How can variables be measured in environments that are too hot, too cold, or moving too fast for traditional circuit-based sensors? A new technology for obtaining multiple, real-time measurements under extreme environmental conditions is being developed under Phase 1 and 2 funding contracts from NASA's Kennedy Space Center’s Small Business Technology Transfer (STTR) program. Opportunities for early deployment licensing and Phase 3 STTR contracts are now being accepted. Passive, remote measuring systems can be created using new Orthogonal Frequency Code (OFC) multiplexing techniques and specially developed, next-generation SAW sensors. As a result, very cost-effective applications such as spaceflight sensing (for instance, temperature, pressure, or acceleration monitoring), remote cryogenic fluid level sensing, or an almost limitless number of other rigorous monitoring applications are possible.

1. 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
dcm@ece.engr.ucf.edu

2. 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

3. Research Areas
UCF SAW Design & Analysis
Thin Films
Sensors
Device/System
Capabilities
Center for Fabrication
Applied
Processing Acoustoelectronics
Measurement
Technology
Material Modeling
Charaterization
Synthesis
• 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
3
• Extensive RF laboratory for SAW technology

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
University of Central Florida 4
School of Electrical Engineering and Computer Science

5. 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

6. 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

7. 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
Quartz Filter
SAW packaged filter
2mm showing 2 transducers,
bus bars, bonding, etc.
10mm

8. Applications of SAW Devices
Military (continued)
A Few Examples
Military Applications Functions Performed
Radar Pulse Compression Pulse Expansion and Compression
Filters
ECM Jammers Pulse Memory Delay Line
ECCM Pulse Shaping, Matched Filters,
Programmable Tapped Delay Lines,
Direct Sequence Spread Spectrum- Convolvers, Fast Hop Synthesizer
Fast Frequency Hopping- Fast Hop Synthesizer
Ranging Pulse Expansion & Compression
Filters

9. SAW 7 Bank Active Channelizer
From Triquint, Inc.

10. Applications of SAW Devices
A Few Examples
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

11. VSB Filter for CATV - Sawtek
Bidirectional Transducer Technology – IF Filter w/
moderate loss; passband shaping and high
selectivity.

12. 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

13. SAW Advantage

14. 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

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

16. SAW Transducer

17. Surface Wave Particle Displacement
SAW is trapped within ~ 1 wavelength of surface

18. Schematic of Apodized SAW Filter
Quartz Filter
2mm
10mm

19. SAW Filter Fabrication Process
Trim (if necessary)
Dice
Clean
Final Trim
Package

20. Mask Structure Device
Features
LiNbO3 Filter
2.5mm
10mm

21. Fabrication – Electrode Widths
From: Siemens

22. RF Probe Station with
Temperature Controlled Chuck
for SAW Device Testing
Top view of chuck
assembly with RF
RF Probe and ANA probes

23. Response of SAW Reflector Test Structure
20_0 20_0 50_ 0 50_0
-10
-20
Reflector response is -20 Direct SAW
-30 a time echo which response
produces a frequency -30
Reflector
-40
ripple s
)
(12
-40 response
)1
S B
(2 -50 d
B -50
d
-60
Transducer -60
-70
response -70
-80 -80
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
Tim e ( µs)
-90
62 64 66 68 70 72 74 76 78 80
Frequency (MHz)
Measurement of S21 using a swept frequency provides the required data.

24. SAW OFC Device Testing
RF Wafer Probing
Actual device with RF
probe

25. 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

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

27. 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
University of Central Florida
School of Electrical Engineering 27
and Computer Science

28. Basic Passive Wireless SAW
System
Interrogator Sensor 1
Clock
Post Processor
Sensor 3
Sensor 2
Goals:
•Interroga-on distance: 1 – 50 meters
• low loss OFC sensor/tag (<6dB)
•# of devices: 10’s – 100’s ‐ coded and dis-nguishable at TxRx
•Space applica-ons – rad hard, wide temp., etc.
•Single plaPorm and TxRx for differing sensor combina-ons
•Sensor #1 Gas, Sensor #2 Temp, Sensor #3 Pressure
28
University of Central Florida School of Electrical Engineering and Computer Science

29. 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

30. SAW Example: Schematic and Actual
Nano-film H2 OFC Gas Sensor
OFC Sensor Schematic
Actual device with RF
probe
•For palladium hydrogen gas sensor, Pd film is in only in one delay path,
a change in differential delay senses the gas (τ1 = τ2)
University of Central Florida 30
School of Electrical Engineering and Computer Science

