WO2015005267A1 - Elastic wave apparatus - Google Patents

Elastic wave apparatus Download PDF

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Publication number
WO2015005267A1
WO2015005267A1 PCT/JP2014/068025 JP2014068025W WO2015005267A1 WO 2015005267 A1 WO2015005267 A1 WO 2015005267A1 JP 2014068025 W JP2014068025 W JP 2014068025W WO 2015005267 A1 WO2015005267 A1 WO 2015005267A1
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electrode
tip
electrode finger
finger
wave device
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PCT/JP2014/068025
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French (fr)
Japanese (ja)
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鈴木　孝尚
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株式会社村田製作所
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Publication of WO2015005267A1 publication Critical patent/WO2015005267A1/en

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/125—Driving means, e.g. electrodes, coils
    • H03H9/145—Driving means, e.g. electrodes, coils for networks using surface acoustic waves
    • H03H9/14544—Transducers of particular shape or position

Definitions

  • the present invention relates to an acoustic wave device in which an IDT electrode is formed on a piezoelectric substrate.
  • Patent Document 1 discloses a surface acoustic wave device in which an IDT electrode is formed on a piezoelectric substrate.
  • the IDT electrode has a plurality of first electrode fingers and a plurality of second electrode fingers interleaved with the plurality of first electrode fingers.
  • a plurality of first dummy electrode fingers are provided so as to face the tips of the plurality of first electrode fingers in the extending direction of the electrode fingers.
  • a plurality of second dummy electrode fingers are provided so as to face the tips of the plurality of second electrode fingers, respectively.
  • Patent Document 1 The conventional acoustic wave device as described in Patent Document 1 has a problem that a nonlinear distortion signal due to electrical nonlinearity is generated. For this reason, it is difficult to obtain good resonance characteristics and filter characteristics.
  • An object of the present invention is to provide an elastic wave device capable of suppressing a nonlinear distortion signal caused by electrical nonlinearity.
  • the elastic wave device includes a piezoelectric substrate and an IDT electrode formed on the piezoelectric substrate.
  • the IDT electrode is connected to first and second bus bar electrodes, a plurality of first electrode fingers electrically connected to the first bus bar electrode, and a second bus bar electrode, A plurality of first electrode fingers and a plurality of second electrode fingers interleaved with each other.
  • the tip of at least one of the first electrode finger and the second electrode finger is opposed to the tip of the electrode finger in the extending direction of the electrode finger and has a potential different from that of the electrode finger.
  • the electrode part to be connected has a specific shape.
  • the shape has a portion shifted with respect to the direction of the polarization axis.
  • the electric field vector has a shape having a portion that is shifted with respect to the extending direction of the electrode finger.
  • the shape of the tip of the electrode finger is asymmetric with the shape of the electrode portion facing the tip of the electrode finger.
  • one of the tip of the electrode finger and the electrode portion facing the tip of the electrode finger has a recess that is open toward the other. And the other has a protruding portion protruding toward the other side.
  • the tip of the electrode finger and the electrode portion facing the tip of the electrode finger have a shape that fits into each other.
  • a plurality of first dummy electrode fingers one end of which is connected to the second bus bar electrode, and one end of which is connected to the first bus bar electrode.
  • a plurality of second dummy electrode fingers a plurality of first dummy electrode fingers, one end of which is connected to the second bus bar electrode, and one end of which is connected to the first bus bar electrode.
  • the electrode portion is a tip of at least one of the first dummy electrode finger and the second dummy electrode finger.
  • the tip of the electrode finger and the electrode portion facing the tip of the electrode finger have an arc shape.
  • a plurality of tip ends of the electrode fingers and the electrode portions facing the tip ends of the electrode fingers respectively protrude toward the other side. It is the shape which has a protrusion part.
  • the tip of at least one of the first electrode finger and the second electrode finger and the electrode portion connected to a potential different from that of the electrode finger have the specific shape. Therefore, the nonlinear distortion signal can be effectively suppressed. Therefore, it is possible to provide an elastic wave device having good resonance characteristics and filter characteristics.
  • FIG. 1A is a plan view of the surface acoustic wave device according to the first embodiment of the present invention
  • FIG. 1B is an enlarged view of a portion indicated by a circle A in FIG.
  • FIG. 1C is a partially enlarged plan view showing the relationship between the facing direction and the direction in which the electric field vector E1 extends.
  • 2A is a schematic plan view showing a schematic configuration of an elastic wave device of a comparative example
  • FIG. 2B is a cross-sectional view along the direction in which the electrode fingers extend
  • FIG. 1A is a plan view of the surface acoustic wave device according to the first embodiment of the present invention
  • FIG. 1B is an enlarged view of a portion indicated by a circle A in FIG.
  • FIG. 1C is a partially enlarged plan view showing the relationship between the facing direction and the direction in which the electric field vector E1 extends.
  • FIG. 3 is a partially enlarged plan view showing the main part of the surface acoustic wave device according to the second embodiment of the present invention.
  • FIG. 4 is a partially enlarged plan view showing the main part of the surface acoustic wave device according to the third embodiment of the present invention.
  • FIG. 5 is a partially enlarged plan view showing the main part of the surface acoustic wave device according to the fourth embodiment of the present invention.
  • FIG. 6 is a partially enlarged plan view showing the main part of the surface acoustic wave device according to the fifth embodiment of the present invention.
  • FIG. 7 is a partially enlarged plan view showing the main part of the surface acoustic wave device according to the sixth embodiment of the present invention.
  • FIG. 8 is a schematic plan view showing an electrode structure of a surface acoustic wave device according to the seventh embodiment of the present invention.
  • FIG. 9 is a diagram illustrating the frequency characteristics of the third-order harmonic distortion signal level in the surface acoustic wave device of the first embodiment and the surface acoustic wave device of the comparative example.
  • FIG. 1A is a schematic plan view of a surface acoustic wave device according to a first embodiment of the present invention.
  • the surface acoustic wave device 1 has a piezoelectric substrate 2.
  • the piezoelectric substrate 2 is made of a piezoelectric single crystal such as LiTaO 3 or LiNbO 3 or a piezoelectric ceramic such as PZT.
  • An IDT electrode 3 is formed on the piezoelectric substrate 2.
  • the IDT electrode 3 is made of an appropriate metal or alloy such as Al.
  • the IDT electrode 3 has a first bus bar electrode 4 and a second bus bar electrode 5. One end of a plurality of first electrode fingers 4 a is connected to the first bus bar electrode 4. One end of a plurality of second electrode fingers 5 a is connected to the second bus bar electrode 5. The plurality of first electrode fingers 4a are extended from the first bus bar electrode 4 toward the second bus bar electrode 5 side. The plurality of second electrode fingers 5 a are extended from the second bus bar electrode 5 toward the first bus bar electrode 4. The plurality of first electrode fingers 4a and the plurality of second electrode fingers 5a are interleaved.
  • one end of a plurality of first dummy electrode fingers 5 b is connected to the second bus bar electrode 5.
  • the tip of the first dummy electrode finger 5b faces the tip of the first electrode finger 4a in the extending direction of the first electrode finger 4a.
  • the part where both face each other is defined as a facing part.
  • a plurality of second dummy electrode fingers 4 b are connected to the first bus bar electrode 4.
  • the tip of the second dummy electrode finger 4b faces the tip of the second electrode finger 5a in the extending direction of the second electrode finger 5a.
  • the first and second dummy electrode fingers 5b and 4b are not essential components.
  • the arrow C in FIG. 1A is the direction in which the polarization axis direction is projected onto the upper surface 2a.
  • the actual polarization axis direction is inclined from the lower surface side to the upper surface side of the piezoelectric substrate 2.
  • a surface acoustic wave is excited by applying an alternating electric field between the first electrode finger 4a and the second electrode finger 5a.
  • the excitation direction of the surface acoustic wave is a direction orthogonal to the extending direction of the first and second electrode fingers 4a and 5a.
  • the feature of this embodiment is that the shape of the tips of the first and second electrode fingers 4a and 5a and the tips of the first and second dummy electrode fingers 5b and 4b facing each tip are
  • the electric field vector extending in FIG. 2 has a shape having a portion that is shifted with respect to the extending direction of the first and second electrode fingers 4a and 5a. Thereby, it is possible to suppress the nonlinear distortion signal. This will be described more specifically with reference to FIGS. 1B and 1C.
  • the “non-linear distortion signal” here is a generic term for N-order harmonic distortion and N-order intermodulation distortion.
  • FIG. 1 (b) is a partially enlarged plan view showing an enlarged portion indicated by a circle A indicated by a broken line in FIG. 1 (a).
