1. Surface Acoustic Wave (SAW) Wireless Passive RF Sensor System Tutorial
Donald C. Malocha
Department of Electrical Engineering & Computer Science
University of Central Florida
Orlando, Fl

2. Don Malocha University of Central Florida
Don Malocha, Professor, University of Central Florida
BS, MS and PhD, Univ. of Illinois, UIUC
Texas Instruments, Corporate Research Laboratory, Dallas, MTS
Sawtek, Orlando, Mgr. of Advanced Product Development
Motorola, Visiting/Member of the Technical Staff, Phoenix and Ft. Lauderdale
Visiting Faculty, ETH, Switzerland, and Univ. of Linz, Austria
Past President, IEEE Ultrasonics, Ferroelectrics and Frequency Control Society
WEB site:
UCF – nations 2nd largest university

3. Mnemonics Inc. (MNI), Melbourne, Fl.
Acknowledgment
The author wishes to thank continuing support from everyone who has aided us at 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 Space Grant Consortium, and NASA STTR and SBIR contracts.
Continuing research is funded through NASA STTR/SBIR contracts and industrial collaboration with our industrial partner
Mnemonics Inc. (MNI), Melbourne, Fl.

4. General Background

5. 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 ~ K
Resonator – coding in frequency
CDMA- time coding, dB loss, wideband
OFC - time & frequency coding, 6-20 dB loss, ultra wide band

6. Why Use SAW Sensors and Tags?
Frequency/time are measured with greatest accuracy compared to any other physical measurement ( ).
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 (practical) ~100 MHz – 3 GHz
Monolithic structure fabricated with current IC photolithography techniques, small, rugged

7. 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
Approximately 4-5 billion SAW devices are produced each year
Applications:
Cellular phones and TV (largest market)
Military (Radar, filters, advanced systems
Currently emerging – sensors, RFID

8. SAW Principle - Piezoelectricity
Squeezing a piezo-crystal creates a voltage.
A voltage can compress or dilate a piezo-crystal.

9. SAW Basics Transduction & Reflection fro SAW Sensors
SAW - mechanical wave trapped to the surface
Transduction via piezoelectric effect
Velocity ~ m/sec
1 GHz ~ 3 um
Line resolution at 1 GHz ~ .75 um
Reflection via Bragg reflector structure
DC Effect
RF to SAW
Bragg reflector

10. SAW Materials to Meet Sensor Needs
Crystal cut
Coupling coefficient
Temperature coefficient
SAW Velocity
Max Temp
LiNbO3
Y,Z
4.6%
94 ppm/ºC
3488 m/s
~500 ºC
128ºY,X
5.6%
72 ppm/ºC
3992 m/s
LiTaO3
0.74%
35 ppm/ºC
3230 m/s
Quartz ST
0.16%
0 ppm/ºC
3157 m/s
550 ºC
Langasite
Y,X
0.37%
38 ppm/ºC
2330 m/s
>1000 ºC
138ºY,26ºX
0.34%
~0 ppm/ºC
2743 m/s
SNGS
0.63%
99 ppm/ºC
2836 m/s
SAW travels ~ 105 slower than EM wave
SAW 1 GHz ~ 3 um

11. SAW/IC Fabrication Techniques
Lines are ~ .8 um
SAW Transducer
SAW reflector gratings
The dark line in each micrograph is a 23 um gold wire
SAW reflector gratings
SAW 1 GHz require submicron lithography.
Standard IC thin films, photolithography and processing are used.