31. Schematic of OFC SAW ID Tag
Example OFC
Tag
f1 f4 f2 f6 f0 f5 f3
)
r Piezoelectric Substrate
a
e
n 1
i
L
(
0.8
e 0.5
d
u
t 0.6
i
n 0
g
a 0.4
M
0.5
0.2
1
0 0 1 2 3 4 5 6 7
0 0.2 0.4 0.6 0.8Normalized Time 1
(Chip Lengths) 1.2 1.4 1.6 1.8
Normalized Frequency
University of Central 31
Florida
School of Electrical
Engineering and

32. S11 of SAW OFC RFID –
Target Reflection
f1 f4 f2 f0 f6 f3 f5
SAW
absorber
Piezoelectric Substrate
S11 w/ absorber and w/o reflectors
OFC Sensor Response
0
-0.05
-0.1
-0.1
)) -0.2
-0.15
BB -0.2
dd -0.3
(( -0.25
11 -0.4
11 -0.3
SS
-0.35
-0.5
-0.4
-0.6
-0.45
-0.5
-0.7 32
100 150 200 250 300 350 400
Frequency (MHz)
University of Central Florida School of Electrical Engineering and Computer Science

33. Dual-sided SAW OFC Sensor
f3 f5 f0 f6 f2 f4 f1 f1 f4 f2 f6 f0 f5 f3
!1 !2
Piezoelectric Substrate
6.75 mm
1.25 mm 1.38 mm 2.94 mm 1.19 mm
f3 f 5 f 0 f 6 f2 f 4 f1
2.00 mm

34. SAW CDMA and OFC Tag Schematics
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
f1 f4 f2 f6 f0 f5 f3
•Multi-frequency (7 shown)
•Long chips, high reflectivity
20
•Orthogonal frequency Piezoelectric Substrate
Magnitude (dB)
reflectors –low loss (0-7dB IL) 30
•Time signal non-uniformity due 40
to transducer design rolloff
50
Experimental
University of Central Florida
COM Simulated 34
School of Electrical Engineering and Computer Science
60
0.6 0.8 1 1.2 1.4 1.6 1.8
Time (us)

35. SAW Velocity vs Temperature

36. OFC SAW Dual-Sided Temperature
Sensor
f3 f5 f0 f6 f2 f4 f1 f1 f4 f2 f6 f0 f5 f3
!1 !2
Piezoelectric Substrate
20
Magnitude (dB)
30
40
50
Experimental
COM Simulated
60
0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4
University of Central Florida 36
Time (us)
Department of Electrical and Computer
Engineering

37. Temperature Sensor using Differential Delay
Correlator Embodiment
Temperature Sensor f3 f5 f0 f6 f2 f4 f1 f1 f4 f2 f6 f0 f5 f3
Example !1 !2
250 MHz LiNbO3, 7 chip
Piezo electric Sub strate
reflector, OFC SAW sensor
tested using temperature
controlled RF probe station
University of Central 37
Florida
School of Electrical
Engineering and

38. OFC Code: Mitigate Code
Collisions
Noise-like signal
• 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

39. Effect of Code Collisions from Multiple SAW
RFID Tags -Simulation
Due 3rdasynchronous nature of passive tags,
to Bit
10 the random summation of multiple correlated
tags can produce false correlation peaks and
Normalized Amplitude
erroneous information
0
10
0 1 2 3 4 5 6 7 8
Time Normalized to a Chip Length
Optimal Correlation Output
Actual Recevied Correlation Output
University of Central Florida School of Electrical Engineering and Computer Science 39

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
Time Response
2
Normalized Amplitude
1
0
!1
!2
0 5 10
Time Normalized to Chip Length
University of Central Florida 40
School of Electrical Engineering and Computer Science

41. 456 MHZ SAW OFC TDD Coding
-55 Simulation
Experiment
-60
-65
-70
)
B -75
d
( -80
1
1
s -85
-90
-95
-100
-105
1.5 2 2.5 3 3.5
Time (µs)
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.
41
University of Central Florida School of Electrical Engineering and Computer Science

42. 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
Sensor #1
Sensor #2
University of Central Florida 42
School of Electrical Engineering and Computer Science

43. 32 Sensor Code Set - TDD
Receiver Antenna Input Receiver Correlation
Not
Optimized
Optimized
43

44. Chirp Interrogation Synchronous
Transceiver- Software Radio
Approach
SAW
sensor
SAW down- SAW up-
chirp filter chirp filter
IF Oscillator
IF Filter
RF Oscillator
A/ D
Digital control and analysis circuitry
University of Central Florida 44
Department of Electrical and Computer Engineering