  • the opposing part in which the tip of the first electrode finger 4a and the tip of the first dummy electrode finger 5b face each other is shown.
  • the tip of the first electrode finger 4a has an arcuate recess 4a1 that opens toward the first dummy electrode finger 5b.
  • the 1st dummy electrode finger 5b has the front-end
  • the protruding tip 5b1 has an arc shape that protrudes toward the recess 4a1.
  • the first dummy electrode finger 5b that is, the second bus bar electrode 5 side is the hot side
  • the first electrode finger 4a side is the ground side.
  • the electric field is applied from the first dummy electrode finger 5b toward the first electrode finger 4a.
  • the direction of the electric field vector is as shown by arrows E1 to E5. The direction is the shortest distance between 4a and the first dummy electrode finger 5b.
  • the electric field vector E3 is a direction parallel to the extending direction of the electrode finger 4a, but at the tip portion other than the apex of the dummy electrode finger 5b, the direction of the electric field vector is indicated by arrows E1, E2, E4, E5. Is shifted from the extending direction of the electrode finger 4a.
  • FIG. 9 is a diagram showing the frequency characteristics of the third-order harmonic distortion signal level in the surface acoustic wave device of the present embodiment and the surface acoustic wave device of the comparative example.
  • the solid line in FIG. 9 shows the result of the above embodiment, and the broken line shows the result of the comparative example.
  • the surface acoustic wave device shown in FIGS. 2 (a) to 2 (c) was constructed. That is, the number of electrode fingers and the capacitance of the IDT electrode are the same as those in the first embodiment. However, as shown in FIG. 2 (a), in the IDT electrode 102 of the surface acoustic wave device of the comparative example, the tips of the first electrode finger 102a and the first dummy electrode finger 102b face each other. The end line is a direction parallel to the surface acoustic wave propagation direction.
  • the electric field vectors E1 to E5 are parallel to the extending direction of the first electrode finger 102a. That is, the directions of the electric field vectors E1 to E5 are parallel to the direction in which the polarization axis direction C is projected onto the upper surface 103a of the piezoelectric substrate 103. Also in this comparative example, the polarization axis C 0, as shown in FIG. 2 (b), are extended in a direction inclined toward the upper surface from the lower surface of the piezoelectric substrate 103.
  • FIG. 2B shows the polarization axis direction C when the piezoelectric substrate is viewed in plan.
  • the distortion level of the third harmonic is effectively reduced over a wide frequency range of the third harmonic distortion generation frequency. It is possible to suppress it.
  • the non-linear distortion signal can be suppressed by having a portion in which the direction in which the electrode finger 4a extends and the direction of the electric field vector are shifted as described above. This is considered to be due to the following reason.
  • the coefficient relating to the electrical nonlinearity of the medium itself in the surface acoustic wave device 1 is ⁇
  • the magnitude of the electric field is E
  • the angle between the electric field direction and the polarization axis direction is ⁇
  • the electrical nonlinearity is caused.
  • the direction of the arrow C obtained by projecting the polarization axis direction on the upper surface 2a is the same as the direction in which the electrode finger 4a extends. Accordingly, as shown in FIG. 1C, for example, the electric field vector E1 is set to a direction that forms an angle ⁇ with respect to the direction indicated by the arrow C. Therefore, the polarization axis direction component of the electric field vector E1 is E1 cos ⁇ .
  • the nonlinear distortion signal can be effectively suppressed. Has been.
  • this passes through the center O of the portion where the first electrode finger 4a and the first dummy electrode finger 5b face each other and is orthogonal to the first electrode finger 4a.
  • the center O means the center of the portion where the first electrode finger 4a and the first dummy electrode finger 5b face each other. That is, it is the center in the facing direction in which the two are facing each other and the center of the facing portion in the surface acoustic wave propagation direction.
  • the electric field vector has a portion shifted with respect to the extending direction of the electrode fingers 4a and 5a as described above. It will be. Therefore, the nonlinear distortion signal can be effectively suppressed.
  • the second to seventh embodiments shown in FIGS. 3 to 8 described below can similarly satisfy the above relationship, so that the nonlinear distortion signal can be effectively suppressed. .
  • the 2nd electrode finger 5a and the 2nd dummy electrode finger 4b are The facing portions are configured similarly. Accordingly, it is possible to suppress the nonlinear distortion signal in the opposite portion at the tip of the second electrode finger 5a as well.
  • the present invention it is only necessary that at least one of the opposing portions at the tips of the first electrode finger 4a and the second electrode finger 5a satisfies the asymmetry as described above. Even in that case, the nonlinear distortion signal can be suppressed according to the present invention.
  • the present invention is not limited to this, and the direction in which the electrode fingers extend and the polarization axis direction do not have to be the same, and the electric field vector and the polarization axis direction need only be shifted.
  • the extending direction of the electrode fingers and the polarization axis direction are the same, and the electric field vector is shifted from these.
  • the tip of the first electrode finger 4a is a protruding portion 4a2 protruding toward the first dummy electrode finger 5b.
  • the tip of the first dummy electrode finger 5b is a recess 5b2 that fits into the protrusion 4a2.
  • the protrusion 4a2 has a tip P.
  • the oblique sides 4a3 and 4a4 extending from the tip P to the pair of side sides of the first electrode finger 4a are extended.
  • the hypotenuse 4a3 and the hypotenuse 4a4 have the same length.
  • a triangle composed of the hypotenuses 4a3 and 4a4 and the side connecting the ends opposite to the tip P of the hypotenuses 4a3 and 4a4 is an isosceles triangle.
  • the tip P is located at the center of the width direction dimension of the first electrode finger 4a, that is, the dimension along the surface acoustic wave propagation direction.
  • the recess 5b2 of the first dummy electrode finger 5b has a shape in which the protrusion 4a2 fits. Therefore, when the first dummy electrode finger 5b is on the hot side, the electric field vectors E1 to E5 extend in the illustrated direction. Also in this embodiment, the electric field vectors E1, E2, E4, E5 are shifted from the direction in which the first electrode finger 4a extends and the direction parallel to the direction C in which the polarization axis is projected on the upper surface. In other words, the protrusion 4a2 at the tip of the first electrode finger 4a and the recess 5b2 of the first dummy electrode finger 5b are asymmetric with respect to the virtual line X3.
  • the virtual line X3 passes through the tip P of the first electrode finger 4a and is parallel to the surface acoustic wave propagation direction, and passes through the tip of the first dummy electrode finger 5b and parallel to the surface acoustic wave propagation direction. This is a virtual line passing through the center between the virtual line X2 and parallel to the surface acoustic wave propagation direction.
  • the first electrode finger 4a has a plurality of triangular protrusions 4a5 at the tip.
  • the tip of the first dummy electrode finger 5b has a plurality of triangular recesses 5b4 that fit into the protrusions 4a5.
  • the electric field vector E1 extends in the direction in which the first electrode finger 4a extends or the direction shifted from the C-axis direction.
  • a protrusion 4a6 having a semicircular contour and a plurality of recesses 4a7 having semicircular recesses are provided at the tip.
  • a recess 5b5 that fits into the protrusion 4a6 and a protrusion 5b6 that fits into the recess 4a7 are provided.
  • the electric field vector E1 extends in a direction in which the extending direction of the electrode finger 4a is shifted from the c-axis direction.
  • the tip of the first electrode finger 4a has a recess 4a8, and the tip of the first dummy electrode finger 5b has a protrusion 5b7.
  • the two are not in a fitting relationship. That is, the inner angle ⁇ 1 of the recess 4a8 is larger than the inner angle ⁇ 2 of the protrusion 5b7.
  • the tip of the first dummy electrode finger 5b and the tip of the first electrode finger 4a do not have to be in a shape that fits each other. Also in this case, as indicated by the electric field vectors E1 and E3, the directions of the electric field vectors E1 and E3 are shifted from the extending direction of the first electrode finger 4a.
  • the tip of the first electrode finger 4a does not have a recess and has a hypotenuse 4a9
  • the tip of the first dummy electrode finger 5b also has a hypotenuse 5b8. It is good.
  • the hypotenuse 4a9 and the hypotenuse 5b8 are expressed as hypotenuses because they are directions intersecting the surface acoustic wave propagation direction. In this embodiment, the hypotenuse 4a9 and the hypotenuse 5b8 are parallel, but they may be non-parallel. Further, the inclination direction of the oblique side 5b8 may be opposite to the inclination direction of the oblique side 4a9 with respect to the surface acoustic wave propagation direction.
  • the electric field vectors indicated by the arrows E1 to E3 are shifted from the direction of the arrow C.
