Advances in RF MEMS and MEMS-Based RF Front-End …people.eecs.berkeley.edu/~ctnguyen/Research/...C....

C. T.-C. Nguyen, “Advances in RF MEMS and MEMS-Based RF Front-End Architectures,” TAPAS’06, 8/5/06

Advances in RF MEMS and MEMS-Based RF Front-End

Architectures

Clark T.-C. Nguyen

Dept. of Electrical Engineering & Computer ScienceUniversity of Michigan

Ann Arbor, Michigan 48105-2122

TAPAS’06August 5, 2006


Outline

• Introduction: Miniaturization of Transceiversneed for high-Qvibrating RF MEMS wish list

• Micromechanical Resonatorsclamped-clamped beamsmicromechanical disksreconfigurable multi-functionalitymicromechanical circuits

• MEMS-Enabled Communication Front-EndsRF channel-selectionall-MEMS front-end

• Conclusions


Wireless Phone

Rec

eive

dPo

wer

FrequencyωRF

DesiredSignal

Motivation: Miniaturization of RF Front Ends

90o0o

A/D

A/D

RF PLL

Diplexer

From TX

RF BPF

Mixer I

Mixer Q

LPF

LPF

RXRF LO

XstalOsc

I

Q

AGC

AGC

LNA

Antenna


Wireless Phone

Rec

eive

dPo

wer

FrequencyωRF


90o0o

A/D

A/D

RF PLL

Diplexer

From TX

RF BPF

Mixer I

Mixer Q

LPF

LPF

RXRF LO

XstalOsc

I

Q

AGC

AGC

LNA

Antenna

Need high Q to minimize loss

lower noise figure


lower noise figureHighly selective

frequency filteringHighly selective

frequency filtering


Wireless Phone

FrequencyωRF


90o0o

A/D

A/D

RF PLL

Diplexer

From TX

RF BPF

Mixer I

Mixer Q

LPF

LPF

RXRF LO

XstalOsc

I

Q

AGC

AGC

LNA

Antenna


lower noise figure


lower noise figureHighly selective

frequency filteringHighly selective

frequency filtering

DesiredSignal


Wireless Phone

FrequencyωRF


90o0o

A/D

A/D

RF PLL

Diplexer

From TX

RF BPF

Mixer I

Mixer Q

LPF

LPF

RXRF LO

XstalOsc

I

Q

AGC

AGC

LNA

Antenna

DesiredSignal

Need high Qor low loss

components to do this

Need high Qor low loss

components to do this


Why High-Q?


• In resonator-based filters: high tank Q ⇔ low insertion loss

• At right: a 0.3% bandwidth filter @ 70 MHz (simulated)

heavy insertion loss for resonator Q < 5,000

Selective Low-Loss Filters: Need Q


• Main Function: provide a stable output frequency• Difficulty: superposed noise degrades frequency stability

ωωο

ivoi

A

Frequency-SelectiveTank

SustainingAmplifier

ov

Ideal Sinusoid: ( ) ⎟⎠⎞⎜

⎝⎛= tofVotov π2sin

Real Sinusoid: ( ) ( ) ( )⎟⎠⎞⎜

⎝⎛⎟

⎠⎞⎜

⎝⎛ ++= ttoftVotov θπε 2sin

ωωο

ωωο=2π/TO

TO

Zero-Crossing Point

Tighter SpectrumTighter Spectrum

Oscillator: Need for High Q

Higher QHigher Q


• Problem: IC’s cannot achieve Q’s in the thousandstransistors consume too much power to get Qon-chip spiral inductors Q’s no higher than ~10off-chip inductors Q’s in the range of 100’s

• Observation: vibrating mechanical resonances Q > 1,000• Example: quartz crystal resonators (e.g., in wristwatches)

extremely high Q’s ~ 10,000 or higher (Q ~ 106 possible)mechanically vibrates at a distinct frequency in a thickness-shear mode

Attaining High-Q


Wireless Phone

So Many Passive Components!

