RF MEMS Circuits - MEMS...MEMS RF Switch Step-Tuned Filter Demo ... UHF 2-Pole MEMS Capacitor Filter Schematic MEMS Capacitor Filter Schematic MEMS Filter, 2 tunable capacitors

RF MEMS CircuitsApplications of MEMS switch and tunable capacitor

Dr. Jeffrey DeNatale,Manager, MEMS DepartmentElectronics Divisionjdenatale@rwsc.com805-373-4439

Panamerican Advanced Studies InstituteMicroElectroMechanical SystemsJune 21-30, 2004

Chart 2

Outline

Motivation for RF MEMS circuits

MEMS Tunable Filters

Switch based

Tunable capacitor based

MEMS Phase Shifters

Low-Loss Switching Networks

Reconfigurable MMIC Circuits

Summary / Acknowledgements

Chart 3

MEMS for RF Communications

MEMS is key enabling technology addressing pervasive trends in communications and radar systems:

tunability / agility / modularity / reconfigurability

increased functionality (component, system)

Substantial performance improvements:

Insertion loss, isolation, linearity, power consumption, bandwidth, size, integration

Range of device concepts under development RF Switches / Relays Tunable Capacitors Micromachined inductors Micromechanical resonators

Building Blocks for High-Performance Miniaturized RF Subsystems

Range of device concepts under development RF Switches / Relays Tunable Capacitors Micromachined inductors Micromechanical resonators

Building Blocks for High-Performance Miniaturized RF Subsystems

X-Band Phase Shifter

80 90 100 110 120 130 140 150 160 170 180-80

-70

-60

-50

-40

-30

-20

-10

0

Frequency (MHz)

S2

1,

dB

Low band Mid band High Band

80 90 100 110 120 130 140 150 160 170 180-80

-70

-60

-50

-40

-30

-20

-10

0

Frequency (MHz)

S2

1,

dB

Low band Mid band High Band

Multi-band (X, Ku) amplifier

2-Pole MEMS Switched Filter

SP4T Routing Network

Leverage small mechanical motions for large RF property excursionsLeverage small mechanical motions for large RF property excursions

Chart 4

RSC MEMS RF Switch

Key Elements of RSC MEMS RF Switch Low-temperature processing (circuit compatible) Broadband (DC- mmWave) Electrostatic drive for low power consumption Low insertion loss (

Chart 5

MEMS RF Switch Step-Tuned Filter Demobenchmark MEMS switch vs. PIN diode

VHF Filter Circuit VHF Step-tuned Bandpass Filter 116-152 MHz

dual MEMS switch replaces 2 PIN dual diodes

increased dynamic range, reduced parts count

Filter Specifications (2-Pole VHF Filter)

Center Freq. Tuning Range: 116-151.975 MHz

Selectivity (fo 8 MHz) 13.4 dB rejection

Tune time: < 75 microseconds

2-pole midband loss < 4.5 dB

2-pole 1 dB compression pt. > +20 dBm

MTO MEMS

DARPADARPA

Derived Component Requirements - RF Switch (Packaged)

Max Rs (on): 1.8 Ohm (0.5 GHz)Max Cs (off): 0.5 pF (0.5 GHz)Min. 3rd Order IP: 50 dBmIRF, VRF (survive): 0.2 A, 10.4 V rmsIRF, VRF (op): 0.03 A, 2.1 V rmsSw Time: 15 usec max.

2-Pole Sub-section

6-Pole Filter

Switch Drivers

Chart 6

VHF 2-Pole MEMS Switched Filter Prototype

2-Pole MEMS Switched Filter Prototype

Packaged MEMS Switches (8X)

Future: IntegratedMonolithic Switches + Capacitors

Packaged circuit with 16 switched capacitors, in one monolithic die

Step-Tunable Filter withMEMS Switches + Discrete Capacitors

500x Improvement in Linearity 42% Parts Count Reduction (123 vs 71 for 2 pole) Static Power Reduced from 0.5W to near-zero (2 pole)

Chart 7

VHF 2-Pole MEMS Switched Filter Test Data

60 70 80 90 100 110 120 130 140 150 160 170 180 19050 200

-70

-60

-50

-40

-30

-20

-10

-80

0

Inse

rtio

n G

ain

(d

B)

Frequency (MHz)

Demonstrate Step-Tuning with good filter characteristics over full band

Demonstrate Step-Tuning with good filter characteristics over full band

Chart 8

VHF 2-Pole MEMS Switched Filter Intermodulationkey parameter for cosite mitigation

3rd Order In-Band IM Distortion - 112.05 MHz Fc

Output Tone Level+20 dBm

IMR3 = -71.5 dBc

IP3o = +55.75 dBm

Chart 9

RSC MEMS Tunable Capacitor (Varactor)

5 m

30 m

100 mSEM micrographs showing the high aspect ratio feature of the MEMS tunable cap.

