JP4467296B2 - Surface acoustic wave device - Google Patents

Description

  The present invention relates to a surface acoustic wave device such as a surface acoustic wave filter or a surface acoustic wave resonator used in a mobile communication device such as a mobile phone, and a communication device including the same.

  In recent years, surface acoustic wave filters that can be miniaturized and non-adjusted have been used in various communication devices, and the surface acoustic wave filters have become wider with the progress of higher frequency and higher functionality of communication devices. The demand to do is increasing. For example, as a 1.9 GHz band cellular phone filter, a high-performance broadband filter having an effective pass bandwidth of 80 MHz or more (specific bandwidth of about 4% or more) is desired.

  In order to realize such a wide band, for example, a dual-mode surface acoustic wave resonator filter using three IDT electrodes (Inter Digital Transducer) on a piezoelectric substrate and using a longitudinal first-order mode and a longitudinal third-order mode Has been proposed.

  FIG. 19 is a plan view seen from above in the electrode structure of a conventional resonator type surface acoustic wave filter. The IDT electrode 204 having a plurality of electrode fingers disposed on the piezoelectric substrate 202 is composed of a pair of comb-like electrodes opposed to each other, and an electric field is applied to the pair of comb-like electrodes to generate a surface acoustic wave. It will cause. By inputting an electric signal from the input terminal 215 connected to one comb-like electrode of the IDT electrode 204, the excited surface acoustic wave is propagated to the IDT electrodes 203 and 205 disposed on both sides of the IDT electrode 204. The In addition, an electric signal is output from one comb-like electrode constituting each of the IDT electrodes 203 and 205 to the output terminals 216 and 217 through the IDT electrodes 206 and 209. In the figure, reference numerals 210, 211, 212, and 213 denote reflector electrodes. Thus, by connecting the resonator electrode patterns in two stages in cascade, the out-of-band attenuation is increased by the mutual interference between the first and second stage standing waves, and the out-of-band attenuation of the filter characteristics is increased. Can be improved. In other words, a surface acoustic wave filter having similar characteristics is configured in a two-stage cascade connection, so that the signal attenuated in the first stage is further attenuated in the second stage, and the out-of-band attenuation is improved by about twice. Can be made.

  Here, by inputting an electric signal to the input terminal 215 connected to the IDT electrode 204, the surface acoustic wave is excited, and this surface acoustic wave is propagated to the IDT electrodes 203 and 205 located on both sides of the IDT electrode 204. The electrical signals are output from the output terminals 216 and 217 connected to the IDT electrodes 207 and 208. Further, the surface acoustic wave is reflected by the reflector electrodes 210, 211, 212, and 213 located at both ends, and becomes a standing wave between the reflector electrodes at both ends.

  This standing wave mode includes a primary mode and its higher-order (third-order) mode by three IDT electrodes. Since the pass characteristics are obtained by the resonance generated in these modes, the pass band can be widened by controlling the interval between the resonance frequencies generated in these modes. Conventionally, in order to control the interval of the resonance frequency, a narrow pitch portion is provided at the end of the IDT electrode, thereby reducing the radiation loss of the bulk wave when the surface wave is converted into the bulk wave, thereby achieving a wider band. It was. As another method, the resonance frequency interval is controlled by controlling the interval d between the IDT electrodes. Further, as another means, a capacitance is added to the output IDT electrode to control the resonance frequency interval.

As described above, in the conventional dual-mode surface acoustic wave resonator filter, when a LiTaO ₃ substrate often used as a piezoelectric substrate is used and two stages are cascaded, the specific bandwidth (the pass bandwidth of the center frequency) Value) was about 0.40% (see, for example, Patent Document 1), and even when capacity was added, only about 2% was obtained (for example, see Patent Document 2). In addition, when the distance d between the IDT electrodes is controlled, a maximum bandwidth of 3.7% is obtained (see, for example, Patent Document 3), but as a filter, temperature fluctuation must be taken into consideration. Since the frequency fluctuates due to variations in the manufactured electrode shape, it has been difficult to apply to a communication device such as a mobile phone that requires a wide pass bandwidth.

  Therefore, by providing a narrow pitch portion of electrode fingers at the end of adjacent IDT electrodes, the radiation loss of bulk waves between the IDT electrodes is reduced, and the resonance mode state is controlled to increase the bandwidth and insertion loss. Improvement has been achieved (see, for example, Patent Documents 4 and 5).

In addition, in order to provide a surface acoustic wave filter with a wide band and low loss and a large out-of-band attenuation on the high band side, an example in which a reflector electrode is inserted between IDT electrodes has been proposed (see, for example, Patent Document 6). .)
JP-A-1-231417 Japanese Patent Laid-Open No. 4-40705 JP 7-58581 A Japanese Patent Laid-Open No. 2002-9587 Special Table 2002-528987 JP-A-8-250969

  However, in the surface acoustic wave devices disclosed in Patent Documents 4 and 5, when the narrow pitch portion is provided at the end of the IDT electrode, there are portions where the electrode finger pitch is different in a coupled state in terms of surface acoustic waves. Therefore, the ripple of the filter characteristic in the pass band becomes large, the shoulder characteristic is deteriorated, and a flat characteristic cannot be obtained. Also, simply providing a narrow pitch portion at the end of the IDT electrode limits the number of basic resonance modes that can be used for excitation of surface acoustic waves to the longitudinal first-order mode and the longitudinal third-order mode. Since it cannot be used, the degree of freedom in design was small. For this reason, there is a limit to widening the bandwidth.

  Further, in the surface acoustic wave device as disclosed in Patent Document 6, the propagation path length increases only by inserting the reflector electrode between the IDT electrodes, so that the propagation loss increases, and the insertion loss in the filter characteristics. Increases, and the pass bandwidth decreases, which is not preferable.

  Although it is conceivable to use five IDT electrodes in place of the three IDT electrodes in order to ensure a sufficient bandwidth, the propagation path length is similarly increased, resulting in an increase in propagation loss and in filter characteristics. This is not preferable because the insertion loss increases and the surface acoustic wave filter size increases.

  As described above, as a means that has been conventionally used to increase the bandwidth, the distance between adjacent IDTs is shortened or a narrow pitch portion is provided at the end of the IDT electrode. Since there are portions where the electrode finger pitch is different in the coupled state, the ripple is large.

  In addition, conventionally used IDT electrodes are connected via a bus bar every other electrode finger, but when the number of electrode fingers of the IDT electrode increases, a certain proportion will be occupied in the resonator, The resonance modes that are allowed to appear are constrained. However, in the design of a surface acoustic wave filter, it is desirable that the resonance mode that can be used to form the pass band has a degree of freedom.

  In general, in a resonator type surface acoustic wave filter, the surface acoustic wave amplitude distribution determines the frequency at which the resonance mode appears, and the surface acoustic wave amplitude distribution can be controlled by the IDT electrode arrangement and IDT electrode connection mode. It becomes. In particular, when the IDT electrodes are connected to each other, the appearance of the amplitude distribution of a specific surface acoustic wave can be suppressed or increased by this connection.

  The present invention has been proposed in view of the above-described conventional problems, and its purpose is to prevent deterioration of insertion loss, to have excellent filter characteristics with a wide pass bandwidth, and to provide a high-quality balanced elastic surface. An object of the present invention is to provide a surface acoustic wave device that can also function as a wave filter and a communication device using the same.