26-MHz XstalOscillator


DiplexerDiplexer

925-960MHz RF SAW Filter925-960MHz

RF SAW Filter

1805-1880MHz RF SAW Filter


897.5±17.5MHz RF SAW Filter


RF Power Amplifier

RF Power Amplifier

Dual-Band Zero-IF Transistor Chip


3420-3840MHz VCO

3420-3840MHz VCO

90o0o

A/D

A/D

RF PLL

Diplexer

From TX

RF BPF

Mixer I

Mixer Q

LPF

LPF

RXRF LO

XstalOsc

I

Q

AGC

AGC

LNA

Antenna

Problem: high-Q passives pose a bottleneck against miniaturizationProblem: high-Q passives pose a bottleneck against miniaturization


Multi-Band Wireless Handsets

Duplexer

90o0o

A/D

A/D

RXRF ChannelSelect PLL

I

Q

LPF

LPF

RXRF LO

I

QAGC

AGC

LNA

Duplexer RF BPF

LNAFrom TX

LNA

LNA

RF BPF

RF BPF

RF BPF

WCDMAWCDMA

CDMACDMA--20002000

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 XstalOsc

Antenna

• The number of off-chip high-Qpassives increases dramatically

• Need: on-chip high-Q passives


High-Q Resonator Needs

Duplexer

90o0o

A/D

A/D


I

Q

LPF

LPF

RXRF LO

I

QAGC

AGC

LNA

Duplexer RF BPF

LNAFrom TX

LNA

LNA

RF BPF

RF BPF

RF BPF

WCDMAWCDMA

CDMACDMA--20002000

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 XstalOsc

Antenna

Best if Q >500Best if Q >500

Would likeQ’s >2,000

Would likeQ’s >2,000 Would like

Q’s >10,000Would likeQ’s >10,000

Best when highest Q

used

Best when highest Q

used


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 200μm for 1.6 GHzlink 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


Vibrating RF MEMS Wish List

•• MicroMicro--scale waferscale wafer--level fabricationlevel fabricationwould like >1,000 parts per die to at least achieve large-scale integration (LSI) complexityneed wafer-level packaging

•• SingleSingle--chip integrated circuit or chip integrated circuit or system capabilitysystem capability

discrete parts not interestingmust allow many different frequencies on a single-chipneed on-chip connectivityintegration w/ transistors desiredneed real time reconfigurability

•• QQ’’s >10,000 at RF might have a s >10,000 at RF might have a revolutionary impactrevolutionary impact

Frequencies should be determined by lateral

dimensions (e.g., by layout)



900 MHz

1800 MHz

433 MHz200 MHz

70 MHz

1900 MHz



Duplexer

90o0o

A/D

A/D


I

Q

LPF

LPF

RXRF LO

I

QAGC

AGC

LNA

Duplexer RF BPF

LNAFrom TX

LNA

LNA

RF BPF

RF BPF

RF BPF

WCDMAWCDMA

CDMACDMA--20002000

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 XstalOsc

Antenna

• The number of off-chip high-Qpassives increases dramatically

• Need: on-chip high-Q passives


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 QTanks

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











900 MHz

1800 MHz

433 MHz200 MHz

70 MHz

1900 MHz

C. T.-C. Nguyen, “Advances in RF MEMS and MEMS-Based RF Front-End Architectures,” TAPAS’06, 8/5/06• Fabrication steps compatible with planar IC processing

Surface Micromachining


• 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 Ckt/MEMS Integration

[Nguyen, Howe 1993][Nguyen, Howe JSSC’99]











Best if systems can be reconfigured w/o the need

for RF MEMS switches

Best if systems can be reconfigured w/o the need

for RF MEMS switches

900 MHz

1800 MHz

433 MHz200 MHz

70 MHz

1900 MHz


Vibrating RF MEMS


Basic Concept: Scaling Guitar StringsGuitar String

Guitar

Vibrating “A”String (110 Hz)Vibrating “A”

String (110 Hz)

High Q

110 Hz Freq.

Vib.