12. Basic Passive Wireless SAW System
Sensor #1 Gas
Sensor #3 Temperature
Sensor #2 Pressure
Goals:
Interrogation distance: 1 – 50 meters
# of devices: 10’s – 100’s - coded and distinguishable at TxRx
Aerospace applications – rad hard, wide temp., solid state, etc.
Single platform and TxRx for differing sensor combinations

13. RFID and SAW Introduction

14. RFID Sensor RFID Acquisition Measurand Extraction
Two primary system functions: RFID and extraction of the measurand. The RFID must first be acquired and then the measurand extracted. The presentation will address these issues for a temperature sensor system.
RFID Acquisition
Priority for system
Coding approach
Demodulation approach
System Parameters
Measurand Extraction
RFID is acquired
S/N ratio
Accuracy
Acquisition rate

15. Diversity for Identification
Frequency Spectrum Diversity per Device
Coding
Divide into frequency bands
Time Delay per Device
Different offset delays per device
Pulse position modulation
Time allocations minimize code collisions
Spatial Diversity – device placement
Sensor & Tx-Rx Antenna Polarization
Use combinations of all to optimize system

16. Brief Introduction to Wireless SAW Sensors
One port devices return the altered interrogation signal
Range depends on embodiment
Range increased using coherent integration of multiple responses
Interrogator used to excite devices
Several embodiments are shown next

17. Reflective Delay Line Sensor
“Wireless Interrogator System for SAW-Identification-Marks and SAW-Sensor Components”,
F. Schmidt, et al, 1996 IEEE International Frequency Control Symposium
First two reflectors define operating temperature range of the sensor
Time difference between first and last echoes used to increase resolution of sensor
No coding as shown

18. SAW Chirp Sensor
“Spread Spectrum Techniques for Wirelessly Interrogable Passive SAW Sensors”,
A. Pohl, et al, 1996 IEEE Symposium on Spread Spectrum Techniques and Applications
Increased sensitivity when compared with simple reflective delay line sensor
Multi-sensor operation not possible due to lack of coding

19. Impedance SAW Sensors
“State of the Art in Wireless Sensing with Surface Acoustic Waves”,
W. Bulst, et al, IEEE UFFC Transactions, April 2001
External classical sensor or switch connected to second IDT which operates as variable reflector
Load impedance causes SAW reflection variations in magnitude and phase
No discrimination between multiple sensors as shown

20. SAW RFID Practical Approaches
Resonator
Fabry-Perot Cavity
Frequency selective, SAW device Q~10,000
Code Division Multiple Access (CDMA)
Delay line – single frequency Bragg reflectors
Pulse position encoding
Orthogonal Frequency Coding (OFC)
Delay line, multi-frequency Bragg reflectors
Frequency coupled with time diversity

21. SAW Resonator Q~10,000 Resonant cavity
Frequency with maximum returned power yields sensor temperature
High Q, long time response
Coding via frequency domain by separating into bands
“Remote Sensor System Using Passive SAW Sensors”,
W. Buff, et al, 1994 IEEE International Ultrasonics Symposium

22. SAW CDMA Delay Line CDMA Tag Concept CDMA Tag
Single frequency Bragg reflectors
Coding via pulse position modulation
Large number of possible codes
Short chips, low reflectivity - (typically dB IL)
Early development by Univ. of Vienna, Siemens, and others

23. SAW OFC Delay Line OFC Tag OFC Tag Multi-frequency (7 chip example)
DUT - RF probe connected to transducer
Bragg reflector gratings at differing frequencies
Micrograph of device under test (DUT)
OFC Tag
Multi-frequency (7 chip example)
Long chips, high reflectivity
Orthogonal frequency reflectors –low loss (6-10 dB)
Example time response (non-uniformity due to transducer)

24. Discussion
Resonator, CDMA, and OFC embodiments have all been successfully demonstrated and applied to various applications. Devices and systems have been built in the 400 MHz, 900 MHz and 2.4 GHz bands by differing groups.
Resonator
Minimal delay
Narrowband PG~1
Fading
Frequency domain coding
High Q – long impulse response
Low loss sensor
CDMA
Delay as reqd. ~ 1usec
Spread Spectrum
Fading immunity
Wideband
PG >1
Time domain coding
Large number of codes using PPM
OFC
Delay as reqd. ~ 1usec
Spread Spectrum
Fading immunity
Ultra Wide Band
PG >>1
Time & frequency domain coding
Large number of codes using PPM and diverse chip frequencies

