JP2005191650A - Surface acoustic wave element using langasite crystal and environment difference detector employing surface acoustic wave element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface acoustic wave element suitable for mass-production stably developing excellent surface acoustic wave propagation performance at all times, and also to provide an environment difference detector employing the surface acoustic wave element as above. <P>SOLUTION: The surface acoustic wave element includes: a three-dimensional base 12 wherein curved surfaces on which a surface acoustic wave can be propagated are consecutive and having a surface including at least part of annular curved face; and an electroacoustic transducing element 14 stimulating the surface acoustic wave, propagating the surface acoustic wave along the surface, and receiving the propagated surface acoustic wave, on the surface. The surface acoustic wave element is characterized in that the three-dimensional base employs a langasite crystal, each of electroacoustic transducing elements on the surface of the three-dimensional base propagates the surface acoustic wave along crossing line between the crystal plane of the crystal and the surface, and that the crossing line is the maximum outer circumferential line of the surface. The environment difference detector compares the surface acoustic wave received signals of the electroacoustic transducing elements on a plurality of the propagation surface zones of the surface acoustic wave element so as to detect the difference of the environment of the space part with which the respective elements are brought into contact. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a surface acoustic wave element using a langasite crystal and an environmental difference detection apparatus using the surface acoustic wave element.

  A substrate having a surface capable of exciting a surface acoustic wave (SAW) and capable of propagating the excited surface acoustic wave, and exciting the surface acoustic wave on the surface of the substrate along the surface. BACKGROUND ART A surface acoustic wave element including an electroacoustic transducer that propagates the surface acoustic wave and can receive the surface acoustic wave propagating is well known.

  The surface acoustic wave element is used as a delay line, an oscillation element, a resonance element, a frequency selection element, for example, various sensors including a chemical sensor, a biosensor, and a pressure sensor, or a remote tag.

  International Publication WO01 / 45255 discloses a spherical surface acoustic wave element. The substrate of the spherical surface acoustic wave element has a spherical surface that can excite the surface acoustic wave and propagate the excited surface acoustic wave. The electroacoustic transducer of the spherical surface acoustic wave element is arranged in a band having a predetermined width that is continuous in an annular shape on the spherical surface of the base, and the surface acoustic wave excited on the surface Is propagated along the direction in which the bands are continuous and repeatedly circulated.

In the spherical surface acoustic wave element, the surface acoustic wave excited by the electroacoustic transducer is substantially attenuated within the surface acoustic wave propagation band in the annular surface acoustic wave propagation band on the surface of the substrate. The above surface can be repeatedly circulated without doing so.
International Publication No. WO01 / 45255

  Since the surface of the surface acoustic wave element propagates the surface acoustic wave along the surface thereof, the entire surface of the substrate can be excited by the surface acoustic wave and can propagate the excited surface acoustic wave. Or by attaching a thin film formed of a surface acoustic wave excitation-propagating material to the surface thereof.

  It has been found that the substrate formed by the combination with the thin film has a high manufacturing cost and is not suitable for mass production at the present time. In the base made of only a material capable of propagating the surface acoustic wave, the elastic surface cannot propagate or circulate in the direction in which the surface acoustic wave is to propagate on the surface of the base. It has been found that there is a difference in the ability to propagate waves. Further, it is difficult to propagate or circulate the surface acoustic wave in a plurality of directions different from each other on the surface.

  The present invention has been made under the above circumstances, and an object of the present invention is a surface acoustic wave element that is suitable for mass production and can always stably exhibit good surface acoustic wave propagation performance. It is an object to provide an environmental difference detection apparatus using a surface acoustic wave element.

In order to achieve the above object, a surface acoustic wave device according to the present invention is:
A three-dimensional substrate having a surface including at least a part of an annular curved surface in which curved surfaces capable of propagating surface acoustic waves are continuous;
An electroacoustic transducer capable of receiving the surface acoustic wave propagating along the surface while exciting the surface acoustic wave on the surface and propagating the surface acoustic wave along the surface;
With
On the surface of the three-dimensional substrate, the electroacoustic transducer propagates the excited surface acoustic wave along a line of intersection between the crystal plane normal to the Z axis, which is the crystal axis of the langasite crystal, and the surface. And the line of intersection is the maximum perimeter line of the surface,
It is characterized by that.

