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

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  • 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

Recommended

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