25. OFC Sensor Embodiment

26. SAW OFC Sensor Introduction
Conventional wisdom at the time:
“ Orthogonality in frequency is not feasible with coded reflective passive SAW sensors.”, “Spread Spectrum Techniques for Wireless Interrogable Passive SAW Sensors”, A. Pohl, et. al., IEEE 4th International Symposium on Spread Spectrum Techniques and Applications, 1996, pp. 730.
“D. Malocha and coworkers recently developed Orthogonal Frequency Coding for SAW tags [25]. …….This approach can be applied to sensors and for identification of a limited number of sensors, but it can hardly be used for ID tags with large numbers of codes.” Review on SAW RFID Tags, V. P. Plessky, and L.M. Reindl, IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, vol. 57, no. 3, March 2010, pp.654
First OFC publication by UCF group in 2004 and working system in The use of spread spectrum frequency and time coding had been overlooked as either not possible or too complicated. For RFID sensors, the approach is both feasible, advantageous, and demonstrated.

27. OFC Historical Development
Chose 1st devices at 250 MHz for feasibility
Several different OFC sensors demonstrated
Demonstrated harmonic operated devices at 456, 915 MHz and 1.6 GHz
Fundamental device operation at 915 MHz
Devices in the +1 GHz range in 2010
First OFC system at 250 MHz
Current OFC system at 915 MHz
First 4 device wireless operation in 2009
Mnemonics demonstrates first chirp OFC correlator receiver in 2010

28. Why OFC SAW Sensors? A game-changing approach
All advatageous of SAW technology
Wireless, passive and multi-coded sensors
Frequency & time offer greatest coding diversity
Single communication platform for diverse sensor embodiments
Radiation hard
Wide operational temperature range

29. Schematic of OFC SAW ID Tag
Sensor bandwidth is dependent on number of chips and sum of chip bandwidths. Frequency domain of Bragg reflectors: contiguous in frequency but shuffled in time
Time domain chips realized in Bragg reflectors having differing carrier frequencies and frequencies are non-sequential which provides coding

30. Example 915 MHz SAW OFC Sensor
US Quarter
SAW Sensor
SAW OFC Reflector Chip Code
f4 f3 f1 f5 f2
FFT
Show picture of device and explain microwave operation
Point out the parts of the tag and how we extract a time delay
Trace out the transducer response
Explain the time response and the decreasing transducer response

31. SAW OFC RFID signal – Target reflection as seen by antenna
absorber
S11 w/ absorber and w/o reflectors
S11 w/o absorber and w/ reflectors
Coded SAW chips are bound in frequency and received sequentially in time

32. OFC: # codes=N!*2N where N= #chips
OFC vs CDMA Number of possible codes versus number of chips for same chip configuration
CDMA: # codes=2N
OFC: # codes=N!*2N where N= #chips

33. Effect of Code Collisions from Multiple SAW RFID Tags -Simulation
Due to asynchronous nature of passive tags, the random summation of multiple correlated tags can produce false correlation peaks and erroneous information

34. OFC Coding
Time division diversity (TDD): Extend the possible number of chips and allow delay and phase modulation
# of codes increases dramatically, M>N chips, >2M*N!
Reduced code collisions in multi-device environment f1 f4 f3 f2
Sensor #1

35. 456 MHZ SAW OFC TDD Coding
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.

36. OFC FDM Coding f1 f4 f3 f2 f6 f7 f5 f8 Sensor #1 Sensor #2
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 f1 f4 f3 f2 f6 f7 f5 f8
Sensor #1
Sensor #2 36

37. Antenna and SAW Sensor Design Considerations

38. SAW Electrically Small Antenna
Gain and Bandwidth
The plots show that there is a minimum size at a given frequency to attain a desired fractional bandwidth.
As the frequency increases, a larger fractional bandwidth is achievable for a smaller antenna size.
As the effective size of the antenna increases, the gain and bandwidth both increase.

