JP2018137517A - Surface acoustic wave resonator, demultiplexer and communication apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface acoustic wave filter, characteristics of which are improved.SOLUTION: A SAW resonator 1 has a board 3, and an IDT electrode 5 and a pair of reflectors 7 placed on the upper surface of the board 3. At least one of multiple strip electrodes 19 of a reflector 7 and electrode fingers 13 at the end 5e of the IDT electrode 5 are thicker than the electrode finger 13 in the central part 5a of the IDT electrode 5. At least one of the following facts holds that the pitch pof the multiple strip electrodes 19 is smaller than the pitch pof the electrode finger 13 in the central part 5a, the gap Gbetween a pair of reflectors 7 and the IDT electrode 5 is smaller than the gap Gbetween the electrode fingers 13 in the central part 5a, the pitch pof the electrode fingers 13 at the end 5e is smaller than the pitch pof the electrode fingers 13 in the central part 5a, and the gap Gbetween the electrode fingers 13 at the end 5e and the electrode fingers 13 in the central part 5a is smaller than the gap Gbetween the electrode fingers 13 in the central part 5a.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a resonator using a surface acoustic wave (SAW), a duplexer including the resonator, and a communication device.

  A surface acoustic wave resonator (SAW resonator) includes, for example, a piezoelectric substrate, an IDT (InterDigital Transducer) electrode positioned on the piezoelectric substrate, and a pair of reflectors (reflection) positioned on both sides of the IDT electrode on the piezoelectric substrate. Electrode). Patent Document 1 discloses that the thickness of the reflector is made larger than the thickness of the IDT electrode.

JP-A-10-209804

  It is desired to provide a surface acoustic wave resonator, a duplexer, and a communication device that can improve characteristics.

A surface acoustic wave resonator according to an aspect of the present disclosure includes a substrate that is a rotated Y-cut LiTaO ₃ plate and a plurality of electrode fingers that are positioned on the upper surface of the substrate and arranged in the propagation direction of the surface acoustic wave. A pair of reflectors having a plurality of strip electrodes arranged on both sides of the propagation direction with respect to the IDT electrode on the upper surface of the substrate and arranged in the propagation direction; And at least one of the plurality of strip electrodes and the electrode fingers on both ends of the IDT electrode has a thicker film part thicker than the electrode fingers on the center side of the IDT electrode, The gap between the pair of reflectors and the IDT electrode is smaller than the gap between the pair of reflectors and the IDT electrodes. Electrode finger At least a pitch between the electrode fingers on the central side and a gap between the electrode fingers on both ends and the central electrode finger is smaller than a gap between the electrode fingers on the central side Either one holds.

  For example, the thickness of the thick film portion is 1.5 times or less the thickness of the electrode finger on the center side.

  For example, at least one of the gap between the pair of reflectors and the IDT electrode and the gap between the electrode fingers on both ends and the central electrode finger is between the electrode fingers on the central side. It is 0.7 times or more and less than 1 time of the gap.

  For example, at least one of the pitch of the plurality of strip electrodes and the pitch of the electrode fingers on both ends is 0.9 times or more and less than 1 times the pitch of the electrode fingers on the center side.

  For example, both the plurality of strip electrodes and the electrode fingers on both end sides of the IDT electrode have the thick film portion.

  For example, the surface acoustic wave resonator includes a first metal layer located on the upper surface of the substrate and a second metal layer located on the first metal layer and made of a material different from that of the first metal layer. And the same material as the first metal layer, the third metal layer located on the second metal layer, and the same material as the second metal layer, on the third metal layer A fourth metal layer that is positioned, the electrode finger on the center side is constituted by the first and second metal layers, and the thick film portion includes the first to fourth layers. It is comprised by the metal layer.

  For example, the plurality of strip electrodes have the thick film portion, and the pair of reflectors have the same thickness as the thick film portion connecting ends of the plurality of strip electrodes. It also has a bus bar.

  For example, the electrode finger on the end side has the thick film portion, and the IDT electrode further has a bus bar connecting ends of the plurality of electrode fingers, and the IDT The bus bar of the electrode has a thickness equivalent to that of the thick film portion at a portion connecting the end portions of the electrode fingers on the end side.

  A duplexer according to an aspect of the present disclosure includes an antenna terminal, a transmission filter that filters a transmission signal and outputs the filtered signal to the antenna terminal, and a reception filter that filters a reception signal from the antenna terminal. At least one of the transmission filter and the reception filter includes the surface acoustic wave resonator described above.

  A communication apparatus according to an aspect of the present disclosure includes an antenna, the duplexer in which the antenna terminal is connected to the antenna, and an IC connected to the transmission filter and the reception filter. ing.

  According to said structure, a characteristic can be improved.

It is a typical perspective view which shows the structure of a SAW resonator. 2A is a cross-sectional view taken along line IIa-IIa in FIG. 1, and FIG. 2B is an enlarged view of region IIb in FIG. FIG. 3A is a diagram illustrating the frequency characteristics of the SAW resonator according to the comparative example and the example, and FIGS. 3B and 3C are diagrams for explaining the operation of the SAW resonator according to the example. FIG. It is a figure which shows the frequency characteristic of the SAW resonator which concerns on a comparative example and an Example. It is a figure which shows the frequency characteristic of the SAW resonator which concerns on a comparative example and an Example. 6A is a diagram illustrating frequency characteristics of the SAW resonators according to the comparative example and the example, and FIGS. 6B to 6D are enlarged views of regions VIb to VId in FIG. 6A. It is. It is a graph which shows the example of the combination of the parameter which a characteristic improves. It is a figure which shows the relationship between the thickness of a reflector, and the gap between an IDT electrode and a reflector in an Example. FIG. 9A is a diagram showing the relationship between the gap between the IDT electrode and the reflector and the pitch of the reflector in the embodiment, and FIG. 9B is the center portion and end portion of the IDT electrode in the embodiment. It is a figure which shows the relationship between the gap between these, and the pitch of the edge part of an IDT electrode. In an Example, it is a figure which shows the relationship between the thickness of a reflector, and the gap between the center part of an IDT electrode, and an edge part. It is a figure which shows the relationship between the gap between a reflector and an IDT electrode in an Example, and the gap between the center part and edge part of an IDT electrode. It is a schematic diagram which shows the duplexer as an example of use of a SAW resonator. It is a block diagram which shows the principal part of the communication apparatus as an example of utilization of a SAW resonator.

  Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the drawings used in the following description are schematic, and the dimensional ratios and the like on the drawings do not necessarily match the actual ones.

(Basic configuration of SAW resonator)
FIG. 1 is a schematic perspective view showing the configuration of the SAW resonator 1.

  The SAW resonator 1 may be either upward or downward, but in the following description, for convenience, an orthogonal coordinate system including a D1 axis, a D2 axis, and a D3 axis is defined, and D3 A word such as a top surface is sometimes used with the positive side of the axis as the upper side. The D1 axis is defined to be parallel to the propagation direction of SAW propagating along the upper surface (usually the widest surface (main surface)) of the substrate 3 described later, and the D2 axis is defined on the upper surface of the substrate 3. It is defined to be parallel and orthogonal to the D1 axis, and the D3 axis is defined to be orthogonal to the upper surface of the substrate 3.

  The SAW resonator 1 constitutes a so-called 1-port SAW resonator. For example, when an electric signal having a predetermined frequency is input from one of the first terminal 31A and the second terminal 31B schematically shown, resonance occurs. The signal causing the resonance is output from the other of the first terminal 31A and the second terminal 31B.