Am

plitu

de

Low Q

r

ro m

kfπ21

=

Freq. Equation:

Freq.

Stiffness

Mass

fo=8.5MHzQvac =8,000

Qair ~50

μMechanical Resonator

Performance:Lr=40.8μm

mr ~ 10-13 kgWr=8μm, hr=2μmd=1000Å, VP=5VPress.=70mTorr

[Bannon et al JSSC’00]


• Constructed in SiC material w/ 30 nm Al metallization for magnetomotive pickup

Lr

Wr

h

Frequency [GHz]

Mag

neto

mot

ive

Res

p. [n

V]

Design/Performance:Lr =1.1 μm, Wr =120 nm, h= 75 nm

fo=1.029 GHz, Q =500 @ 4K, vacuum

Design/Performance:Lr =1.1 μm, Wr =120 nm, h= 75 nm

fo=1.029 GHz, Q =500 @ 4K, vacuum

[Roukes, Zorman 2002]

Nanomechanical Vibrating Resonator


Scaling-Induced Performance Limitations

Mass Loading Noise

• Differences in rates of adsorption and desorption of contaminant molecules

mass fluctuationsfrequency fluctuations

Temperature Fluctuation Noise

• Absorption/emission of photons

temperature fluctuationsfrequency fluctuations

ContaminantMolecules

NanoresonatorMass ~10-17 kg

mk

2π1

of =

Photons

NanoresonatorVolume ~10-21 m3

• Problem: if dimensions too small phase noise significant!• Solution: operate under optimum pressure and temperature

[J. R. Vig, 1999]


Radial-Contour Mode Disk Resonator

VP

vi

Input Electrode

Output Electrode

io ωωο

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

RE

mkf

r

ro

121

⋅∝=ρπ

Frequency:

R

VP

C(t)

dtdCVi Po =

Note: If VP = 0V device off

Note: If VP = 0V device off


Low Loss Switch Needs

Duplexer

90o0o

A/D

A/D


I

Q

LPF

LPF

RXRF LO

I

QAGC

AGC

LNA

Duplexer RF BPF

LNAFrom TX

LNA

LNA

RF BPF

RF BPF

RF BPF

WCDMAWCDMA

CDMACDMA--20002000

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 XstalOsc

Antenna

Low loss switch

Low loss switch


Micromechanical Switch

[C. Goldsmith, 1995]

• Operate the micromechanical beam in an up/down binary fashion

• Performance: I.L.~0.1dB, IIP3 ~ 66dBm (extremely linear)• Issues: switching voltage ~ 50V, switching time: 1-5μs

Electrode

OutputInput

Dielectric


RF MEMS Switch (Radant)

• Metal cantilever DC switch3-terminal devicePt contact interfacehigh R silicon substrateelectrostatic actuation

Vactuate ~ 90V• Package: wafer-to-wafer

glass frit bonded caplow costenv. protection

100 μm

Drain

Gate

Beam

Source

Contact Detail

Packaged Device

• Reliability (gov’t tested):>1 T mechanical cycles>700 B cycles 100mW RF cold switch

• Reliability (Radant tested):>2.5 B cycles 2W RF cold switched>100 B cycles 0.5W RF cold switched

[Radant]


RF BPF

RF BPF

RF BPF


Duplexer

90o0o

A/D

A/D


I

Q

LPF

LPF

RXRF LO

I

QAGC

AGC

LNA

Duplexer RF BPF

LNAFrom TX

LNA

LNA

RF BPF

WCDMAWCDMA

CDMACDMA--20002000

DCS 1800DCS 1800

PCS 1900PCS 1900

LNA

Duplexer

LNA RF BPF

GSM 900GSM 900

CDMACDMA

From TX

From TX90o

0o

I

Q

Tank

÷ (N+1)/N XstalOsc

Antenna

Capacitively transduced

micromechanical resonators switch

themselves

Capacitively transduced

micromechanical resonators switch

themselves

No need for switches!

