanical
Systems (MEMS)
Clark T.-C. Nguyen
Dept. of Electrical Engineering & Computer SciencesUniversity of California
Berkeley, California 94720E-mail: [email protected]
BEARS’07Feb.15, 2007
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
Outline
• Motivation: Miniaturization of Transceiversneed for high-Q
• Micromechanical Resonatorsclamped-clamped beamsmicromechanical disks
• Micromechanical Circuitsmicromechanical filtersarraying techniques
• Towards RF Channel-Selection
• Conclusions
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
Wireless Phone
Motivation: Miniaturization of RF Front-Ends
26-MHz Xstal Oscillator
26-MHz Xstal Oscillator
DiplexerDiplexer
925-960MHz RF SAW Filter
925-960MHz RF SAW Filter
1805-1880MHz RF SAW Filter
1805-1880MHz RF SAW Filter
897.517.5MHz RF SAW Filter
897.517.5MHz RF SAW Filter
RF Power Amplifier
RF Power Amplifier
Dual-Band Zero-IF Transistor Chip
Dual-Band Zero-IF Transistor Chip
3420-3840MHz VCO
3420-3840MHz VCO
Problem: high-Q passives pose a bottleneck against miniaturizationProblem: high-Q passives pose a bottleneck against miniaturization
90o
0o
A/D
A/D
RF PLL
Diplexer
From TX
RF BPF
Mixer I
Mixer Q
LPF
LPF
RXRF LO
Xstal Osc
I
Q
AGC
AGC
LNA
Antenna
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
Multi-Band Wireless Handsets
Duplexer
90o
0o
A/D
A/D
RXRF ChannelSelect PLL
I
Q
LPF
LPF
RXRF LO
I
QAGC
AGC
LNA
Duplexer RF BPF
LNA
From TX
LNA
LNA
RF BPF
RF BPF
RF BPF
WCDMAWCDMA
CDMA-2000CDMA-2000
DCS 1800DCS 1800
PCS 1900PCS 1900
LNA
RF BPF
Duplexer
LNA RF BPF
GSM 900GSM 900
CDMACDMA
From TX
From TX90o
0o
I
Q
Tank
÷ (N+1)/N Xstal Osc
Antenna
• The number of off-chip high-Q passives increases dramatically
• Need: on-chip high-Q passives
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
All High-Q Passives on a Single Chip
WCDMARF Filters
(2110-2170 MHz)
CDMA-2000RF Filters
(1850-1990 MHz)
DCS 1800 RF Filter(1805-1880 MHz)
PCS 1900 RF Filter(1930-1990 MHz)
GSM 900 RF Filter(935-960 MHz)
CDMA RF Filters(869-894 MHz)
0.25 mm
0.5 mm
Low Freq. Reference Oscillator Ultra-High
Q Tank
Optional RF Oscillator
Ultra-High Q Tanks
Vibrating Resonator62-MHz, Q~161,000
Vibrating Resonator62-MHz, Q~161,000
Vibrating Resonator1.5-GHz, Q~12,000
Vibrating Resonator1.5-GHz, Q~12,000
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
Thin-Film Bulk Acoustic Resonator (FBAR)
• Piezoelectric membrane sandwiched by metal electrodesextensional mode vibration: 1.8 to 7 GHz, Q ~500-1,500dimensions on the order of 200m for 1.6 GHz link individual FBAR’s together in ladders to make filters
Agilent FBAR
• Limitations:Q ~ 500-1,500, TCf ~ 18-35 ppm/oCdifficult to achieve several different freqs. on a single-chip
h
freq ~ thicknessfreq ~ thickness
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
Vibrating RF MEMS
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
Basic Concept: Scaling Guitar Strings
Guitar String
Guitar
Vibrating “A”String (110 Hz)
Vibrating “A”String (110 Hz)
High Q
110 Hz Freq.
Vib
. A
mp
litu
de
Low Q
r
ro m
kf
21
Freq. Equation:
Freq.
Stiffness
Mass
fo=8.5MHzQvac =8,000
Qair ~50
Mechanical Resonator
Performance:Lr=40.8m
mr ~ 10-13 kgWr=8m, hr=2md=1000Å, VP=5VPress.=70mTorr
[Bannon et al JSSC’00]
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06• Fabrication steps compatible with planar IC processing
Surface Micromachining
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
• Completely monolithic, low phase noise, high-Q oscillator (effectively, an integrated crystal oscillator)
• To allow the use of >600oC processing temperatures, tungsten (instead of aluminum) is used for metallization
OscilloscopeOutput
Waveform
Single-Chip MEMS-Transistor Integration
[Nguyen, Howe 1993][Nguyen, Howe JSSC’99]
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
Basic Concept: Scaling Guitar Strings
Guitar String
Guitar
Vibrating “A”String (110 Hz)
Vibrating “A”String (110 Hz)
High Q
110 Hz Freq.
Vib
. A
mp
litu
de
Low Q
r
ro m
kf
21
Freq. Equation:
Freq.