  Such a SAW resonator 1 includes, for example, a substrate 3 and an electrode portion located on the substrate 3. The electrode part is composed of a layered conductor (for example, metal) provided on the substrate 3, and has an IDT electrode 5 and a pair of reflectors 7 positioned on both sides of the IDT electrode 5.

  FIG. 1 schematically shows the main part to the last, and the SAW resonator 1 may have appropriate components in addition to the above. The SAW resonator 1 may be of a so-called wafer level package in which a cover that constitutes a space is placed on the substrate 3 on the IDT electrode 5 and the reflector 7, or may be mounted on another circuit board. It may be mounted with the upper surface of the substrate 3 facing each other through a space.

The substrate 3 is a piezoelectric substrate and is made of, for example, a single crystal having piezoelectricity. The single crystal is, for example, a lithium tantalate (LiTaO ₃ ) single crystal. The cut angle may be appropriately set according to the type of SAW used. For example, the substrate 3 has a rotational Y-cut X propagation. That is, the X axis is parallel to the upper surface (D1 axis) of the substrate 3, and the Y axis is inclined at a predetermined angle with respect to the normal line of the upper surface of the substrate 3. The predetermined angle is, for example, 42 ° ± 10 °. In addition, the board | substrate 3 may be formed comparatively thinly, and the support substrate which consists of an inorganic material or an organic material may be bonded together by the back surface (D3 axis | shaft negative surface).

  The IDT electrode 5 has a pair of comb electrodes 9. Each comb-tooth electrode 9 has a bus bar 11, a plurality of electrode fingers 13 extending in parallel with each other from the bus bar 11, and a plurality of dummy electrodes 15 protruding from the bus bar 11 between the plurality of electrode fingers 13. . The pair of comb electrodes 9 are arranged so that the plurality of electrode fingers 13 are engaged with each other (intersect). That is, the two bus bars 11 of the pair of comb-teeth electrodes 9 are arranged to face each other, and the electrode finger 13 of one comb-teeth electrode 9 and the electrode finger 13 of the other comb-teeth electrode 9 are arranged in the width direction. They are basically arranged alternately. Further, the tips of the plurality of dummy electrodes 15 of the one comb-tooth electrode 9 are opposed to the tips of the electrode fingers 13 of the other comb-tooth electrode 9.

  For example, the bus bar 11 is formed in a long shape having a substantially constant width and extending linearly in the SAW propagation direction (D1 axis direction). The pair of bus bars 11 oppose each other in a direction (D2 axis direction) orthogonal to the SAW propagation direction. The bus bar 11 may have a varying width or may be inclined with respect to the SAW propagation direction.

  Each electrode finger 13 is formed in a long shape extending in a straight line in a direction (D2 axis direction) orthogonal to the SAW propagation direction with a substantially constant width, for example. For example, the plurality of electrode fingers 13 are arranged in the SAW propagation direction and have the same length. The IDT electrode 5 may be subjected to so-called apodization in which the lengths of the plurality of electrode fingers 13 (crossing width in another viewpoint) change according to the position in the propagation direction.

  The number of electrode fingers 13 may be appropriately set according to the electrical characteristics required for the SAW resonator 1. Since FIG. 1 and the like are schematic diagrams, the number of electrode fingers 13 is small. Actually, more (for example, 50 or more) electrode fingers 13 than shown may be arranged.

The pitch of the plurality of electrode fingers 13 (electrode finger pitch, see p _{0 in} FIG. 2A) is, for example, substantially constant over the entire IDT electrode 5. However, as will be described later, in this embodiment, some pitches may be made smaller than most pitches. The pitch is basically half (p ₀ = λ / 2) of the wavelength λ of the SAW having the same frequency as the frequency to be resonated among the SAWs propagating on the substrate 3.

  For example, the plurality of dummy electrodes 15 project linearly in a direction (D2 axis direction) perpendicular to the SAW propagation direction with a substantially constant width. The gap between the tip and the tips of the plurality of electrode fingers 13 is, for example, the same among the plurality of dummy electrodes 15. The plurality of dummy electrodes 15 have the same width, number and pitch as the plurality of electrode fingers 13. The width of the dummy electrode 15 may be different from that of the electrode finger 13. The IDT electrode 5 may not have the dummy electrode 15.

  The reflector 7 is formed in a lattice shape, for example. That is, the reflector 7 includes a pair of bus bars 17 facing each other and a plurality of strip electrodes 19 extending between the pair of bus bars 17.

  The shape and the like of the bus bar 17 and the strip electrode 19 may be the same as the bus bar 11 and the electrode finger 13 of the IDT electrode 5 except that both ends of the strip electrode 19 are connected to a pair of bus bars 17.

  For example, the pair of bus bars 17 are formed in an elongated shape having a substantially constant width and linearly extending in the SAW propagation direction (D1 axis direction), and are opposed to each other in a direction intersecting the SAW propagation direction. Yes. The plurality of strip electrodes 19 are formed in an elongated shape extending in a straight line in a direction (D2 axis direction) perpendicular to the SAW propagation direction with a substantially constant width, and are arranged at a constant pitch in the SAW propagation direction. ing. The pair of bus bars 17 may be inclined with respect to the SAW propagation direction, and the distance between the pair of bus bars 17 (the length of the strip electrode 19) depends on the position of the SAW propagation direction. And may change.

  The width and pitch of the plurality of strip electrodes 19 are equal to, for example, the width and pitch of the plurality of electrode fingers 13 (most of them). However, as will be described later, in the present embodiment, the pitch of the plurality of strip electrodes 19 may be made smaller than the pitch of the plurality of electrode fingers 13.

  The number of strip electrodes 19 is set so that, for example, the reflectance of SAW in a mode intended for use is approximately 100% or more. The theoretical minimum necessary number is, for example, about several to ten, and is usually set to 20 or more or 30 or more with a margin.

  The pair of reflectors 7 are adjacent to both sides of the IDT electrode 5 in the SAW propagation direction, for example. Therefore, the plurality of strip electrodes 19 are arranged following the arrangement of the plurality of electrode fingers 13. The pitch between the strip electrode 19 and the electrode finger 13 that are adjacent to each other between the reflector 7 and the IDT electrode 5 is, for example, the same as the pitch of the electrode fingers 13 (most of them). However, as will be described later, in the present embodiment, this pitch may be smaller than the pitch of the plurality of electrode fingers 13.

Although not particularly illustrated, the upper surface of the substrate 3 may be covered with a protective film made of SiO ₂ or the like from above the IDT electrode 5 and the reflector 7. The protective film may be merely for suppressing corrosion of the IDT electrode 5 or the like, or may contribute to temperature compensation. Further, when a protective film is provided, an additional film made of an insulator or metal may be provided on the upper or lower surface of the IDT electrode 5 and the reflector 7 in order to improve the SAW reflection coefficient.

  When a voltage is applied to the pair of comb electrodes 9, a voltage is applied to the substrate 3 by the electrode fingers 13, and a SAW in a predetermined mode propagating in the D1 axis direction along the upper surface is excited near the upper surface of the substrate 3. Is done. The excited SAW is mechanically reflected by the electrode fingers 13. As a result, a standing wave having a half wavelength of the pitch of the electrode fingers 13 is formed. The standing wave is converted into an electric signal having the same frequency as that of the standing wave, and is taken out by the electrode finger 13. In this way, the SAW resonator 1 functions as a resonator. The resonance frequency is substantially the same as the SAW frequency propagating on the substrate 3 with the electrode finger pitch as a half wavelength.

