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

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Fig : Basic Structure of SAW Device

Surface Acoustic Wave(SAW)

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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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SAW Based Touch Screen

Application

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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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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