Surface Acoustic Wave (SAW) Wireless Passive RF Sensor Systems

  • 5,437 views
Uploaded on

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 …

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.

More in: Technology , Business
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Be the first to comment
No Downloads

Views

Total Views
5,437
On Slideshare
0
From Embeds
0
Number of Embeds
2

Actions

Shares
Downloads
223
Comments
0
Likes
3

Embeds 0

No embeds

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
    No notes for slide

Transcript

  • 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 70
  • 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 71
  • 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