In order to solve the above problems, a surface acoustic wave device according to the present invention 1) electrically connects a plurality of IDT electrodes having a plurality of long electrode fingers on a piezoelectric substrate in a direction orthogonal to the propagation direction of the surface acoustic wave. The IDT electrode group which is connected to the IDT electrode group, and the other IDT electrodes which are electrically unconnected to the IDT electrode group and the elastic member are arranged between the IDT electrodes constituting the IDT electrode group. One or more reflector electrodes having a plurality of long electrode fingers in a direction orthogonal to the propagation direction of the surface wave are arranged as separation electrodes, and one of the IDT electrode groups. a constant electrode finger pitch than the IDT electrode, and said one of said IDT electrodes constituting the IDT electrode group, the average electrode finger of at least one of the IDT electrodes of the IDT electrodes located at both ends of the IDT electrodes Pitch, characterized in that narrower than the average electrode finger pitch of all the other electrodes of the electrode group consisting of the IDT electrodes and the separation electrode. Here, the average electrode finger pitch means the average of the distances from the center position of one electrode finger in the propagation direction of the surface acoustic wave to the center position of the other electrode finger in adjacent electrode fingers.

  2) In the surface acoustic wave device according to 1), the electrode group composed of the IDT electrode group and the separation electrode includes two adjacent IDT electrodes or the adjacent IDT electrode and the reflector electrode. The average electrode finger pitch is different from each other and is electrically disconnected.

  3) In the surface acoustic wave device according to 1) or 2) above, the electrode group composed of the IDT electrode group and the separation electrode is averaged from one end of the IDT electrode group to the other end. A narrow pitch electrode group composed of one or more electrodes having a narrow electrode finger pitch and a wide pitch electrode group composed of one or more electrodes having a wide average electrode finger pitch have adjacent regions. It is characterized by.

  4) In the surface acoustic wave device according to any one of 1) to 3) above, a plurality of electrode groups each including the IDT electrode group and the separation electrode are arranged in a direction orthogonal to the propagation direction of the surface acoustic wave. The electrode groups are arranged in stages, and the electrode groups of the plurality of stages are electrically connected to each other.

  5) In the surface acoustic wave device according to any one of 1) to 4), one or more mode resonances are performed in series, parallel, or series-parallel with respect to the IDT electrodes constituting the IDT electrode group. The surface acoustic wave resonator to be generated is electrically connected.

  A communication apparatus according to the present invention includes 6) at least one of a reception circuit and a transmission circuit having the surface acoustic wave device according to any one of 1) to 5) above.

  According to the surface acoustic wave device of 1) above, in the electrode group composed of the IDT electrode group and the separation electrode, by providing the separation electrode composed of at least one of the IDT electrode and the reflector electrode, The degree of freedom of selection is widened, the degree of freedom of control of the surface acoustic wave amplitude distribution is increased, and as a result, it is possible to control the filter characteristics such as widening the band while reducing the ripple. In addition, by adopting a non-connected configuration in which separation electrodes (non-adjacent IDT electrodes or the like) of other IDT electrode groups are electrically connected or not connected, the degree of freedom in selecting a resonance mode is further increased. Can be increased.

Also, when you widen the spacing between the forcibly resonant mode trying broadband tends to S ₂₁ is a transmission characteristic between the resonance peak and the resonance peak is reduced. As described above, it is possible to arrange the resonance frequencies with a certain degree of interval when the degree of freedom of selection of the possible resonance modes is large (resonance frequencies suitable for wideband characteristics can be easily arranged). This is advantageous for widening the bandwidth.

  In addition, the electrode finger pitch of one or more IDT electrodes in the IDT electrode group is constant, and the average electrode finger pitch of IDT electrodes located at one or both ends of the IDT electrode group is the remaining electrode finger pitch in one electrode group. Since it is narrower than the average electrode finger pitch of all the electrodes, it becomes possible to prevent the radiation loss of the surface acoustic wave to the bulk wave, and as a result, the pass band width of the filter characteristic can be widened.

  Also, according to the surface acoustic wave device of 2) above, the two adjacent IDT electrodes or the adjacent IDT electrodes and the reflector electrodes have different average electrode finger pitches and are not electrically connected to each other. Therefore, the degree of freedom of selection of the resonance mode is increased, and the surface acoustic wave coupling remains as it is, and the electrical coupling is disconnected, so that the ripple can be reduced and particularly the shoulder characteristics can be improved. As a result, a wide band can be realized.

  According to the surface acoustic wave device of 3), the electrode group including the IDT electrode group and the separation electrode has one or more narrower average electrode finger pitches from one end of the IDT electrode group to the other end. The surface acoustic wave according to 1) above has a region in which a narrow pitch electrode group composed of the above-mentioned electrodes and a wide pitch electrode group composed of one or more electrodes having a wide average electrode finger pitch are adjacent to each other. In addition to the effects of the device, the Q value of the entire surface acoustic wave filter can be increased, and radiation loss of the surface acoustic wave to the bulk wave can be prevented, and the first-order mode, the third-order mode, and their harmonic modes It is possible to finely adjust the resonance frequency in the narrow pitch electrode group, so that it is possible to realize a surface acoustic wave device with good electrical characteristics in a wider band while preventing deterioration of insertion loss.

  Further, according to the surface acoustic wave device of 4), the electrode group composed of the IDT electrode group and the separation electrode is arranged in a plurality of stages in a direction orthogonal to the propagation direction of the surface acoustic wave. The electrode groups of the stages are electrically connected. As a result, for example, the number of paths connected from the first stage to the second stage can be increased, the degree of freedom in designing the passband is increased, and the passband width can be more effectively widened.

  According to the surface acoustic wave device of 5) above, impedance matching can be achieved by connecting and adding surface acoustic wave resonators in series, parallel or series-parallel to the IDT electrodes constituting the IDT electrode group. Thus, it is possible to form an attenuation pole by connecting a surface acoustic wave resonator, and the characteristics can be controlled so that the out-of-band attenuation amount satisfies the specifications required for high attenuation.

  Further, for example, one of the plurality of opposing comb-like electrodes constituting at least one IDT electrode is divided, and the divided comb-like electrode is connected to the input and output balanced signals. By using the electrodes, it is possible to provide a surface acoustic wave device having the function of an unbalanced-balanced signal converter.

  Also, for example, in the first and second electrode groups (for example, composed of a plurality of IDT electrodes and reflector electrodes) arranged along the propagation direction of the surface acoustic wave, one electrode group is connected to the other. When the electrode group is moved in parallel, if it is arranged so that both electrode groups substantially coincide with each other, a surface acoustic wave device that is remarkably excellent in insertion loss, amplitude balance, and phase balance can be provided. Furthermore, it is possible to realize a surface acoustic wave device excellent in quality by widening the pass bandwidth of the filter characteristics.

  As described above, the sensitivity of the communication device such as a communication device including the reception circuit or the transmission circuit having the surface acoustic wave device according to any one of 1) to 5) is remarkably improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The surface acoustic wave device of the present invention will be described by taking a resonator type surface acoustic wave filter having a simple structure as an example. In addition, in drawing demonstrated below, the same code | symbol shall be attached | subjected to the same structure. In addition, the number of electrodes, the distance between electrodes, and the like, such as the size of each electrode and the distance between the electrodes, are schematically illustrated for explanation.