Stiffness
Mass
fo=8.5MHzQvac =8,000
Qair ~50
Mechanical Resonator
Performance:Lr=40.8m
mr ~ 10-13 kgWr=8m, hr=2md=1000Å, VP=5VPress.=70mTorr
[Bannon et al JSSC’00]
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
Radial-Contour Mode Disk Resonator
VP
vi
Input Electrode
Output Electrode
io
ivoi
Q ~10,000Disk
Supporting Stem
Smaller mass higher freq. range and lower series Rx
Smaller mass higher freq. range and lower series Rx(e.g., mr = 10-13 kg)(e.g., mr = 10-13 kg)
Young’s Modulus
Density
Mass
Stiffness
R
E
m
kf
r
ro
1
2
1
Frequency:
R
VP
C(t)
dt
dCVi Po
Note: If VP = 0V device off
Note: If VP = 0V device off
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
-100
-98
-96
-94
-92
-90
-88
-86
-84
1507.4 1507.6 1507.8 1508 1508.2
1.51-GHz, Q=11,555 Nanocrystalline Diamond Disk
Mechanical Resonator• Impedance-mismatched stem for reduced anchor dissipation
• Operated in the 2nd radial-contour mode
• Q ~11,555 (vacuum); Q ~10,100 (air)
• Below: 20 m diameter disk
PolysiliconElectrode R
Polysilicon Stem(Impedance Mismatched
to Diamond Disk)
GroundPlane
CVD DiamondMechanical Disk
Resonator Frequency [MHz]
Mix
ed
Am
plit
ud
e [
dB
]
Design/Performance:R=10m, t=2.2m, d=800Å, VP=7V
fo=1.51 GHz (2nd mode), Q=11,555
fo = 1.51 GHzQ = 11,555 (vac)Q = 10,100 (air)
[Wang, Butler, Nguyen MEMS’04]
Q = 10,100 (air)
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
Commercialization of MEMS Timekeepers
High-Q, low drift, make possible a very stable, low
power timekeeper
High-Q, low drift, make possible a very stable, low
power timekeeper$3.5 Billion
Market
‘s pure silicon high-Q vibrating mechanical resonator oscillator
Discera TCMO
Smaller size Lower cost Lower power
consumption
Smaller size Lower cost Lower power
consumption
Package Package CapCap
ASICASICMechanical Mechanical
Resonator DieResonator Die
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
OutputOutput
Custom IC fabricated via TSMC 0.35m process
Custom IC fabricated via TSMC 0.35m process
InputInput
GSM-Compliant Oscillator
[Y.-W. Lin, Nguyen, IEDM’05]
-160
-140
-120
-100
-80
-60
-40
-20
1.E+01 1.E+02 1.E+03 1.E+04 1.E+05
Offset Frequency [Hz]
Ph
ase
No
ise
[d
Bc/
Hz]
9-Wine-Glass Disk ArrayQQ = 118,900 = 118,900 , Rx = 2.56 k9-Wine-Glass Disk ArrayQQ = 118,900 = 118,900 , Rx = 2.56 k
9-WG Disk Array @ 62 MHz9-WG Disk Array @ 62 MHz
Single WG Disk @ 62 MHzSingle WG Disk @ 62 MHz
Down to 13 MHz
Down to 13 MHz
GSM specGSM spec
Satisfies Global System for Mobile Communications (GSM)
phase noise specifications!
Satisfies Global System for Mobile Communications (GSM)
phase noise specifications!
All made possible by mechanical circuit design!
All made possible by mechanical circuit design!
