UCF Wireless SAW Sensor Systems

Surface Acoustic Wave (SAW) Wireless Passive RF Sensor

Systems

Donald C. Malocha

School of Electrical Engineering & Computer Science

University of Central Florida

Orlando, Fl. 32816-2450

[email protected]

mailto:[email protected]

Univ. of Central Florida SAW• UCF Center for Acoustoelectronic

Technology (CAAT) has been actively doing SAW and BAW research for over 25 years

• Research includes communication devices and systems, new piezoelectric materials, & sensors

• Capabilities include SAW/BAW analysis, design, mask generation, device fabrication, RF testing, and RF system development

• Current group has 8 PhDs and 1 MS

• Graduated 14 PhDs and 38 MS students 2

UCF SAW Capabilities

• Class 100 & 1000 cleanrooms– Sub micron mask pattern generator– Submicron device capability– Extensive photolithography and thin film

• RF Probe stations• Complete SAW characterization facility• Extensive software for data analysis and parameter

extraction• Extensive RF laboratory for SAW technology

3

Research Areas

Thin Films

Processing

Material Charaterization

Measurement

SensorsDesign & Analysis

Center forApplied

AcoustoelectronicsTechnology

Device/SystemFabrication

Synthesis

Modeling

University of Central FloridaSchool of Electrical Engineering and Computer Science

4

What is a typical SAW Device?• A solid state device

– Converts electrical energy into a mechanical wave on a single crystal substrate

– Provides very complex signal processing in a very small volume

• It is estimated that approximately 4 billion SAW devices are produced each year

Applications:Cellular phones and TV (largest market)

Military (Radar, filters, advanced systems

Currently emerging – sensors, RFID

SAW Sensors

• This is a very new and exciting area

• Since SAW devices are sensitive to temperature, stress, pressure, liquids, viscosity and surface effects, a wide range of sensors are possible

Sensor Wish-list– Passive, Wireless, Coded– Small, rugged, cheap– Operate over all temperatures and

environments– Measure physical, chemical and biological

variables– No cross sensitivity– Low loss and variable frequency– Radiation hard for space applications– Large range to 100’s meters or more

• SAW sensors meet many of these criteria

SAW Background• Solid state acoustoelectronic technology

• Operates from 10MHz to 3 GHz

• Fabricated using IC technology

• Manufactured on piezoelectric substrates

• Operate from cryogenic to 1000 oC

• Small, cheap, rugged, high performance

2mm

10mm

Quartz Filter

SAW packaged filter showing 2 transducers, bus bars, bonding, etc.

Applications of SAW DevicesMilitary (continued)

Military Applications Functions Performed

Radar Pulse Compression Pulse Expansion and Compression Filters

ECM Jammers Pulse Memory Delay Line

ECCM Direct Sequence Spread Spectrum-

Fast Frequency Hopping-

Pulse Shaping, Matched Filters, Programmable Tapped Delay Lines, Convolvers, Fast Hop Synthesizer

Fast Hop Synthesizer

Ranging Pulse Expansion & Compression Filters

A Few Examples

SAW 7 Bank Active Channelizer

From Triquint, Inc.

Applications of SAW Devices

Consumer Applications Functions Performed

TV IF Filter

Cellular Telephones RF and IF Filters

VCR IF Filter & Output Modulator Resonators

CATV Converter IF Filter, 2nd LO & Output Modulator Resonators

Satellite TV Receiver IF Filter & Output Modulator

A Few Examples

VSB Filter for CATV - Sawtek

Bidirectional Transducer Technology – IF Filter w/ moderate loss; passband shaping and high selectivity.

Basic Wave Parameters

Waves may be graphed as a function of time or distance. A single frequency wave will appear as a sine wave in either case. From the distance graph the wavelength may be determined. From the time graph, the period and frequency can be obtained. From both together, the wave speed can be determined.

