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INTRODUCTION
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SAW
filter consists
of two transducers
with interdigital
arrays(IDT ; Inter
digital Transducer)
of thin metal electrodes
deposited on a piezoelectric
substrate, and converts
the incoming electric
signal to an acoustic
one, Surface Acoustic
Wave, and vice-versa.
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PIEZOELECTRIC
MATERIAL
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Rayleigh
Wave :
The
waves that propagate
at the surface of
materials (described
by Lord Rayleigh
in 1885)
IDT(Inter
digital Transducer)
:
Transducer
that convert the
incoming electric
signal to an acoustic
one (SAW), and vice-versa.
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-
A SAW Filter consists
of two interdigital
transducers (IDTs)
on a piezoelectric
crystal substrate
. The IDTs consist
of interleaved metal
electrodes which
are used to launch
and receive the
waves, so that an
electrical signal
is converted to
an acoustic wave
and then back to
an electrical signal.
- An impulse
voltage applied
to the transducer
generates, due to
piezoelectricity,
mechanical displacements
in the crystal between
electrodes (or fingers)
of opposite polarity.
These crystal displacements
propagate and create
a wave at the surface
of the crystal perpendicular
to the electrodes.
The inverse phenomenon
occurs when this
acoustic wave travels
under another transducer:
it in turn creates
an electromagnetic
output signal. The
characteristic of
frequency depends
on the pattern of
electrodes
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