<Embodiment 1>
As shown in FIG. 1, a multimode resonator type surface acoustic wave filter includes an IDT electrode (IDT electrode) having a plurality of long electrode fingers on a piezoelectric substrate 1 in a direction orthogonal to the propagation direction of the surface acoustic wave. 31 to 52) are arranged, and the electrode finger pitch of one or more IDT electrodes among these IDT electrodes is constant (in this example, the electrode finger pitch is within one IDT electrode in all IDT electrodes). The IDT electrodes (IDT electrodes 31 and 33, 34 and 38, 39 and 41, 42 and 44, 45 and 49, 50 and 52) located at both ends are electrically connected to each other. And one or more electrode groups to which adjacent IDT electrodes are not electrically connected. That is, the electrode group 21 (configured by IDT electrodes 31, 32, 33 (configured by an IDT electrode group composed of electrically connected IDT electrodes 31, 33 and an IDT electrode 32 serving as a separation electrode)), electrode group 22 (IDT Electrode 34, 35, 36, 37, 38 (consisting of an IDT electrode group consisting of IDT electrodes 34, 36, 38 and an IDT electrode 35, 37 which is a separate electrode)), electrode group 23 (IDT electrodes 39, 40, 41 (configured with an IDT electrode group consisting of IDT electrodes 39 and 41 and an IDT electrode 40 serving as a separation electrode), and an electrode group 24 (configured with IDT electrodes 42, 43 and 44 (IDT electrodes composed of IDT electrodes 42 and 44) Group) and an electrode group 25 (consisting of IDT electrodes 45, 46, 47, 48, 49) (an IDT electrode group comprising IDT electrodes 45, 47, 49 and an IDT being a separation electrode) Electrode 46, 48)) and electrode group 26 (IDT electrodes 50, 5) 1 and 52 (consisting of an IDT electrode group consisting of IDT electrodes 50 and 52 and an IDT electrode 51 as a separation electrode). In addition, the average electrode finger pitch (= one electrode finger in the adjacent electrode fingers) of IDT electrodes (IDT electrodes 33, 34, 38, 39, 44, 45, 49, 50) located at one end or both ends of the IDT electrode group. The average distance from the center position of the electrode finger to the center position of the other electrode finger) is smaller than the average electrode finger pitch of all other electrodes, that is, all other electrodes in one electrode group.

  That is, in the surface acoustic wave element A composed of a plurality of electrode groups at the first stage, the average electrode finger pitch of the IDT electrodes 33 is smaller than the average electrode finger pitch of the IDT electrodes 31 and 32. Further, the average electrode finger pitch of the IDT electrodes 34 is smaller than the average electrode finger pitch of the IDT electrodes 35, 36, 37 and 38. Further, the average electrode finger pitch of the IDT electrodes 38 is smaller than the average electrode finger pitch of the IDT electrodes 34, 35, 36, and 37. Further, the average electrode finger pitch of the IDT electrodes 39 is smaller than the average electrode finger pitch of the IDT electrodes 40 and 41.

  In the surface acoustic wave element B composed of a plurality of electrode groups at the second stage, the average electrode finger pitch of the IDT electrodes 42 is smaller than the average electrode finger pitch of the IDT electrodes 43 and 44. The average electrode finger pitch of the IDT electrode 45 is smaller than the average electrode finger pitch of the IDT electrodes 46, 47, 48, and 49. Further, the average electrode finger pitch of the IDT electrodes 49 is smaller than the average electrode finger pitch of the IDT electrodes 45, 46, 47 and 48. Further, the average electrode finger pitch of the IDT electrodes 51 is smaller than the average electrode finger pitch of the IDT electrodes 52 and 53.

  Further, adjacent IDT electrodes are not electrically connected. In addition, at both ends of the surface acoustic wave element of each stage, a plurality of long electrode fingers are provided in a direction orthogonal to the propagation direction of the surface acoustic wave, and the reflector electrodes 2 and 3 having the same electrode finger pitch are provided. , 4 and 5 are arranged. The first and second stage surface acoustic wave elements are connected in cascade. Note that 6 is an input terminal, and 7 is an output terminal.

  In the surface acoustic wave device according to the first embodiment, a plurality of IDT electrodes having a plurality of long electrode fingers in a direction orthogonal to the propagation direction of the surface acoustic wave are electrically connected to each other on the piezoelectric substrate 1. IDT electrode groups are arranged side by side along the propagation direction of the surface acoustic wave, and other IDT electrodes that are electrically unconnected to the IDT electrode group between at least two IDT electrodes of the IDT electrode group. One or more separation electrodes are arranged, and the electrode finger pitch of one or more IDT electrodes in the IDT electrode group is constant, and is positioned at at least one end (one end or both ends) of the IDT electrode group. The average electrode finger pitch of the IDT electrodes to be performed is narrower than the average electrode finger pitch of all the other electrodes in one electrode group. Further, the electrode group composed of the IDT electrode group and the separation electrode is characterized in that two adjacent IDT electrodes have different average electrode finger pitches and are electrically disconnected. Further, the electrode group composed of the IDT electrode group and the separation electrode includes a narrow pitch electrode group composed of one or more electrodes having a narrow average electrode finger pitch from one end of the IDT electrode group to the other end. And a wide pitch electrode group composed of one or more electrodes having a wide average electrode finger pitch. Further, the electrode group composed of the IDT electrode group and the separation electrode has a plurality of stages, and these electrode groups are electrically connected to each other.

  With these structures, first, by separating the individual IDT electrodes constituting the electrode group, the degree of freedom in selecting the resonance mode is increased, so that the degree of freedom in controlling the surface acoustic wave amplitude distribution is increased and the filter characteristics are controlled. It becomes possible to use it. When the degree of freedom in selecting the resonance mode is larger, the resonance frequency can be arranged with a certain interval or more, and as a result, it is advantageous for widening the band. Furthermore, in one electrode group, the average electrode finger pitch of the IDT electrodes at one or both ends of the IDT electrode group is smaller than the average electrode finger pitch of the other electrodes, thereby reducing the radiation loss of the surface acoustic wave to the bulk wave. As a result, the pass bandwidth of the filter characteristic can be widened. In addition, since two adjacent IDT electrodes or adjacent IDT electrodes and reflector electrodes have different average electrode finger pitches and are not electrically connected to each other, the degree of freedom in selecting a resonance mode is increased. In addition, since the electrical coupling is disconnected while the surface acoustic wave coupling is kept as it is, ripples can be reduced and, in particular, the shoulder characteristics can be improved. As a result, a wide band can be realized. In addition, the electrode group composed of the IDT electrode group and the separation electrode includes a narrow pitch electrode group composed of one or more electrodes having a narrow average electrode finger pitch from one end of the IDT electrode group to the other end; Since the wide pitch electrode group composed of one or more electrodes having a wide average electrode finger pitch has an adjacent region, the Q value of the entire surface acoustic wave filter is increased, and the surface acoustic wave is converted into a bulk wave. It is possible to prevent radiation loss and finely adjust the resonance frequency between the first-order mode, third-order mode and their harmonic modes in the narrow-pitch electrode group, thus preventing deterioration of insertion loss. However, it is possible to realize a surface acoustic wave device having a wider band and good electrical characteristics. Further, an electrode group composed of an IDT electrode group and a separation electrode is arranged in a plurality of stages in a direction orthogonal to the propagation direction of the surface acoustic wave, and the electrode groups of the plurality of stages are electrically connected to each other. Thus, for example, the number of paths connected from the first stage to the second stage can be increased, the degree of freedom in designing the passband is increased, and the passband width can be more effectively widened.