39. SAW Target – SAW + Antenna
UCF Initial Design
250 MHz Disk Monopole Antennas
Large dinner plate design met fractional bandwidth, but hardly miniature compared to SAW sensor size

40. Target Gain vs. Frequency Analysis points to ~1 GHz
where f is in GHz
Good fo region
%BW
SAW, antenna and net gain in dB, and fractional bandwidth, versus frequency for a 3cm radius ESA. Assumes a SAW propagation length of 5 usec.

41. Wideband Open-Sleeve Dipole Antenna
Designed on 32mil FR4 (εr=4.7 and tan(δ)=0.015)
Entire structure optimized in IE3D between 800MHz and 1GHz
Explain antenna design 41

42. Fully integrated on-wafer SAW OFC sensor and antenna
915 MHz
Fully integrated on-wafer SAW OFC sensor and antenna
Wireless OFC SAWtenna time domain response
Test wafer-level SAW & antenna integration

43. Miniature 915MHz Integrated OFC SAW-Patch Antenna

44. Synchronous Correlator Transceiver

45. Synchronous Transceiver - Software Radio
Pulse Interrogation: Chirp or RF burst
Correlator Receiver Synchronous
Software Radio Based
915 MHz Pulsed RF Transceiver Block Diagram

46. Temperature Extraction Using Adaptive Correlator
Comparison of ideal and measured matched filter of two different SAW sensors : 5-chip frequency(below)
Normalized amplitude (dB) versus time
NS401
NS403
Stationary plots represent idealized received SAW sensor RFID signal at ADC. Adaptive filter matches sensor RFID temperature at the point when maximum correlation occurs.

47. Synchronous Correlator Receiver
Block diagram of a correlator receiver using ADC
OFC Single Sensor Signal
Correlation Output
Temperature Extraction

48. 250 MHz Wireless Pulsed RF OFC SAW System - 2nd Pass
An 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.

49. SAW 915 MHz Correlator Transceiver

50. MNI Transceiver Design
Pulsed RF Chirp
Correlator Receiver
Synchronous operation
Integration of multiple “pings”
OFC processing gain
Adaptive filter temperature extraction
Software radio based approach for versatility

51. Current Sensor System Results
915 MHz transceiver developed by Mnemonics, Inc. (MNI), Melbourne, Fl
RF Chirp 700nsec, 28dBm peak power
Synchronous receiver
OFC SAW temperature sensors developed by UCF
YZ LiNbO3, 5 chip OFC delay line sensor
915 MHz fundamental, 0.8 um electrodes
Correlator software developed at UCF

52. Critical Transceiver Operational Parameters
EM Path Loss Considerations
Electrically Small Antennas (ESA)
SAW Device Propagation Loss
Target Gain versus Center Frequency
Integrated SAW and Antenna

53. EM Path Loss versus Range
EM isotropic two-way path loss for 3 differing operational frequencies: 0.25, 0.5 and 1 GHz - solid lines.
The dotted traces are the thermal noise levels at 3 differing bandwidths, 25, 72, and 200 MHz.
Path loss 40dB/decade w/ increasing range or frequency

54. RF Transceiver: Sensor Overview
OFC with single wideband transducer
Center Frequency: 915 MHz
Bandwidth: Chirp - ~78 MHz
Number of Chips: 5
Chip length 54ns/each, total reflector length 270ns
Substrate: YZ LiNbO3

55. SAW 915 MHz OFC Sensor SAW sensor acts as RFID and sensor
All antenna & transducer effects are doubled
Antenna gain and bandwidth are dependent on size scaled to frequency
SAW propagation loss is frequency dependent

56. Parameter Definitions (extensive list of variables)
ADC= ideal analog-to-digital converter
MDS= minimum detectable signal at ADC
S= signal power measured at ADC
N= noise power measured at ADC
kT= thermal noise energy
EIRP= equivalent radiated power
GRFIDS= RFIDS gain (less than unity for passive device)
GRx-ant= gain of the receiver antenna
GRx= receiver gain from antenna output to ADC
PG= signal processing gain of the system (= τ·B)
PL= path loss
NF= receiver noise figure
Next= external noise source referenced to antenna output
NADC= ADC equivalent noise
Nsum= number of synchronous integrations in ADC
PGC = pulse compression gain from chirp interrgogation