  The SAW excited at the IDT electrode 5 is mechanically reflected by the strip electrode 19 of the reflector 7. Further, since the adjacent strip electrodes 19 are connected to each other by the bus bar 17, the SAW from the IDT electrode 5 is also electrically reflected by the strip electrode 19. Thereby, the divergence of SAW is suppressed, the standing wave in the IDT electrode 5 stands strongly, and the function of the SAW resonator 1 as a resonator is improved.

(Thick film part)
In general, the thickness of the IDT electrode 5 and the pair of reflectors 7 is constant over the whole. In the present embodiment, the end portion 5e of the IDT electrode 5 in the D1 axis direction and at least one of the reflectors 7 (both in FIG. 1) are formed thicker than the central portion 5a of the IDT electrode 5 in the D1 axis direction. Yes.

  In other words, at least one of the electrode finger 13 and the strip electrode 19 at the end 5e has a thicker film portion (reference numeral omitted) than the electrode finger 13 at the central portion 5a. When the electrode finger 13 at the end 5e has a thick film portion, the bus bar 11 of the IDT electrode 5 has a thickness equivalent to that of the thick film portion, for example, at a portion where the electrode finger 13 at the end 5e is connected. ing. In the case where the strip electrode 19 has a thick film portion, the bus bar 17 of the reflector 7 has a thickness equivalent to the thick film portion, for example.

The thickness of the thick portion (see _{t e} and _{t r} in FIG. 2 (b)), the thickness of the central portion 5a (the majority of the IDT electrode 5 in another aspect) (see _{t 0} shown in FIG. 2 (b) ) May be set appropriately. For example, the former is more than 1 time and less than 1.5 times the latter. The thickness t ₀ of the central portion 5a, for example, is set as the excitation efficiency of the SAW is highest. For example, the normalized thickness t _e / 2p ₀ obtained by normalizing the thickness t ₀ with the pitch p ₀ of the central portion 5a is 0.07 or more and 0.1 or less in the case of an electrode using Al or an Al alloy.

  The number of electrode fingers 13 at one end 5e may be set as appropriate, but is, for example, 5 or more and 10 or less. Since FIG. 1 and the like are schematic diagrams, the number of electrode fingers 13 at the end portion 5e is shown to be smaller than that in the above example.

(Pitch and gap)
2A is a cross-sectional view taken along line IIa-IIa in FIG.

As shown in this figure, the pitch of the electrode fingers 13 in the central portion 5a of the IDT electrode 5 and p _0, the pitch of the electrode fingers 13 in the end portion 5e and p _e, the pitch of the strip electrodes 19 in the reflector 7 p _{Let r} . These pitches are distances between the centers of the adjacent electrode fingers 13 or adjacent strip electrodes 19. Also, the size of the gap between the electrode fingers 13 and G ₀ in the central portion 5a, the size of the gap between the electrode fingers 13 and electrode fingers 13 of the end portion 5e of the central portion 5a and G _e, IDT electrodes 5 between the electrode fingers 13 the size of the gap between the strip electrode 19 of the reflector 7 and G _r. The size of these gaps is the distance between the edges of adjacent electrode fingers 13 or strip electrodes 19. For convenience, the size of the gap may be abbreviated as a gap.

In general, the pitches p ₀ and p _e of the electrode fingers 13 are constant over the entire IDT electrode 5. As a result, in general, the gaps G ₀ and G _e of the electrode fingers 13 are constant over the entire IDT electrode 5. In general, the pitch _{p r} of the reflector 7 is equal to the pitch _{p 0} and _{p e} of the electrode fingers 13. In general, the pitch between the electrode fingers 13 and the strip electrodes 19 adjacent (not numbered) is equal to the pitch p ₀ and p _e of the electrode fingers 13. As a result, the gap G _r between the IDT electrode 5 and the reflector 7 is equal to the gaps G ₀ and G _e of the electrode finger 13.

However, in the present embodiment, the pitch and / or the gap are set so that at least one of the following holds. Pitch _{p e} at the end portion 5e is smaller than the pitch _{p 0} in the central portion 5a. Gap _{G e} between the central portion 5a and the end portion 5e is smaller than the gap _{G 0} between the electrode fingers 13 in the central portion 5a. Pitch _{p r} in reflector 7 is smaller than the pitch _{p 0} in the central portion 5a. Gap _{G r} between the IDT electrode 5 and the reflector 7 is smaller than the gap _{G 0} between the electrode fingers 13 in the central portion 5a.

More specifically, for example, the gap G _e and / or the gap G _r is 0.7 times or more and less than 1 time of the gap G ₀ . Pitch _{p e} and / or pitch _{p r} is, for example, less than 1 times 0.9 times the pitch _{p 0.}

Note that the pitch p ₀ of the central portion 5a (most part of the IDT electrode 5) is the basic size already mentioned. That is, the pitch p ₀ is half (p ₀ = λ / 2) of the SAW wavelength λ having a frequency equivalent to the frequency to be resonated among the SAWs propagating on the substrate 3. However, the IDT electrode 5 may be provided with a narrow pitch portion or a wide pitch portion in a part of the plurality of electrode fingers 13 in order to improve or finely adjust the characteristics. Further, the appropriate number (for example, three) of the electrode fingers 13 of the pair of comb electrodes 9 arranged alternately is eliminated, or the width or arrangement of the electrode fingers 13 substantially equivalent to this is changed. So-called thinning may be performed. In specifying the pitch p ₀ of the central portion 5a, such a unique portion pitch is excluded. In the case where the pitch p ₀ varies within the minute range over the entire central portion 5a, the average value may be used.

Further, the gap _{G 0} of the central portion 5a has a width w of the pitch _{p 0} and the electrode finger 13 (in another aspect duty (w _{/ p} 0)) is determined by the. For example, the width w is constant for the IDT electrode 5 and the reflector 7 as a whole. For example, the duty of the central portion 5a is set so that the SAW excitation efficiency is the highest. For example, the duty is 0.4 or more and 0.6 or less.

(Thick film part material)
FIG. 2B is an enlarged view of region IIb (two places) in FIG.

  The SAW resonator 1 includes, for example, a first conductive layer 21A, a second conductive layer 21B, a third conductive layer 21C, and a fourth conductive layer 21D, which are sequentially stacked on the substrate 3. A portion of the IDT electrode 5 and the reflector 7 that is not a thick film portion (the whole central portion 5a in the illustrated example) is constituted by the first conductive layer 21A and the second conductive layer 21B among these four layers. On the other hand, the thick film portion (the entire end portion 5e and the entire reflector 7 in the illustrated example) is composed of these four layers.

  The combination of the material of the first conductive layer 21A and the material of the second conductive layer 21B and the combination of the material of the third conductive layer 21C and the material of the fourth conductive layer 21D are, for example, the same. For example, the material of the first conductive layer 21A and the third conductive layer 21C is titanium (Ti). The material of the second conductive layer 21B and the fourth conductive layer 21D is aluminum (Al) or an Al alloy. The Al alloy is, for example, an Al—Cu alloy.

For example, the first conductive layer 21A is thinner than the second conductive layer 21B. For example, the thickness of the first conductive layer 21A is 5% or less of the total thickness (t ₀ ) of the first conductive layer 21A and the second conductive layer 21B. The thickness of the third conductive layer 21C is, for example, equal to the thickness of the first conductive layer 21A. The thickness of the fourth conductive layer 21D is, for example, the desired thickness for the thick portion in the thickness of the first conductive layer 21A~ third conductive layer 21C, which is set as described above (t _e and / or t _r ).