45. 250 MHz OFC TxRx Demo
System
Synchronous TxRx SAW OFC correlator prototype
system RF
clock ADC &
section Post
processor
output
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.
University of Central Florida School of 45
Electrical Engineering and Computer Science

46. WIRELESS SAW
TEMPERATURE SENSOR
DEMONSTRATION
Post
processor
25 cm 25 cm
output
5 cm 5 cm
Receiver
Interrogator
(Transmitter)
SAW
Sensor/Tag
Thermal
78°C Couple
Thermal Hot Plate
Controller
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.
46

47. 915 MHz Transceiver System

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

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

50. 250 MHz Wireless OFC SAW System 1st Pass
50 cm 50 cm
An initial OFC SAW
Interrogator
(Transmitter )
30 cm 30 cm
Receiver temperature sensor data
SAW
Sensor /Tag
Thermal
run on a free running
78°C
Thermal
Controller
Hot Plate
Couple
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 .

51. 250 MHz Wireless OFC SAW System - 2nd Pass
50 cm 50 cm
30 cm 30 cm
Receiver
Interrogator
(Transmitter )
A final OFC SAW temperature sensor data
SAW
Sensor /Tag
Thermal
78°C
Thermal
Controller
Hot Plate
Couple
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.

52. 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.

53. 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
Temperature Sensor Results
200
(
180
e
r 160
u 140
)
t
C
a
° 120
r
e 100
p 80
m
e 60
T
40
LiNbO3 SAW Sensor
20
Thermocouple
0
0 20 40 60 80 100 120 140 160 180 200
Time (min)
• 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
University of Central Florida 54
School of Electrical Engineering and Computer Science

55. OFC Cryogenic Sensor Results
50
Thermocouple
LiNbO 3 SAW Sensor
Scale
0
Vertical: +50 to -200 oC (
e
r
u
)
Horizontal: Relative time (min)
-50
t
C
°
a
r
e
p
m -100
e
T
OFC SAW temperature -150
sensor results and
comparison with -200
0 5 10
Time (min)
15 20 25
thermocouple
measurements at cryogenic Measurement
temperatures. Temperature system with
scale is between +50 to -200 liquid
oC and horizontal scale is nitrogen
Dewar and
relative time in minutes. vacuum
chamber for
DUT
University of Central Florida
School of Electrical Engineering and Computer Science 55

56. Schematic and Actual OFC Gas Sensor
OFC Sensor Schematic
Actual device with RF
probe
•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)
University of Central Florida 56
School of Electrical Engineering and Computer
Science

57. 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 Without H2
Pd are dependent on substrate
CONTACT
CONTACT
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 – With H2
Resistivity increases
CONTACT
CONTACT
• Examine these effects for ultra-
thin films (<5nm) on SAW
devices
HILE - Each small circle
represents a nano-sized
cluster of Pd atoms
57

58. Measured E-Beam Evaporated Palladium
Conductivity v Film Thickness
σinf = 9.5·104 S/cm
Conductivity
measurements made in-situ
under vacuum
58

59. 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

60. Pd Films on SAW Devices
Schematic of Test Conditions
• Control: SAW delay line on YZ
LiNbO3 wafers w/ 2
transducers and reflector w/o
Pd film
• Center frequency 123 MHz
1.27 mm
• (A) SAW delay line w/ Pd in
Pd Film
propagation path between (A)
transducer and reflector
Pd Film
• (B) SAW delay line w/ Pd on (B)
reflector only
60

61. Test Conditions and Measurement
S21 Time Response
• S21 time domain 0
4 SAW Main
8
Reflector
measurement of SAW 12
16
20
Normalized Magnitude (dB)
delay line 24
28
32
TTE
– Main response
36
40
44
48
– TTE 52
56
60
64
– Reflector return 68
72
76
response 80
0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25
Time (micro-seconds)
DL w/o Pd
Before Exp Pd Film
During 1st Exp
After 1st Exp
During 2nd Exp
After 2nd Exp
During 3rd Exp
After 3rd Exp
During 4th Exp
61
After 4th Exp

62. SAW Propagation Loss and Reflectivity
Pd Film ~ 15 Ang. (prior to H2)
No
• S21 time domain comparison of Pd S21 Time Response
delay line with Pd in propagation 20
23
path vs. on the reflector
26
29
32
• Greater loss when Pd is placed in 35
Normalized Magnitude (dB)
38 Pd Film
propagation path than in the 41
44
reflector 47
50
– ~7dB loss when Pd is on
53
Pd Film
56
59
reflector 62
65
• reflector length 1.47 mm 68
71
– ~22dB loss when Pd is in 74
77
propagation path 80
1.7 1.75 1.8 1.85 1.9 1.95 2 2.05 2.1 2.15 2.2 2.25
• 1.27 mm one-way path length Time (micro-seconds)
DL w/o Pd
• Propagation loss ~75dB/cm loss DL w/ Pd In Delay Path
DL w/ Pd on Reflector Bank
m
v fs := 3488
s
62