Velocity*time=distance

Velocity=distance/time= T

The amplitude of the wave can be absolute, relative or normalized. Often the amplitude is normalized to the wavelength in a mechanical wave. A=0.1*wavelength

SAW Advantage

SAW Transducer & Reflector Degrees of Freedom

• Parameter Degrees of Freedom– Electrode amplitude and/or length– Electrode phase (electrical)– Electrode position (delay)– Instantaneous electrode frequency

• Device Infrastructure Degrees of Freedom– Material Choice– Thin Films on the Substrate– Spatial Diversity on the Substrate– Electrical Networks and Interface

Piezoelectricity (pie-eezo-e-lec-tri-ci-ty)

SAW Transducer

Surface Wave Particle Displacement

SAW is trapped within ~ 1 wavelength of surface

R:\Presentations\RayleighSAW.exe

Schematic of Apodized SAW Filter

2mm

10mm

Quartz Filter

SAW Filter Fabrication Process

Trim (if necessary)DiceCleanFinal TrimPackage

Mask Structure Device Features

2.5mm

10mm

LiNbO3 Filter

Fabrication – Electrode Widths

From: Siemens

RF Probe Station with Temperature Controlled Chuck

for SAW Device Testing

RF Probe and ANA

Top view of chuck assembly with RF probes

Response of SAW Reflector Test Structure

Measurement of S21 using a swept frequency provides the required data.

62 64 66 68 70 72 74 76 78 80-90

-80

-70

-60

-50

-40

-30

-20

Frequency (MHz)

dB

(S21

)

Transducer response

Reflector response is a time echo which produces a frequency ripple

20λ0 50λ0 50λ020λ0 20λ0 50λ0 50λ020λ0

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-80

-70

-60

-50

-40

-30

-20

-10

Time (s)

dB

(s

21)

Direct SAW response

Reflector response

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-80

-70

-60

-50

-40

-30

-20

-10

Time (s)

dB

(s

21)

Direct SAW response

Reflector response

SAW OFC Device TestingRF Wafer Probing

Actual device with RF probe

Why Use SAW Sensors and Tags?• Frequency/time are measured with greatest

accuracy compared to any other physical measurement (10-10 - 10-14).

• External stimuli affects device parameters (frequency, phase, amplitude, delay)

• Operate from cryogenic to >1000oC• Ability to both measure a stimuli and to

wirelessly, passively transmit information• Frequency range ~10 MHz – 3 GHz• Monolithic structure fabricated with current IC

photolithography techniques, small, rugged

Goals• Applications: SAW sensors for NASA ground,

space-flight, and space-exploration• SAW Wireless, Passive, Orthogonal

Frequency Coded (OFC) Spread Spectrum Sensor System

• Multiple sensors (temperature, gas, liquid, pressure, other) in a single platform

• Operation up to 50 meters at ~ 1 GHz• Ultra-wide band operation

26University of Central Florida School of Electrical Engineering and Computer Science

SAW OFC Properties• Extremely robust

• Operating temperature range: cryogenic to ~1000 oC• Radiation hard, solid state

• Wireless and passive (NO BATTERIES)• Coding and spread spectrum embodiments

• Security in coding; reduced fading effects• Multi-sensors or tags can be interrogated

• Wide range of sensors in a single platform• Temperature, pressure, liquid, gas, etc.

• Integration of external sensor

27University of Central Florida

School of Electrical Engineering and Computer Science

Basic Passive Wireless SAW System

Sensor 3

Sensor 1

Sensor 2

Clock

Interrogator

Post Processor


Goals:•Interrogation distance: 1 – 50 meters

• low loss OFC sensor/tag (<6dB)•# of devices: 10’s – 100’s - coded and distinguishable at TxRx•Space applications – rad hard, wide temp., etc.•Single platform and TxRx for differing sensor combinations

•Sensor #1 Gas, Sensor #2 Temp, Sensor #3 Pressure

Multi-Sensor TAG Approaches• Silicon RFID – integrated or external sensors

– Requires battery, energy scavenging, or transmit power– Radiation sensitive– Limited operating temperature & environments