(Example of action)
About the SAW resonator which concerns on a comparative example and an Example, the simulation calculation was performed and the characteristic was investigated. Hereinafter, the operation of the above-described configuration (a combination of the thick film portion and pitch or gap reduction) will be described with reference to an example of the calculation result.

FIG. 3A is a diagram illustrating frequency characteristics of the SAW resonators according to the comparative example and the example. In this figure, the horizontal axis represents frequency and the vertical axis represents impedance phase. The simulation used the finite element method (FEM), and the parameters of the basic model were as follows.
· The number of SAW resonator 1 child of electrode fingers 13: the number of 150 present-reflectors 7 of the strip electrodes 19: 20 This electrode fingers 13: material Al, thickness t0 = 0.16um, the pitch _p 0 = 1um, Duty ratio 0.5
Reflector 7: Material Al, Duty ratio 0.5

A line L1 indicates the characteristics of a normal SAW resonator (comparative example; hereinafter, sometimes referred to as “normal resonator”). Normal resonator here, the thickness of the IDT electrode 5 and the reflector 7 _(t 0, _{t e} and _{t r)} is constant throughout these electrodes, the pitch of the electrode fingers 13 and strip electrode 19 ( p ₀ , p _e and p _r ) are constant over the entire IDT electrode 5 and reflector 7 (and thus G ₀ , G _e and G _r are the same).

A line L2 indicates the characteristics of the resonator according to another comparative example. Comparative Example line L2 is only in that the thickness _{t r} of the reflector 7 was thicker than the thickness of the IDT electrode 5 _{(t 0} and _{t e)} is different from the normal resonator (line L1). From another viewpoint, in the comparative example of the line L2, the reflector 7 is thicker than that of the normal resonator. In the simulation, _tr / t ₀ = 1.25.

A line L3 indicates the characteristics of the resonator according to the example. Example of the line L3 is only in that the pitch p _r of the reflector 7 is narrower than the pitch p ₀ of the central portion 5a is different from the comparative example of line L2. From another point of view, in the embodiment of the line L3, the reflector 7 is thicker and the pitch _pr is narrower than that of the normal resonator (line L1). In the simulation, p _r / p ₀ = 0.98.

  As indicated by lines L1 to L3, in the range from the vicinity of the resonance frequency (about 1980 MHz) to the vicinity of the anti-resonance frequency (about 2050 MHz), the phase of the impedance is about 90 °, and in the frequency range outside the resonance frequency, The phase of the impedance is about −90 °. In the following description, the low frequency side in the range where the impedance phase is about 90 ° may be referred to as the resonance side, and the high frequency side in the above range may be referred to as the anti-resonance side.

  As indicated by the line L1, in the normal resonator, a ripple is generated on the resonance side (region Ar1), and a ripple is also generated on the antiresonance side (region Ar2). On the other hand, when the reflector 7 is made thicker than the IDT electrode 5 as indicated by the line L2, the characteristic on the resonance side of the normal resonator (line L1) is improved. That is, the ripple in the region Ar1 is reduced and the phase is approaching −90 °. This indicates that the electrical loss is reduced in this region. However, the characteristic on the antiresonance side is equivalent to that of a normal resonator.

Then, as indicated by line L3, when the reflector 7 thicker than the IDT electrode 5, and the pitch p _r of the reflector 7 narrower than the pitch p ₀ of the IDT electrode 5, the resonance side and antiresonant On both sides, the characteristics are improved over the normal resonator (line L1). That is, the ripple in the region Ar2 becomes smaller and the phase approaches −90 °. This indicates that the electrical loss is reduced in this region. Further, not only the region Ar2, but also the electrical loss in the frequency region from the region Ar2 to anti-resonance is reduced. However, in the illustrated example, the improvement amount of the characteristic on the resonance side is lower than that of the comparative example of the line L2.

  FIG. 3B and FIG. 3C are schematic diagrams for explaining the reason why the characteristics are improved as described above. In these drawings, the horizontal axis f indicates the frequency, and the vertical axis | Z | indicates the absolute value of the impedance.

  A line L5 indicates the relationship between the frequency and the absolute value of the impedance in the SAW resonator (for example, a normal resonator). In the SAW resonator, the absolute value of the impedance has a minimum value at the resonance frequency (resonance point P1), and a maximum value at the antiresonance frequency (antiresonance point P2).

  A line L6 indicates the operating range (stop band) of the reflector 7 in the normal resonator. In a normal resonator, the lower end (end on the low frequency side) of the operating range matches the resonance frequency. In the normal resonator, the upper end (end on the high frequency side) of the operating range is higher than, for example, the antiresonance frequency.

  Since the lower end of the operating range of the reflector 7 coincides with the resonance frequency, the effect of confining the SAW is lowered on the lower frequency side than the resonance frequency. Further, SAW other than the mode to be used occurs in the reflector 7. As a result, ripples occur on the low frequency side. Further, due to a mismatch between the IDT electrode 5 and the reflector 7, back scattering BAW (Bulk Acoustic Wave) that is suppressed in an ideal (a uniform IDT electrode 5 having an infinite period) is generated. As a result, a ripple occurs near the antiresonance frequency or at the upper end of the operating range of the reflector 7.

  Here, when the reflector 7 is thickened, as shown by a line L7 in FIG. 3B, the width of the operation range is widened to the low frequency side. That is, the lower end of the operating range of the reflector 7 is lower than the resonance frequency of the IDT electrode 5. As a result, as shown by line L2 in FIG. 3A, the generation of ripples on the resonance side is reduced.

Furthermore, reducing the pitch p _r of the reflector 7, as shown by line L8 in FIG. 3 (c), the operating range of the reflector 7 moves to the higher frequency side. As a result, the spurious on the antiresonance side is reduced as indicated by the line L3 in FIG. At this time, while moving the operating range of the reflector 7 to the high frequency side, the lower end of the operating range of the reflector 7 is kept lower than the resonance frequency of the IDT electrode 5, compared to a normal resonator, The generation of ripple on the resonance side is also reduced.

By thus configuration as to reduce the pitch p _r structure and reflector 7 to thicken the reflector 7 are combined, the high frequency of extension and the operating range of the low-frequency side of the operating range of the reflector 7 This is combined with the movement to the side, and thus the characteristics are improved on both the resonance side and the anti-resonance side. Naturally, when the pitch _pr is reduced without increasing the thickness of the reflector 7, the resonance-side characteristics deteriorate. Therefore, the configuration in which the pitch _pr is decreased is combined with the configuration in which the reflector 7 is increased in thickness. This is the first effective configuration for improving the characteristics.

  FIG. 4 is a view similar to FIG. 3A showing the frequency characteristics of the SAW resonators according to the comparative example and other examples. The line L1 in this figure is the same as the line L1 in FIG.

A line L11 indicates the characteristics of the resonator according to the comparative example. Comparative Example line L11 is only in that gap G _r between the IDT electrode 5 and the reflectors 7 are narrower than the gap G ₀ of the IDT electrode 5 is different from the normal resonator. From another viewpoint, the gap _Gr is narrower in the comparative example of the line L11 than in the normal resonator (line L1). Note that G _r / G ₀ = 0.8.

A line L12 indicates the characteristics of the resonator according to the example. Example of the line L12 is, only in that the thickness _{t r} of the reflector 7 was thicker than the thickness of the IDT electrode 5 _{(t 0} and _{t e)} is different from the comparative example of line L11. From another point of view, in the embodiment of the line L12, the reflector 7 is thicker and the gap _Gr is narrower than that of the normal resonator (line L1). Note that G _r / G ₀ = 0.8.