  Since the number of IDT electrodes 31 to 52 and reflector electrodes 2, 3, 4 and 5 electrode fingers ranges from several to several hundreds, the shapes are simplified in the drawing for simplicity. Yes. The drawing similar to FIG. 1 showing the surface acoustic wave filter described below is assumed to be simplified as in FIG.

<Embodiment 2>
FIG. 2 is a diagram for explaining a modification of the first embodiment. Although the overall configuration is the same as that shown in FIG. 1, only the connection structure between the stages of the surface acoustic wave element at the first stage and the surface acoustic wave element at the second stage is different.

  Specifically, compared to the configuration of FIG. 1, in the electrode group of the surface acoustic wave element C at the first stage, the IDT electrode 32 and the IDT electrode 35 which are separation electrodes are not electrically connected. Similarly, the IDT electrode 37 and the IDT electrode 40 which are separation electrodes are not electrically connected. In the electrode group of the surface acoustic wave element D at the second stage, like the surface acoustic wave element C at the first stage, the IDT electrode 43 and the IDT electrode 45 are not electrically connected and are not connected. The electrode 50 and the IDT electrode 52 are not electrically connected and are not connected. An IDT electrode 32 and an IDT electrode 43, an IDT electrode 35 and an IDT electrode 46, an IDT electrode 37 and an IDT electrode 48, and an IDT electrode 40 and an IDT electrode 51 are connected in cascade.

  Further, as in FIG. 1, the IDT electrodes located at both ends are electrically connected to each other, and at least one IDT electrode group to which the adjacent IDT electrodes are not electrically connected is provided. The average electrode finger pitch of IDT electrodes located at one end or both ends is smaller than the average electrode finger pitch of all other electrodes.

  According to the second embodiment, since the cascade connection is made as described above, the degree of freedom in selecting the resonance mode is increased by the cascade connection between the separation electrodes as in the first embodiment. The degree of freedom in controlling the wave amplitude distribution is increased and it can be used for controlling the filter characteristics. When the degree of freedom in selecting the resonance mode is larger, the resonance frequency can be arranged with a certain interval or more, and as a result, it is advantageous for widening the band.

<Embodiment 3>
In the structure of the surface acoustic wave filter shown in FIG. 3, the electrode structure of FIG. 1 is used as a basic structure, and the reflector electrode 61, 62, 63, 64, 65 is replaced with the IDT electrode of the separation electrode located between the electrode groups. , 66, 67, 68 are arranged adjacent to each IDT electrode group. Similarly to FIG. 1, three or more IDT electrodes each having a plurality of long electrode fingers in the direction orthogonal to the propagation direction of the surface acoustic wave are arranged on the piezoelectric substrate 1 (IDT electrodes 31, 33, 34, 36, 37, 39, 41, 42, 44, 45, 47, 49, 50, 52), among these IDT electrodes, the electrode finger pitch of one or more IDT electrodes is constant (all IDT electrodes and reflectors) In the electrode, the electrode finger pitch is constant in one IDT electrode and one reflector electrode), IDT electrodes located at both ends are electrically connected to each other, and adjacent IDT electrodes or reflector electrodes are electrically connected One or more IDT electrode groups that are not connected to each other are provided. That is, electrode group 21 (comprised of IDT electrodes 31, 33 and reflector electrode 61), electrode group 22 (configured of IDT electrodes 34, 36, 38 and reflector electrodes 62, 63), electrode group 23 (IDT electrodes 39, 41 and reflector electrode 64), electrode group 24 (consisting of IDT electrodes 42 and 44 and reflector electrode 65), electrode group 25 (comprising IDT electrodes 45, 47 and 49 and reflector electrodes 66 and 67) and The electrode group 26 (consisting of IDT electrodes 50 and 52 and the reflector electrode 68) is provided, and in one IDT electrode group, the average electrode finger pitch of the IDT electrodes located at one end or both ends is the other Less than the average electrode finger pitch of all electrodes.

  Thus, in the first stage surface acoustic wave element E, the average electrode finger pitch of the IDT electrode 33 is smaller than the average electrode finger pitch of the IDT electrode 31 and the reflector electrode 61. The average electrode finger pitch of the IDT electrode 34 is smaller than the average electrode finger pitch of the IDT electrodes 36 and 38 and the reflector electrodes 62 and 63. The average electrode finger pitch of the IDT electrode 38 is smaller than the average electrode finger pitch of the IDT electrodes 34, 36, 38 and the reflector electrodes 62, 63. The average electrode finger pitch of the IDT electrode 39 is smaller than the average electrode finger pitch of the IDT electrode 41 and the reflector electrode 64.

  In the second stage surface acoustic wave element F, the average electrode finger pitch of the IDT electrode 42 is smaller than the average electrode finger pitch of the IDT electrode 44 and the reflector electrode 65. The average electrode finger pitch of the IDT electrode 45 is smaller than the average electrode finger pitch of the IDT electrodes 47 and 49 and the reflector electrodes 66 and 67. The average electrode finger pitch of the IDT electrode 49 is smaller than the average electrode finger pitch of the IDT electrodes 45 and 47 and the reflector electrodes 66 and 67. Further, the average electrode finger pitch of the IDT electrode 51 is smaller than the average electrode finger pitch of the IDT electrode 53 and the reflector electrode 68.

  Further, adjacent IDT electrodes or reflector electrodes are not electrically connected. In addition, reflector electrodes 2, 3, 4, and 5 having the same electrode finger pitch are disposed at both ends. Further, the first-stage and second-stage surface acoustic wave elements are connected in cascade. The number of electrode fingers constituting the reflector electrodes 61, 62, 63, 64, 65, 66, 67, 68 may be one or more. Further, the reflector electrodes constituting the electrode group are grounded in the third embodiment. The reflector electrodes constituting the electrode group may be grounded, floating, or used for interstage connection. When the reflector electrode is not electrically connected and is in a floating state, there is an advantage that the wiring can be easily routed.

  Thus, in the third embodiment, an IDT electrode group formed by electrically connecting a plurality of IDT electrodes having a plurality of long electrode fingers on the piezoelectric substrate 1 in a direction orthogonal to the propagation direction of the surface acoustic wave. Are arranged side by side along the propagation direction of the surface acoustic wave, and are separated electrodes that are electrically non-connected to the IDT electrode group between at least two IDT electrodes of the IDT electrode group. One or more IDT electrodes of the IDT electrode group have a constant electrode finger pitch, and an average electrode finger pitch of IDT electrodes located at one or both ends of the IDT electrode group is It is narrower than the average electrode finger pitch of all the other electrodes in one electrode group. In addition, the electrode group consisting of the IDT electrode group and the separation electrode has two adjacent IDT electrodes and the adjacent reflector electrode and IDT electrode so that their average electrode finger pitches are different from each other and electrically disconnected. It is characterized by that. Further, the electrode group composed of the IDT electrode group and the separation electrode includes a narrow pitch electrode group composed of one or more electrodes having a narrow average electrode finger pitch from one end of the IDT electrode group to the other end. And a wide pitch electrode group composed of one or more electrodes having a wide average electrode finger pitch. Further, the electrode group composed of the IDT electrode group and the separation electrode has a plurality of stages, and these electrode groups are electrically connected to each other.