Tuning range: >8:1Base capacitance: 1.5 - 2pFElectrical Q: 30-150Max tuning voltage: 6-40VMechanical Resonance : 0.4 - 2kHz typElectrical self-resonance: 6GHz

Tuning range: >8:1Base capacitance: 1.5 - 2pFElectrical Q: 30-150Max tuning voltage: 6-40VMechanical Resonance : 0.4 - 2kHz typElectrical self-resonance: 6GHz

Capacitor Tuning Range

0

2

4

6

8

10

12

14

0 1 2 3 4 5 6 7 8 9

Voltage (V)

Cap

acita

nce

(pF)

8.4X

Tuning range >8.4XTuning range >8.4X

Chart 10

Voltage Tunable Filter Demonstrationbenchmark MEMS vs. semiconductor varactor

UHF Filter Circuit UHF Voltage-tuned Bandpass Filter 225-400 MHz

MEMS variable capacitor replaces varactor diode array

increased dynamic range, drastically reduced parts count

Filter Specifications (2-Pole UHF Filter) Center Freq.Tuning Range: 225-399.975 MHz

Selectivity (fo 13 MHz) 10.75 dB rejection Tune time: < 27 microseconds

2-pole midband loss < 5.5 dB

MTO MEMS

DARPADARPA

Derived Component Requirements -Variable Capacitor (Packaged)

Cap. Range: 2.5 - 10 pF (4:1)

Tune V Range: 1-6 VDC

Max Rs: 1.0 Ohm @ 10 pF

IRF, VRF (op): 0.18 A, 21 V rms

Tune Time: 10 usec max.

16-diode series-parallel array for high IP (1 array per pole)

16-diode series-parallel array for high IP (1 array per pole)

Chart 11

UHF 2-Pole MEMS Capacitor Filter Schematic

MEMS Capacitor Filter Schematic

MEMS Filter, 2 tunable capacitors

Dramatic (90%) parts count reduction validated for MEMS circuit

Slightly improved IP3 (+30 to +37dBm)

Dramatic (90%) parts count reduction validated for MEMS circuit

Slightly improved IP3 (+30 to +37dBm)

Existing Varactor Version16-diode series-parallel arrays

Chart 12

UHF 2-Pole MEMS Capacitor Filter Test Data

-80

-75

-70

-65

-60

-55

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

150.0 200.0 250.0 300.0 350.0 400.0 450.0

Frequency (MHz)

Ins

ert

ion

Ga

in (

dB

)

228 MHz Fo

312.5 MHz Fo

398 MHz Fo

Nearly full octave tuning achievedNearly full octave tuning achieved

Chart 13

Tunable Capacitor Improvements Required Results from tunable capacitor filter demo

Initial filter insertion validated utility of MEMS tunable capacitor in filter tuning circuit, but issues noted:

Device Q: series resistance ~1 (solution: improvedmetalization, device design)

Tuning speed, Vibration Immunity: (solution: stiff flexures, reduced mass, package environment)

Mechanical Ringing: settling time ~4msec (solution: package environment)

Maximum capacitance value: ~12pF (solution:thicker device layer, package environment - up to 25pF demonstrated)

Tunable Capacitor Response Time

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

-0.0005 0.0005 0.0015 0.0025 0.0035 0.0045 0.0055 0.0065 0.0075 0.0085

Time (seconds)

Rel

ativ

e C

apac

itan

ce (

Arb

)

Filtered Response

0

0.2

0.4

0.6

0.8

1

1.2

-0.0005 0.0015 0.0035 0.0055 0.0075 0.0095

Time (sec)

Fil

tere

d O

utp

ut

AirDamping

NearCriticalDamping

Tunable Capacitor with 80m deep combs

Filtered response to step input

Effect of damping on device response time

Chart 14

MEMS TTD Phase Shifter DevelopmentKey Component for Steerable Phased Arrays

Switchable Delay Line MEMS Switch can enable significant advances in reconfigurable electronics

Low insertion loss compatible with multi-switch implementation

High isolation reduces resonant effects of off-state leakage

Metal-Metal contacts enable broad bandimplementation

Compatible with MMIC processing

Exploit low-loss, broadband characteristics for multi-bit True

Time Delay (TTD) Circuit

Exploit low-loss, broadband characteristics for multi-bit True

Time Delay (TTD) Circuit

Steering of main lobe at

= cos-1(-/d)

Powerdivider

Phaseshifter

Antenna

2 30

d

Chart 15

MEMS-Based Phase Shifter Circuits

RSC has demonstrated broad portfolio of MEMS-based phase shifter circuits

Exploit low-loss, broadband nature of RSC MEMS switch

Novel circuits demonstrated for low loss, compact size, broad bandwidth

3-Bit Ka-Band (2.2dB avg)

6-Bit Broad Band

4-Bit Broad Band (2.4dB avg)

2-Bit X-Band(1dB avg)

2-Bit Low LossX-Band (.56 dB avg)

4-Bit Low LossX-Band (1.2 dB avg)

Miniature 2-bit, 4-bit X-Band (0.7dB 9.5GHz

Chart 16

4-Bit Broadband TTD Phase Shifter Circuitexploit broadband nature of RSC switch

4-Bit TTD circuits implemented (16 MEMS switches per circuit)

2.2 to 2.6 dB insertion loss at 10GHz

Mismatch loss below 15 dB at all frequencies

group delay ripple

Chart 17

Low-Loss SP4T-Based Phase Shifters (RSC/U