  • the first and second dummy electrode fingers are not necessarily provided. In the seventh embodiment shown in FIG. 8, the first and second dummy electrode fingers are not provided. In the IDT electrode 11 shown in FIG. 8, a plurality of first electrode fingers 4a and a plurality of second electrode fingers 5a are interleaved with each other.
  • the tip of the first electrode finger 4a has an arcuate protruding portion 4c.
  • a concave portion 5c is formed in a portion of the second bus bar electrode 5 facing the protruding portion 4c.
  • the recess 5c has an arc shape. Accordingly, the nonlinear distortion signal can be suppressed at the portion where the protrusion 4c and the recess 5c face each other as in the case of the first embodiment.
  • the second electrode finger 5a also has an arcuate protrusion 5d at the tip.
  • a recess 4 d is formed at a position facing the protruding portion 5 d of the first bus bar electrode 4.
  • the concave portion 4d has an arc shape like the concave portion 5c. Therefore, it is possible to suppress the generation of the nonlinear distortion signal even in the facing portion where the second electrode finger 5a and the first bus bar electrode 4 are facing each other.
  • the electrode portion facing the first or second electrode finger is not limited to the dummy electrode finger, but other bus bars such as the bus bar electrodes 4 and 5. It may be an electrode part.
  • the present invention can also be applied to other surface acoustic wave devices such as a boundary acoustic wave device.
  • SYMBOLS 1 Surface acoustic wave apparatus 2 ... Piezoelectric substrate 2a ... Upper surface 3 ... IDT electrode 4 ... 1st bus-bar electrode 4a ... 1st electrode finger 4a1, 4a7, 4a8, 4d ... Recessed part 4a2, 4a5, 4a6, 4c ... Projection part 4a3, 4a4, 4a9 ... hypotenuse 4b ... second dummy electrode finger 5 ... second bus bar electrode 5a ... second electrode finger 5b ... first dummy electrode finger 5b1 ... tip 5b2, 5b4, 5b5, 5c ... concave portion 5b6, 5b7, 5d ... projecting portion 5b8 ... hypotenuse 11 ... IDT electrodes E1-E5 ... electric field vector

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  • Acoustics & Sound (AREA)
  • Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)

Abstract

　The present invention provides an elastic wave apparatus capable of suppressing a non-linearly distorted signal. This elastic wave apparatus (1) has an IDT electrode (3) formed on a piezoelectric substrate (2). In the IDT electrode (3), a tip of a first electrode finger (4a) and/or a second electrode finger (5a) and an electrode portion facing the tip are formed so as to have a shape such that an electrode vector extending between portions facing each other across a virtual line (X) that passes through the center of the facing portion and extends in a direction parallel to the direction of propagation of an elastic wave is shifted relative to a direction in which the electrode finger (4a) extends.

Description

弾性波装置Elastic wave device
　本発明は、圧電基板上にＩＤＴ電極が形成されている弾性波装置に関する。 The present invention relates to an acoustic wave device in which an IDT electrode is formed on a piezoelectric substrate.
　従来、帯域フィルタや共振子として、弾性波装置が広く用いられている。例えば下記の特許文献１には、圧電基板上にＩＤＴ電極が形成されている弾性表面波装置が開示されている。この弾性表面波装置では、ＩＤＴ電極は、複数本の第１の電極指と、複数本の第１の電極指と間挿し合っている複数本の第２の電極指とを有する。また、複数本の第１の電極指の先端と、該電極指の延びる方向において対向するように、複数本の第１のダミー電極指が設けられている。さらに、複数本の第２の電極指の先端とそれぞれ対向するように、複数本の第２のダミー電極指が設けられている。 Conventionally, elastic wave devices have been widely used as bandpass filters and resonators. For example, Patent Document 1 below discloses a surface acoustic wave device in which an IDT electrode is formed on a piezoelectric substrate. In this surface acoustic wave device, the IDT electrode has a plurality of first electrode fingers and a plurality of second electrode fingers interleaved with the plurality of first electrode fingers. A plurality of first dummy electrode fingers are provided so as to face the tips of the plurality of first electrode fingers in the extending direction of the electrode fingers. Furthermore, a plurality of second dummy electrode fingers are provided so as to face the tips of the plurality of second electrode fingers, respectively.
特開２００２－３１４３６６号公報JP 2002-314366 A
　特許文献１に記載のような従来の弾性波装置では、電気的非線形性を原因とする非線形歪み信号が発生するという問題があった。そのため、良好な共振特性やフィルタ特性を得ることが困難であった。 The conventional acoustic wave device as described in Patent Document 1 has a problem that a nonlinear distortion signal due to electrical nonlinearity is generated. For this reason, it is difficult to obtain good resonance characteristics and filter characteristics.
　本発明の目的は、電気的非線形性に起因する非線形歪み信号を抑制することが可能である弾性波装置を提供することにある。 An object of the present invention is to provide an elastic wave device capable of suppressing a nonlinear distortion signal caused by electrical nonlinearity.
　本発明に係る弾性波装置は、圧電基板と、圧電基板上に形成されたＩＤＴ電極とを備える。上記ＩＤＴ電極は、第１，第２のバスバー電極と、前記第１のバスバー電極に電気的に接続された複数本の第１の電極指と、第２のバスバー電極に接続されており、前記複数本の第１の電極指と互いに間挿し合っている複数本の第２の電極指とを有する。前記第１の電極指及び第２の電極指のうちの少なくとも一方の電極指の先端と、該電極指の先端と該電極指の延びる方向において対向しており、かつ該電極指と異なる電位に接続される電極部分とが、特定の形状とされている。すなわち、上記少なくとも一方の電極指の先端と、上記電極部分とが、対向方向中心を通りかつ該電極指の延びる方向と直交する仮想線に対し、対向し合っている部分間に延びる電場ベクトルが、分極軸の方向に対してずらされている部分を有する形状とされている。 The elastic wave device according to the present invention includes a piezoelectric substrate and an IDT electrode formed on the piezoelectric substrate. The IDT electrode is connected to first and second bus bar electrodes, a plurality of first electrode fingers electrically connected to the first bus bar electrode, and a second bus bar electrode, A plurality of first electrode fingers and a plurality of second electrode fingers interleaved with each other. The tip of at least one of the first electrode finger and the second electrode finger is opposed to the tip of the electrode finger in the extending direction of the electrode finger and has a potential different from that of the electrode finger. The electrode part to be connected has a specific shape. That is, the electric field vector extending between the opposing portions with respect to a virtual line in which the tip of the at least one electrode finger and the electrode portion pass through the center of the opposing direction and is orthogonal to the extending direction of the electrode finger. The shape has a portion shifted with respect to the direction of the polarization axis.
　本発明に係る弾性波装置のある特定の局面では、前記電場ベクトルが、電極指の延びる方向に対してずらされている部分を有する形状とされている。 In a specific aspect of the acoustic wave device according to the present invention, the electric field vector has a shape having a portion that is shifted with respect to the extending direction of the electrode finger.
　本発明に係る弾性波装置の他の特定の局面では、前記電極指の先端と、該電極指の先端と対向している前記電極部分とが対向している部分において、前記仮想線に対し、電極指の先端の形状と、該電極指の先端と対向している前記電極部分の形状とが非対称である。 In another specific aspect of the acoustic wave device according to the present invention, in the portion where the tip of the electrode finger and the electrode portion facing the tip of the electrode finger are opposed to the virtual line, The shape of the tip of the electrode finger is asymmetric with the shape of the electrode portion facing the tip of the electrode finger.
　本発明に係る弾性波装置の他の特定の局面では、前記電極指の先端と、該電極指の先端と対向している前記電極部分とのうち、一方が他方に向かって開いた凹部を有し、他方が相手方に向かって突出している突出部を有する。 In another specific aspect of the acoustic wave device according to the present invention, one of the tip of the electrode finger and the electrode portion facing the tip of the electrode finger has a recess that is open toward the other. And the other has a protruding portion protruding toward the other side.
　本発明に係る弾性波装置のさらに他の特定の局面では、前記電極指の先端と、該電極指の先端と対向している前記電極部分とが、互いに嵌り合う関係にある形状を有する。 In still another specific aspect of the acoustic wave device according to the present invention, the tip of the electrode finger and the electrode portion facing the tip of the electrode finger have a shape that fits into each other.
　本発明に係る弾性波装置のさらに他の特定の局面では、前記第２のバスバー電極に一端が接続されている複数本の第１のダミー電極指と、前記第１のバスバー電極に一端が接続されている複数本の第２のダミー電極指とがさらに備えられている。そして、前記電極部分が、前記第１のダミー電極指及び第２のダミー電極指のうちの少なくとも一方の先端である。 In still another specific aspect of the elastic wave device according to the present invention, a plurality of first dummy electrode fingers, one end of which is connected to the second bus bar electrode, and one end of which is connected to the first bus bar electrode. And a plurality of second dummy electrode fingers. The electrode portion is a tip of at least one of the first dummy electrode finger and the second dummy electrode finger.