• SAW RFID Tags - integrated or external sensors

– Passive – powered by interrogation signal

– Radiation hard

– Operational temperatures ~ 0 - 500+ K• Single frequency (no coding, low loss, jamming)• CDMA( coding, 40-50 dB loss, code collision)• OFC( coding, 3-20 dB loss, code collision solutions, wideband)

29

University of Central Florida School of Electrical Engineering and Computer Science

30

SAW Example: Schematic and Actual Nano-film H2 OFC Gas Sensor

Piezoelectric Substrate

f1 f0f2 f3f1f0 f2f3

•For palladium hydrogen gas sensor, Pd film is in only in one delay path, a change in differential delay senses the gas (τ1 = τ2)

OFC Sensor Schematic


0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.80

0.2

0.4

0.6

0.8

Normalized Frequency

Mag

nit

ude (

Lin

ear)


31

Schematic of OFC SAW ID Tag Schematic of OFC SAW ID Tag

0 1 2 3 4 5 6 71

0.5

0

0.5

1

Normalized Time (Chip Lengths)


f1 f4 f6 f0f2 f5 f3

Example OFC Tag


f1 f4 f2 f6 f5f0 f3

100 150 200 250 300 350 400-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0

Frequency (MHz)

S1

1 (

dB

)

OFC Sensor Response

100 150 200 250 300 350 400-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0

Frequency (MHz)

S1

1 (

dB

)

OFC Sensor Response

100 150 200 250 300 350 400-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0

Frequency (MHz)

S1

1 (

dB

)

OFC Sensor Response

100 150 200 250 300 350 400-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0

Frequency (MHz)

S1

1 (

dB

)

OFC Sensor Response

100 150 200 250 300 350 400-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0

Frequency (MHz)

S1

1 (

dB

)

OFC Sensor Response

100 150 200 250 300 350 400-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0

Frequency (MHz)

S1

1 (

dB

)

OFC Sensor Response

100 150 200 250 300 350 400-0.5

-0.45

-0.4

-0.35

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

0

Frequency (MHz)

S1

1 (

dB

)

OFC Sensor Response

100 150 200 250 300 350 400-0.5

-0.45

-0.4

-0.35

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

0

Frequency (MHz)

S1

1 (

dB

)

OFC Sensor Response

S11 of SAW OFC RFID – Target Reflection

S11 w/ absorber and w/o reflectors

32

University of Central Florida School of Electrical Engineering and Computer Science

SAW

absorber

Dual-sided SAW OFC Sensor

2.00 mm

1.25 mm 1.38 mm 1.19 mm2.94 mm

6.75 mm

f3 f5 f0 f6 f2 f4 f1


f3 f5 f0 f6f2 f4 f1

f1 f4 f2 f6f0 f5 f3

SAW CDMA and OFC Tag Schematics


f1 f4 f6 f0f2 f5 f3

0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.460

50

40

30

20

ExperimentalCOM Simulated

Time (us)

Mag

nitu

de (

dB)

CDMA Tag

•Single frequency

•Time signal rolloff due to reflected energy yielding reduced transmission energy

•Short chips, low reflectivity

-(typically 40-50 dB IL)

•OFC Tag

•Multi-frequency (7 shown)

•Long chips, high reflectivity

•Orthogonal frequency reflectors –low loss (0-7dB IL)

•Time signal non-uniformity due to transducer design rolloff


SAW Velocity vs Temperature

University of Central FloridaDepartment of Electrical and Computer Engineering

36

OFC SAW Dual-Sided Temperature Sensor


f1 f4 f6 f0f2 f5 f3f1f4f6f0 f2f5f3

0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.460

50

40

30

20

ExperimentalCOM Simulated

Time (us)

Mag

nitu

de (

dB)