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
Integrated Micromechanical Circuits
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
Micromechanical Filter Design Basics
RQ
vo
vi
RQ
VP
xovi
o
xovi
o
vovi
o
vovi
o
Disk Resonator
Coupling Beam
Bridging Beam
Termination Resistor
Loss Pole
Loss Pole
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
-60
-50
-40
-30
-20
-10
0
8.7 8.9 9.1 9.3Frequency [MHz]
Tra
nsm
issi
on
[d
B]
Pin=-20dBm
In Out
VP
Sharper roll-off
Sharper roll-off
Loss PoleLoss Pole
Performance:fo=9MHz, BW=20kHz, PBW=0.2%
I.L.=2.79dB, Stop. Rej.=51dB20dB S.F.=1.95, 40dB S.F.=6.45
Performance:fo=9MHz, BW=20kHz, PBW=0.2%
I.L.=2.79dB, Stop. Rej.=51dB20dB S.F.=1.95, 40dB S.F.=6.45
Design:Lr=40m
Wr=6.5m hr=2m
Lc=3.5mLb=1.6m VP=10.47VP=-5dBm
RQi=RQo=12k
[S.-S. Li, Nguyen, FCS’05]
3CC 3/4 Bridged Mechanical Filter
[Li, et al., UFFCS’04]
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
Micromechanical Filter Circuit
1/krmr cr1/krmr cr
1/krmr cr-1/ks -1/ks
1/ks
-1/ks -1/ks
1/ks
1/kb 1/kb
-1/kb
Co Co
1:e e:1
1:c 1:cc:1 c:1
1:b b:1
/4
/4
/4Input
Outputvi
RQ
RQ
vo
VP
Bridging Beam
Coupling Beam
Resonator
vovi
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
Micromechanical Filter Circuit
1/krmr cr1/krmr cr
1/krmr cr-1/ks -1/ks
1/ks
-1/ks -1/ks
1/ks
1/kb 1/kb
-1/kb
Co Co
1:e e:1
1:c 1:cc:1 c:1
1:b b:1
/4
/4
/4Input
Outputvi
RQ
RQ
vo
VP
Bridging Beam
Coupling Beam
Resonator
vovi
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
Micromechanical Filter Circuit
1/krmr cr1/krmr cr
1/krmr cr-1/ks -1/ks
1/ks
-1/ks -1/ks
1/ks
1/kb 1/kb
-1/kb
Co Co
1:e e:1
1:c 1:cc:1 c:1
1:b b:1
/4
/4
/4Input
Outputvi
RQ
RQ
vo
VP
Bridging Beam
Coupling Beam
Resonator
vovi
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
vovi
Micromechanical Filter Circuit
1/krmr cr1/krmr cr
1/krmr cr-1/ks -1/ks
1/ks
-1/ks -1/ks
1/ks
1/kb 1/kb
-1/kb
Co Co
1:e e:1
1:c 1:cc:1 c:1
1:b b:1
/4
/4
/4Input
Outputvi
RQ
RQ
vo
VP
Bridging Beam
Coupling Beam
Resonator
All circuit element values determined
by CAD layout
All circuit element values determined
by CAD layout
Amenable to automated circuit
generation
Amenable to automated circuit
generation
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
-60
-50
-40
-30
-20
-10
0
8.7 8.9 9.1 9.3Frequency [MHz]
Tra
nsm
issi
on
[d
B]
Pin=-20dBm
In Out
VP
Sharper roll-off
Sharper roll-off
Loss PoleLoss Pole
Performance:fo=9MHz, BW=20kHz, PBW=0.2%
I.L.=2.79dB, Stop. Rej.=51dB20dB S.F.=1.95, 40dB S.F.=6.45
Performance:fo=9MHz, BW=20kHz, PBW=0.2%
I.L.=2.79dB, Stop. Rej.=51dB20dB S.F.=1.95, 40dB S.F.=6.45
Design:Lr=40m
Wr=6.5m hr=2m
Lc=3.5mLb=1.6m VP=10.47VP=-5dBm
RQi=RQo=12k
[S.-S. Li, Nguyen, FCS’05]
3CC 3/4 Bridged Mechanical Filter
[Li, et al., UFFCS’04]
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
Square-Plate Micromechanical
Resonator
Coupling Beam
h
Ws
gap, do
Lr
50-Terminated 68-MHz Coupled-Array Mechanical
Filter
-21
-18
-15
-12
-9
-6
-3
0
67.60 67.80 68.00 68.20 68.40 68.60
Frequency [MHz]
Tran
smis
sion
[dB
]
Use square-plate mechanical
resonator arrays
Use square-plate mechanical
resonator arrays
Lower end resonator impedance & raise
power handling
Lower end resonator impedance & raise
power handling
50 termination w/ L-network
50 termination w/ L-network
Lr = 16mh = 2.2mdo = 90nm
Lr = 16mh = 2.2mdo = 90nm
RQ = 12kRterm = 50
RQ = 12kRterm = 50
fo=68MHzBW=190kHzPBW=0.28%I.L.<2.7dB
fo=68MHzBW=190kHzPBW=0.28%I.L.<2.7dB
[Demirci, Nguyen 2005]
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
RF Channel-Selection
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
Motivation: Need for High Q
Antenna
Demodulation Electronics
The higher the Q of the Pre-
Select Filter the simpler the demodulation
electronics
The higher the Q of the Pre-
Select Filter the simpler the demodulation
electronics
Pre-SelectFilter in the GHz Range
Presently use resonators
with Q’s ~ 400
Presently use resonators
with Q’s ~ 400
Wireless Phone
Rec
eive
dP
ower
FrequencyRF
DesiredSignal
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
Motivation: Need for High Q
Antenna
Demodulation Electronics
The higher the Q of the Pre-
Select Filter the simpler the demodulation
electronics
The higher the Q of the Pre-
Select Filter the simpler the demodulation
electronics
Pre-SelectFilter in the GHz Range