  As described above, since the electrode group is separated into the individual IDT electrodes and reflector electrodes constituting the electrode group, the degree of freedom in selecting the resonance mode is increased as in the first embodiment, and therefore the surface acoustic wave amplitude is increased. The degree of freedom in controlling the distribution increases, and it can be used for controlling the filter characteristics. When the degree of freedom in selecting the resonance mode is larger, the resonance frequency can be arranged with a certain interval or more, and as a result, it is advantageous for widening the band. Furthermore, in one electrode group, the average electrode finger pitch of the IDT electrodes at one or both ends of the IDT electrode group is smaller than the average electrode finger pitch of the other IDT electrodes or reflector electrodes. As a result, it is possible to widen the pass bandwidth of the filter characteristics.

<Embodiment 4>
The surface acoustic wave filter shown in FIG. 4 has three or more IDT electrodes (IDT electrodes 71 to 85) each having a plurality of long electrode fingers in a direction orthogonal to the propagation direction of the surface acoustic wave on the piezoelectric substrate. The electrode finger pitch of one or more IDT electrodes among these IDT electrodes is constant (in the fourth embodiment, in the IDT electrodes 71, 74, 77, 78, 81, 82, 85, the electrodes within one IDT electrode) The electrode pitch is constant, and IDT electrodes (IDT electrodes 72 and 76, 79 and 81, 82 and 84) located at both ends are electrically connected to each other, and adjacent IDT electrodes are not electrically connected One or more groups (electrode group 27 (comprising IDT electrodes 72 to 76), electrode group 28 (comprising IDT electrodes 79, 80, 81), electrode group 29 (comprising IDT electrodes 82, 83, 84), IDT Electrode group (electrode group composed of IDT electrodes 72, 74, 76, IDT electrode IDT electrodes (IDT electrodes 72 and 76 in the electrode group 27, IDTs in the electrode group 28) located at one or both ends of an electrode group composed of 79 and 81 and an electrode group composed of IDT electrodes 82 and 84) The average electrode finger pitch of the IDT electrodes 84) in the electrode 79 and the electrode group 29 is smaller than the average electrode finger pitch of the IDT electrodes other than the end portions.

  Thus, in the first stage surface acoustic wave element, the average electrode finger pitch of the IDT electrodes 72 is smaller than the average electrode finger pitch of the IDT electrodes 73, 74, 75, 76. Further, the average electrode finger pitch of the IDT electrodes 76 is smaller than the average electrode finger pitch of the IDT electrodes 72, 73, 74 and 75. Further, in the second stage surface acoustic wave element, the average electrode finger pitch of the IDT electrodes 79 is smaller than the average electrode finger pitch of the IDT electrodes 80 and 81. Further, the average electrode finger pitch of the IDT electrodes 84 is smaller than the average electrode finger pitch of the IDT electrodes 82 and 83. Also, adjacent IDT electrodes are not electrically connected.

  The electrode groups 27, 28, and 29 include one or more IDT electrodes (IDT electrodes 74, 81, 82) having a constant electrode finger pitch, and IDT electrodes (electrode groups 27) other than IDT electrodes having a constant electrode finger pitch. IDT electrodes 72, 73, 75, and 76, IDT electrodes 79 and 80 in the electrode group 28, IDT electrodes 83 and 84 in the electrode group 29) gradually move toward one end or both ends of the IDT electrode group. Is shorter. Further, the first-stage and second-stage surface acoustic wave elements are connected in cascade. 6 is an input terminal, and 7 and 8 are output terminals.

  In the fourth embodiment, the IDT electrodes constituting the electrode group are connected between the stages (IDT electrodes 73 and 80, 75 and 83). Further, IDT electrodes other than both ends of the electrode group may be grounded, electrically floating, connected to IDT electrodes of other electrode groups, or used for interstage connection. It doesn't matter. When the IDT electrodes constituting the electrode group are not electrically connected and are in an electrically floating state, there is an advantage that the wiring can be easily routed.

  Here, various modes in which the electrode finger pitch changes in the entire section of the IDT electrode are shown in FIG. In FIG. 5, (a) shows a case where the electrode finger pitch of the IDT electrode changes linearly in the entire section in the end direction of the IDT electrode. (B), (c), and (d) are cases where the electrode finger pitch of the IDT electrode changes nonlinearly in the entire direction toward the end of the IDT electrode, and (b) shows the change in the electrode finger pitch downward. When it is convex, (c) is when the change of the electrode finger pitch is upward, and (d) is when there is an inflection point of the change of the electrode finger pitch. Thus, the way in which the electrode finger pitch gradually decreases in the direction toward one end or both ends of the electrode group includes linear and non-linear cases. (E) is a diagram showing a case where the electrode finger pitch of the IDT electrode is constant in all sections.

  As described above, by separating the individual IDT electrodes constituting the electrode group in the same manner as in the first embodiment, the degree of freedom in selecting the resonance mode is increased, and the higher the degree of freedom, the more the resonance occurs with a certain interval. It becomes possible to arrange the frequency, and as a result, it is advantageous for widening the band. Furthermore, the IDT electrodes other than the IDT electrodes having a constant electrode finger pitch gradually reduce the electrode finger pitch in the direction toward one end or both ends of the IDT electrode group. Radiation loss can be prevented, and as a result, the pass band width of the filter characteristic can be widened.

<Embodiment 5>
FIG. 6 is a diagram illustrating a modification of the fourth embodiment. The overall configuration is similar to that shown in FIG. 4, and only the connection method between the stages of the first-stage surface acoustic wave element and the second-stage surface acoustic wave element is different, and the configuration is characterized.

  Specifically, compared to the configuration of FIG. 4, IDT electrodes 73 and 75 in the electrode group of the first stage surface acoustic wave element and IDT electrodes 80 and 83 in the IDT electrode group of the second stage surface acoustic wave element. Is not used for interstage connection. It is not electrically connected to other IDT electrodes and is in an electrically floating state. When the IDT electrode is not electrically connected and is in a floating state, there is an advantage that the wiring can be easily routed.

  Also in the fifth embodiment, as in FIG. 1, one or more IDT electrode groups including one or more IDT electrode groups in which IDT electrodes located at both ends are electrically connected to each other and adjacent IDT electrodes are not electrically connected are provided. In the IDT electrode group, the average electrode finger pitch of the IDT electrodes located at one end or both ends of the IDT electrode group is smaller than the average electrode finger pitch of the other IDT electrodes, and the IDT electrode group is an IDT electrode having a constant electrode finger pitch. An IDT electrode other than the IDT electrode including one or more and having a constant electrode finger pitch has a structure in which the electrode finger pitch gradually decreases in a direction toward one end or both ends of the IDT electrode group. Further, the IDT electrodes other than both ends of the IDT electrode group are not electrically connected in the fifth embodiment and are in an electrically floating state. Accordingly, by adopting an interstage connection structure different from that of the fourth embodiment in the cascade connection, it is possible to select a resonance mode different from that of the fourth embodiment, and it is possible to arrange the resonance frequencies with a certain interval. As a result, it is possible to widen the bandwidth using an approach different from that of the fourth embodiment.