A line L13 indicates the characteristics of the resonator according to another embodiment. Example of the line L13 is, only in that the pitch _{p r} of the reflector 7 is narrower than the pitch of the IDT electrode 5 _{(p 0} and _{p e)} differs from the embodiment of the line L12. From another point of view, in the embodiment of the line L13, the reflector 7 is thickened, the gap _Gr is narrowed, and the pitch _pr is narrowed compared to the normal resonator (line L1). Note that P _r / P ₀ = 0.98 and G _r / G ₀ = 0.8.

As shown by line L11, when narrowing the gap G _r between the IDT electrode 5 and the reflector 7, usually compared with the resonator (the line L1), the characteristics of the antiresonant side is improved. This is because, for example, the mismatch between the IDT electrode 5 and the reflector 7 is reduced, and the occurrence of backscattering BAW is reduced. However, on the other hand, in the comparative example of the line L11, the characteristic is degraded on the resonance side. That is, the resonance frequency moves to the high frequency side, the frequency difference (Δf) between resonance and antiresonance is reduced, and a large ripple is generated on the resonance side. This is because, for example, the operating range of the reflector 7 has moved to the high frequency side by narrowing the gap _Gr .

As shown by line L12, the reflector 7 thicker than the IDT electrode 5, and is narrower than the gap _{G 0} of the IDT electrode 5 a gap _{G r} between the IDT electrode 5 and the reflector 7, On both the resonance side and the anti-resonance side, the characteristics are improved as compared with the normal resonator (line L1). The characteristic improvement amount on the anti-resonance side in the example of the line L12 is obtained to the same extent as the characteristic improvement amount on the anti-resonance side in the comparative example of the line L11. The reason why the characteristic on the resonance side is improved in the embodiment of the line L12 is the same as the reason described with reference to FIG.

As it is shown by line L13, a reflector 7 thicker than the IDT electrode 5, and narrower than the gap _{G 0} of the IDT electrode 5 a gap _{G r} between the IDT electrode 5 and the reflector 7, and When the pitch p _r of the reflector 7 made narrower than the pitch p ₀ of the IDT electrode 5, in both the resonant side and the anti-resonant side characteristics are improved over comparative example of a line L11. Note that the reason why the characteristics on the resonance side improve in the example of the line L13 as compared with the comparative example of the line L11 is the same as the reason described with reference to FIG. Although the example of the line L13 is smaller than the comparative example of L11, a large ripple is still generated on the resonance side, and the characteristic on the resonance side is deteriorated as compared with the normal resonator (line L1). It is also possible to improve the resonance-side characteristics as compared with a normal resonator by making the reflector 7 thicker.

  FIG. 5 is a diagram similar to FIG. 3A showing the frequency characteristics of the SAW resonators according to the comparative example and other examples. Lines L1 and L11 in this figure are the same as lines L1 and L11 in FIG.

A line L15 indicates the characteristics of the resonator according to the comparative example. Comparative Example line L15 is, only in that the thickness _{t e} of the end portion 5e of the IDT electrode 5 was thicker than the thickness _{t 0} of the central portion 5a is different from the normal resonator (line L1). In another aspect, a comparative example of line L15, compared with the normal resonator, the thickness t _e is thicker. The edge part 5e was made into 5 electrode fingers of both ends of the electrode finger.

A line L16 indicates characteristics of the resonator according to the example. Example of the line L16 is, only in that the pitch _{p e} of the end 5e of the IDT electrode 5 is narrower than the pitch _{p 0} of the central portion 5a is different from the comparative example of line L15. In another aspect, embodiments of the line L16, compared with the normal resonator (line L1), the thickness t _e is thicker, the pitch p _e is narrow. In the simulation, p _e / p ₀ = 0.98.

  As shown by the line L15, when the end portion 5e of the IDT electrode 5 is thickened, for example, characteristics are improved on both the resonance side and the antiresonance side as compared with the normal resonator (line L1). This is because, for example, by increasing the thickness of the end portion 5e, the reflection band at the end portion 5e moves to the low frequency side, and the same effect as when the reflector 7 is brought closer to the end portion 5e is produced. It is.

As shown by line L16, the thickened end portion 5e of the IDT electrode 5, and to narrow the pitch p _e of the end portion 5e, usually compared with the resonator (the line L1), characteristics in antiresonance side On the other hand, on the resonance side, there is no deterioration in characteristics. More specifically, the anti-resonance side characteristic improvement amount is higher than that of the comparative example of the line L15 and lower than that of the comparative example of the line L11. Further, the resonance side has improved characteristics as compared with the comparative example of the line L11. The reason for such an action is the same as the reason described with reference to FIGS. 3B and 3C, for example.

  FIG. 6A is a diagram similar to FIG. 3A showing the frequency characteristics of the SAW resonators according to the comparative example and other examples. FIGS. 6B, 6C, and 6D are enlarged views of regions VIb, VIc, and VId of FIG. 6A. Lines L1 and L11 in these figures are the same as lines L1 and L11 in FIG.

A line L21 indicates the characteristic of the resonator according to the example. Example of the line L21, the comparison of only the point that thicker than the thickness _{t 0} of the thickness _{t e} of the end portion 5e of the thickness _{t r} and the IDT electrode 5 of the reflector 7 central portion 5a the line L11 Different from the example. In another aspect, embodiments of the line L21, compared with the normal resonator, the thickness t _r and t _e are thick and the gap G _r between the IDT electrode 5 and the reflector 7 is narrower Yes. Incidentally, it was _{t r / t 0 = t e} / t 0 = 1.25, the end portion 5e is the electrode finger across the electrode fingers 5 duty in the simulation. In addition, G _r / G ₀ = 0.8.

A line L22 indicates characteristics of the resonator according to another embodiment. Example of the line L22 is (which is equivalent to the line L21) reflectors 7 of the thickness _{t r} and the thickness _{t e} of the end portion 5e of the IDT electrode 5 thicker than the thickness _{t 0} of the central portion 5a, and only in that the pitch p _e of the pitch p _r and the end portion 5e of the reflector 7 is narrower than the pitch p ₀ of the central portion 5a is different from the normal resonator (line L1). In another aspect, embodiments of the line L22, compared with the normal resonator, the thickness t _r and t _e are thick and the pitch p _r and the pitch p _e is narrow.

In any of the embodiments of the line L21 and the line L22, the characteristics are improved on both the resonance side and the antiresonance side as compared with the normal resonator. Also, in each of the examples, on the anti-resonance side, an improvement effect equivalent to that of the comparative example of the line L11 can be obtained, and on the resonance side, the characteristics are improved as compared with the comparative example of the line L11. Yes. Thus, by combining structure and to increase the thickness t _r of the reflector 7, the structure and to increase the thickness t _e of the end portion 5e of the IDT electrode 5, the characteristics in both the resonant side and the anti-resonant side Can be greatly improved.

(Example of combinations with improved characteristics)
7, the thickness _{t r} and _{t e,} the gap _{G r} and _{G e} and pitch _{p r} and _{p e,} graphically showing an example of a combination of characteristics of the SAW resonator 1 is improved (Examples 1 to 20) is there. This combination is obtained by simulation calculation.