No need for switches!


Input Electrode

Output Electrode

Disk

Supporting Stem

R11 22

VP vLO

LxCx Rx

VPCo Co

11 22

0V

Reconfigurable Capacitive Transducer

33

Open Circuit11 22

Co Co

ForceInput

ElectricalSignal Input

ωRFωLO

ωRFωLOωIF

ω

ω

FilterResponse

vLO

vRF11

2233

ωIF

( ) ( )tVVxCvvF LORFRFLORFLOd ωω −−∂∂

−= cos~21 2


-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 μMechanical 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 μm diameter disk

PolysiliconElectrode R

Polysilicon Stem(Impedance Mismatched

to Diamond Disk)

GroundPlane

CVD DiamondμMechanical Disk

Resonator Frequency [MHz]

Mix

ed A

mpl

itude

[dB

]

Design/Performance:R=10μm, t=2.2μm, d=800Å, VP=7Vfo=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)


Self-Aligned Fabrication Process

• Strategy: make stem misalignment impossible• Below:

successive film depositionssimultaneous definition of disk shape and stem location

Silicon Substrate

SiliconNitridePolysiliconOxide Polydiamond



• Below:define electrode-to-resonator gap spacing via sacrificial oxide sidewall spaceretch stem anchor

Silicon Substrate

SacrificialOxide

SidewallSpacer

Photoresist



• Below:deposit thick polysiliconpattern to define stem and electrodes

Silicon Substrate

Polysilicon



• Result: micromechanical disk with perfectly centered stem and nano-scale electrode-to-resonator gaps

Silicon Substrate

Sturdy PolysiliconElectrode (stronger

than previous metal)

Sturdy PolysiliconElectrode (stronger

than previous metal)

Tiny Gaps (50 nm gaps have been achieved)

Tiny Gaps (50 nm gaps have been achieved)

Micromechanical Disk Structure

Micromechanical Disk Structure

Self-Aligned Stem Perfectly Placed at Disk Center

Self-Aligned Stem Perfectly Placed at Disk Center


Output

Input Anchor

d = 80 nm• Right: zoom-in on the 80 nm gap achieved via the sacrificial sidewall spacer process

Tiny Lateral Transducer Gaps


All Silicon Spoke-Supported Rings

Frequency

vi

Support Beam

vovo

Input Electrode

Output ElectrodeNotchedSupport VP

Frequency

vi

Support Beam

vovo

Input Electrode


Refill StemRefill Stem

Frequency

vi

Support Beam

vovo

Input Electrode


Frequency

vi

Support Beam

vovo

Input Electrode


Refill StemRefill Stem

[S.-S Li, et al., MEMS’04]

1204.3 1204.4 1204.5 1204.6 1204.7 1204.8 1204.9 1205 1205.1 1205.2 1205.3-101

-100

-99

-98

-97

-96

-95

-94

-93

-92

-91

ri=11.8μm ro=18.7μm VP=8Vfo=1.205GHz Q=14,603vRF=6.32VvLO=10VPP

Frequency [MHz]

Tran

smis

sion

[dB

m]

3rd Mode via mixing measurement

Notch in UHF

1204.3 1204.4 1204.5 1204.6 1204.7 1204.8 1204.9 1205 1205.1 1205.2 1205.3-101

-100

-99

-98

-97

-96

-95

-94

-93

-92

-91


Frequency [MHz]

Tran

smis

sion

[dB

m]



Frequency [MHz]

Tran

smis

sion

[dB

m]


Notch in UHF

Q ~ 14,600 at 1.2GHzQ ~ 14,600 at 1.2GHz

Reflect energy back into the ring structure Allow high Q

in an all-silicon structure

Reflect energy back into the ring structure Allow high Q

in an all-silicon structure

Direct Support

λ/4λ/4 λ/4λ/4

Longitudinal Mode Quarter Wavelength

Supports

Longitudinal Mode Quarter Wavelength

Supports

Notched Support

Mix

ed A

mpl

itude

[dB

m]