37

Temperature Sensor using Differential Delay Correlator Embodiment


f1 f4 f6 f0f2 f5 f3f1f4f6f0 f2f5f3

Temperature Sensor Example

250 MHz LiNbO3, 7 chip reflector, OFC SAW sensor tested using temperature controlled RF probe station

OFC Code: Mitigate Code Collisions

• Multi-layered coding– OFC– PN (pseudo noise)

– TDMA (time division multiple access)

• (-1,0,1 coding)

– FDMA (frequency division multiple access)

32 OFC codes simultaneously received at antenna:

non-optimized

Noise-like signal

Effect of Code Collisions from Multiple SAW RFID Tags -Simulation

0 1 2 3 4 5 6 7 810

0

10

Optimal Correlation OutputActual Recevied Correlation Output

3rd Bit

Time Normalized to a Chip Length

Nor

mal

ized

Am

plitu

de

Due to asynchronous nature of passive tags, the random summation of multiple correlated tags can produce false correlation peaks and

erroneous information



40

OFC Coding• Time division diversity (TDD): Extend the possible

number of chips and allow +1, 0, -1 amplitude– # of codes increases dramatically, M>N chips, >2M*N!– Reduced code collisions in multi-device environment

Sensor #1

0 5 102

1

0

1

2

Time Response

Time Normalized to Chip Length

Norm

ali

zed

Am

pli

tud

e

456 MHZ SAW OFC TDD Coding

University of Central Florida School of Electrical Engineering and Computer Science41

A 456 MHz, dual sided, 5 chip, tag COM-predicted and measured time responses illustrating OFC-PN-TDD coding. Chip amplitude variations are primarily due to polarity weighted transducer effect and fabrication variation.

1.5 2 2.5 3 3.5-105

-100

-95

-90

-85

-80

-75

-70

-65

-60

-55

Time (s)

s 11 (

dB

)

Simulation

Experiment


OFC FDM Coding• Frequency division multiplexing: System uses N-frequencies

but any device uses M < N frequencies– System bandwidth is N*Bwchip

– OFC Device is M*BWchip• Narrower fractional bandwidth• Lower transducer loss• Smaller antenna bandwidth

42

Sensor #1

Sensor #2

32 Sensor Code Set - TDD

43

Optimized

Not Optimized

Receiver CorrelationReceiver Antenna Input

University of Central FloridaDepartment of Electrical and Computer Engineering

44

Chirp Interrogation Synchronous Transceiver- Software Radio Approach

SAWsensor

RF Oscillator

Digital control and analysis circuitry

SAW up-chirp filter

SAW down-chirp filter

IF Oscillator

A / D

IF Filter

250 MHz OFC TxRx Demo System

Synchronous TxRx SAW OFC correlator prototype system RF

clock section

Digital section


Wireless 250 MHz SAW OFC temperature test using a free running hot plate. The red dashed curve is a TC and the solid blue curve is the SAW extracted temperature.

ADC & Post processor output

WIRELESS SAW TEMPERATURE SENSOR

DEMONSTRATION

46

25 cm 25 cm

5 cm 5 cm

SAW Sensor/Tag

Interrogator(Transmitter)

Receiver

Hot Plate

78°CThermal

Controller

Thermal Couple

Real-time wireless 250 MHz SAW OFC temperature test using a free running hot plate. The red dashed curve is a TC and the solid blue curve is the SAW extracted temperature.

Post processor output

915 MHz Transceiver System

Packaged 915 MHz SAW OFC temperature sensor and antenna used on sensors and transceiver.

• Principle of operation of the adaptive matched OFC ideal filter response to maximize the correlation waveform and extract the SAW sensor temperature.

An initial OFC SAW temperature sensor data run on a free running hotplate from an initial 250 MHz transceiver system. The system used 5 chips and a fractional bandwidth of approximately 19%. The upper curve is a thermocouple reading and the jagged curve is the SAW temperature

extracted data.