  In order to achieve the above object, an environmental difference detection apparatus according to the present invention excites surface acoustic waves to a plurality of electroacoustic transducers along a plurality of intersection lines on the surface of the surface acoustic wave element according to the present invention. Propagating and receiving the surface acoustic wave propagating and outputting a reception signal, comparing reception signals output from a plurality of electroacoustic transducers, a plurality of portions where a plurality of surface acoustic waves propagate on the surface It is characterized by detecting a difference in environment in a plurality of portions of a space that touches.

  In the present invention, pseudo surface acoustic waves and, for example, corridor waves excited and propagated by an electroacoustic transducer just below the surface of the crystal material forming the three-dimensional substrate are also referred to as surface acoustic waves. . Furthermore, even an elastic wave that normally propagates along the surface of a three-dimensional substrate in contact with a different substance on the surface, such as a boundary acoustic wave, that is not usually referred to as a surface acoustic wave is used here. It is described as a wave.

  Even if any film is formed on the surface of the three-dimensional substrate where surface acoustic waves propagate, or the electroacoustic transducer is formed on the surface via any film, such a film. The presence of such a film is allowed if it does not substantially interfere with the desired propagation of surface acoustic waves.

  Further, in the claims, the description and the drawings of the present application, the crystal axis of the langasite crystal of the three-dimensional substrate is expressed using the signs of + and − and the X, Y and Z axes. Is a well-known expression method for the crystal axis of a piezoelectric crystal.

  The surface acoustic wave element according to the present invention and the environmental difference detection device according to the present invention using the surface acoustic wave element according to the present invention have a surface for propagating the surface acoustic wave. A three-dimensional substrate is formed of a langasite crystal and propagates a surface acoustic wave excited on the surface by an electroacoustic transducer along an intersection line between a specific crystal plane of the crystal and the surface. By making the intersecting line the maximum outer peripheral line of the surface, it is possible to mass-produce surface acoustic wave elements easily and inexpensively, and always exhibit good surface acoustic wave propagation performance stably. It is possible to make it.

  The “transmission / reception part” described in the present invention for exciting and receiving a surface acoustic wave on the surface of a three-dimensional substrate has two functions that are separated into a “transmission part” and a “reception part”. It can also be configured as a part. If the “transmission part” and the “reception part” are configured as mutually independent parts in this way, the design of the drive circuit and the detection circuit for these becomes easy. Since the surface acoustic wave passes through the “transmission part” and the “reception part” which are independent from each other in each round, the propagation efficiency of the surface acoustic wave is mutually different between the “transmission part” and the “reception part”. Although it is somewhat lower than the case where it is not configured as an independent part, there is no problem in practical use.

[First Embodiment]
Hereinafter, a first embodiment of a surface acoustic wave device according to the present invention will be described in detail with reference to FIGS. 1 to 4 in the accompanying drawings.

  FIG. 1 shows the appearance of the surface acoustic wave device 10 according to the first embodiment. The surface acoustic wave device 10 includes: a three-dimensional substrate 12 having a surface including a propagation surface band 12a formed by at least a part of an annular curved surface in which curved surfaces capable of propagating surface acoustic waves are continuous; An electroacoustic transducer 14 capable of exciting the surface acoustic wave to propagate the surface acoustic wave along the propagation surface zone 12a and receiving the surface acoustic wave propagating to the propagation surface zone 12a.

  Here, the propagation surface band 12a is drawn so that the dimension in the width direction W is constant in the direction in which the propagation surface band 12a continues in an annular shape for simplification of the drawing. While the surface acoustic wave propagates in the direction in which the propagation surface band 12a continues in an annular shape on the surface of 12, the surface acoustic wave may have a constant dimension in the width direction W as shown in FIG. In addition, the dimension in the width direction W may repeat diffusion and contraction.

  In any case, it is practically desired that the surface acoustic wave propagating in the propagation surface band 12a propagates at a desired distance from the electroacoustic transducer 14 or at least 80% of energy per round.

  In this embodiment, the entire three-dimensional substrate 12 is formed in a spherical shape by a trigonal langasite crystal. Therefore, in this embodiment, the propagation surface band 12 a is continuous in an annular shape on the spherical surface of the three-dimensional substrate 12. The propagation surface band 12a is continuous along the maximum outer peripheral line 12b of the three-dimensional substrate 12, and preferably includes the maximum outer peripheral line 12b within the range of the propagation surface band 12a.