　本発明に係る弾性波装置のさらに別の特定の局面では、前記電極指の先端と、該電極指の先端と対向している前記電極部分とが、円弧状の形状を有する。 In yet another specific aspect of the acoustic wave device according to the present invention, the tip of the electrode finger and the electrode portion facing the tip of the electrode finger have an arc shape.
　本発明に係る弾性波装置のさらに別の特定の局面では、前記電極指の先端と、該電極指の先端と対向している前記電極部分が、それぞれ、相手方に向かって突出している複数個の突出部を有する形状とされている。 In still another specific aspect of the elastic wave device according to the present invention, a plurality of tip ends of the electrode fingers and the electrode portions facing the tip ends of the electrode fingers respectively protrude toward the other side. It is the shape which has a protrusion part.
　本発明によれば、第１の電極指及び第２の電極指のうちの少なくとも一方の電極指の先端と、上記電極指と異なる電位に接続される電極部分とが、上記特定の形状とされているため、非線形歪み信号を効果的に抑制することができる。従って良好な共振特性やフィルタ特性を有する弾性波装置を提供することが可能となる。 According to the present invention, the tip of at least one of the first electrode finger and the second electrode finger and the electrode portion connected to a potential different from that of the electrode finger have the specific shape. Therefore, the nonlinear distortion signal can be effectively suppressed. Therefore, it is possible to provide an elastic wave device having good resonance characteristics and filter characteristics.
図１（ａ）は、本発明の第１の実施形態に係る弾性表面波装置の平面図であり、図１（ｂ）は図１（ａ）中の円Ａで示す部分を拡大して示す部分拡大平面図であり、図１（ｃ）は対向方向と電場ベクトルＥ１の延びる方向との関係を示す図である。FIG. 1A is a plan view of the surface acoustic wave device according to the first embodiment of the present invention, and FIG. 1B is an enlarged view of a portion indicated by a circle A in FIG. FIG. 1C is a partially enlarged plan view showing the relationship between the facing direction and the direction in which the electric field vector E1 extends. 図２（ａ）は、比較例の弾性波装置の概略構成を示す模式的平面図であり、図２（ｂ）はその電極指が延びる方向に沿う断面図であり、図２（ｃ）は図２（ａ）の破線Ｂで示した部分の部分拡大平面図である。2A is a schematic plan view showing a schematic configuration of an elastic wave device of a comparative example, FIG. 2B is a cross-sectional view along the direction in which the electrode fingers extend, and FIG. It is the elements on larger scale of the part shown with the broken line B of Fig.2 (a). 図３は、本発明の第２の実施形態に係る弾性表面波装置の要部を示す部分拡大平面図である。FIG. 3 is a partially enlarged plan view showing the main part of the surface acoustic wave device according to the second embodiment of the present invention. 図４は、本発明の第３の実施形態に係る弾性表面波装置の要部を示す部分拡大平面図である。FIG. 4 is a partially enlarged plan view showing the main part of the surface acoustic wave device according to the third embodiment of the present invention. 図５は、本発明の第４の実施形態に係る弾性表面波装置の要部を示す部分拡大平面図である。FIG. 5 is a partially enlarged plan view showing the main part of the surface acoustic wave device according to the fourth embodiment of the present invention. 図６は、本発明の第５の実施形態に係る弾性表面波装置の要部を示す部分拡大平面図である。FIG. 6 is a partially enlarged plan view showing the main part of the surface acoustic wave device according to the fifth embodiment of the present invention. 図７は、本発明の第６の実施形態に係る弾性表面波装置の要部を示す部分拡大平面図である。FIG. 7 is a partially enlarged plan view showing the main part of the surface acoustic wave device according to the sixth embodiment of the present invention. 図８は、本発明の第７の実施形態に係る弾性表面波装置の電極構造を示す模式的平面図である。FIG. 8 is a schematic plan view showing an electrode structure of a surface acoustic wave device according to the seventh embodiment of the present invention. 図９は、第１の実施形態の弾性表面波装置と、比較例の弾性表面波装置における３次高調波歪み信号レベルの周波数特性を示す図である。FIG. 9 is a diagram illustrating the frequency characteristics of the third-order harmonic distortion signal level in the surface acoustic wave device of the first embodiment and the surface acoustic wave device of the comparative example.
　以下、図面を参照しつつ、本発明の具体的な実施形態を説明することにより、本発明を明らかにする。 Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.
　図１（ａ）は、本発明の第１の実施形態に係る弾性表面波装置の模式的平面図である。弾性表面波装置１は、圧電基板２を有する。圧電基板２は、ＬｉＴａＯ３、ＬｉＮｂＯ３などの圧電単結晶またはＰＺＴなどの圧電セラミックスからなる。 FIG. 1A is a schematic plan view of a surface acoustic wave device according to a first embodiment of the present invention. The surface acoustic wave device 1 has a piezoelectric substrate 2. The piezoelectric substrate 2 is made of a piezoelectric single crystal such as LiTaO 3 or LiNbO 3 or a piezoelectric ceramic such as PZT.
　圧電基板２上に、ＩＤＴ電極３が形成されている。ＩＤＴ電極３は、Ａｌなどの適宜の金属もしくは合金からなる。 An IDT electrode 3 is formed on the piezoelectric substrate 2. The IDT electrode 3 is made of an appropriate metal or alloy such as Al.
　ＩＤＴ電極３は、第１のバスバー電極４と、第２のバスバー電極５とを有する。第１のバスバー電極４には、複数本の第１の電極指４ａの一端が接続されている。第２のバスバー電極５には、複数本の第２の電極指５ａの一端が接続されている。上記複数本の第１の電極指４ａは、第１のバスバー電極４から、第２のバスバー電極５側に向って延ばされている。複数本の第２の電極指５ａは、第２のバスバー電極５から、第１のバスバー電極４に向って延ばされている。複数本の第１の電極指４ａと、複数本の第２の電極指５ａとは、間挿し合っている。 The IDT electrode 3 has a first bus bar electrode 4 and a second bus bar electrode 5. One end of a plurality of first electrode fingers 4 a is connected to the first bus bar electrode 4. One end of a plurality of second electrode fingers 5 a is connected to the second bus bar electrode 5. The plurality of first electrode fingers 4a are extended from the first bus bar electrode 4 toward the second bus bar electrode 5 side. The plurality of second electrode fingers 5 a are extended from the second bus bar electrode 5 toward the first bus bar electrode 4. The plurality of first electrode fingers 4a and the plurality of second electrode fingers 5a are interleaved.
　本実施形態では、第２のバスバー電極５に、複数本の第１のダミー電極指５ｂの一端が接続されている。第１のダミー電極指５ｂの先端は、第１の電極指４ａの先端と第１の電極指４ａの延びる方向において対向している。両者が対向している部分を対向部とする。 In the present embodiment, one end of a plurality of first dummy electrode fingers 5 b is connected to the second bus bar electrode 5. The tip of the first dummy electrode finger 5b faces the tip of the first electrode finger 4a in the extending direction of the first electrode finger 4a. The part where both face each other is defined as a facing part.
　同様に、第１のバスバー電極４に、複数本の第２のダミー電極指４ｂが接続されている。第２のダミー電極指４ｂの先端は、第２の電極指５ａの先端と第２の電極指５ａの延びる方向において対向している。 Similarly, a plurality of second dummy electrode fingers 4 b are connected to the first bus bar electrode 4. The tip of the second dummy electrode finger 4b faces the tip of the second electrode finger 5a in the extending direction of the second electrode finger 5a.
　なお、本発明において、第１，第２のダミー電極指５ｂ，４ｂは必須の構成ではない。 In the present invention, the first and second dummy electrode fingers 5b and 4b are not essential components.
　図１（ａ）の矢印Ｃは、分極軸方向を上面２ａに投影した方向である。実際の分極軸方向は、圧電基板２の下面側から上面側に向って傾斜している。 The arrow C in FIG. 1A is the direction in which the polarization axis direction is projected onto the upper surface 2a. The actual polarization axis direction is inclined from the lower surface side to the upper surface side of the piezoelectric substrate 2.
　弾性表面波装置１では、第１の電極指４ａと、第２の電極指５ａとの間に交番電界を印加することにより、弾性表面波が励振される。弾性表面波の励振方向は、第１，第２の電極指４ａ，５ａの延びる方向と直交する方向である。 In the surface acoustic wave device 1, a surface acoustic wave is excited by applying an alternating electric field between the first electrode finger 4a and the second electrode finger 5a. The excitation direction of the surface acoustic wave is a direction orthogonal to the extending direction of the first and second electrode fingers 4a and 5a.