Presently use resonators
with Q’s ~ 400
Presently use resonators
with Q’s ~ 400
Wireless Phone
Rec
eive
dP
ower
FrequencyRF
DesiredSignal
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
Motivation: Need for Q’s > 10,000
Antenna
Demodulation Electronics
The higher the Q of the Pre-
Select Filter the simpler the demodulation
electronics
The higher the Q of the Pre-
Select Filter the simpler the demodulation
electronics
Pre-SelectFilter in the GHz Range
Presently use resonators
with Q’s ~ 400
Presently use resonators
with Q’s ~ 400
Wireless Phone
Rec
eive
dP
ower
FrequencyRF
DesiredSignal
If can have resonator
Q’s > 10,000
If can have resonator
Q’s > 10,000
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
Motivation: Need for Q’s > 10,000
Antenna
Demodulation Electronics
The higher the Q of the Pre-
Select Filter the simpler the demodulation
electronics
The higher the Q of the Pre-
Select Filter the simpler the demodulation
electronics
Pre-SelectFilter in the GHz Range
Presently use resonators
with Q’s ~ 400
Presently use resonators
with Q’s ~ 400
Wireless Phone
Rec
eive
dP
ower
FrequencyRF
DesiredSignal
If can have resonator
Q’s > 10,000
If can have resonator
Q’s > 10,000
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
Motivation: Need for Q’s > 10,000
Antenna
Demodulation Electronics
The higher the Q of the Pre-
Select Filter the simpler the demodulation
electronics
The higher the Q of the Pre-
Select Filter the simpler the demodulation
electronics
Pre-SelectFilter in the GHz Range
Presently use resonators
with Q’s ~ 400
Presently use resonators
with Q’s ~ 400
If can have resonator
Q’s > 10,000
If can have resonator
Q’s > 10,000
Wireless Phone
Non-Coherent FSK Detector?(Simple, Low Frequency, Low Power)
Front-End RF Channel Selection
Front-End RF Channel Selection
Rec
eive
dP
ower
FrequencyRF
DesiredSignal
Substantial Savings in Cost and Battery PowerSubstantial Savings in
Cost and Battery Power
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
Motivation: Need for Q’s > 10,000
Antenna
Demodulation Electronics
The higher the Q of the Pre-
Select Filter the simpler the demodulation
electronics
The higher the Q of the Pre-
Select Filter the simpler the demodulation
electronics
Pre-SelectFilter in the GHz Range
Presently use resonators
with Q’s ~ 400
Presently use resonators
with Q’s ~ 400
If can have resonator
Q’s > 10,000
If can have resonator
Q’s > 10,000
Wireless Phone
Direct-Sampling A/D Converter Software-Defined Radio
Maximum Flexibility one circuit satisfies all
comm. standards
Maximum Flexibility one circuit satisfies all
comm. standardsFront-End RF
Channel SelectionFront-End RF
Channel Selection
Rec
eive
dP
ower
FrequencyRF
DesiredSignal
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
RF Channel-Select Filter Bank
Bank of UHF mechanical
filters
Bank of UHF mechanical
filters
Switch filters on/off via
application and removal of dc-bias VP, controlled by
a decoder
Switch filters on/off via
application and removal of dc-bias VP, controlled by
a decoder
Tra
nsm
iss
ion
Freq.
Tra
nsm
iss
ion
Freq.
Tra
nsm
iss
ion
Freq.
1 2 n3 4 5 6 7RF Channels
Remove all interferers!
Remove all interferers!
C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06
Conclusions
• Vibrating RF MEMS have achievedVibrating RF MEMS have achievedQ’s >10,000 at GHz frequencies in sizes less than 20 m in
diameter and w/o the need for vacuum encapsulationTCf’s < -0.24 ppm/oC (better than quartz)aging at least on par with quartzcircuit-amenable characteristics VLSI potential
• Probable evolution of products based on vibrating RF MEMS:Probable evolution of products based on vibrating RF MEMS: timing devices using micromechanical resonatorscommunication-grade frequency synthesizerssingle-chip of all needed high-Q passivesmechanical radio front-ends …
• In ResearchIn Research: Time to turn our focus towards mechanical circuit : Time to turn our focus towards mechanical circuit design and mechanical integrationdesign and mechanical integrationmaximize, rather than minimize, use of high-Q componentse.g., RF channelizer paradigm-shift in wireless designeven deeper frequency computation
• What’s possible with an unlimited supply of high-What’s possible with an unlimited supply of high-QQ passives? passives?