Conditions common to the embodiment shown in FIG. 7 are as follows.
Substrate 3:
Material: LiTaO ₃ single crystal Crystal orientation: 42 ° rotated Y plate IDT electrode 5 and reflector 7:
First conductive layer 21A:
Material: Ti
Thickness: 6nm
Second conductive layer 21B:
Material: Al-Cu alloy Thickness: 115nm
Third conductive layer 21C:
Material: Ti
Thickness: 6nm
Fourth conductive layer 21D:
Materials: Al-Cu alloy thickness: _t varies in accordance with the _r and / or _{t e} pitch _p 0: 1.00 .mu.m
Duty: 0.5

  The number of electrode fingers 13 at one end 5e of the IDT electrode 5 is 5 in Examples 4 to 7 (a total of 10 at both ends 5e), and 10 in the other examples (a total of 20 at both ends 5e). Book).

In Figure _{7, t r, t e,} G r, G e, p r and _{p e} is the ratio of the value of the central portion _{5a (t r / t 0,} t e / t 0, G r / G 0, G _e / G ₀ , p _r / p ₀ and p _e / p ₀ ). In addition, the column in which these values are 1 is set to “−” for easy viewing of the chart.

In Example 4, none of G _r / G ₀ , G _e / G ₀ , p _r / p ₀ and p _e / p ₀ is less than 1, which is a comparative example. Here, for the sake of convenience, numbers are given following the examples.

Evaluation of properties was performed based on the obtained by narrowing the gap G _r (see line L11 in FIG. 4, for example) between the IDT electrode 5 and the reflectors 7 for normal resonator. The reason for this is as follows. Since the improvement amount on the resonance side with respect to the normal resonator is relatively small, it is easier to ensure objectivity in determining whether or not there is an improvement when compared with the comparative example in which the gap _Gr is narrowed. On the other hand, on the anti-resonance side, it is clear that even if the improvement amount with respect to the comparative example in which the gap _Gr is narrowed is small (even if it is difficult to determine whether or not there is improvement), it is improved for the normal resonator. . As compared with the comparative example in which the gap _Gr is narrowed, if the characteristics are improved on the resonance side and the equivalent characteristics can be obtained on the antiresonance side, the configuration in which the gap or pitch is reduced, and the electrode film thickness It can be said that the effect of the combination with the thickening structure appears.

Gap _G r / _{G 0} of the comparative example in which a reference of evaluation in Examples 1-7 was 0.8, in other embodiments 0.9.

  FIG. 7 shows the evaluation results on the “resonance side” and the “anti-resonance side” in the “evaluation” column. In each column of “resonance side” and “anti-resonance side”, “◯” means that the characteristics are improved with respect to the comparative example. “=” Means that the characteristics are equivalent to those of the comparative example. “Δ” means that the characteristics are deteriorated with respect to the comparative example.

  Since FIG. 7 shows a combination example of parameters whose characteristics are improved, the evaluation is basically “good”. In Examples 1 and 4, the evaluation on the antiresonance side is Δ. However, compared with a normal resonator, the antiresonance side characteristics are also improved in these embodiments. In Example 10, although the evaluation on the resonance side is Δ, the degree of the decrease is relatively small, but the improvement amount of the characteristic on the anti-resonance side is remarkable, so the parameter for improving the characteristic It is illustrated as a combination of.

In the example in which the characteristics of FIG. 7 are improved, each parameter is in the following range. t _r / t ₀ and t _e / t ₀ are 1.1 or more and 1.4 or less, respectively. G _r / G ₀ is 0.75 or more and 0.90 or less, and may be 1 as long as p _r / p ₀ and / or p _e / p ₀ are less than 1. G _e / G ₀ is 0.78 or more and 0.98 or less, and may be 1 if G _r / G ₀ , p _r / p ₀ and / or p _e / p ₀ is less than 1. p _r / p ₀ is 0.98, and may be 1 as long as G _r / G ₀ , G _e / G ₀ and / or p _e / p ₀ are less than 1. p _e / p ₀ is 0.97 or more and 0.99 or less, and may be 1 if G _r / G ₀ , G _e / G ₀ and / or p _r / p ₀ is less than 1.

FIG. 7 does not show a combination of parameters positioned at a boundary between a combination of parameters whose characteristics are improved and a combination of parameters whose characteristics are not improved. For example, examples 12 to 15 _show a _G e / _{G 0} which generally most characteristic becomes better when appropriately set the _{t r / t 0, t e} / t 0 and _G r / _{G 0.} Therefore, even if the above range is expanded, the characteristics are improved.

For example, from the example shown in FIG. 7 and other simulation calculations or experimental results, each parameter may be in the following range. t _r / _{t 0} and / or _t e / _{t 0} is 1 ultra 1.5. G _r / G ₀ is 0.70 or more and less than 1, and may be 1 if G _e / G ₀ , p _r / p ₀ and / or p _e / p ₀ is less than 1. G _e / G ₀ is 0.70 or more and less than 1, and may be 1 if G _r / G ₀ , p _r / p ₀ and / or p _e / p ₀ is less than 1. p _r / p ₀ is 0.9 or more and less than 1, and may be 1 if G _r / G ₀ , G _e / G ₀ and / or p _e / p ₀ is less than 1. p _e / p ₀ is 0.9 or more and less than 1, and may be 1 if G _r / G ₀ , G _e / G ₀ and / or p _r / p ₀ is less than 1.

(Parameter interaction)
FIG. 8 is a diagram illustrating the relationship between _tr / t ₀ (horizontal axis) and G _r / G ₀ (vertical axis) of the examples in which G _r / G ₀ is less than 1. In FIG. 7, Example 10 in which the resonance side evaluation is Δ is plotted as Δ in FIG. 8, and other examples are plotted as “◯” in FIG. 8.

As understood from the operation described with reference to FIG. 3, if the reduction amount of the gap G _r is larger than the increase amount of the thickness _tr , the characteristic on the resonance side is deteriorated. However, as shown in FIG. 8, at least from the line L26 (G _r / G ₀ = 0.85-0.5 × (t _r / t ₀ −1)) on the upper right side of the drawing, the resonance side and the anti-resonance side In both cases, the characteristics can be improved, or the characteristics on the anti-resonance side can be improved with almost no decrease in characteristics on the resonance side.

In Examples plotted are rich in those gaps or pitch other than the gap G _r it was also reduced. Reduction of the gap or pitch other than the gap G _r, like the reduction of the gap G _r, the operating range of the reflector 7 is moved to the high-frequency side, there is a possibility of lowering the characteristics of the resonant side. Therefore, also the embodiment gap or pitch other than the gap G _r are narrower are plotted does not affect on the above findings.

In addition, the plotted examples include many cases in which not only the thickness _tr but also the thickness _te is increased. Increase in the thickness t _e reduces the risk of resonance side of characteristic degradation. However, not only plotted Example 10 thickness t _r at △, while being thicker thickness t _e, located in the upper right of the line L26, and the closest performed Example 10 8 example _{2 (t r / t 0 =} 1.25, G r / G 0 = 0.8) , the thickness _{t e} has not been thickened. Therefore, it can be said that those thicker thickness t _e are plotted, little effect on the finding that characteristic in the resonance side is secured in the upper right side of the line L26.

9 (a) is the _{G r} and _p Examples 1 and 2 or to reduce the one mutually different _r, the relationship between the _G r / G ₀ (horizontal axis) and _p r / _{p 0} (vertical axis) FIG.

As shown in this figure, schematically, a value reduction amount and can be expected the same effects of 1/10 and the pitch p _r of the reduced amount of the gap G _r. Thus, for _example, may be set to _{G r} and / or _{p r} as _{G r / G 0 -10 × (} 1-p r / p 0) is located at the upper right of the line L26 of FIG.