  In addition, IDT electrodes other than both ends of the electrode group are used for interstage connection even when they are grounded, electrically floating, or connected to IDT electrodes of other IDT electrode groups. It doesn't matter. Further, the mode in which the electrode finger pitch changes in the entire section of the IDT electrode can take the state shown in FIG.

<Embodiment 6>
In the structure of the surface acoustic wave filter shown in FIG. 7, the electrode structure shown in FIG. 4 is used as a basic structure, and the reflector electrodes 91, 92, 93, 94 are arranged adjacent to each other by replacing the IDT electrodes located between the IDT electrode groups. I am letting. Similar to FIG. 4, an IDT electrode (IDT electrodes 71, 72, 74, 76, 77, 78, 79. 81, 82, 84, 85) are arranged, and among these IDT electrodes, the electrode finger pitch of one or more IDT electrodes is constant (in the fifth embodiment, IDT electrodes 71, 74, 77, 78, 81, 82, and 85, the electrode finger pitch is constant within one IDT electrode), and the IDT electrodes (IDT electrodes 72 and 76, 79 and 81, 82 and 84) located at both ends are electrically connected to each other. And at least one IDT electrode group to which adjacent IDT electrodes or reflector electrodes are not electrically connected (electrode group 27 (IDT electrode group (consisting of IDT electrodes 72, 74, 76) and reflector electrodes 91, 92). Electrode group 28 (IDT electrode group (comprising IDT electrodes 79 and 81)) and reflector electrode 93. Configuration), electrode group 29 (IDT electrode group (consisting of IDT electrodes 82 and 84) and reflector electrode 94)), IDT electrodes (in electrode group 27 in one end or both ends of these IDT electrode groups) The average electrode finger pitch of the IDT electrodes 72 and 76, the IDT electrode 79 in the electrode group 28 and the IDT electrode 84 in the electrode group 29) is smaller than the average electrode finger pitch of the other IDT electrodes or reflector electrodes (first step) In the surface acoustic wave element, the average electrode finger pitch of the IDT electrode 72 is smaller than the average electrode finger pitch of the IDT electrodes 74 and 76 and the reflector electrodes 91 and 92. The average electrode finger pitch of the IDT electrode 76 is less than the IDT electrode 72, 74 is smaller than the average electrode finger pitch between the reflector electrodes 93 and 94. Further, in the second stage surface acoustic wave element, the average electrode finger pitch between the IDT electrode 79 is equal to the average electrode finger pitch between the IDT electrode 81 and the reflector electrode 93. Yo In addition, the average electrode finger pitch of the IDT electrode 84 is smaller than the average electrode finger pitch of the IDT electrode 83 and the reflector electrode 94), and the adjacent IDT electrodes are not electrically connected.

  The electrode groups 27, 28, 29 include one or more IDT electrodes (IDT electrodes 74, 81, 82) having a constant electrode finger pitch, and IDT electrodes or reflector electrodes other than IDT electrodes having a constant electrode finger pitch. (IDT electrodes 72 and 76 and reflector electrodes 91 and 92 in electrode group 27, IDT electrode 79 and reflector electrode 93 in electrode group 28, IDT electrode 83 and reflector electrode 94 in electrode group 29) are the IDT electrode group. The electrode finger pitch gradually decreases in the direction toward one end or both ends of the electrode. In addition, reflector electrodes 2, 3, 4, and 5 having the same electrode finger pitch are disposed at both ends. Further, the first-stage and second-stage surface acoustic wave elements are connected in cascade. 6 is an input terminal, and 7 and 8 are output terminals. The number of electrode fingers constituting the reflector electrodes 91, 92, 93, 94 may be one or more. In addition, the reflector electrode constituting the electrode group may be grounded, floated, or used for interstage connection. It is advantageous in the case of a piezoelectric substrate having pyroelectric properties such as lithium tantalate. The mode in which the electrode finger pitch changes in the entire section of the IDT electrode can take the state shown in FIG.

  As described above, in the sixth embodiment, as in the first embodiment, by separating the individual IDT electrodes constituting the electrode group, the degree of freedom in selecting the resonance mode is increased. It is possible to arrange the resonance frequency with a gap, and as a result, it is advantageous for widening the band. Furthermore, since the reflector electrode is inserted into the IDT electrode group and the electrode finger pitch of the reflector electrode is changed, it is possible to achieve a wide band with a reduced ripple in the passband. Further, as a synergistic effect, the IDT electrode or reflector electrode other than the IDT electrode having a constant electrode finger pitch is gradually shortened in the direction toward one end or both ends of the IDT electrode group. It becomes possible to prevent the radiation loss of the surface acoustic wave to the bulk wave, and as a result, the pass bandwidth of the filter characteristic can be widened.

<Embodiment 7>
FIG. 8 is a view showing a modification of the first embodiment. FIG. 1 shows a surface acoustic wave filter connected in two stages, whereas FIG. 8 shows a surface acoustic wave filter in one stage. The average electrode finger pitch of the IDT electrodes (IDT electrodes 33, 34, 38, 39) located at one or both ends of the IDT electrode group has the same structure as the first stage of the first embodiment. It is smaller than the average electrode finger pitch of IDT electrodes other than the electrode group end. That is, the average electrode finger pitch of the IDT electrodes 33 is smaller than the average electrode finger pitch of the IDT electrodes 31 and 32. Further, the average electrode finger pitch of the IDT electrodes 34 is smaller than the average electrode finger pitch of the IDT electrodes 35, 36, 37 and 38. Further, the average electrode finger pitch of the IDT electrodes 38 is smaller than the average electrode finger pitch of the IDT electrodes 34, 35, 36, and 37. Further, the average electrode finger pitch of the IDT electrodes 39 is smaller than the average electrode finger pitch of the IDT electrodes 40 and 41. Adjacent IDT electrodes are not electrically connected. Further, reflector electrodes 2 and 3 having the same electrode finger pitch are disposed at both ends.

  In the seventh embodiment, as in the first embodiment, in all IDT electrodes, the electrode finger pitch is constant in the IDT electrode group as in the fourth embodiment, even if the electrode finger pitch is constant in one IDT electrode. An IDT electrode other than an IDT electrode including one or more IDT electrodes and having a constant electrode finger pitch may have a gradually decreasing electrode finger pitch in a direction toward one end or both ends of the IDT electrode group.

  As described above, in the seventh embodiment, as in the first embodiment, the individual IDT electrodes constituting the electrode group are separated and electrically connected to the IDT electrodes other than the IDT electrode group. The degree of freedom is increased, so that the degree of freedom in controlling the surface acoustic wave amplitude distribution is increased, and it can be used for controlling the filter characteristics. When the degree of freedom in selecting the resonance mode is larger, the resonance frequency can be arranged with a certain interval or more, and as a result, it is advantageous for widening the band. Furthermore, in one electrode group, the average electrode finger pitch of the IDT electrodes at one or both ends of the IDT electrode group is smaller than the average electrode finger pitch of the other electrodes, thereby reducing the radiation loss of the surface acoustic wave to the bulk wave. As a result, the pass bandwidth of the filter characteristic can be widened.