Output

Input

Input

Output

Support Beams

Wine Glass Disk Resonator

R = 32 μm

Anchor

Anchor

Resonator DataR = 32 μm, h = 3 μmd = 80 nm, Vp = 3 V

Resonator DataR = 32 μm, h = 3 μmd = 80 nm, Vp = 3 V

-100

-80

-60

-40

61.325 61.375 61.425

fo = 61.37 MHzQ = 145,780

Frequency [MHz]

Unm

atch

ed T

rans

mis

sion

[dB

]

Wine-Glass Disk Resonator

[Y.-W. Lin, Nguyen, JSSC Dec. 04]

node

node

node

node

Compound Mode (2,1)


•Freq.-Q product rising exponentially over the past years

1990 1995 2000 2005 2010

1015

109

1010

1011

1012

1013

1014

Year

Freq

uenc

y-Q

Prod

uct

silicon

diamond

silicon

silicon

silicon

silicon

silicon

fo = 1.51 GHzQ = 11,555

fo = 1.51 GHzQ = 11,555

silicon

μMechanical Resonator fo-Q Product

Intrinsic material Q limit nowhere

in sight?

Intrinsic material Q limit nowhere

in sight?


Matching ToleranceMatching ToleranceMatching Tolerance

1.5GHz, Q >10,000 in air [Wang, Nguyen, MEMS’04]

1.5GHz, Q >10,000 in air [Wang, Nguyen, MEMS’04]

Breaking Down the Device Barriers

Frequency RangeFrequency RangeNoiseNoise

Quality FactorQuality Factor

71MHz Array, Rx~480Ω[Demirci, Nguyen, Trans’05]71MHz Array, Rx~480Ω

[Demirci, Nguyen, Trans’05]

473MHz, Rx~80Ω[Piazza, Pisano, MEMS’05]

473MHz, Rx~80Ω[Piazza, Pisano, MEMS’05]

13.1MHz Osc. [Kaajakari, Seppa, EDL’04]

13.1MHz Osc. [Kaajakari, Seppa, EDL’04]

16kHz Osc. [Nguyen, Franke, King, Howe,

‘93-’02]

16kHz Osc. [Nguyen, Franke, King, Howe,

‘93-’02]

18ppm over 25-125oC [Hsu, Nguyen, MEMS’02]

18ppm over 25-125oC [Hsu, Nguyen, MEMS’02] <2ppm over 12 mos.

[Kim, Kenny, Trans’05]<2ppm over 12 mos.[Kim, Kenny, Trans’05]

Thermal Stability

Thermal Stability

Aging StabilityAging

Stability

High ImpedanceHigh ImpedanceHigh ImpedanceRF MEMS CktRF MEMS Ckt

Power Handling

Power HandlingPower

HandlingIntegration w/ Transistors

PackagingPackagingPackagingIntegration w/ Transistors

Integration w/ Transistors

Absolute ToleranceAbsolute Tolerance


Integrated Micromechanical Circuits


Micromechanical Filter Design Basics

RQ

vo

vi

RQ

VP

ω

xovi

ωo ω

xovi

ωo ω

vovi

ωo ω

vovi

ωo

Disk Resonator

Coupling Beam

Bridging Beam

Termination Resistor

Loss Pole

Loss Pole


-60

-50

-40

-30

-20

-10

0

8.7 8.9 9.1 9.3Frequency [MHz]

Tran

smis

sion

[dB

]

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=40μm

Wr=6.5μm hr=2μm

Lc=3.5μmLb=1.6μm VP=10.47VP=-5dBm

RQi=RQo=12kΩ

[S.-S. Li, Nguyen, FCS’05]

3CC 3λ/4 Bridged μMechanical Filter

[Li, et al., UFFCS’04]