  As shown in FIG. 2, the maximum outer peripheral line 12 b on the outer surface of the three-dimensional substrate 12 is a propagation surface zone on the crystal plane normal to the Z axis of the langasite crystal and on the outer surface of the three-dimensional substrate 12. Since the maximum outer peripheral line 12b along which 12a extends propagates on one crystal face of the langasite crystal, the energy of the surface acoustic wave does not diffuse greatly in the direction intersecting the crystal face. Surface acoustic waves can be propagated most efficiently on the outer surface of the three-dimensional substrate 12.

  The actual width of the surface acoustic wave propagating on the surface of the three-dimensional substrate 12 in the direction orthogonal to the propagation direction along the surface is determined by, for example, attaching water droplets to the surface. Since the surface acoustic wave does not propagate in the portion where water droplets are attached, it can be estimated visually.

  In general, when interdigital electrodes are used as electroacoustic transducers to excite high-frequency surface acoustic waves, the effective width of the interdigital electrodes (that is, interdigital transducers with respect to the surface of the three-dimensional substrate). A direction in which the electrode can excite surface acoustic waves and propagate in a desired direction and can receive the surface acoustic waves propagated on the surface, in a direction perpendicular to the desired direction along the surface The effective width is the maximum outer perimeter line (indicated by reference numeral 12a in FIG. 1) where the surface acoustic wave propagates on the surface is the desired direction ( In FIG. 1, the surface acoustic wave is excited and received when the radius of curvature is greater than 1.5 times the radius of curvature of the curvature in the direction orthogonal to (indicated by reference numeral 12b). Efficiency is found to be greatly reduced.

  The three-dimensional substrate 12 is supported on a support base 18 via a support arm 16 at a portion other than the propagation surface band 12 a on which the surface acoustic wave excited by the electroacoustic transducer 14 propagates on the outer surface. In order not to have any influence on the surface acoustic wave propagating through the propagation surface band 12a, nothing is brought into contact with the propagation surface band 12a except for the electroacoustic transducer 14. Therefore, in this embodiment, in order to excite the surface acoustic wave in the electroacoustic transducer 14 in the propagation surface band 12a, the surface acoustic wave propagated through the propagation surface zone 12a and received by the electroacoustic transducer 14 is electroacoustic. The electroacoustic transducer control unit 20 for receiving from the transducer 14 is connected to the electroacoustic transducer 14 by a lead wire extending from the electroacoustic transducer 14 on a region other than the propagation surface band 12a on the outer surface of the three-dimensional substrate 12. Has been. As shown in FIG. 1, for example, the electroacoustic transducer control unit 20 includes an impedance matching circuit 20a, a circulator 20, a transmitter 20c including a high frequency power supply, an amplifier 20d, a digital oscilloscope 20e, and the like. A high-frequency radio wave receiving antenna can be used instead of the transmitter 20c.

  As shown in FIG. 3A, the electroacoustic transducer 14 has an azimuth MD at which the density of the surface acoustic wave energy flowing to the propagation surface band 12a is maximized relative to the maximum outer circumferential line 12b. It is preferable to be configured to be within 20 °. This angle is more preferably within 10 °, and further preferably within 5 °. This means that the surface acoustic wave excited on the propagation surface band 12a by the electroacoustic transducer 14 keeps 80% or more of the energy along the maximum outer peripheral line 12b on the outer surface of the three-dimensional substrate 12, for example, every turn. If it can circulate with a small attenuation rate, it may tend to diffuse from the maximum outer peripheral line 12b rather than the width immediately after being excited as it propagates, but it is preferably within the above angle range. Means.

  The term “along the maximum outer circumferential line” described in the present invention refers to the direction in which the density of the surface acoustic wave energy flow is maximum with respect to the maximum outer circumferential line when the surface acoustic wave propagates around the circulation or propagation path. The case is preferably within 20 °, more preferably within 10 °, and still more preferably within 5 °.

  In this embodiment, the electroacoustic transducer 14 is directly formed on the outer surface of the three-dimensional substrate 12 within the range of the propagation surface band 12a. In this embodiment, the electroacoustic transducer 14 is an interdigital electrode 22 such as a comb-shaped electrode, and is formed on the outer surface by various known methods such as vapor deposition, printing, sputtering, sol-gel method, and the like. It can be formed directly.