50 cm 50 cm

30 cm 30 cm

SAW Sensor/Tag


Receiver

Hot Plate

78°CThermal

Controller

Thermal Couple

250 MHz Wireless OFC SAW System 1st Pass

250 MHz Wireless OFC SAW System - 2nd Pass

A final OFC SAW temperature sensor data run on a free running hotplate from an improved 250 MHz transceiver system. The system used 5 chips and a fractional bandwidth of approximately 19%. The dashed curve is a thermocouple reading and the solid curve is the SAW temperature extracted data. The SAW sensor is tracking the thermocouple very well; the slight offset is probably due to the position and conductivity of the thermocouple.

50 cm 50 cm

30 cm 30 cm

SAW Sensor/Tag


Receiver

Hot Plate

78°CThermal

Controller

Thermal Couple

915 MHz Sensor System - 1st Pass

Initial results of the 915 MHz SAW OFC temperature sensor transceiver system. Four OFC SAW sensors are co-located in close range to each other; two are at room temperature and one is at +62◦C and another at -38◦C. Data was taken simultaneously from all four sensors and then temperature extracted in the correlator receiver software.

UCF OFC Sensor Successful Demonstrations

• Temperature sensing– Cryogenic: liquid nitrogen – Room temperature to 250oC– Currently working on sensor for operation to

750oC

• Cryogenic liquid level sensor: liquid nitrogen

• Pressure/Strain sensor• Hydrogen gas sensor


54

Temperature Sensor Results

• 250 MHz LiNbO3, 7 chip reflector, OFC SAW sensor tested using temperature controlled RF probe station

• Temp range: 25-200oC• Results applied to simulated

transceiver and compared with thermocouple measurements

0 20 40 60 80 100 120 140 160 180 2000

20

40

60

80

100

120

140

160

180

200Temperature Sensor Results

Time (min)

Te

mp

era

ture

( C)

LiNbO3 SAW Sensor

Thermocouple

University of Central FloridaSchool of Electrical Engineering and Computer Science 55

OFC Cryogenic Sensor Results

0 5 10 15 20 25-200

-150

-100

-50

0

50

Time (min)

Tem

pera

ture

( C

)

ThermocoupleLiNbO

3 SAW Sensor

Scale

Vertical: +50 to -200 oC

Horizontal: Relative time (min)

Measurement system with liquid nitrogen Dewar and vacuum chamber for DUT

OFC SAW temperature sensor results and comparison with thermocouple measurements at cryogenic temperatures. Temperature scale is between +50 to -200 oC and horizontal scale is relative time in minutes.


56

Schematic and Actual OFC Gas Sensor


f1 f0f2 f3f1f0 f2f3

•For palladium hydrogen gas sensor, Pd film is in only in one delay path, a change in differential delay senses the gas (τ1 = τ2) (in progress)

OFC Sensor Schematic


Palladium Background Information• The bulk of PD research has

been performed for Pd in the 100-10000 Angstrom thickness

• Morphology of ultra-thin films of Pd are dependent on substrate conditions, deposition and many other parameters

• Pd absorbs H2 gas which causes lattice expansion of the Pd film – called Hydrogen Induced Lattice Expansion (HILE) – Resistivity reduces

• Pd absorbs H2 gas which causes palladium hydride formation – Resistivity increases

• Examine these effects for ultra-thin films (<5nm) on SAW devices

HILE - Each small circle represents a nano-sized

cluster of Pd atoms

CO

NTA

CT

CO

NTA

CT

W ithout H2

CO

NTA

CT

CO

NTA

CT

With H2

57

Measured E-Beam Evaporated Palladium Conductivity v Film Thickness

Conductivity measurements made in-situ under vacuum

σinf = 9.5·104 S/cm

58

Ultra-thin Pd on SAW Devices for Hydrogen Gas Sensing

• Pd is known to be very sensitive to hydrogen gas

•Due to the SAW AE interaction with resistive films and the potentially large change in Pd resistivity, a sensitive SAW hydrogen sensor is possible

