SURFACE ACOUSTIC WAVE (SAW) TRANSDUCERS AND DEVICES /topic 152
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Why interest in SAW devices and transducers.
Current status, particularly in Poland
The area of research interest
Our recent developments (2005-6):
i. Theory of interdigital transducers (electrostatics, SAW diffraction)
ii. Modeling of thick transducer teeth and combs.
5. Conclusions – also see the draft monograph http://www.ippt.gov.pl/~edanicki/danickibook.pdf
Eugeniusz Danicki and Yurij Tasinkevych
1. What are SAW devices? They are in principle mechanical devices exploiting surface acoustic
waves for manipulation of high-frequency electric signals. The best features of mechanical
vibrations: stability and reliability make the devices very attractive for modern applications in
radars, cellular phones, in sensors, SAW identification-tags, and others. All these devices use
interdigital transducers (IDTs) for generation and detection of surface acoustic waves on
piezoelectric crystals by electric means, the subject of our theoretical research, also applicable
for quantitative modeling of SAW comb transducers for ultrasonic surface-oriented NDE.
2. In Poland, we have developed some SAW devices for pulse-compression radars. There exists
technology for development of RFID devices (like for Q-Free or for medical applications up to
UH frequency band), and particularly for efficient contact-less comb transducers for NDE.
Interdigital transducer with thick elastic strips and a concept of contact-less comb transducer.
3. The wave phenomena of our theoretical research interest include:
a. characterization of SAWs and piezoelectric substrates for transducer modeling,
b. electrostatics of strips, including “scattering” problem peculiar to the subject,
c. interaction of SAW with thick periodic elastic strips including SAW diffraction,
d. that also arises in theory of comb transducers – the scattering by periodic grooves.
These problem are very attractive from fundamental research point of view, they are of great
importance to current technology but still weekly investigated. Profiting from good theoretical
level of mechanical science here, we feel we can contribute well to the solution of all of them,
and perhaps propose some novel devices. Verifying experiments are also in consideration.
4. Four recent developments are presented here: two electrostatic problems (the “scattering” that
resulted in the original spectral theory of SPUDTs and the full-field model of final aperturewidth IDTs), modeling of periodic elastic strips interacting with SAWs (verifying the earlier
perturbation theory), and the analysis of contact-less comb transducers showing its feasibility.
Spectral theory of IDTs: induced charge distribution in scattering by strips, frequency characteristics of SPUDT evaluated
accounting for SAW scatterting and strip elasticity. Modeling apodized IDTs accounting for diffraction – example radiation
conductance of uniform IDT and transmission efficiency characteristicsbetween transducers distorted by SAW diffraction.
Stopbands in SAW propagation under contact-less comb and the estimated efficiency of the comb teeth. Modeling of IDTs
with thick elastic strips – parameters of planar harmonic Green function of strips and the resulting SAW stopband edges.
5. Conclusions.
These original research address the unsolved fundamental problems of SAW devices and
novel mode-matching methods of NDE (providing quantitative theory of comb transducers).