Micromechanical Filter Circuit

1/krmr cr 1/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:ηe ηe:11:ηc 1:ηcηc:1 ηc:1

1:ηb ηb:1

λ/4

λ/4

3λ/4Input

Outputvi

RQ

RQ

vo

VP

Bridging BeamCoupling Beam

Resonator

ω

vovi


ω

vovi

Micromechanical Filter Circuit

1/krmr cr 1/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:ηe ηe:11:ηc 1:ηcηc:1 ηc:1

1:ηb ηb:1

λ/4

λ/4

3λ/4Input

Outputvi

RQ

RQ

vo

VP

Bridging BeamCoupling 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


-60

-50

-40

-30

-20

-10

0

8.7 8.9 9.1 9.3

High-Order Micromechanical Filter

[Wang, MEMS’97]

High-Order Micromechanical Filter

[Wang, MEMS’97]HF Micromech. Filter[Bannon, IEDM’96]

HF Micromech. Filter[Bannon, IEDM’96]

fo = 340kHzIL < 0.6dBRQ = 364kΩ

fo = 340kHzIL < 0.6dBRQ = 364kΩ

Frequency [MHz]

Tran

smis

sion

[dB

]

Sharper roll-offs

Sharper roll-offs

Bridged μMech. Filter[S.-S. Li, UFFCS’2004]Bridged μMech. Filter[S.-S. Li, UFFCS’2004]

fo = 9.3MHzIL < 2.8dBRQ = 12kΩ

fo = 9.3MHzIL < 2.8dBRQ = 12kΩ

fo = 7.8 MHzIL < 2dBRQ = 14.7kΩ

fo = 7.8 MHzIL < 2dBRQ = 14.7kΩ

Loss poleLoss pole

• MEMS Filters excellent insertion loss• Problem: High Impedance & poor power handling

Demo’ed Micromechanical FiltersMD2


Square-Plate Micromechanical

Resonator

Coupling Beam

h

Ws

gap, do

Lr

50Ω-Terminated 68-MHz Coupled-Array μMechanical Filter

-21

-18

-15

-12

-9

-6

-3

0

67.60 67.80 68.00 68.20 68.40 68.60Frequency [MHz]

Tran

smis

sion

[dB

]

Use square-plate μmechanical

resonator arrays

Use square-plate μmechanical

resonator arrays

Lower end resonator impedance & raise

power handling

Lower end resonator impedance & raise

power handling

50Ω termination w/ L-network

50Ω termination w/ L-network

Lr = 16μmh = 2.2μmdo = 90nm

Lr = 16μmh = 2.2μmdo = 90nm

RQ = 12kΩRterm = 50ΩRQ = 12kΩRterm = 50Ω

fo=68MHzBW=190kHzPBW=0.28%I.L.<2.7dB

fo=68MHzBW=190kHzPBW=0.28%I.L.<2.7dB

[Demirci, Nguyen 2005]


Wine Glass Disk Array Oscillator

VDD = 1.65 V

VSS = -1.65V

M3M4

M1 M2

MRf

Vbias2

Vbias1

M11 M12 M13 M14

Vcm

M17M18

M16M15Output

Input

M5

Shunt-Shunt Feedback Tranresistance Amplifier

Common Mode Feedback Bias Circuit

VP

vi

Bond Wire

Bond Wire

MOS ResistorMOS

Resistor

io

Wine-Glass Disk Array-Composite Resonator

Wine-Glass Disk Array-Composite Resonator

VP=7V Rx=2.5kΩ

Q = 118,900

VP=7V Rx=2.5kΩ

Q = 118,900


OutputOutputCustom IC fabricated via TSMC 0.35μm process

Custom IC fabricated via TSMC 0.35μm 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]

Phas

e N

oise

[dB

c/H

z]

9-Wine-Glass Disk ArrayQ = 118,900 , Rx = 2.56 kΩ9-Wine-Glass Disk ArrayQQ = 118,900 = 118,900 , Rx = 2.56 kΩ

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!