•Experimental investigation of the SAW-Pd-H2 interaction

59

Pd Films on SAW DevicesSchematic of Test Conditions

• Control: SAW delay line on YZ LiNbO3 wafers w/ 2 transducers and reflector w/o Pd film

• Center frequency 123 MHz

• (A) SAW delay line w/ Pd in propagation path between transducer and reflector

• (B) SAW delay line w/ Pd on reflector only

Pd Film

(A )

(B )

Pd

Film

1.27 mm

60

Test Conditions and Measurement

• S21 time domain measurement of SAW delay line– Main response– TTE– Reflector return

response Pd Film

0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.2580

76

72

68

64

60

56

52

48

44

40

36

32

28

24

20

16

12

8

4

0

DL w/o PdBefore ExpDuring 1st ExpAfter 1st ExpDuring 2nd ExpAfter 2nd ExpDuring 3rd ExpAfter 3rd ExpDuring 4th ExpAfter 4th Exp

S21 Time Response

Time (micro-seconds)

Nor

mal

ized

Mag

nitu

de (

dB)

TTE

SAW MainReflector

61

SAW Propagation Loss and Reflectivity Pd Film ~ 15 Ang. (prior to H2)

• S21 time domain comparison of

delay line with Pd in propagation path vs. on the reflector

• Greater loss when Pd is placed in propagation path than in the reflector– ~7dB loss when Pd is on

reflector• reflector length 1.47 mm

– ~22dB loss when Pd is in propagation path

• 1.27 mm one-way path length • Propagation loss ~75dB/cm loss

1.7 1.75 1.8 1.85 1.9 1.95 2 2.05 2.1 2.15 2.2 2.2580

77

74

71

68

65

62

59

56

53

50

47

44

41

38

35

32

29

26

23

20

DL w/o PdDL w/ Pd In Delay PathDL w/ Pd on Reflector Bank

S21 Time Response


Nor

mal

ized

Mag

nitu

de (

dB)

vfs 3488m

s

Pd Film

Pd Fil m

No Pd

62

SAW DevicePd in Propagation Path w/ 2% H2 Exposure

• Close-up of reflector bank S21 time domain response.

• A comparison of the traces labeled “DL w/o Pd” and” Before Exp” shows a change in reflectivity due to the presence of the Pd film.

• A gradual reduction in propagation loss with increased H2 exposure.– Irreversible change– ~ 20 dB reduction in loss

• Minimum propagation loss ~6.8 dB/cm

1.7 1.75 1.8 1.85 1.9 1.95 2 2.05 2.1 2.15 2.2 2.2580

77

74

71

68

65

62

59

56

53

50

47

44

41

38

35

32

29

26

23

20


S21 Time Response

Time (micro-seconds)N

orm

aliz

ed M

agni

tude

(dB

)

63

Pd

Film

SAW DevicePd on Reflector w/ 2% H2 Exposure

• Close-up of reflector bank S21 time domain response.

• A comparison of the traces labeled “DL w/o Pd” and” Before Exp” shows a change in delay as well as reflectivity due to the presence of the Pd film.

• A gradual increase in reflectivity with each exposure to H2 gas is observed

– ~ 7 dB change in IL– Irreversible

1.7 1.75 1.8 1.85 1.9 1.95 2 2.05 2.1 2.15 2.2 2.2580

76

72

68

64

60

56

52

48

44

40

36

32

28

24

20

16

12

8

4

0


S21 Time Response


Nor

mal

ized

Mag

nitu

de (

dB)

64

Pd Film

Hydrogen Gas Sensor Results:

2% H2 gas

65

1.7 1.8 1.9 2 2.1 2.280

76

72

68

64

60

56

52

48

44

40

36

32

28

24

20

Delay Line w/o PdAfter Pd FilmDuring 1st H2 ExposureAfter 1st H2 ExposureDuring 2nd H2 ExposureAfter 2nd H2 ExposureDuring 3rd H2 ExposureAfter 3rd H2 ExposureDuring 4th H2 ExposureAfter 4th H2 Exposure


