Surface acoustic wave

Surface acoustic wave From Wikipedia, the free encyclopediaA surface acoustic wave (SAW ) is an acoustic wave traveling along the surface of a material exhibiting elasticity,with an amplitude that typically decays exponentially with depth into the substrate.DiscoverySAWs were first explained in 1885 by Lord Rayleigh, who described the surface acoustic mode of propagation and predicted its properties in his classic paper.[1] Named after their discoverer, Rayleigh waves have a longitudinal and a vertical shear component that can couple with any media in contact with the surface. This coupling strongly affects the amplitude and velocity of the wave, allowing SAW sensors to directly sense mass and mechanical properties.SAW devicesSAW devices use SAW wave in electronic components to provide a number of different functions, including as delay lines, filters, correlators and DC to DC converters.Application in electronic componentsThis kind of wave is commonly used in devices called SAW devices in electronic circuits. SAW devices are used as filters, oscillators and transformers,Experimental image of surface acoustic waves on a crystal of tellurium oxide.[1] (http://kino-ap.eng.hokudai.ac.jp/index.html)Contents1 Discovery2 SAW devices 2.1 Application in electronic components 2.2 SAW device applications in radio and television3 SAW in geophysics4 SAW in microfluidics5 See also6 External links and references7 Referencesdevices that are based on the transduction of acoustic waves. The transduction from electric energy to mechanical energy (in the form of SAWs) is accomplished by the use of piezoelectric materials.Electronic devices employing SAWs normally use one or more interdigital transducers (IDTs) to convert acoustic waves to electrical signals and vice versa by exploiting the piezoelectric effect of certain materials (quartz, lithium niobate, lithium tantalate, lanthanum gallium silicate, etc.).[2] These devices are fabricated by photolithography, the process used in the manufacture of silicon integrated circuits.SAW filters are now used in mobile telephones, and provide significant advantages in performance, cost, and size over other filter technologies such as quartz crystals (based on bulk waves), LC filters, and waveguide filters.Much research has been done in the last 20 years in the area of surface acoustic wave sensors.[3] Sensor applications include all areas of sensing (such as chemical, optical, thermal, pressure, acceleration, torque and biological). SAW sensors have seen relatively modest commercial success to date, but are commonly commercially available for some applications such as touchscreen displays.SAW device applications in radio and televisionSAW resonators are used in many of the same applications in which quartz crystals areused, because they can operate at higher frequency. They are often used in radio transmitterswhere tunability is not required. They are often used in applications such as garage dooropener remote controls, short range radio frequency links for computer peripherals, andother devices where channelization is not required. Where a radio link might use severalchannels, quartz crystal oscillators are more commonly used to drive a phase locked loop.Since the resonant frequency of a SAW device is set by the mechanical properties of thecrystal, it does not drift as much as a simple LC oscillator, where conditions such ascapacitor performance and battery voltage will vary substantially with temperature and age.SAW filters are also often used in radio receivers, as they can have accurately determinedand narrow passbands. This is helpful in applications where a single antenna must be sharedbetween a transmitter and a receiver operating at closely spaced frequencies. SAW filtersare also frequently used in television receivers, for extracting subcarriers from the signal;until the analog switchoff, the extraction of digital audio subcarriers from the intermediatefrequency strip of a television receiver or video recorder was one of the main markets forSAW filters. They are also often used in digital receivers, and are well suited to superhetSchematic picture of a typical SAW device design.this is a typical photo of SAW (surface acoustic wave) resonator commonly used in garage door opener remote control and rf modules.applications. This is because the intermediate frequency signal is always at a fixed frequency after the local oscillator has been mixed with the received signal, and so a filter with a fixed frequency and high Q provides excellent removal of unwanted or interference signals.In these applications, SAW filters are almost always used with a phase locked loop synthesized local oscillator, or a varicap driven oscillator. SAW in geophysicsIn seismology surface acoustic waves travelling along the Earth's surface play an important role, since they can be the most destructive type of seismic wave produced by earthquakes.[4]SAW in microfluidicsIn recent years, attention has been drawn to using SAWs to drive microfluidic actuation and a variety of processes. Owing to the mismatch of sound velocities in the SAW substrate and fluid, SAWs can be efficiently transferred into the fluid, to create significant inertial force and fluid velocities. This mechanism can be exploited to drive fluid actions such as pumping, mixing, jetting, as well as others.[5] To drive these processes there is a change of mode of the wave at the liquid substrate interface. In the substrate the SAW wave is a transverse wave and inside the droplet the wave becomes a longitudinal wave. [6] It is this longitudinal wave that creates the flow of fluid within the microfluidic droplet.See alsoLinear elasticityLove wavePhononPicosecond ultrasonicsRayleigh waveUltrasoundUltrasonicsExternal links and referencesSAW Filter (http://www3.sympatico.ca/colin.kydd.campbell/) - understanding SAW devicesSAW Sensor (/articles/1000/68/main.shtml)Watching ripples on crystals (http://kino-ap.eng.hokudai.ac.jp/ripples.html)References[7]1.^ Lord Rayleigh (1885). "On Waves Propagated along the Plane Surface of an Elastic Solid" (/cgi/reprint/s1-17/1/4). Proc. LondonMath. Soc.s1-17 (1): 4–11. /cgi/reprint/s1-17/1/4.2.^ R. Weigel; D. P. Morgan; J. M. Owens; A. Ballato; K. M. Lakin; K. Hashimoto; C. C. W. Ruppel (2002). Microwave acoustic materials, devices, andapplications. 50. pp. 738–749. doi:10.1109/22.989958 (/10.1109/22.989958).3.^ E. Benes; M, Gröschl; F. Seifert (1998). "Comparison Between BAW and SAW Sensor Principles" (/xpls/abs_all.jsp?arnumber=638514). IEEE Trans. Ultrason. Ferro. Freq. Control45. doi:10.1109/FREQ.1997.638514 (/10.1109/FREQ.1997.638514)./xpls/abs_all.jsp?arnumber=638514.4.^ K. Aki and P. G. Richards, Quantitative Seismology, Freeman and Co., New York, 1980.5.^ Yeo, L.Y.; Friend, J.R. (March 2009). "Ultrafast microfluidics using surface acoustic waves" (/articlerender.fcgi?tool=pmcentrez&artid=2717600). Biomicrofluidics3 (1). doi:10.1063/1.3056040 (/10.1063/1.3056040). PMC 2717600(/articlerender.fcgi?tool=pmcentrez&artid=2717600). PMID 19693383 (/pubmed/19693383)./articlerender.fcgi?tool=pmcentrez&artid=2717600.6.^ K. Sritharan, C. J. Strobl, M. F. Schneider, A. Wixforth and Z. Guttenberg. "Acoustic mixing at low Reynold’s numbers", Applied physics letters, 88(1),054102, 2006.7.^ Two-dimensional visualization of SAWs travelling over crystal surfaces: Y. Sugawara, O. B. Wright, O. Matsuda, M. Takigahira, Y. Tanaka, S. Tamura and V.E. Gusev, "Watching ripples on crystals", Phys. Rev. Lett. 88, 185504 (2002) (/abstract/PRL/v88/i18/e185504)Retrieved from "/w/index.php?title=Surface_acoustic_wave&oldid=478921620"Categories:Waves MicrotechnologyThis page was last modified on 26 February 2012 at 10:18.Text is available under the Creative Commons Attribution-ShareAlike License; additional terms may apply. See Terms of use for details.Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization.。