<Eighth embodiment>
FIG. 9 is a view showing a modification of the fourth embodiment. 4 shows a surface acoustic wave filter connected in two stages, whereas FIG. 9 shows a surface acoustic wave filter in one stage. An IDT electrode having the same structure as that of the first stage of the fourth embodiment and having an average electrode finger pitch of IDT electrodes (IDT electrodes 72 and 76) positioned at both ends of the IDT electrode group other than the ends of the electrode group. Smaller than the average electrode finger pitch. That is, the average electrode finger pitch of the IDT electrode 72 is smaller than the average electrode finger pitch of the IDT electrodes 73, 74, 75, 76. The average electrode finger pitch of the IDT electrode 76 is smaller than the average electrode finger pitch of the IDT electrodes 72, 73, 74, 75. Adjacent IDT electrodes are not electrically connected. The electrode group 27 includes one or more IDT electrodes (IDT electrodes 74) having a constant electrode finger pitch, and IDT electrodes other than IDT electrodes having a constant electrode finger pitch (IDT electrodes 72, 73, 75 in the electrode group 27). , 76), the electrode finger pitch gradually decreases in the direction toward one end or both ends of the IDT electrode group. Further, reflector electrodes 2 and 3 having the same electrode finger pitch are disposed at both ends.

<Ninth Embodiment>
FIG. 10 is a view showing a modification of the eighth embodiment. The electrode group 27 in FIG. 8 is composed of five IDT electrodes, whereas in the modification of FIG. 10, it is composed of nine IDT electrodes. The average electrode finger pitch of the IDT electrodes (IDT electrodes 302 and 310) located at both ends of the electrode group 201 is smaller than the average electrode finger pitch of the IDT electrodes other than the ends of the electrode group. That is, the average electrode finger pitch of the IDT electrodes 302 is smaller than the average electrode finger pitch of the IDT electrodes 303 to 310. Further, the average electrode finger pitch of the IDT electrodes 310 is smaller than the average electrode finger pitch of the IDT electrodes 302 to 309. Adjacent IDT electrodes are not electrically connected. Further, reflector electrodes 2 and 3 having the same electrode finger pitch are disposed at both ends. In the ninth embodiment, as in the first embodiment, in all IDT electrodes, the electrode finger pitch is constant in the IDT electrode group as in the fourth embodiment, even if the electrode finger pitch is constant in one IDT electrode. An IDT electrode other than an IDT electrode including one or more IDT electrodes and having a constant electrode finger pitch may have a gradually decreasing electrode finger pitch in a direction toward one end or both ends of the IDT electrode group. The IDT electrodes constituting the IDT electrode group are electrically connected to IDT electrodes other than the IDT electrode group. The IDT electrodes 303 and 305 constituting the electrode group 201 are connected to the IDT electrode 301 other than the electrode group 201, and the IDT electrodes 307 and 309 constituting the electrode group 201 are connected to the IDT electrode 311 other than the electrode group 201. Connected with.

  As described above, in the ninth embodiment, as in the seventh embodiment, the number of individual IDT electrodes constituting the electrode group is further divided into a plurality of pieces and electrically connected to IDT electrodes other than the IDT electrode group. The method of selecting the resonance mode is different from that of the seventh embodiment, and the resonance frequency can be arranged with a certain interval or more, and as a result, the bandwidth can be broadened by an approach different from that of the seventh embodiment. Furthermore, in one electrode group, the average electrode finger pitch of the IDT electrodes at one or both ends of the IDT electrode group is smaller than the average electrode finger pitch of the other electrodes, thereby reducing the radiation loss of the surface acoustic wave to the bulk wave. As a result, the pass bandwidth of the filter characteristic can be widened.

<Embodiment 10>
FIG. 11 is a view showing a modification of the ninth embodiment. The surface acoustic wave filter is composed of nine IDT electrodes as in FIG. 10 has the same structure, but the IDT electrodes constituting the electrode group 201 are electrically connected to IDT electrodes other than the electrode group 201 and are not electrically connected in the electrode group 201. The IDT electrode in a floating state is arranged. That is, the IDT electrode 303 constituting the electrode group 201 is connected to the IDT electrode 301 other than the electrode group 201, and the IDT electrode 309 constituting the electrode group 201 is connected to the IDT electrode 311 other than the electrode group 201. Has been. The IDT electrodes 305 and 307 are not electrically connected and are in an electrically floating state.

  An electrode finger pitch mode of the IDT electrode or the reflector electrode in the electrode group 201 is shown in FIG. When the electrode finger pitch is constant in the entire section of one IDT electrode, two types shown in FIGS. 12A and 12B are allowed. Electrode FIG. 12 (a) shows the case where the electrode finger pitch of the IDT electrodes is successively reduced in the direction toward the end of the IDT electrode group. FIG. 12B shows a case where IDT electrodes having a slightly larger electrode finger pitch are arranged in the direction toward the end of the IDT electrode group while the electrode finger pitch of the IDT electrodes is reduced. This is because IDT electrodes having a slightly larger electrode finger pitch are arranged in this way for the purpose of reducing ripples. In FIG. 12C, the electrode finger pitch of the IDT electrodes at one end or both ends of the IDT electrode group is gradually shortened over the entire section. In the direction toward one end or both ends of the IDT electrode group, the IDT electrode or reflector electrode other than the IDT electrode having a constant electrode finger pitch may be gradually shortened over the entire section.

  As described above, in the tenth embodiment, as in the ninth embodiment, the IDT electrodes that constitute the electrode group are further separated into a plurality of IDT electrodes. Since the resonant connection is selected, the resonance mode selection method is different, and it is possible to arrange the resonance frequency with a certain interval. As a result, it is possible to broaden the bandwidth by an approach different from that of the ninth embodiment. It becomes. Furthermore, in one electrode group, the average electrode finger pitch of the IDT electrodes at one or both ends of the IDT electrode group is smaller than the average electrode finger pitch of the other electrodes, thereby reducing the radiation loss of the surface acoustic wave to the bulk wave. As a result, the pass bandwidth of the filter characteristic can be widened.

<Embodiment 11>
In the structure of the surface acoustic wave filter shown in FIG. 13, an IDT electrode is formed out of the IDT electrodes 47 located at the center of the second-stage resonator type surface acoustic wave filter, with the electrode structure of FIG. 3 as a basic structure. One of the comb-like electrodes is divided into two so as to correspond to balanced input / output. In the figure, reference numerals 10 and 11 denote output terminals or input terminals.

  Similar to FIG. 3, three or more IDT electrodes having a plurality of long electrode fingers are arranged on the piezoelectric substrate in a direction orthogonal to the propagation direction of the surface acoustic wave, and one or more of these IDT electrodes are arranged. The IDT electrodes of the IDT electrodes are constant, the IDT electrodes located at both ends are electrically connected to each other, and one or more IDT electrodes that are not electrically connected to adjacent IDT electrodes or reflector electrodes are provided, IDT electrodes adjacent to one end or both ends of the IDT electrode group have an average electrode finger pitch smaller than that of other IDT electrodes, or IDT electrodes or reflector electrodes other than the end portions, and adjacent IDT electrodes Alternatively, the reflector electrode is not electrically connected. The electrode finger pitch of the IDT electrode 47 of the second stage surface acoustic wave element is the same over the entire section.