  In the case where the electroacoustic transducer 14 is formed by the interdigital electrode 22, the interdigital electrode 22 is formed with respect to the propagation surface band 12a in the interdigital electrode 22, as well shown in FIG. A line perpendicular to the outer surface of the three-dimensional substrate 12 with respect to a transmitting / receiving portion (a portion having the above-described effective width) capable of exciting a surface acoustic wave and receiving a surface acoustic wave propagating to the propagation surface zone 12a is a propagation surface zone. It is preferable to be configured so as to fall within a range of 10 ° or less with respect to the corresponding maximum outer peripheral line 12b along which 12a extends. More specifically, the transmitting / receiving portion (in the case of the interdigital electrode 22), each terminal (line element) 22 a of the pattern extends along the maximum outer peripheral line 12 b in each terminal (line element) 22 a of the interdigital electrode 22 pattern. This means that the orthogonal line OL extending along the outer surface of the propagation surface band 12a with respect to the portion overlapping each other in the direction is preferably within a range of 10 ° or less with respect to the maximum outer peripheral line 12b. .

  The reason for this is that, as described above with reference to FIG. 3A, the electroacoustic transducer 14 has the maximum azimuth MD at which the density of the surface acoustic wave energy flow excited in the propagation surface band 12a is maximized. This is the same as the reason why it is preferable to configure the outer peripheral line 12b to be within 20 °.

  Further, the arrangement period P of the plurality of terminals 22a (see FIG. 3B) of the interdigital electrode 22 pattern in the direction along the maximum outer peripheral line 12b is 1/10 or less of the radius of curvature of the maximum outer peripheral line 12b. Preferably there is. The arrangement period P corresponds to the length of one wavelength (ie, vibration period) of the surface acoustic wave excited by the interdigital electrode 22.

  The wavelength of the surface acoustic wave (that is, the arrangement period P of the plurality of terminals 22a of the interdigital electrode 22 pattern) is the radius of curvature of the maximum outer peripheral line 12b included in the propagation surface band 12a through which the surface acoustic wave propagates (the propagation surface band 12a). Is formed by a part of a spherical surface as in this embodiment, if it is larger than 1/10 of the radius of the spherical surface), the geometric feature of the curved propagation surface band 12a is The function of suppressing the surface acoustic wave propagating through 12a from spreading is weakened. Accordingly, when a surface acoustic wave having a relatively long wavelength is to be propagated to the propagation surface band 12a on the surface of the three-dimensional substrate 12 by a desired distance, the radius of curvature of the maximum outer peripheral line 12b included in the propagation surface body 12a. Must be set in advance to satisfy the above-described relationship with the wavelength.

  Therefore, in order to propagate the surface acoustic wave efficiently in the propagation surface band 12b, it is preferable to use the arrangement period.

  The diameter of the spherical three-dimensional substrate of the langasite crystal actually produced by the inventors of this application according to this embodiment is 25.4 mm, and the interdigital electrode used as the electroacoustic transducer is used as the spherical three-dimensional substrate. The outer surface of the crystal was formed at a position corresponding to the + X direction of the crystal as viewed from the center of the three-dimensional substrate. After forming a film by vapor deposition of 1000 angstroms of chromium or 1000 angstroms of gold on the outer surface of the three-dimensional substrate, the interdigital electrodes have terminals (line elements) as described above. It was formed by being subjected to a photolithography process so as to be orthogonal to the direction of circling on the spherical outer surface around the Z-axis direction of the langasite crystal. The arrangement period P of the terminals (line elements) of the interdigital electrode pattern formed at this time is 0.532 mm, and a plurality of terminals (line elements) each having a width of 0.133 mm are arranged at intervals of 0.133 mm. Then, a desired pulse voltage is applied between terminals (line elements) adjacent to each other. And the length of the overlapping part of each adjacent terminal (line element) which an electric field produces mutually by applying a pulse voltage is 3.1 mm.

  Here, the inventor of the present application has described the dimensions of an example of the interdigital electrode used as the electroacoustic conversion element actually produced on the outer surface of the spherical three-dimensional substrate of the langasite crystal. As long as the functions or effects required by the present invention can be achieved on the outer surface of the electrode, a currently known interdigital electrode of any material, size and shape can be used.

  Then, when an impulse signal having a half-value width of 2 nanoseconds was applied to the interdigital electrode of the spherical surface acoustic wave element configured as described above at a voltage of 100 V, as a result, in the direction of circulation from the interdigital electrode. A digital oscilloscope confirmed that a burst signal having a center frequency of about 42.7 MHz was output at least 50 times at intervals of 33.7 μsec. This means that, as described above, surface acoustic waves are generated at least 50 times at a speed of 2368 m / s on an average on the outer surface of the spherical three-dimensional substrate of a langasite crystal having a diameter of 25.4 mm. It means that you have circulated.