　本実施形態の特徴は、第１，第２の電極指４ａ，５ａの先端と、各先端と対向している第１，第２のダミー電極指５ｂ，４ｂの先端の形状が、両者の間において延びる電場ベクトルが第１，第２の電極指４ａ，５ａの延びる方向に対してずらされている部分を有する形状とされていることにある。それによって、非線形歪み信号を抑圧することが可能とされている。これを、図１（ｂ）及び図１（ｃ）を参照してより具体的に説明する。なお、ここでいう「非線形歪み信号」とは、Ｎ次高調波歪みおよびＮ次相互変調歪みを総称したものを表す。 The feature of this embodiment is that the shape of the tips of the first and second electrode fingers 4a and 5a and the tips of the first and second dummy electrode fingers 5b and 4b facing each tip are The electric field vector extending in FIG. 2 has a shape having a portion that is shifted with respect to the extending direction of the first and second electrode fingers 4a and 5a. Thereby, it is possible to suppress the nonlinear distortion signal. This will be described more specifically with reference to FIGS. 1B and 1C. The “non-linear distortion signal” here is a generic term for N-order harmonic distortion and N-order intermodulation distortion.
　図１（ｂ）は、図１（ａ）中の破線で示す円Ａで示す部分を拡大して示す部分拡大平面図である。 FIG. 1 (b) is a partially enlarged plan view showing an enlarged portion indicated by a circle A indicated by a broken line in FIG. 1 (a).
　第１の電極指４ａの先端と、第１のダミー電極指５ｂの先端とが対向している対向部が図示されている。この対向部において、第１の電極指４ａの先端は、第１のダミー電極指５ｂ側に向って開いた円弧状の凹部４ａ１を有する。 The opposing part in which the tip of the first electrode finger 4a and the tip of the first dummy electrode finger 5b face each other is shown. In this facing portion, the tip of the first electrode finger 4a has an arcuate recess 4a1 that opens toward the first dummy electrode finger 5b.
　他方、第１のダミー電極指５ｂは、第１の電極指４ａ側に向かって突出した先端部５ｂ１を有する。この突出した先端部５ｂ１は、凹部４ａ１側に向かって突出している円弧状の形状を有する。 On the other hand, the 1st dummy electrode finger 5b has the front-end | tip part 5b1 which protruded toward the 1st electrode finger 4a side. The protruding tip 5b1 has an arc shape that protrudes toward the recess 4a1.
　例えば第１のダミー電極指５ｂ、すなわち第２のバスバー電極５側がホット側であり、第１の電極指４ａ側がアース側であるとする。その場合には、電界が第１のダミー電極指５ｂから第１の電極指４ａ側に向かって印加されることになる。この場合、第１の電極指４ａの先端及び第１のダミー電極指５ｂの先端が上記の形状とされているため、電場ベクトルの向きは、矢印Ｅ１～Ｅ５で示す通り、第１の電極指４ａと第１のダミー電極指５ｂが対向する最短距離の方向となる。すなわち、電場ベクトルＥ３は、電極指４ａの延びる方向と平行な方向であるが、ダミー電極指５ｂの頂点以外の先端部分では、矢印Ｅ１，Ｅ２，Ｅ４，Ｅ５で示すように、電場ベクトルの向きは、電極指４ａの延びる方向とずらされている。 For example, it is assumed that the first dummy electrode finger 5b, that is, the second bus bar electrode 5 side is the hot side, and the first electrode finger 4a side is the ground side. In that case, the electric field is applied from the first dummy electrode finger 5b toward the first electrode finger 4a. In this case, since the tip of the first electrode finger 4a and the tip of the first dummy electrode finger 5b have the above-described shape, the direction of the electric field vector is as shown by arrows E1 to E5. The direction is the shortest distance between 4a and the first dummy electrode finger 5b. In other words, the electric field vector E3 is a direction parallel to the extending direction of the electrode finger 4a, but at the tip portion other than the apex of the dummy electrode finger 5b, the direction of the electric field vector is indicated by arrows E1, E2, E4, E5. Is shifted from the extending direction of the electrode finger 4a.
　図９は、本実施形態の弾性表面波装置と、比較例の弾性表面波装置における３次高調波歪み信号レベルの周波数特性を示す図である。図９の実線が上記実施形態の結果を示し、破線が比較例の結果を示す。 FIG. 9 is a diagram showing the frequency characteristics of the third-order harmonic distortion signal level in the surface acoustic wave device of the present embodiment and the surface acoustic wave device of the comparative example. The solid line in FIG. 9 shows the result of the above embodiment, and the broken line shows the result of the comparative example.
　なお、比較例としては、図２（ａ）～図２（ｃ）に示す弾性表面波装置を構成した。すなわち、ＩＤＴ電極の電極指の本数及び静電容量は第１の実施形態の場合と同一とした。もっとも、図２（ａ）に示すように、比較例の弾性表面波装置のＩＤＴ電極１０２では、第１の電極指１０２ａと第１のダミー電極指１０２ｂが対向している部分において、両者の先端の端線は、弾性表面波伝搬方向と平行な方向とされている。 As a comparative example, the surface acoustic wave device shown in FIGS. 2 (a) to 2 (c) was constructed. That is, the number of electrode fingers and the capacitance of the IDT electrode are the same as those in the first embodiment. However, as shown in FIG. 2 (a), in the IDT electrode 102 of the surface acoustic wave device of the comparative example, the tips of the first electrode finger 102a and the first dummy electrode finger 102b face each other. The end line is a direction parallel to the surface acoustic wave propagation direction.
　従って、図２（ｃ）に示すように、第１のダミー電極指１０２ｂがホット側の場合、電場ベクトルＥ１～Ｅ５は第１の電極指１０２ａの延びる方向と平行な方向となっている。すなわち、分極軸方向Ｃを圧電基板１０３の上面１０３ａに投影した方向に対し、電場ベクトルＥ１～Ｅ５の方向が平行な方向とされている。なお、この比較例においても、分極軸方向Ｃ０は、図２（ｂ）に示すように、圧電基板１０３の下面から上面側に向かって傾斜する方向に延ばされている。図２（ｂ）では、圧電基板を平面視した場合の分極軸方向Ｃが示されている。 Therefore, as shown in FIG. 2C, when the first dummy electrode finger 102b is on the hot side, the electric field vectors E1 to E5 are parallel to the extending direction of the first electrode finger 102a. That is, the directions of the electric field vectors E1 to E5 are parallel to the direction in which the polarization axis direction C is projected onto the upper surface 103a of the piezoelectric substrate 103. Also in this comparative example, the polarization axis C 0, as shown in FIG. 2 (b), are extended in a direction inclined toward the upper surface from the lower surface of the piezoelectric substrate 103. FIG. 2B shows the polarization axis direction C when the piezoelectric substrate is viewed in plan.
　図９から明らかなように、破線で示す比較例の場合に比べ、上記実施形態によれば、３次高調波歪み発生周波数の広い周波数域にわたり、３次高調波の歪みレベルを、効果的に抑圧することが可能とされている。 As apparent from FIG. 9, compared to the comparative example indicated by the broken line, according to the embodiment, the distortion level of the third harmonic is effectively reduced over a wide frequency range of the third harmonic distortion generation frequency. It is possible to suppress it.
　本実施形態において、非線形歪み信号を抑圧し得るのは、上記のように、電極指４ａの延びる方向と電場ベクトルの方向がずらされている部分を有することによる。これは以下の理由によると考えられる。 In the present embodiment, the non-linear distortion signal can be suppressed by having a portion in which the direction in which the electrode finger 4a extends and the direction of the electric field vector are shifted as described above. This is considered to be due to the following reason.
　弾性表面波装置１における媒質そのものが有する電気的非線形性に係る係数をχ、電場の大きさをＥ、電場の向きと分極軸方向のなす角度をθとすると、電気的非線形性を原因とするＮ次の非線形歪み信号の大きさＤ（Ｎ）は、Ｄ（Ｎ）＝（χ・Ｅｃｏｓθ）Ｎで表されると考えられる。従って、Ｅｃｏｓθを小さくすれば、Ｎ次の非線形歪み信号の大きさＤ（Ｎ）を小さくすることができると考えられる。 If the coefficient relating to the electrical nonlinearity of the medium itself in the surface acoustic wave device 1 is χ, the magnitude of the electric field is E, and the angle between the electric field direction and the polarization axis direction is θ, the electrical nonlinearity is caused. The magnitude D (N) of the Nth-order nonlinear distortion signal is considered to be represented by D (N) = (χ · Ecos θ) N. Therefore, it is considered that the magnitude D (N) of the Nth-order nonlinear distortion signal can be reduced by reducing Ecosθ.
