The document discusses surface acoustic wave sensors. It introduces SAW sensors as sensors that rely on modulating surface acoustic waves to sense physical phenomena. The sensor converts an electrical signal to a mechanical wave that can be influenced by external factors, then converts it back to an electrical signal. Changes in amplitude, phase, frequency or time-delay can be used for measurement. Key properties of SAW sensors are that they are passive, can be accessed wirelessly, have a wide operating range, rugged compact structure, high stability, sensitivity and low cost. The basic device consists of a piezoelectric substrate and input/output interdigitated transducers to launch and receive the waves. Emerging applications include automotive, medical and industrial

1. GROUP MEMBERS:
ADU KANKAM MICHAEL
AGYEMANG PREMPEH ANTHONY
TOPIC:
SURFACE ACOUSTIC SENSOR
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2. INTRODUCTION
 SAW sensors are sensors which rely on the modulation of surface acoustic waves to
sense a physical phenomenon
 The sensor transduces an input electrical signal into a mechanical wave which, unlike
an electrical signal, can be easily influenced by physical phenomena.
 Transduces this wave back into an electrical signal.
 Changes in amplitude, phase, frequency or the time-delay between the input and
output electrical signals can be used to measure the presence of the desired
phenomenon.
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3. PROPERTIES
 The SAW sensors are passive elements
 SAW sensors can be accessed wirelessly
 Works in the range of 10MHz to several GHz
 The sensors have the rugged compact structure
 outstanding stability
 high sensitivity
 low cost
 fast real time response
 extremely small size
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4. DEVICE LAYOUT
1. The basic surface acoustic wave device consists
of
 a piezoelectric substrate,
 an input interdigitated transducer (IDT)
 a second, output interdigitated transducer
on the other side of the substrate.
2. Delay line because the signal which is a
mechanical wave at this point moves much
slower than its electromagnetic form, causing
appreciable delay
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5. DEVICE MODE OF OPERATION
 The input IDT launches and the output IDT receives the waves
 Acoustic wave sensors are so named because their detection mechanism
is a mechanical, or acoustic, wave.
 As the acoustic wave propagates through or on the surface of the
material, any changes to the characteristics of the propagation path affect
the velocity and/or amplitude of the wave.
 Changes in velocity can be monitored by measuring the frequency or
phase characteristics of the sensor and
 can then be correlated to the corresponding physical quantity being
measured.
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6. INHERENT FUNCTIONALITY
 The phenomena of pressure, strain, torque, temperature, and mass can be
sensed by the basic device.
 These phenomena can all cause a change in length along the surface of
the device.
 A change in length will affect both the spacing between the interdigitated
electrodes---altering the pitch---and the spacing between IDTs---altering
the delay.
 This can be sensed as a phase-shift, frequency-shift, or time-delay in the
output electrical signal.
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7. APPLICATIONS
 Several of the emerging applications for acoustic wave devices as sensors
may eventually equal the demand of the telecommunications market.
These include
 automotive applications (torque and tire pressure sensors),
 medical applications (chemical sensors), and
 industrial and commercial applications (vapor, humidity, temperature, and
mass sensors).
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8. END OF PRESENTATION
THANK YOU
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