The position of the outer surface of each of the two types of spherical surface acoustic wave elements configured as described above by the inventor of the present application is separated from the interdigital electrode in the direction in which the circuit circulates (that is, the surface acoustic wave circulation path). When a cotton swab containing water is brought into contact with the top), no output can be obtained from the interdigital electrode even if an impulse signal is applied to the interdigital electrode as described above, and the surface acoustic wave circulates. It turns out that it is obstructed. Further, the two types of spherical surface acoustic wave elements configured as described above are separated from the interdigital electrode by 5 mm or more in the direction perpendicular to the direction of the circumference (that is, the surface acoustic wave). When the impulse signal is applied to the interdigital electrode as described above, the burst signal as described above repeats from the interdigital electrode as described above. It was output and it turned out that the circumference | surroundings of a surface acoustic wave as mentioned above are not inhibited.
[Second Embodiment]
Next, a second embodiment of the surface acoustic wave device according to the present invention will be described in detail with reference to FIG.

  In the surface acoustic wave element 40 according to the second embodiment, the three-dimensional substrate 12 has a recess or a hollow portion, and the surface 12c of the recess or the hollow portion can propagate the surface acoustic wave. The curved surface includes a propagation surface band 12a that is continuous in an annular shape. FIG. 4 shows a three-dimensional substrate 12 having a through hole which is a kind of hollow portion.

  The three-dimensional substrate 12 is entirely formed of a langasite crystal in the same manner as the three-dimensional substrate 12 of the first embodiment described above. The crystal plane peculiar to the crystal forming the three-dimensional substrate 12 on the outer surface of the three-dimensional substrate 12 of the first embodiment and the first or second modification and the outer surface In the same manner as the maximum outer peripheral line 12b serving as a reference for causing the propagation surface band 12a to follow the intersecting line is defined on the inner surface of the three-dimensional substrate 12 of the surface acoustic wave element 40 according to the second embodiment. At least one maximum outer peripheral line 12b is defined as a reference for allowing the propagation surface band 12a to follow the line of intersection between the crystal plane unique to the crystal forming the three-dimensional substrate 12 and the inner surface. A propagation surface band 12a is defined so as to continuously extend along the maximum outer peripheral line 12b on the inner surface. The method of defining the propagation surface band 12a on the inner surface of the three-dimensional substrate 12 of this embodiment is the same as the method of defining the propagation surface band 12a on the outer surface of the three-dimensional substrate 12 of the first embodiment. It is. Therefore, the maximum outer peripheral line 12b is preferably included in the range of the propagation surface band 12a on the inner surface.

  Then, the electroacoustic acoustic wave is also propagated to the propagation surface band 12a on the inner surface of the three-dimensional substrate 12 of this embodiment along the maximum outer peripheral line 12b within the propagation surface band 12a without being greatly attenuated. A conversion element 14 is formed, and the electroacoustic conversion element control unit 20 is connected to the electroacoustic conversion element 14.

  Also in this embodiment, as long as the propagation surface band 12a is defined by the predetermined method described above, the shape of the portion other than the propagation surface band 12a is arbitrary.

The surface acoustic wave element 40 according to this embodiment is excited by the electroacoustic transducer 14 on the propagation surface band 12a and propagates in the propagation surface band 12a without significant attenuation while maintaining energy of, for example, 80% or more per round. The surface acoustic wave changes in response to various changes in the fluid (gas or fluid) passing through the internal space of the through hole, which is the environment in contact with the propagation surface band 12a on the inner surface of the three-dimensional substrate 12. By receiving as an electrical signal by the electroacoustic transducer control unit 20 via the acoustic transducer 14, it is possible to detect the change in the environment, that is, the difference.
[Third Embodiment]
Next, a third embodiment of the surface acoustic wave device according to the present invention will be described in detail with reference to FIGS.

  The surface acoustic wave device 50 according to the third embodiment is entirely formed of a langasite crystal in the same manner as the three-dimensional substrate 12 of the first embodiment and the first or second modification. A spherical three-dimensional substrate 12 is provided. On the outer surface of the three-dimensional substrate 12, at least one of a plurality of intersecting lines between a plurality of crystal planes of the material of the three-dimensional substrate 12 and the outer surface is a maximum outer peripheral line 12b, and an annular shape is formed along the maximum outer peripheral line 12b. A continuous propagation surface zone 12a is defined. The propagation surface band 12a on the outer surface of the three-dimensional substrate 12 of the surface acoustic wave element 50 of this embodiment is also the three-dimensional substrate 12 of the first embodiment and the first or second modification. Similar to the propagation surface zone 12a on the outer surface of the substrate, it preferably includes a maximum outer peripheral line 12b within the range of the propagation surface zone 12a.

