Post on 18-Aug-2015
Surface Acoustic Wave Technology
Presented By:AKHIL BARAIK
Outline
• Introduction• Terminology• Surface Acoustic Wave(SAW)
- Components- Properties
• SAW Principle• Applications• Advantages & Disadvantages• Conclusion• References
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Surface Acoustic Wave TechnologyBrief History:• Surface Acoustic Waves (SAW) were discovered in 1885
by Lord Rayleigh• SAW device was invented by White and Voltmer in 1965• Around 1970, developed for Pulse Compression Radar,
oscillators, and bandpass filters for domestic TV• Diverse applications in consumer and highly professional
electronic devices and systems • Perform different functions in the frequency range from
10 MHz to several GHz.
Introduction
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Terminology• Surface: Outside part or uppermost layer of something.
• Acoustic : Science deals with the study of all mechanical waves in gases, liquids, and solids.
• Wave: Oscillation accompanied by transfer of energy that travels through space or mass.
• Acoustic Wave : Type of longitudinal wave propagates by means of adiabatic compression and decompression.
Introduction
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Definition
• A Surface Acoustic Wave (SAW) is an Acoustic Wave traveling along the surface of an elastic substrate.
• Frequency of SAW:F=V/ λV=Velocity of SAW (~ 2500m/s-10000m/s) λ=wavelength
• Type of mechanical wave motion travels along the surface of solid material.
Surface Acoustic Wave(SAW)
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SAW Device
.
Fig : Basic Structure of SAW Device
Surface Acoustic Wave(SAW)
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Continued...
SAW Device?• A solid state device
– Converts electrical energy into a mechanical wave(Acoustic) on a single crystal substrateand vice versa
– Provides very complex signal processing in a very small volume• Approximately 4-5 billion SAW devices are produced each year
Surface Acoustic Wave(SAW)
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SAW Device Components
• Transducers(IDT)• Piezoelectric Substrate
– Crystal Quartz(SiO2)
– Lithium Niobates(LiNbO3)
– Lithium Tantalates(LiTaO3) etc.
• Reflectors
Surface Acoustic Wave(SAW)
Fig : Typical Piezoelectric Transducer
Fig : SAW Reflector Gratings
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SAW Properties
• Piezoelectric Substrate : Acoustoelectric Conversion• Small Surface Perturbation: 0.1-20 A0
• Velocity: ~2,500 -10,000 m/s• Efficient Transduction• Frequency Range: ~10MHz to 3GHz
Surface Acoustic Wave(SAW)
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SAW Comparison with EM wave
Vsaw=~3000 m/s Vem=~3 x108 m/s
F λ=V
Surface Acoustic Wave(SAW)
F=10MHz F=1GHz
λsaw300 µm 3µm
λ EM30m 3m
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SAW Principle
• Based on Piezoelectric Effect: Useful in applications:– production and detection of sound– generation of high voltages etc
• Based on Acoustic Wave : Wave propagates by means of adiabatic
compression and decompression.
SAW Fundamentals
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Continued... Piezoelectric Effect
• Also called as Piezoelectricity
• The ability of certain materials to generate an voltage when subjected to mechanical stress
• Reverse is also true.
SAW Fundamentals
Fig : Piezoelectric Effect
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• SAW Touch Screen• SAW Filter • Delay Line• Resonator• Sensors• RFID
Applications
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SAW Touch Screen
Application
•An electronic visual display locates the coordinates of users touch within display area
•Works independently of what is being displayed on screen
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Continued...
SAW Based Touch Screen
Application
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Continued...
SAW Touch Screen
• Surface consists of glass overlay with transmitting and receiving transducers• Electrical signals sent to the transmitting
transducers• Waves are directed across screen by
reflectors then directed to receiving transducers
Application
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Continued...
SAW Touch Screen
• When finger touches screenit absorbs waves
• Received values are compared tostored digital maps to calculate x and y coordinates
Application
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Illustration
Application
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Application of SAW Touch Screen
• ATMs• Amusement Parks• Gaming Environments• kiosks• Industrial Control Rooms
Application
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Why SAW Touch Screen?
• Advantages:– Best optical quality– High surface durability– Activated by multiple sources – High “touch-life”
• Disadvantages:– Expensive– Contaminates on screen can cause false-touches– Non conductive material can not activate screen
Application
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Surface Acoustic Wave
ADVANTAGES:• Low Velocity• Low attenuation• Low cost• Simple design and fabrication• Low power consumption
DISADVANTAGES:• Can not be operated in liquids• Piezoelectric substrates are temperature dependent
ADVANTAGES & DISADVANTAGES
OutlineCONCLUSION
• Surface Acoustic Wave Technology is widely used technology.
• Applied to design filters, different sensors, resonators, delay lines and many commercial devices.
• Most emerging technology across the world.• All the electronics equipments and devices use SAW
technology.• The demand of SAW technology will never abate
because of its fruitful advantages than disadvantages.
Works Cited
http://en.wikipedia.org/wiki/Surface_Acoustic_wave http://www.dmccoltd.com/english/museum/touchscreens/technologies/AcousticWave.asp http://www.elotouch.com/technologies/intellitouch/default.asp http://admetro.com/products/surface-acoustic-wave-saw http://www.baanto.com/surface-acoustic-wave-saw-touch-screen http://www.analog.com/library/analogDialogue/archives/44-02/touch_screen.html http://apcmag.com/inside-touch-how-touchscreen-technologies-work.html http://www.slideshare.net/mshirif/touch-screen-technologies# http://computer.howstuffworks.com/question716.htm