Nor

mal

ized

Mag

nitu

de (

dB)

Pd

Film

100 1 103

1 104

1 105

0

40

80

120

160

200

240

3410

3425

3440

3455

3470

3485

3500

Loss/cm @ 123 MHzLoss/cm due to Pd FilmLoss/cm due to Pd Film After Final H2 Gas ExposureLoss/cm due to successive H2 exposureSAW VelocitySAW Velocity due to Pd FilmSAW Velocity due to Pd Film After Final H2 Gas ExposureSAW Velocity due to successive H2 exposure

Propagation Loss (dB/cm) and Velocity(m/s) vs. Film Resistivity

Resistivity (ohm-cm)

Los

s (d

B/c

m)

SA

W V

eloc

ity (

m/s

)

Pd

Film

Nano-Pd Film – 25 Ang.

•The change in IL indicates >10x change in Pd resistivity – WOW!

•The large change suggests an unexpected change in Pd film morphology.

OFC Cantilever Strain Sensor

• Measure Delay versus Strain

66

Plot generated by ANSYS demonstrating the strain distribution along the z-axis of the crystal.

Test fixture, this shows the surface mount package, which contains the cantilever device, securely clamped down onto a PC board which is connected to a Network Analyzer.

OFC Cantilever Strain Sensor

School of Electrical Engineering and Computer Science68

Applications

• Current efforts include OFC SAW liquid level, hydrogen gas, pressure and temperature sensors

• Multi-sensor spread spectrum systems• Cryogenic sensing• High temperature sensing• Space applications• Turbine generators• Harsh environments• Ultra Wide band (UWB) Communication

– UWB OFC transducers• Potentially many others

Vision for Future• Multiple access, SAW RFID sensors• SAW RFID sensor loss approaching 0 dB

– Unidirectional transducers– Low loss reflectors

• New and novel coding approaches using OFC-type transducers and reflectors

• Operation in the 1-3 GHz range for small size• Single platform for various sensors

(temperature, gas, pressure, etc.)• SAW sensors in space flight and support

operations in 2 to 5 yearsUniversity of Central Florida

School of Electrical Engineering and Computer Science

69

NASA Support and Collaborations

• NASA support– KSC

• 4 Phase I STTRs and 4 Phase II STTRs: 2005-2011

• Latest STTR Phase II begins this summer

– JSC• 900 MHz device development in 2008

– Langley• GRA OFC sensor funding: 2008-2010

70

Collaborations• Micro System Sensors 2005-2006, STTR

• ASR&D, 2007-present, STTR

• Mnemonics, 2007-present, STTR– United Space Alliance (USA): 2nd order collaboration

• MtronPTI – 1995-present, STTR• Triquint Semiconductor -2009

• Vectron -2009 (SenGenuity 2nd order collaboration)

• Univ. of South Florida 2005-present, SAW sensors

• Univ. of Puerto Rico Mayaguez – initiating SAW sensor activity

71

SAW Research at UCF• Approximately 200 publications and 7 patents

+ (5 pending) on SAW technology • Approximately $5M in SAW contracts and

grants• Approximately 50 graduate students• Many international collaborations• Contracts with industry, DOD and NASA• Current efforts on SAW sensors for space

applications funded by NASA

Current Graduate Research Student Contributors

• Brian Fisher

• Daniel Gallagher

• Mark Gallagher

• Nick Kozlovski

• Matt Pavlina

• Luis Rodriguez

• Mike Roller

• Nancy Saldanha


74

Acknowledgment

Thank you for your attention!

•The authors wish to thank continuing support from NASA, and especially Dr. Robert Youngquist, NASA-KSC.

•The foundation of this work was funded through NASA Graduate Student Research Program Fellowships, the University of Central Florida - Florida Solar Energy Center (FSEC), and NASA STTR contracts.

•Continuing research is funded through NASA STTR contracts and industrial collaboration with Applied Sensor Research and Development Corporation, and Mnemonics Corp.