  The surface acoustic wave element 50 of this embodiment is different from the surface acoustic wave element 10 of the first embodiment in that surface acoustic waves are excited in the propagation surface band 12a on the outer surface of the three-dimensional substrate 12. The electroacoustic transducer 14 that propagates the excited surface acoustic wave along the maximum outer peripheral line 12b within the range of the propagation surface band 12a is not directly formed on the propagation surface band 12a on the outer surface of the three-dimensional substrate 12. That is.

  In this embodiment, the propagation surface zone facing region in which the pedestal 52 that supports a portion other than the propagation surface zone 12a on the outer surface of the three-dimensional substrate 12 faces the propagation surface zone 12a with a predetermined gap S therebetween. The electroacoustic transducer 14 is formed in the propagation surface zone facing region 52 a of the pedestal 52. The dimensions and arrangement of the electroacoustic transducer 14 with respect to the propagation surface band 12a are the same as those in the surface acoustic wave device 10 of the first embodiment and the first and second modifications. It is the same as the case where it is formed.

  When the electroacoustic transducer 14 is a comb-like electrode 22 such as a comb-shaped electrode, the predetermined gap S is an array period P of a plurality of line elements (terminals) of the pattern of the comb-like electrode 22 ((B in FIG. 4). It is preferable that it is 1/4 or less of (see)). When the predetermined gap S is not less than ¼ of the arrangement period P (see FIG. 4B), the electroacoustic transducer 14 has a desired elasticity on the propagation surface band 12a on the outer surface of the three-dimensional substrate 12. It becomes difficult to always reliably excite surface waves.

The surface acoustic wave element 50 according to the third embodiment can be used in the same manner as the three-dimensional substrate 12 of the first embodiment described above. Moreover, when the electroacoustic transducer 14 faces the propagation surface band 12a on the outer surface of the three-dimensional substrate 12 via a predetermined gap S, the propagation surface band 12a on the outer surface of the three-dimensional substrate 12 Compared with the case where the electroacoustic transducer 14 is directly formed, the electroacoustic transducer 14 formed directly on the propagation surface band 12a is excited by the electroacoustic transducer 14 to the propagation surface zone 12a and the propagation surface zone 12a. It is possible to eliminate the influence that may slightly affect the surface acoustic wave propagating through the inside, and it is possible to detect the change of the surface acoustic wave propagating through the propagating surface band 12a more precisely.
[Fourth Embodiment]
Next, a fourth embodiment of a surface acoustic wave device according to the present invention will be described in detail with reference to FIG.

  The surface acoustic wave element 60 according to the fourth embodiment includes a three-dimensional substrate 12 ′ having a hemispherical shape, and a curved surface capable of propagating surface acoustic waves is formed on the outer surface of the three-dimensional substrate 12 ′. It includes a propagation surface band 12′a formed by a part of at least a continuous annular curved surface.

  The hemispherical three-dimensional substrate 12 ′ is entirely formed of a langasite crystal in the same manner as the three-dimensional substrate 12 of the first embodiment described above. The crystal plane peculiar to the crystal forming the three-dimensional substrate 12 on the outer surface of the three-dimensional substrate 12 of the first embodiment and the first or second modification and the outer surface The three-dimensional substrate 12 of the surface acoustic wave element 60 according to the fourth embodiment is defined in the same manner as the maximum outer peripheral line 12b serving as a reference for continuously following the propagation surface body 12a along the intersecting line. Criteria for continuously following the propagation surface body 12'a so as to coincide with the line of intersection between the crystal surface peculiar to the crystal forming the three-dimensional substrate 12 'on the hemispherical outer surface and the outer surface At least one maximum outer peripheral line 12'b is defined. The maximum outer peripheral line 12'b is preferably included in the range of the propagation surface band 12'a.

  The method of defining the maximum outer peripheral line 12′b, which serves as a reference for the propagation surface band 12′a along the outer surface of the three-dimensional substrate 12 ′ of this embodiment, is the same as that in the first embodiment and the first embodiment. This is the same as the method of defining the maximum outer peripheral line 12b on the outer surface of the three-dimensional substrate 12.

