Talk:Surface acoustic wave

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Comment
Complete diagram of SAW Filter and working, Construction of SAW. Thank You

"Acoustic" Wave
Not to be a pedant but I have a question about the nature of the mechanical waves used / detected in these devices. In complete generality, linear elastic media exhibit waves made up of dilatational and shear strain fields and, at some boundaries and discontinuities, combinations of the two. Linear elastic fluid waves are dilatational only, and it is these that are usually referred to as "acoustic" by theoretical mechanics types. However, for the purposes for which SAW devices are used, it may be true that the shear vs. dilation distinction is irrelevant, and that any & all mechanical waves in the device are considered "acoustic" to distinguish them from the EM phenomenon.

Is that the case?

Correct, acoustic wave generally refers to a traveling mechanical disturbance through a medium. However in the case of most SAW devices a piezoelectric effect exists which means that there will also be a corresponding electric field traveling with the wave (this phenomena cannot be neglected as it drastically effects the waves characteristics). A SAW is a truely separate mode from bulk waves, and is generally considered a SAW if energy is traped at the surface boundary and the wave exists in the far field (ironically the most common "SAW" device on LiTaO3 found in cell phones utilizes a wave which leaks energy to the bulk and does not exist far field, this wave is called a "psuedosaw"). As you mention these waves may have any combination of shear and longitudinal components (in crystals these modes depend on crystal orientation). If you want to know more obtain a copy of "Surface Acoustic Wave Devices for Signal Processing" by Morgan, it is an excellent introductory text.


 * It is actually not correct. Not all mechanical waves are acoustic waves. Only waves that have a longitudinal component, i.e. amplitude change parallel to the direction of wave propagation, are acoustic waves. Acoustic waves are also called pressure waves or sound waves as the longitudinal amplitude change generates a pressure difference. A pure shear wave, for example, is not an acoustic wave as the amplitude change is transversal to the direction of propagation. If such an acoustic wave is bound to the surface then it is called surface acoustic wave. Propagation of that SAW results in deformation of the underlying material along the wave path, also away from the source. If the material is piezoelectric this deformation also generates an electric field due to a change in polarization along the wave path. However, this is not to be confused with a propagating electromagnetic wave (they are purely transversal) in free space. --193.222.161.35 (talk) 11:32, 23 July 2019 (UTC)

Shouldn't Surface Acoustic Wave Device be given its own article and this article refer to the physical SAW phenomena only? This article would then have links to related ones on SAW devices, earthquakes, nondestructive evaluation etc? There are many volumes written on both of these topics.

update
removed a commercial link and added a link to a whole explanation of the SAW filters--bloublou 08:36, 31 August 2006 (UTC)

SAW filter article, maybe?
Even though this article is not very big, perhaps it would be good to separate SAW filters from the surface acoustic wave article. Books are written about SAW filters. It's a complicated subject that includes many disciplines. --HelgeStenstrom (talk) 20:11, 7 May 2008 (UTC)

Different types of SAWS
Yes, this article should strictly be separated into devices only and physics only. For surface acoustic waves one should talk about pseudo-surface waves and other interface waves such as Stonely waves and Scholte waves. There would be plenty to write about. Femtoquake (talk) 14:51, 18 December 2008 (UTC)

Is this an evanescent wave?
If this phenomenon is an evanescent wave, a link to that page would be useful. Evanescent waves can also exist at the boundaries of non-elastic media, such as inviscid compressible fluids, or at the edge of a bubble cloud in a fluid. If SAW are evanescent waves, the first sentence of this article should be modified. The criterion is that the material can support wave propagation. —Preceding unsigned comment added by 86.80.203.194 (talk) 11:04, 28 December 2008 (UTC)

SAW image
Just to point out that the colorful image on this page is not a simulation. It is experimental data.Femtoquake (talk) 02:43, 29 November 2009 (UTC)