63. SAW Device
Pd in Propagation Path w/ 2% H2 Exposure
• Close-up of reflector bank S21 Time Response
S21 time domain response. 20
23
• A comparison of the traces 26
29
labeled “DL w/o Pd” and”
32
35
Normalized Magnitude (dB)
38
Before Exp” shows a 41
44
change in reflectivity due to 47
50
the presence of the Pd film. 53
56
59
• A gradual reduction in 62
65
propagation loss with 68
71
increased H2 exposure. 74
77
– Irreversible change
80
1.7 1.75 1.8 1.85 1.9 1.95 2 2.05 2.1 2.15 2.2 2.25
Time (micro-seconds)
– ~ 20 dB reduction in DL w/o Pd
loss
Before Exp
Pd Film
During 1st Exp
After 1st Exp
• Minimum propagation During 2nd Exp
loss ~6.8 dB/cm After 2nd Exp
During 3rd Exp
After 3rd Exp
During 4th Exp
After 4th Exp
63

64. SAW Device
Pd on Reflector w/ 2% H2 Exposure
S21 Time Response
• Close-up of reflector bank 0
S21 time domain response. 4
8
12
• A comparison of the traces 16
20
Normalized Magnitude (dB)
labeled “DL w/o Pd” and” 24
28
Before Exp” shows a change 32
36
in delay as well as reflectivity 40
44
48
due to the presence of the 52
56
Pd film. 60
64
• A gradual increase in 68
72
76
reflectivity with each 80
1.7 1.75 1.8 1.85 1.9 1.95 2 2.05 2.1 2.15 2.2 2.25
exposure to H2 gas is Time (micro-seconds)
observed DL w/o Pd
Before Exp
Pd Film
During 1st Exp
– ~ 7 dB change in IL After 1st Exp
During 2nd Exp
– Irreversible After 2nd Exp
During 3rd Exp
After 3rd Exp
During 4th Exp
64 After 4th Exp

65. Nano-Pd Film – 25 Ang.
20
Hydrogen Gas
24
28
Normalized Magnitude (dB)
32
Sensor Results:
36
40
44
48
2% H2 gas 52
56
Pd F ilm
60
64
68
72
Propagation Loss (dB/cm) and Velocity(m/s) vs. Film Resistivity 76
240 3500
80
SAW Velocity (m/s)
200 3485
1.7 1. 8 1.9 2 2.1 2.2
Loss (dB/cm)
160 3470
120 3455
Time (micro-seconds)
80 3440 Delay Line w/o Pd •The change in IL
40 3425 After Pd Film indicates >10x
0 3410 During 1st H2 Exp osure
100
3
1 .10
4
1 .10 1 .10
5
After 1s t H2 Exp osure
change in Pd
Resistivity (ohm-cm)
During 2nd H2 Exp osure resistivity – WOW!
Loss/cm @ 123 MHz
Pd Film
After 2n d H2 Exposure
Loss/cm due to Pd Film •The large change
Loss/cm due to Pd Film After Final H2 Gas Exposure During 3rd H2 Exposure
Loss/cm due to successive H2 exposure suggests an
SAW Velocity After 3rd H2 Exposure
SAW Velocity due to Pd Film During 4th H2 Exposure unexpected change in
SAW Velocity due to Pd Film After Final H2 Gas Exposure
SAW Velocity due to successive H2 exposure After 4th H2 Exposure Pd film morphology.
65

66. OFC Cantilever Strain Sensor
• Measure Delay
versus Strain
66

67. OFC Cantilever Strain Sensor
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.

68. 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
School of Electrical Engineering and Computer Science
68

69. 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 years
69
University of Central Florida
School of Electrical Engineering and Computer Science

70. 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
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71. 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
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72. 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

73. Current Graduate Research
Student Contributors
• Brian Fisher
• Daniel Gallagher
• Mark Gallagher
• Nick Kozlovski
• Matt Pavlina
• Luis Rodriguez
• Mike Roller
• Nancy Saldanha

74. Acknowledgment
•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.
Thank you for your attention!
University of Central Florida 74
School of Electrical Engineering and Computer Science

75. Contact US
Contact:
Doug Foster
Fuentek, LLC
(919) 249-0327
www.fuentek.com/technologies/SAW.htm
University of Central Florida 75
School of Electrical Engineering and Computer Science