  Further, the surface acoustic wave per round is also applied to the propagation surface band 12′a on the outer surface of the three-dimensional substrate 12 ′ of this embodiment along the maximum outer peripheral line 12′b within the range of the propagation surface band 12′a. The electroacoustic transducer 14 is directly formed to propagate and maintain at least 80% or more energy, and the electroacoustic transducer control unit 20 is connected to the electroacoustic transducer 14.

  In this embodiment, the propagation of the surface acoustic wave that is excited by the electroacoustic transducer 14 within the range of the propagation surface zone 12′a and propagates along the maximum outer peripheral line 12′b within the range of the propagation surface zone 12′a. A surface acoustic wave reflector 62 is formed at a position away from the electroacoustic transducer 14 in the direction. The surface acoustic wave reflector 62 transmits the surface acoustic wave propagated from the electroacoustic transducer 14 through the propagation surface zone 12'a toward the surface acoustic wave reflector 62 through the propagation surface zone 12'a through the same path. Reflected toward the acoustic transducer 14.

  Also in this embodiment, the shape of the portion other than the propagation surface band 12'a is arbitrary as long as the propagation surface band 12'a is defined by the predetermined method described above.

  Also in this embodiment, the three-dimensional substrate 12 'is supported by a pedestal (not shown) except for the propagation surface band 12'a.

  The surface acoustic wave device 60 according to this embodiment is excited by the electroacoustic transducer 14 to the propagation surface band 12'a formed of at least a part of an annular curved surface, and does not significantly attenuate the inside of the propagation surface band 12'a. The propagating surface acoustic wave changes in response to various changes in the fluid (gas or fluid) contained in the external space, which is the environment in contact with the propagating surface band 12'a on the outer surface of the three-dimensional substrate 12. Is received as an electrical signal by the electroacoustic transducer control unit 20 via the electroacoustic transducer 14, so that the environmental change, that is, the difference can be detected.

  Furthermore, in this embodiment, as in the surface acoustic wave element 40 of the third embodiment described above with reference to FIG. 4, for example, a hemispherical recess or cavity formed in the three-dimensional substrate 12 A propagation surface band 12a formed by at least a part of an annular curved surface with a center line 12b on the inner surface is defined, and such propagation surface bands 12a are separated from each other along the center line 12a and face each other. The acoustic conversion element 14 and the surface acoustic wave reflector 62 can be modified to be installed.

  Furthermore, in this embodiment as well, as in the surface acoustic wave device 50 of the fourth embodiment described above with reference to FIGS. 5 and 6, the electric power is directly applied to the propagation surface band 12 a of the three-dimensional substrate 12 ′. Instead of forming the acoustic transducer 14, the electroacoustic transducer 14 can be formed on a pedestal (not shown) so as to face the propagation surface band 12 a via a predetermined gap S, or the three-dimensional substrate 12. A common excitation electroacoustic transducer 14 'is formed on the above-mentioned pedestal (not shown) so as to oppose the intersecting regions of the plurality of propagation surface bands 12'a on the outer surface of the sheet with a predetermined gap S and a plurality of propagation surfaces. The receiving electroacoustic transducer 14 '' can be formed on the above-mentioned pedestal (not shown) so as to face each other through the predetermined gap S other than the intersecting region in each of the bands 12'a.

  Furthermore, another electroacoustic transducer 14 to which the above-described electroacoustic transducer control unit 20 is connected can be used instead of the surface acoustic wave reflector 62.