57. Range Prediction
For passive RFIDS, the range is given from Friis equation as
Range =r = PL.25·[vEM/(4·π·fo)] ;
where vEM=free space velocity
A minimum S/N is determined for detection, and the maximum range, in meters, achievable, given in dB, is obtained as
rmax-dB=.25·{GPDL+Gsys+Nsum-[S/Nmin]} -10·log[(4·π·f)/vEM],
where
GPDL=[EIRP/(NF*·kT/τau)] = power-detection level gain
and Gsys = [(GRFIDS·GRx-ant)]

58. RF Chirp Transceiver Parameters
Power to antenna = 30dBm
Pulse-length = 700ns, 20Vpp
Antenna Gain = 9dB
Bandwidth = 74MHz
Receiver Gain = 45dB
NF = 15dB
PGC= 49 = 17 dB

59. Range Prediction for MNI Receiver for RFID Detection (not sensor)
Range is a function of the complete system loop gain, shown in solid line (red). Loop gain is dependent on the transmit power, noise and gain in the system. Typical loop gains are realistically achievable between 100 to 180 dB. The box shows the predicted loop gain for the MNI/UCF system, which is very close to measurements obtained.

60. Chirp Transceiver: SAW OFC Sensor Range Experiment
Single sensor only; no signal integration
Multiple distances from 1.2m to 20m
0 to 20dB additional attenuation at each step
128 readings taken per distance per attenuation
Longest distance of successful interrogation 7m
Reading error .07 corresponds to 60% of all data points within 5°C (3.5%)

61. Practical Extension NF = 18dB → 8dB (∆G = 10dB)
GSAW = -23dB → -10dB (∆G = 13dB)
GPSI = 12dB → 22dB (∆G = 10dB)
Total improvement: 33dB
Approximately extended range: 80m
1.21 jigga watts

62. 915 MHz OFC Temperature Sensor System Measured Device Data in a Hallway
Data is measured in a hallway approximately 2.1 meters wide. Antennas: transmit is a wideband 1 dB dipole; receive is a 9 dB Yagi. The system loop gain is calculated at ~40 dB (+/-3 dB). Transmit signal is a single, 700 nsec, 915 MHz chirp pulse. The OFC SAW device uses 5 chips, each with an approximate 15 MHz bandwidth. SAW device processing gain is 25. Slope of the fit measured data is dB/decade; close to the 40 dB/decade expected for isotropic radiation path loss. The hallway is probably producing a waveguiding effect and external noise was low during testing. Test shows that some environments can produce long ranges.

63. OFC SAW Correlator Receiver Tag Ranging
Distance from interrogator to the sensor can be extracted based on EM delay (8m per chip length – 54ns)
X-axis indicates various distances at which sensor was placed away from interrogator
Cross-marks indicate distance from interrogator on y-axis
128 Measurements were made for each step
Blue box indicates spread of a half of all data
Black boundaries indicate spread of 99.3% of all data
Red pluses indicate outliers

64. UCF Sensor Development
There is an extensive body of knowledge on sensing
Wired SAW sensing has quite an extensive body of knowledge and continues
Wireless SAW sensing has been most successfully demonstrated for single, or very few devices and in limited environments
The following are a few of the successful UCF sensor projects
The aim is to enable wireless acquisition of the sensors data
The further goal is to develop a multi-sensor system for aerospace applications
Successful wireless sensing has been demonstrated for temperature, liquid, closure, and range

65. 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
Closure sensor with temperature

66. Four-sensor operation
Four OFC SAW sensors are co-located in close range to each other at a distance of 0.8m to 1.2m
Sensors NS402 and NS404 remained at room temperature
Sensor NS401 heated to 140°C
Sensor NS403 cooled to -130°C
Data was taken simultaneously from all four sensors and then temperature extracted in the correlator receiver software
Error is within ±5°C (±3.5% for given dynamic range)
Explain the set-up better, this is very important stuff, speak to the slide, read the plot