FIG. 9B shows the relationship between G _e / G ₀ (horizontal axis) and p _e / p ₀ (vertical axis) for Examples 17 and 18 in which either G _e or p _e is reduced. FIG.

As shown in this figure, it can be generally understood that 1/10 of the reduction amount of the gap G _{e and} the reduction amount of the pitch p _e are values that can be expected to have the same effect. Thus, for _example, may be set to _{G e} and / or _{p e} as _{G e / G 0 -10 × (} 1-p e / p 0) does not exceed the range of values of _{G e} to be described later.

Figure 10 _is exemplary of _{t r / t 0, t e} / t 0, G r / G 0 and _G e / _{G 0} is set _{appropriately,} p r / _{p 0} and _p e / _{p 0} is a constant examples 13 to 15 (14-4 excluded), for 18 and _{20, t} r / t ₀ (horizontal axis. _t r = _{t e} in these _examples), with G e / _{G 0} (vertical axis) It is a figure which shows a relationship. As already mentioned, these examples seek G _e / G ₀ that generally has the best characteristics when t _r / t ₀ , t _e / t ₀ and G _r / G ₀ are set appropriately. . Lines L31, L32, and L33 correspond to G _r / G ₀ = 0.9, 0.85, or 0.8, respectively.

FIG. 11 is a diagram illustrating a relationship between G _r / G ₀ (horizontal axis) and G _e / G ₀ (vertical axis) in Examples 13 to 15, 18 and 20 that are substantially overlapped with the above. Line L35, L36, L37 and L38 correspond to the _t r _{/ t} 0 = 1.15,1.2,1.3 or 1.4, respectively.

As shown in FIG. 10, as the film thickness increases, G _e decreases the characteristic is generally best. This is because the operating range of the reflector 7 as if with a reduced G _r by reducing the G _e is shifted to the high frequency side. The rate of change is substantially equivalent to the line L26 in FIG.

As shown in FIG. 11, the smaller G _r is, the larger G _{e that} has the best characteristics is. However, the film thickness becomes thick to some extent, the G _e is reduced to a certain extent, the effect of the change in G _r is on changes in G _e is small, or eliminated. It will also be appreciated from a comparison of FIGS. 10 and 11, the range shown _{(t r / t 0 <1.5} , G r / G 0> 0.7), the _{G e} by _{G r} change If the change of _{G e} due to _{t r} is larger than the.

Thus, for _example, in the t r / _{t 0} 1.3 greater, regardless of the value of _{G r,} may be set to _{G e} as _{G e} is located in the upper right than the line L26 in FIG. Further, for _example, in the t r / _{t 0} is 1.3 or _{less, G r} and to be located in the upper right than the line L26 of the _{G r / G 0 -a × (} 1-G e / G 0) is 8 G _e may be set. a is, for _example, one in t r / _{t 0} is 1 super 1.1 or _less, t r / _{t 0} 0.4 a 1.1 ultra _1.2, t r / _{t 0} 1.2 It is 0.2 when it is less than 1.3.

(Demultiplexer)
FIG. 12 is a schematic diagram showing a duplexer 101 as an example of use of the SAW resonator 1.

  The duplexer 101 filters, for example, the transmission signal from the transmission terminal 105 and outputs it to the antenna terminal 103, and filters the reception signal from the antenna terminal 103 and outputs it to the pair of reception terminals 107. A reception filter 111.

  The transmission filter 109 is configured by, for example, a ladder type filter. That is, the transmission filter 109 has one or more series resonators and one or more parallel resonators connected in a ladder shape. At least one of these resonators (all in the illustrated example) is constituted by the SAW resonator 1. The plurality of SAW resonators 1 are provided on the same substrate 3, for example.

  The reception filter 111 includes, for example, a SAW resonator 1 and a SAW filter 113 that are connected in series with each other. The IDT electrode 5 and the pair of reflectors 7 constituting these are provided on the same substrate 3, for example. The substrate 3 on which the reception filter 111 is configured may be the same as or different from the substrate 3 on which the transmission filter 109 is configured.

  The SAW filter 113 is, for example, a longitudinally coupled multimode (including a double mode) type resonator filter, and includes a plurality of IDT electrodes 5 arranged in the SAW propagation direction, and a pair of electrodes arranged on both sides thereof. And a reflector 7.

(Communication device)
FIG. 13 is a block diagram illustrating a main part of a communication device 151 as an example of use of the SAW resonator 1.

  The communication device 151 performs wireless communication using radio waves. The communication device 151 uses the SAW resonator 1 by including the duplexer 101 described above. Specifically, it is as follows.

  In the communication device 151, a transmission information signal TIS including information to be transmitted is modulated and increased in frequency (converted to a high frequency signal of a carrier frequency) by an RF-IC (Radio Frequency Integrated Circuit) 153, and is transmitted to the transmission signal TS. Is done. Unnecessary components other than the transmission passband are removed from the transmission signal TS by the bandpass filter 155, amplified by the amplifier 157, and input to the duplexer 101 (transmission terminal 105). Then, the duplexer 101 removes unnecessary components other than the transmission passband from the input transmission signal TS, and outputs the transmission signal TS after the removal from the antenna terminal 103 to the antenna 159. The antenna 159 converts the input electric signal (transmission signal TS) into a radio signal (radio wave) and transmits it.

  In the communication device 151, a radio signal (radio wave) received by the antenna 159 is converted into an electric signal (reception signal RS) by the antenna 159 and input to the duplexer 101 (antenna terminal 103). The duplexer 101 removes unnecessary components other than the reception passband from the input reception signal RS and outputs the result to the amplifier 161 via the reception terminal 107. The output received signal RS is amplified by the amplifier 161, and unnecessary components other than the reception passband are removed by the band pass filter 163. Then, the reception signal RS is subjected to frequency reduction and demodulation by the RF-IC 153 to be a reception information signal RIS.

  The transmission information signal TIS and the reception information signal RIS may be low-frequency signals (baseband signals) including appropriate information, for example, analog audio signals or digitized audio signals. The passband of the radio signal may conform to various standards such as UMTS (Universal Mobile Telecommunications System). The modulation method may be any of phase modulation, amplitude modulation, frequency modulation, or a combination of any two or more thereof. Although the direct conversion method is exemplified in FIG. 13 as the circuit method, other appropriate methods may be used. For example, a double superheterodyne method may be used. FIG. 13 schematically shows only the main part, and a low-pass filter, an isolator or the like may be added at an appropriate position, and the position of an amplifier or the like may be changed.

As described above, in this embodiment, the SAW resonator 1 includes the substrate 3, the IDT electrode 5 positioned on the upper surface of the substrate 3, and the SAW propagation direction (D 1) with respect to the IDT electrode 5 on the upper surface of the substrate 3. And a pair of reflectors 7 located on both sides in the axial direction). The substrate 3 is a rotating Y-cut LiTaO ₃ plate. The IDT electrode 5 has a plurality of electrode fingers 13 arranged in the D1 axis direction. The pair of reflectors 7 includes a plurality of strip electrodes 19 arranged in the D1 axis direction. At least one of the plurality of strip electrodes 19 and the electrode fingers 13 on both end sides (end portions 5 e) of the IDT electrodes 5 has a thicker film portion than the electrode fingers 13 on the center side (center portion 5 a) of the IDT electrodes 5. ing. The pitch _{p r} of the plurality of strip electrodes 19 is smaller than the pitch _{p 0} of the electrode fingers 13 of the central portion 5a, 1-to-electrode gap _{G r} is the central portion 5a between the reflector 7 and the IDT electrode 5 smaller than the gap _{G 0} between the fingers 13, the pitch _{p e} is smaller than the pitch _{p 0} of the electrode fingers 13 of the central portion 5a, and the end portion 5e of the electrode fingers 13 and the central portion 5a of the electrode fingers 13 of the end portion 5e The gap G _e between the electrode fingers 13 is smaller than the gap G ₀ between the electrode fingers 13 in the central portion 5a.