1 is a schematic view of a surface acoustic wave device according to a first embodiment of the present invention. (A) is a propagation that propagates a surface acoustic wave to the outer surface of the three-dimensional substrate when the entire three-dimensional substrate of the surface acoustic wave device according to the first embodiment of the present invention is formed of a langasite crystal. It is a perspective view which shows a mode that the largest outer peripheral line used as the reference | standard of a surface zone is prescribed | regulated along one of the three crystal planes of a langasite crystal. (A) is a schematic view of a preferable state in which the electroacoustic transducer is arranged with respect to the corresponding maximum outer peripheral line in the propagation surface zone of the three-dimensional substrate of the surface acoustic wave device according to the first embodiment of the present invention. And (B) is a comb-shaped electrode with respect to the corresponding maximum outer peripheral line in the propagation surface zone of the three-dimensional substrate of the surface acoustic wave device according to the first embodiment of the present invention. It is a figure which shows schematically the further more preferable state by which the electroacoustic conversion element by is arrange | positioned. It is a perspective view which shows roughly the surface acoustic wave element according to 3rd Embodiment of this invention. It is a perspective view which shows roughly the surface acoustic wave element according to 4th Embodiment of this invention. FIG. 5 schematically shows that the electroacoustic transducer is formed on the base of the three-dimensional substrate so as to face the propagation surface band on the outer surface of the three-dimensional substrate of the surface acoustic wave device of FIG. FIG. It is a perspective view which shows roughly the surface acoustic wave element according to 5th Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Surface acoustic wave element, 12 ... Three-dimensional base | substrate, 12a ... Propagation surface zone, 12b ... Maximum outer periphery line, 12c ... Inner surface, 14 ... Electroacoustic transducer, 14 '... Electroacoustic transducer for common excitation, 14' '... Receiving electroacoustic transducer, 22 ... Interdigital electrode, 22a ... Line element (terminal), CA ... Crystal axis direction, P ... Arrangement period.

Claims (12)

A three-dimensional substrate having a surface including at least a part of an annular curved surface in which curved surfaces capable of propagating surface acoustic waves are continuous;
An electroacoustic transducer capable of receiving the surface acoustic wave propagating along the surface while exciting the surface acoustic wave on the surface and propagating the surface acoustic wave along the surface;
With
On the surface of the three-dimensional substrate, the electroacoustic transducer propagates the excited surface acoustic wave along a line of intersection between the crystal plane normal to the Z axis, which is the crystal axis of the langasite crystal, and the surface. The surface acoustic wave device is characterized in that the intersecting line is a maximum outer peripheral line of the surface. The electroacoustic transducer on the surface of the three-dimensional substrate has the excited surface acoustic wave along both a crystal plane having a normal to the Z axis that is a crystal axis of a langasite crystal and an intersection line of the surface. Each of the intersecting lines is the maximum outer circumference of the surface,
The surface acoustic wave device according to claim 1.   3. The surface acoustic wave device according to claim 1, wherein the surface of the three-dimensional substrate has at least a part of a spherical surface. The surface has a curved surface in which the surface acoustic wave can propagate and is continuous in an annular shape,
The electroacoustic transducer is configured to excite the surface acoustic wave on the surface and propagate and circulate the surface acoustic wave along the intersection line.
The surface acoustic wave device according to claim 1, wherein the surface acoustic wave device is provided.   The surface acoustic wave device according to claim 4, wherein the surface of the three-dimensional substrate is a spherical surface. In the direction intersecting with the extending direction of the intersecting line along the surface, the electroacoustic transducer excites a surface acoustic wave on the surface, and the energy of the surface acoustic wave along the intersecting line is 80% per round. Propagating while maintaining the above, the dimension capable of receiving the surface acoustic wave is 1 / 1.5 or less of the curvature radius of the curved surface extending in the direction perpendicular to the intersecting line on the surface,
The surface acoustic wave device according to claim 1, wherein the surface acoustic wave device is provided.   The electroacoustic transducer has a direction in which the energy flow density of the surface acoustic wave emitted from the electroacoustic transducer along the intersecting line is maximum within 20 ° with respect to the corresponding intersecting line. The surface acoustic wave device according to claim 6, wherein the surface acoustic wave device is disposed on a surface.   The surface acoustic wave device according to any one of claims 1 to 7, wherein the electroacoustic transducer is formed in the propagation surface zone.   The electroacoustic transducer includes an interdigital electrode, and the interdigital electrode excites a surface acoustic wave to the surface at a plurality of terminals of the interdigital electrode and transmits the surface acoustic wave propagating to the surface. The surface acoustic wave device according to any one of claims 1 to 8, wherein a receivable transmission / reception part includes a part of a corresponding intersection line.   10. The surface acoustic wave device according to claim 9, wherein an arrangement period of the plurality of terminals of the interdigital electrode in a direction along the intersecting line is 1/10 or less of a radius of curvature of the intersecting line. .   11. The surface acoustic wave device according to claim 1, wherein the surface of the three-dimensional substrate is an outer surface of the three-dimensional substrate.   The said three-dimensional base | substrate has a recess or a hollow part, The said surface is an inner surface of the recess or hollow part of the said three-dimensional base | substrate, The any one of Claim 1 thru | or 11 characterized by the above-mentioned. The surface acoustic wave device according to Item.

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