67. Differential SAW OFC Thin Film Gas Sensor Embodiment

68. Temperature Sensor using Differential Delay Correlator Embodiment
Temperature Sensor Example
250 MHz LiNbO3, 7 chip reflector, OFC SAW sensor tested using temperature controlled RF probe station

69. Temperature Sensor Results
250 MHz LiNbO3, 7 chip reflector, OFC SAW sensor tested using temperature controlled RF probe station
Temp range: oC
Results applied to simulated transceiver and compared with thermocouple measurements

70. OFC Cryogenic Sensor Results
Scale
Vertical: +50 to -200 oC
Horizontal: Relative time (min)
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.
Measurement system with liquid nitrogen Dewar and vacuum chamber for DUT

71. Schematic and Actual OFC Gas Sensor
Differential mode 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)

72. Hydrogen Gas sensor Palladium Background Information
The bulk of PD research has been performed for Pd in the 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

73. 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
(A) SAW delay line w/ Pd in propagation path between transducer and reflector
(B) SAW delay line w/ Pd on reflector only
1.27 mm

74. Hydrogen Gas Sensor Results: 2% H2 gas
Nano-Pd Film – 25 Ang.
Hydrogen Gas Sensor Results: 2% H2 gas
Theory (lines) versus measurement data
The change in IL indicates a <20 dB sensitivity range and further tests were < 50 dB!
Sensitive hydrogen sensor is possible.

75. Cantilever Sensor Results
Initial cantilever sensor results
Apply results to strain and pressure sensors

76. OFC Cantilever Strain Sensor
Measure Delay versus Strain

77. 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.

78. 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

79. Current to Future

80. Vision for Future Multiple access, SAW RFID sensors
SAW RFID sensor loss approaching 6 dB
Unidirectional transducers
Low loss reflectors
New and novel coding
New and novel sensors
New materials for high temperature (1000oC) and harsh environments
SAW sensors in test space flight and support operations in 1 to 5 years

81. Ultra Wide Band BW defined by chirp, not by individual sensors
Could use a frequency hopped chirp system
Frequency diversity is increased
Code coliision reduction
Multi-bands for multi-sensors
Subsets of sensors activated at any given time
Narrower band antennas, lower loss devices

82. SAW Research at UCF
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 6 PhDs & 1 Post-doc

83. Capabilities
Proprietary software: COM analysis & design, parameter extraction, data acquisition and test
UCF device fabrication to < .8um resolution
In-house mask fab & thin film capabilities
Complete RF SAW characterization facility
Extensive RF laboratory for system development

84. UCF SAW OFC Contracts & Intellectual Property
A. 6 – Phase I and 4 –Phase II STTR/SBIRs on SAW OFC Sensors B. NASA KSC, Langley, and JSC contracts C. Fellowships from NASA, NSF, Motorola, NSDEG, UCF, McKnight, and Florida Space Grant D. Patents on SAW OFC: #7,642,898 D.C. Malocha and Puccio, Orthogonal Frequency Coding for Surface Acoustic Wave Communications, Tag, and Sensors, Jan. 5, #7,623,037 D.C. Malocha, Multi-transducer/antenna surface acoustic wave device sensor and tag, November 24, #7,825,805, D.C. Malocha and D. Puccio, Delayed Offset Multi-Track OFC Sensors and Tags, Nov. 2, #7,777,625, D.C. Malocha and D. Puccio, Weighted Reflectors for OFC Coding, Aug. 17, #7,791,249, D.C. Malocha and N.Y. Kozlovski, SAW Coding for OFC Devices, Appl # 12,618,034, D.C. Malocha and N. Kozlovski, Coding for Surface Acoustic Wave Devices, Filed Nov. 13, Several in process

85. Conclusion
915 MHz OFC SAW temperature sensor system has been demonstrated
Current tests show 10 meter open range
4 sensors have been simultaneously interrogated and measured
Range predictions and measured data have been shown
Wireless passive SAW sensors are a “game-changing” technology