　本実施形態では、分極軸方向を上面２ａに投影した矢印Ｃの方向が、電極指４ａの延びる方向と同一とされている。従って、図１（ｃ）に示すように、例えば電場ベクトルＥ１は、矢印Ｃで示す方向に対してθの角度をなす方向とされている。よって、電場ベクトルＥ１の分極軸方向成分は、Ｅ１ｃｏｓθとなる。 In this embodiment, the direction of the arrow C obtained by projecting the polarization axis direction on the upper surface 2a is the same as the direction in which the electrode finger 4a extends. Accordingly, as shown in FIG. 1C, for example, the electric field vector E1 is set to a direction that forms an angle θ with respect to the direction indicated by the arrow C. Therefore, the polarization axis direction component of the electric field vector E1 is E1 cos θ.
　本実施形態では、上記のように、矢印Ｅ１，Ｅ２，Ｅ４，Ｅ５において、ｃｏｓθが１未満であるため、それによって非線形歪み信号の歪みを小さくすることが可能とされていると考えられる。 In this embodiment, as described above, since cos θ is less than 1 at the arrows E1, E2, E4, and E5, it is considered that the distortion of the nonlinear distortion signal can be reduced thereby.
　上記のように、第１の実施形態の弾性表面波装置１では、第１の電極指４ａの先端と、第１のダミー電極指５ｂの先端とが対向している部分において、両者の先端の形状が、両者の間において延びる電場ベクトルが電極指４ａ，５ａの延びる方向とずらされている方向となる部分を有する形状とされているため、非線形歪み信号を効果的に抑圧することが可能とされている。 As described above, in the surface acoustic wave device 1 according to the first embodiment, at the portion where the tip of the first electrode finger 4a and the tip of the first dummy electrode finger 5b face each other, Since the shape has a shape in which the electric field vector extending between the two is shifted from the extending direction of the electrode fingers 4a and 5a, the nonlinear distortion signal can be effectively suppressed. Has been.
　これは、言い換えれば、図１（ｂ）において、第１の電極指４ａと、第１のダミー電極指５ｂとが対向している部分の中心Ｏを通り、第１の電極指４ａと直交する方向に延びる仮想線Ｘに対し、第１の電極指４ａと、第１のダミー電極指５ｂの先端とが非対称の形状とされていればよいことを意味する。ここで、中心Ｏとは、第１の電極指４ａと、第１のダミー電極指５ｂとが対向している部分の中心を意味する。すなわち、両者が対向している対向方向において中央であって、かつ弾性表面波伝搬方向における対向部の中心でもある。 In other words, in FIG. 1B, this passes through the center O of the portion where the first electrode finger 4a and the first dummy electrode finger 5b face each other and is orthogonal to the first electrode finger 4a. This means that the first electrode finger 4a and the tip of the first dummy electrode finger 5b only need to be asymmetrical with respect to the virtual line X extending in the direction. Here, the center O means the center of the portion where the first electrode finger 4a and the first dummy electrode finger 5b face each other. That is, it is the center in the facing direction in which the two are facing each other and the center of the facing portion in the surface acoustic wave propagation direction.
　上記のように仮想線Ｘに対して、対向し合っている部分が非対称とされておれば、上述したように、電場ベクトルが電極指４ａ，５ａの延びる方向に対してずらされた部分を有することとなる。従って、非線形歪み信号を効果的に抑圧することができる。 If the portion facing each other with respect to the virtual line X is asymmetric as described above, the electric field vector has a portion shifted with respect to the extending direction of the electrode fingers 4a and 5a as described above. It will be. Therefore, the nonlinear distortion signal can be effectively suppressed.
　よって、本発明においては、次に述べる図３～図８に示す第２～第７の実施形態においても、同様に、上記関係を満たし得るため、非線形歪み信号を効果的に抑圧することができる。 Therefore, in the present invention, the second to seventh embodiments shown in FIGS. 3 to 8 described below can similarly satisfy the above relationship, so that the nonlinear distortion signal can be effectively suppressed. .
　なお、上記第１の電極指４ａと第１のダミー電極指５ｂとが対向している部分につき説明したが、本実施形態では、第２の電極指５ａと第２のダミー電極指４ｂとが対向している部分も同様に構成されている。従って、第２の電極指５ａの先端の対向部においても、同様に、非線形歪み信号を抑圧することが可能とされている。 In addition, although demonstrated about the part which the said 1st electrode finger 4a and the 1st dummy electrode finger 5b oppose, in this embodiment, the 2nd electrode finger 5a and the 2nd dummy electrode finger 4b are The facing portions are configured similarly. Accordingly, it is possible to suppress the nonlinear distortion signal in the opposite portion at the tip of the second electrode finger 5a as well.
　もっとも、本発明においては、第１の電極指４ａ及び第２の電極指５ａの各先端の対向部のうち少なくとも一方において、上記のように非対称性が満たされておればよい。その場合であっても、本発明に従って非線形歪み信号を抑圧することはできる。好ましくは、上記実施形態のように、第１の電極指４ａの先端の対向部、並びに第２の電極指５ａの対向部の双方において、上記非対称性が満たされていることが望ましい。 However, in the present invention, it is only necessary that at least one of the opposing portions at the tips of the first electrode finger 4a and the second electrode finger 5a satisfies the asymmetry as described above. Even in that case, the nonlinear distortion signal can be suppressed according to the present invention. Preferably, as in the above-described embodiment, it is desirable that the asymmetry is satisfied in both the facing portion at the tip of the first electrode finger 4a and the facing portion of the second electrode finger 5a.
　また、上記実施形態では、電場ベクトルが電極指４ａ，５ａの延びる方向に対してずらされた部分を有する構成であった。すなわち、分極軸方向を上面２ａに投影した矢印Ｃの方向が、電極指４ａの延びる方向と同一とされている場合であった。本発明においては、これに限るものではなく、電極指の延びる方向と分極軸方向とが同一でなくともよく、電場ベクトルと分極軸方向がずらされていればよい。好ましくは、電極指の延びる方向と分極軸方向が同じであり、これらと電場ベクトルがずらされているのがよい。 Moreover, in the said embodiment, it was the structure which has the part by which the electric field vector was shifted with respect to the direction where electrode finger 4a, 5a is extended. That is, the direction of the arrow C in which the polarization axis direction is projected on the upper surface 2a is the same as the direction in which the electrode finger 4a extends. The present invention is not limited to this, and the direction in which the electrode fingers extend and the polarization axis direction do not have to be the same, and the electric field vector and the polarization axis direction need only be shifted. Preferably, the extending direction of the electrode fingers and the polarization axis direction are the same, and the electric field vector is shifted from these.
　図３に示す第２の実施形態では、第１の電極指４ａの先端が、第１のダミー電極指５ｂに向かって突出している突出部４ａ２とされている。第１のダミー電極指５ｂの先端は、突出部４ａ２と嵌まり合う凹部５ｂ２とされている。より具体的には、突出部４ａ２は、先端Ｐを有する。先端Ｐから、第１の電極指４ａの一対の側辺に至る斜辺４ａ３，４ａ４が延ばされている。斜辺４ａ３と斜辺４ａ４とは等しい長さを有する。従って、斜辺４ａ３，４ａ４と、斜辺４ａ３，４ａ４の先端Ｐとは反対側の端部同士を結ぶ辺とからなる三角形は二等辺三角形となる。言い換えれば、先端Ｐは、第１の電極指４ａの幅方向寸法、すなわち弾性表面波伝搬方向に沿う寸法の中心に位置している。 In the second embodiment shown in FIG. 3, the tip of the first electrode finger 4a is a protruding portion 4a2 protruding toward the first dummy electrode finger 5b. The tip of the first dummy electrode finger 5b is a recess 5b2 that fits into the protrusion 4a2. More specifically, the protrusion 4a2 has a tip P. The oblique sides 4a3 and 4a4 extending from the tip P to the pair of side sides of the first electrode finger 4a are extended. The hypotenuse 4a3 and the hypotenuse 4a4 have the same length. Therefore, a triangle composed of the hypotenuses 4a3 and 4a4 and the side connecting the ends opposite to the tip P of the hypotenuses 4a3 and 4a4 is an isosceles triangle. In other words, the tip P is located at the center of the width direction dimension of the first electrode finger 4a, that is, the dimension along the surface acoustic wave propagation direction.