Therefore, as described with reference to FIGS. 3 to 7, the characteristics are improved on both the resonance side and the anti-resonance side, or the deterioration of one characteristic on the resonance side and the anti-resonance side is suppressed, while the other characteristic is suppressed. Can be improved. Specifically, the anti-resonance side characteristics can be improved by reducing at least one of p _r , G _r , p ₀ and G ₀ . Further, by thickening at least one of t _r and t _e, suppressing reduction of the above p _r, G _r, p ₀ and the resonance side properties due to the reduced any one or more of G _0, Alternatively, the resonance side characteristics can be improved. If thicker t _e is thereby not only the resonance side, characteristics of the antiresonant side can be improved.

  In the present embodiment, the SAW resonator 1 includes the first conductive layer 21A to the fourth conductive layer 21D. The first conductive layer 21 </ b> A is located on the upper surface of the substrate 3. The second conductive layer 21B is located on the first conductive layer 21A and is made of a material different from that of the first conductive layer 21A. The third conductive layer 21C is made of the same material as the first conductive layer 21A and is located on the second conductive layer 21B. The fourth conductive layer 21D is made of the same material as the second conductive layer 21B and is located on the third conductive layer 21C. The electrode finger 13 in the central portion 5a is composed of the first conductive layer 21A and the second conductive layer 21B. The end portion 5e and the thick film portion of the reflector 7 are constituted by the first conductive layer 21A to the fourth conductive layer 21D.

  Therefore, for example, when the thick film portion is formed by CVD (chemical vapor deposition) or sputtering, the crystallinity and orientation can be improved as compared with the case where the single metal material is thickened. As a result, for example, the actual film thickness, pitch and / or gap can be brought close to the design value. As a result, the effectiveness of the characteristic improvement by these fine adjustments becomes high. In addition, for example, power durability can be improved.

In the present embodiment, for example, the plurality of strip electrodes 19 have a thick film portion ( _tr is thicker than t ₀ ). The pair of reflectors 7 further includes a bus bar 17 having a thickness equivalent to that of the strip electrode 19, which connects the ends of the plurality of strip electrodes 19.

Similarly, in the present embodiment, for example, the electrode fingers 13 of the end portion 5e is (thicker than t _e is t ₀₎ has a thick portion. The IDT electrode 5 further includes a bus bar 11 that connects the ends of the plurality of electrode fingers 13. The bus bar 11 has a thickness equivalent to that of the thick film portion of the electrode finger 13 at a portion connecting the ends of the electrode fingers 13 of the end portion 5e.

  Therefore, for example, when the thick strip electrode 19 and / or the electrode finger 13 is formed by CVD or sputtering, the connection portion between the strip electrode 19 and the bus bar 17 and / or the connection portion between the electrode finger 13 and the bus bar 11 is ensured. Can be thickened.

  The technique of this indication is not limited to the above embodiment, You may implement in a various aspect.

  When the strip electrode of the reflector has a thick film portion, the bus bar of the reflector may not have the same thickness as the thick film portion but may have the same thickness as the electrode finger on the center side of the IDT electrode. Similarly, when the electrode finger on the end side of the IDT electrode has a thick film portion, the bus bar of the IDT electrode does not have the same thickness as that of the thick film portion on the end side, but the electrode on the center side of the IDT electrode It may be the same thickness as the finger. When both the electrode fingers on the end side of the IDT electrode and the strip electrode of the reflector have thick film portions, the thicknesses of the two may be different from each other.

  The thick film part and the part other than the thick film part may be configured by an appropriate number of conductive layers. For example, both the thick film part and the part other than the thick film part may be formed by one layer, or both are formed by two layers, and the thickness of the first layer is common and the thickness of the second layer is the same. They may be different from each other.

  DESCRIPTION OF SYMBOLS 3 ... Board | substrate, 5 ... IDT electrode, 5a ... Center part, 5e ... End part, 7 ... Reflector, 13 ... Electrode finger, 19 ... Strip electrode.

Claims (10)

A substrate that is a rotating Y-cut LiTaO ₃ plate;
An IDT electrode having a plurality of electrode fingers positioned on the upper surface of the substrate and arranged in the propagation direction of the surface acoustic wave;
A pair of reflectors having a plurality of strip electrodes arranged on both sides of the propagation direction with respect to the IDT electrode on the upper surface of the substrate and arranged in the propagation direction;
Have
At least one of the electrode fingers on both ends of the plurality of strip electrodes and the IDT electrode has a thicker film part thicker than the electrode finger on the center side of the IDT electrode,
The pitch between the plurality of strip electrodes is smaller than the pitch between the center-side electrode fingers, the gap between the pair of reflectors and the IDT electrodes is smaller than the gap between the center-side electrode fingers, The pitch between the electrode fingers on both ends is smaller than the pitch on the center electrode fingers, and the gap between the electrode fingers on both ends and the center electrode fingers is larger than the gap between the center electrode fingers Is a surface acoustic wave resonator. The surface acoustic wave resonator according to claim 1, wherein a thickness of the thick film portion is 1.5 times or less a thickness of the electrode finger on the center side. At least one of the gap between the pair of reflectors and the IDT electrode and the gap between the electrode fingers on both ends and the central electrode finger is a gap between the electrode fingers on the central side. The surface acoustic wave resonator according to claim 1, wherein the surface acoustic wave resonator is 0.7 times or more and less than 1 time. The pitch of the plurality of strip electrodes and the pitch of the electrode fingers on both ends are 0.9 times or more and less than 1 times the pitch of the electrode fingers on the center side. The surface acoustic wave resonator according to item. 5. The surface acoustic wave resonator according to claim 1, wherein both of the plurality of strip electrodes and electrode fingers on both ends of the IDT electrode have the thick film portion. A first conductive layer located on an upper surface of the substrate;
A second conductive layer located on the first conductive layer and made of a different material from the first conductive layer;
A third conductive layer made of the same material as the first conductive layer and located on the second conductive layer;
A fourth conductive layer made of the same material as the second conductive layer and located on the third conductive layer,
The electrode finger on the center side is composed of the first and second conductive layers,
The surface acoustic wave resonator according to claim 1, wherein the thick film portion is configured by the first to fourth conductive layers. The plurality of strip electrodes have the thick film portion,
The pair of reflectors further includes a bus bar having a thickness equivalent to that of the thick film portion, which connects ends of the plurality of strip electrodes. A surface acoustic wave resonator according to claim 1. The electrode fingers on the end side have the thick film part,
The IDT electrode further includes a bus bar connecting ends of the plurality of electrode fingers,
The said bus bar of the said IDT electrode has thickness equivalent to the said thick film part in the part which connects the edge parts of the electrode finger of the said edge part side. Surface acoustic wave resonators. An antenna terminal;
A transmission filter that filters a transmission signal and outputs the filtered signal to the antenna terminal;
A reception filter for filtering a reception signal from the antenna terminal;
Have
At least one of the transmission filter and the reception filter is a duplexer including the surface acoustic wave resonator according to any one of claims 1 to 8. An antenna,
The duplexer according to claim 9, wherein the antenna terminal is connected to the antenna.
An IC connected to the transmission filter and the reception filter;
A communication device.

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