Wireless Phone

So Many Passive Components!



DiplexerDiplexer

925-960MHz RF SAW Filter925-960MHz

RF SAW Filter





RF Power Amplifier

RF Power Amplifier



3420-3840MHz VCO

3420-3840MHz VCO

90o0o

A/D

A/D

RF PLL

Diplexer

From TX

RF BPF

Mixer I

Mixer Q

LPF

LPF

RXRF LO

XstalOsc

I

Q

AGC

AGC

LNA

Antenna

Problem: high-Q passives pose a bottleneck against miniaturizationProblem: high-Q passives pose a bottleneck against miniaturizationNo longer a problem!No longer a problem!

Use as many high-Qpassives as desired!Use as many high-Qpassives as desired!

Seemingly limitless possibilities …

Seemingly limitless Seemingly limitless possibilities possibilities ……


RF Channel-Selection


Motivation: Need for High Q

Antenna

Demodulation Electronics

The higher the Q of the Pre-

Select Filter the simpler the demodulation

electronics



electronics

Pre-SelectFilter in the GHz Range

Presently use resonators

with Q’s ~ 400


with Q’s ~ 400

Wireless Phone

Rec

eive

dPo

wer

FrequencyωRF

DesiredSignal


Motivation: Need for Q’s > 10,000

Antenna




electronics



electronics



with Q’s ~ 400


with Q’s ~ 400

Wireless Phone

Rec

eive

dPo

wer

FrequencyωRF

DesiredSignal

If can have resonator

Q’s > 10,000


Q’s > 10,000



Antenna




electronics



electronics



with Q’s ~ 400


with Q’s ~ 400


Q’s > 10,000


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

dPo

wer

FrequencyωRF

DesiredSignal

Substantial Savings in Cost and Battery PowerSubstantial Savings in

Cost and Battery Power



Antenna




electronics



electronics



with Q’s ~ 400


with Q’s ~ 400


Q’s > 10,000


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

dPo

wer

FrequencyωRF

DesiredSignal


RF Channel-Select Filter Bank

Bank of UHF μmechanical

filters

Bank of UHF μmechanical

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 decoderTr

ansm

issi

on

Freq.

Tran

smis

sion

Freq.

Tran

smis

sion

Freq.

1 2 n3 4 5 6 7RF Channels

Removes all interferers!

Removes all interferers!


02468

101214161820

100 1000 10000 100000

RF Channel-Selection: Need Q >10,000

• Below: plots for a 4-resonator Chebyshev filter with 0.01dB passband ripple

Constituent Resonator Q

Filte

r Ins

ertio

n Lo

ss [d

B]

DCS 1800Pre-Select4.17%BW

DCS 1800Pre-Select4.17%BW

WCDMARF Ch-Select

0.23%BW

WCDMARF Ch-Select

0.23%BWDCS 1800

RF Ch-Select0.03%BW

DCS 1800RF Ch-Select

0.03%BW

CDMA-2000RF Ch-Select

0.07%BW

CDMA-2000RF Ch-Select

0.07%BW


Conclusions

•• Vibrating RF MEMS have achievedVibrating RF MEMS have achievedQ’s >10,000 at GHz frequencies in sizes less than 20 μm 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 : Time to turn our focus towards mechanical circuit design and mechanical integrationcircuit design and mechanical integration

maximize, rather than minimize, use of high-Q componentse.g., RF channelizer paradigm-shift in wireless designeven deeper frequency computation

•• Beginnings of a revolution reminiscent of the IC revolution?Beginnings of a revolution reminiscent of the IC revolution?

Advances in RF MEMS and MEMS-Based RF Front-End …people.eecs.berkeley.edu/~ctnguyen/Research/...C....

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Transcript of Advances in RF MEMS and MEMS-Based RF Front-End …people.eecs.berkeley.edu/~ctnguyen/Research/...C....