　他方、第１のダミー電極指５ｂの凹部５ｂ２は、上記突出部４ａ２が嵌まり合う形状とされている。よって、第１のダミー電極指５ｂがホット側の場合、電場ベクトルＥ１～Ｅ５が図示の方向に延びることとなる。本実施形態においても、電場ベクトルＥ１，Ｅ２，Ｅ４，Ｅ５が、第１の電極指４ａの延びる方向及び分極軸を上面に投影した方向Ｃと平行な方向からずらされている。言い換えれば、仮想線Ｘ３に対し、第１の電極指４ａの先端の突出部４ａ２と、第１のダミー電極指５ｂの凹部５ｂ２とが非対称の形状とされている。 On the other hand, the recess 5b2 of the first dummy electrode finger 5b has a shape in which the protrusion 4a2 fits. Therefore, when the first dummy electrode finger 5b is on the hot side, the electric field vectors E1 to E5 extend in the illustrated direction. Also in this embodiment, the electric field vectors E1, E2, E4, E5 are shifted from the direction in which the first electrode finger 4a extends and the direction parallel to the direction C in which the polarization axis is projected on the upper surface. In other words, the protrusion 4a2 at the tip of the first electrode finger 4a and the recess 5b2 of the first dummy electrode finger 5b are asymmetric with respect to the virtual line X3.
　よって、第１の実施形態と同様に非線形歪み信号を抑制することができる。なお、仮想線Ｘ３は、第１の電極指４ａの先端Ｐを通り弾性表面波伝搬方向に平行な仮想線Ｘ１と、第１のダミー電極指５ｂの先端を通り、弾性表面波伝搬方向に平行な仮想線Ｘ２との間の中心を通り、弾性表面波伝搬方向に平行な仮想線である。 Therefore, the nonlinear distortion signal can be suppressed as in the first embodiment. The virtual line X3 passes through the tip P of the first electrode finger 4a and is parallel to the surface acoustic wave propagation direction, and passes through the tip of the first dummy electrode finger 5b and parallel to the surface acoustic wave propagation direction. This is a virtual line passing through the center between the virtual line X2 and parallel to the surface acoustic wave propagation direction.
　図４に示す第３の実施形態では、第１の電極指４ａが先端に、複数の三角形状の突出部４ａ５を有する。他方、第１のダミー電極指５ｂの先端は、上記突出部４ａ５に嵌まり合う複数の三角形状の凹部５ｂ４を有する。この場合においても、電場ベクトルＥ１を代表して示すように、第１の電極指４ａの延びる方向やＣ軸方向とずらされた方向に電場ベクトルＥ１が延びている。 In the third embodiment shown in FIG. 4, the first electrode finger 4a has a plurality of triangular protrusions 4a5 at the tip. On the other hand, the tip of the first dummy electrode finger 5b has a plurality of triangular recesses 5b4 that fit into the protrusions 4a5. Also in this case, as representatively shown by the electric field vector E1, the electric field vector E1 extends in the direction in which the first electrode finger 4a extends or the direction shifted from the C-axis direction.
　図５に示す第４の実施形態では、先端に、半円状の輪郭を有する突出部４ａ６と、半円状の凹部を有する複数の凹部４ａ７とが設けられている。第１のダミー電極指５ｂの先端には、突出部４ａ６に嵌まり合う凹部５ｂ５と、凹部４ａ７に嵌まり合う突出部５ｂ６とが設けられている。この場合においても、電場ベクトルＥ１を代表して示すように、電極指４ａの延びる方向がｃ軸方向とずらされた方向に電場ベクトルＥ１が延びている。 In the fourth embodiment shown in FIG. 5, a protrusion 4a6 having a semicircular contour and a plurality of recesses 4a7 having semicircular recesses are provided at the tip. At the tip of the first dummy electrode finger 5b, a recess 5b5 that fits into the protrusion 4a6 and a protrusion 5b6 that fits into the recess 4a7 are provided. Also in this case, as representative of the electric field vector E1, the electric field vector E1 extends in a direction in which the extending direction of the electrode finger 4a is shifted from the c-axis direction.
　図６に示す第５の実施形態では、第１の電極指４ａの先端が、凹部４ａ８を有し、第１のダミー電極指５ｂの先端が突出部５ｂ７を有する。もっとも、本実施形態では、両者は嵌まり合う関係にはない。すなわち、凹部４ａ８の内角θ１が、突出部５ｂ７の内角θ２よりも大きくなっている。このように、第１のダミー電極指５ｂの先端と、第１の電極指４ａの先端とは、互いが嵌まり合う形状とされておらずともよい。この場合においても、電場ベクトルＥ１及びＥ３で示すように、電場ベクトルＥ１，Ｅ３の向きが、第１の電極指４ａの延びる方向とずらされた方向となる。 In the fifth embodiment shown in FIG. 6, the tip of the first electrode finger 4a has a recess 4a8, and the tip of the first dummy electrode finger 5b has a protrusion 5b7. However, in the present embodiment, the two are not in a fitting relationship. That is, the inner angle θ1 of the recess 4a8 is larger than the inner angle θ2 of the protrusion 5b7. Thus, the tip of the first dummy electrode finger 5b and the tip of the first electrode finger 4a do not have to be in a shape that fits each other. Also in this case, as indicated by the electric field vectors E1 and E3, the directions of the electric field vectors E1 and E3 are shifted from the extending direction of the first electrode finger 4a.
　さらに、図７に示す第６の実施形態のように、第１の電極指４ａの先端が凹部を有せず斜辺４ａ９を有し、第１のダミー電極指５ｂの先端も斜辺５ｂ８を有する形状としてもよい。なお、斜辺４ａ９及び斜辺５ｂ８は、弾性表面波伝搬方向に対して交差する方向であるため、斜辺と表現している。本実施形態では、斜辺４ａ９と，斜辺５ｂ８とは平行とされているが、両者は非平行であってもよい。さらに、斜辺５ｂ８の傾斜方向は、斜辺４ａ９の傾斜方向と、弾性表面波伝搬方向に対して逆方向とされていてもよい。 Further, as in the sixth embodiment shown in FIG. 7, the tip of the first electrode finger 4a does not have a recess and has a hypotenuse 4a9, and the tip of the first dummy electrode finger 5b also has a hypotenuse 5b8. It is good. The hypotenuse 4a9 and the hypotenuse 5b8 are expressed as hypotenuses because they are directions intersecting the surface acoustic wave propagation direction. In this embodiment, the hypotenuse 4a9 and the hypotenuse 5b8 are parallel, but they may be non-parallel. Further, the inclination direction of the oblique side 5b8 may be opposite to the inclination direction of the oblique side 4a9 with respect to the surface acoustic wave propagation direction.
　本実施形態においても、矢印Ｅ１～Ｅ３で示す電場ベクトルは、矢印Ｃ方向とずらされた方向とされている。 Also in this embodiment, the electric field vectors indicated by the arrows E1 to E3 are shifted from the direction of the arrow C.
　図３～図７に示した第２～第６の実施形態においても、第１の実施形態と同様に、前述した対向部における対向方向中心を通り弾性表面波伝搬方向と平行な方向に延びる仮想線に対し、第１の電極指４ａの先端と、第１のダミー電極指５ｂの先端とが非対称の形状とされているため、第１の実施形態と同様に、非線形歪み信号を効果的に抑圧することができる。 Also in the second to sixth embodiments shown in FIGS. 3 to 7, as in the first embodiment, a virtual that extends in the direction parallel to the surface acoustic wave propagation direction through the opposite direction center of the opposite portion described above. Since the tip of the first electrode finger 4a and the tip of the first dummy electrode finger 5b have an asymmetric shape with respect to the line, as in the first embodiment, the nonlinear distortion signal is effectively generated. Can be suppressed.
　なお、本発明においては、第１，第２のダミー電極指は必ずしも設けられずともよい。図８に示す第７の実施形態では、第１，第２のダミー電極指は設けられていない。図８に示すＩＤＴ電極１１では、複数本の第１の電極指４ａと、複数本の第２の電極指５ａとが互いに間挿し合っている。 In the present invention, the first and second dummy electrode fingers are not necessarily provided. In the seventh embodiment shown in FIG. 8, the first and second dummy electrode fingers are not provided. In the IDT electrode 11 shown in FIG. 8, a plurality of first electrode fingers 4a and a plurality of second electrode fingers 5a are interleaved with each other.
　第１の電極指４ａの先端は、円弧状の形状の突出部４ｃを有する。第２のバスバー電極５の突出部４ｃと対向している部分には凹部５ｃが形成されている。凹部５ｃは円弧状の形状を有する。従って、突出部４ｃと凹部５ｃが対向している部分において、第１の実施形態の場合と同様に、非線形歪み信号を抑制することができる。 The tip of the first electrode finger 4a has an arcuate protruding portion 4c. A concave portion 5c is formed in a portion of the second bus bar electrode 5 facing the protruding portion 4c. The recess 5c has an arc shape. Accordingly, the nonlinear distortion signal can be suppressed at the portion where the protrusion 4c and the recess 5c face each other as in the case of the first embodiment.
　なお、第２の電極指５ａも先端に円弧状の突出部５ｄを有する。第１のバスバー電極４の突出部５ｄと対向している位置には凹部４ｄが形成されている。凹部４ｄは、凹部５ｃと同様に円弧状の形状を有する。従って、第２の電極指５ａと第１のバスバー電極４とが対向している対向部においても、非線形歪み信号の発生を抑圧することが可能とされている。 The second electrode finger 5a also has an arcuate protrusion 5d at the tip. A recess 4 d is formed at a position facing the protruding portion 5 d of the first bus bar electrode 4. The concave portion 4d has an arc shape like the concave portion 5c. Therefore, it is possible to suppress the generation of the nonlinear distortion signal even in the facing portion where the second electrode finger 5a and the first bus bar electrode 4 are facing each other.
　第７の実施形態から明らかなように、本発明においては、第１または第２の電極指と対向している電極部分は、ダミー電極指に限らず、バスバー電極４，５のような他の電極部分であってもよい。 As is clear from the seventh embodiment, in the present invention, the electrode portion facing the first or second electrode finger is not limited to the dummy electrode finger, but other bus bars such as the bus bar electrodes 4 and 5. It may be an electrode part.
　なお、上述した実施形態では弾性表面波装置につき説明したが、本発明は、弾性境界波装置などの他の弾性波装置にも適用することができる。 Although the surface acoustic wave device has been described in the above-described embodiment, the present invention can also be applied to other surface acoustic wave devices such as a boundary acoustic wave device.
１…弾性表面波装置
２…圧電基板
２ａ…上面
３…ＩＤＴ電極
４…第１のバスバー電極
４ａ…第１の電極指
４ａ１，４ａ７，４ａ８，４ｄ…凹部
４ａ２，４ａ５，４ａ６，４ｃ…突出部
４ａ３，４ａ４，４ａ９…斜辺
４ｂ…第２のダミー電極指
５…第２のバスバー電極
５ａ…第２の電極指
５ｂ…第１のダミー電極指
５ｂ１…先端部
５ｂ２，５ｂ４，５ｂ５，５ｃ…凹部
５ｂ６，５ｂ７，５ｄ…突出部
５ｂ８…斜辺
１１…ＩＤＴ電極
Ｅ１～Ｅ５…電場ベクトル DESCRIPTION OF SYMBOLS 1 ... Surface acoustic wave apparatus 2 ... Piezoelectric substrate 2a ... Upper surface 3 ... IDT electrode 4 ... 1st bus-bar electrode 4a ... 1st electrode finger 4a1, 4a7, 4a8, 4d ... Recessed part 4a2, 4a5, 4a6, 4c ... Projection part 4a3, 4a4, 4a9 ... hypotenuse 4b ... second dummy electrode finger 5 ... second bus bar electrode 5a ... second electrode finger 5b ... first dummy electrode finger 5b1 ... tip 5b2, 5b4, 5b5, 5c ... concave portion 5b6, 5b7, 5d ... projecting portion 5b8 ... hypotenuse 11 ... IDT electrodes E1-E5 ... electric field vector

Claims (8)

  1. 　圧電基板と、
    　前記圧電基板上に形成されたＩＤＴ電極とを備え、
    　前記ＩＤＴ電極が、第１，第２のバスバー電極と、前記第１のバスバー電極に電気的に接続された複数本の第１の電極指と、前記第２のバスバー電極に接続されており、前記複数本の第１の電極指と互いに間挿し合っている複数本の第２の電極指とを有し、
    　前記第１の電極指及び前記第２の電極指のうちの少なくとも一方の電極指の先端と、該電極指の先端と該電極指の延びる方向において対向しており、かつ該電極指と異なる電位に接続される電極部分が、対向方向中心を通り、かつ該電極指の延びる方向と直交する仮想線に対し、対向し合っている部分間に延びる電場ベクトルが、分極軸の方向に対してずらされている部分を有する形状とされている、弾性波装置。     A piezoelectric substrate;
    An IDT electrode formed on the piezoelectric substrate;
    The IDT electrode is connected to the first and second bus bar electrodes, a plurality of first electrode fingers electrically connected to the first bus bar electrode, and the second bus bar electrode, The plurality of first electrode fingers and a plurality of second electrode fingers interleaved with each other;
    The tip of at least one of the first electrode finger and the second electrode finger is opposed to the tip of the electrode finger in the direction in which the electrode finger extends and is different from the potential of the electrode finger. The electric field vector extending between the opposing portions is shifted with respect to the direction of the polarization axis with respect to a virtual line passing through the center of the opposing direction and perpendicular to the extending direction of the electrode fingers. An elastic wave device having a shape having a portion that is formed.
  2. 　前記電場ベクトルが、前記電極指の延びる方向に対してずらされている部分を有する形状とされている、請求項１に記載の弾性波装置。 The elastic wave device according to claim 1, wherein the electric field vector has a shape having a portion shifted with respect to a direction in which the electrode fingers extend.
  3. 　前記電極指の先端と、該電極指の先端と対向している前記電極部分が対向している部分において、前記仮想線に対し、前記電極指の先端の形状と、該電極指の先端と対向している前記電極部分の形状が非対称である、請求項１または２に記載の弾性波装置。 The shape of the tip of the electrode finger and the tip of the electrode finger are opposed to the virtual line at the portion where the tip of the electrode finger and the electrode portion facing the tip of the electrode finger are facing each other. The elastic wave device according to claim 1, wherein a shape of the electrode portion is asymmetric.
  4. 　前記電極指の先端と、該電極指の先端と対向している前記電極部分のうち、一方が他方に向かって開いた凹部を有し、他方が相手方に向かって突出している突出部を有する、請求項１～３のいずれか１項に記載の弾性波装置。 Of the electrode finger tip and the electrode part facing the tip of the electrode finger, one has a recess that opens toward the other, and the other has a protrusion that protrudes toward the other side, The elastic wave device according to any one of claims 1 to 3.
  5. 　前記電極指の先端と、該電極指の先端と対向している前記電極部分が、互いに嵌り合う関係にある形状を有する、請求項１～４のいずれか１項に記載の弾性波装置。 The elastic wave device according to any one of claims 1 to 4, wherein a tip of the electrode finger and the electrode portion facing the tip of the electrode finger have a shape that fits into each other.
  6. 　前記第２のバスバー電極に一端が接続されている複数本の第１のダミー電極指と、前記第１のバスバー電極に一端が接続されている複数本の第２のダミー電極指をさらに備え、
    　前記電極部分が、前記第１のダミー電極指及び前記第２のダミー電極指のうちの少なくとも一方の先端である、請求項１～５のいずれか１項に記載の弾性波装置。     A plurality of first dummy electrode fingers having one end connected to the second bus bar electrode; and a plurality of second dummy electrode fingers having one end connected to the first bus bar electrode;
    The acoustic wave device according to any one of claims 1 to 5, wherein the electrode portion is a tip of at least one of the first dummy electrode finger and the second dummy electrode finger.
  7. 　前記電極指の先端と、該電極指の先端と対向している前記電極部分が、円弧状の形状を有する、請求項１～６のいずれか１項に記載の弾性波装置。 The elastic wave device according to any one of claims 1 to 6, wherein a tip of the electrode finger and the electrode portion facing the tip of the electrode finger have an arc shape.
  8. 　前記電極指の先端と、該電極指の先端と対向している前記電極部分が、それぞれ、相手方に向かって突出している複数個の突出部を有する形状とされている、請求項１～６のいずれか１項に記載の弾性波装置。 The tip of the electrode finger and the electrode portion facing the tip of the electrode finger are each shaped to have a plurality of projecting portions projecting toward the other side. The elastic wave apparatus of any one of Claims.
PCT/JP2014/068025 2013-07-08 2014-07-07 Elastic wave apparatus WO2015005267A1 (en)

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JP2019021997A (en) * 2017-07-12 2019-02-07 京セラ株式会社 Acoustic wave element, splitter, and communication device
JP6994855B2 (en) 2017-07-12 2022-01-14 京セラ株式会社 Elastic wave elements, demultiplexers and communication devices
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CN116938183A (en) * 2023-09-13 2023-10-24 锐石创芯(深圳)科技股份有限公司 Elastic filter device, multiplexer and RF front-end module
CN116938183B (en) * 2023-09-13 2024-01-09 锐石创芯(深圳)科技股份有限公司 Elastic filter device, multiplexer and RF front-end module

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