  As described above, in the eleventh embodiment, in addition to the effect of widening the band of the third embodiment, among the IDT electrodes 47 positioned at the center of the second-stage resonator-type surface acoustic wave filter, Since the comb-like electrode is divided into two, the surface acoustic wave filter can be adapted to balanced input / output.

<Embodiment 12>
The surface acoustic wave filter shown in FIG. 14 is formed by cascading two stages of surface acoustic wave elements based on the electrode structure of FIG. 3 and the resonator electrode pattern of the two stages of surface acoustic wave elements. Are characterized by having substantially the same electrode finger repetitive shape. That is, the electrode group of the electrode group (surface acoustic wave resonator) composed of the resonator electrode pattern of the first stage surface acoustic wave element and the electrode group composed of the resonator electrode pattern of the second stage surface acoustic wave element ( The arrangement of the electrode fingers of the surface acoustic wave resonators is substantially the same by parallel movement.

  Similar to FIG. 3, three or more IDT electrodes having a plurality of long electrode fingers are arranged on the piezoelectric substrate in a direction orthogonal to the propagation direction of the surface acoustic wave, and one or more of these IDT electrodes are arranged. An IDT electrode having a constant electrode finger pitch, and having at least one electrode group in which IDT electrodes located at both ends are electrically connected to each other and adjacent IDT electrodes or reflector electrodes are not electrically connected, The average electrode finger pitch of IDT electrodes located at one end or both ends of the electrode group is smaller than the average electrode finger pitch of other IDT electrodes, or IDT electrodes or reflector electrodes other than the end portions, and adjacent IDT electrodes or reflections. The electrode is not electrically connected. The number of electrode fingers constituting the reflector electrodes 61, 62, 63, 64, 65, 66, 67, 68 may be one or more. The reflector electrode of the IDT electrode group is grounded in the third embodiment. The reflector electrode of the IDT electrode group may be grounded, floating, or used for interstage connection. When the reflector electrode is not electrically connected and is in a floating state, there is an advantage that the wiring can be easily routed.

  The IDT electrode 36 located at the center of the first stage is used as an unbalanced input section or output section. The IDT electrode 47 located at the center of the second-stage resonator electrode pattern is used as a balanced input unit or a balanced output unit, and is connected to the first balanced input / output terminal 10 and the second balanced input / output terminal 11. .

  According to the twelfth embodiment, in addition to the effect of widening the band by adjusting the electrode finger pitch between the IDT electrode and the reflector electrode, the resonator pattern is composed of two, so that the filter has a high attenuation. This is advantageous in that characteristics can be obtained. In addition, with the above structure, both the amplitude balance and the phase balance are improved over the conventional resonator type surface acoustic wave filter.

<Embodiment 13>
The resonator-type surface acoustic wave filter shown in FIG. 15 is the same as the second-stage surface acoustic wave filter shown in FIG. 13, except that the IDT electrode generates one or more mode resonances in series or in parallel with the IDT electrode. The resonators 12 and 13 including the reflector electrodes sandwiching the IDT electrode are connected.

  Specifically, in the surface acoustic wave filter of FIG. 15A, as in FIG. 8, an IDT electrode having a plurality of long electrode fingers on the piezoelectric substrate in a direction orthogonal to the propagation direction of the surface acoustic wave. Of the IDT electrodes, the electrode finger pitch of one or more IDT electrodes is constant, the IDT electrodes located at both ends are electrically connected to each other, and adjacent IDT electrodes are One or more electrode groups that are not electrically connected are provided, and the average electrode finger pitch of the IDT electrodes located at one end or both ends of the IDT electrode group is the other electrode IDT or the average electrode finger pitch of the IDT electrodes other than the ends. Smaller and adjacent IDT electrodes are not electrically connected. In the surface acoustic wave filter of FIG. 15B, similarly to FIG. 13, among the IDT electrodes 47 at the center of the resonator type surface acoustic wave filter of the second stage, one comb-tooth shape constituting the IDT electrode It is characterized in that the electrode is divided into two to correspond to balanced input / output. In the figure, reference numerals 10 and 11 denote output terminals or input terminals.

  Further, as a method for adding a surface acoustic wave resonator, one or more resonators may be combined and added in series, parallel, or series-parallel. In the above structure, a ladder in which a surface acoustic wave resonator is added to a ladder circuit. The surface acoustic wave resonator may be a lattice type surface acoustic wave resonator so as to be a lattice type circuit.

  By adjusting the electrode finger pitch of the IDT electrode and reflector electrode, the above structure can reduce the degradation of insertion loss, broaden the pass band width of the filter characteristics, and further improve the quality of the elastic surface. A wave filter can be provided. Further, by adding surface acoustic wave resonators in series and in parallel, impedance matching can be achieved, and by connecting surface acoustic wave resonators, attenuation poles can be formed, and a plurality of IDT electrodes can be formed. By adjusting the electrode finger pitch of the reflector electrode, it is possible to form a plurality of attenuation poles and control their formation, and the design that satisfies the more highly required specifications with high out-of-band attenuation It becomes possible.

  As described above, three or more IDT electrodes provided with a plurality of long electrode fingers in the direction orthogonal to the propagation direction of the surface acoustic wave are arranged on the piezoelectric substrate, and one or more IDTs among these IDT electrodes are arranged. An IDT electrode having at least one IDT electrode group in which the electrode finger pitch of the electrodes is constant, the IDT electrodes located at both ends are electrically connected to each other, and the adjacent IDT electrodes or reflector electrodes are not electrically connected The average electrode finger pitch of IDT electrodes located at one end or both ends of the group is smaller than the average electrode finger pitch of other IDT electrodes, or IDT electrodes or reflector electrodes other than the end portions, and adjacent IDT electrodes or reflections. Since the electrode is not electrically connected, the band can be expanded while maintaining a low insertion loss.

  The electrode structure of the surface acoustic wave filter shown in FIGS. 1 to 15 is not limited to the illustrated embodiment. An electrode finger that is long in the direction orthogonal to the propagation direction of the surface acoustic wave is placed on the piezoelectric substrate. A plurality of IDT electrodes provided with a plurality of IDT electrodes are arranged, and among these IDT electrodes, the electrode finger pitch of one or more IDT electrodes is constant, and the IDT electrodes located at both ends are electrically connected to each other, And one or more IDT electrode groups to which adjacent IDT electrodes or reflector electrodes are not electrically connected, and an average electrode finger pitch of IDT electrodes located at one end or both ends of the IDT electrode group is equal to other IDT electrodes, or As long as it is smaller than the average electrode finger pitch of the IDT electrodes or reflector electrodes other than the end portions and the adjacent IDT electrodes or reflector electrodes are not electrically connected, it can be arranged in multiple stages. It is also possible to.

  As the piezoelectric substrate 1 for the surface acoustic wave filter, 36 ° ± 3 ° Y-cut X propagation lithium tantalate single crystal, 42 ° ± 3 ° Y cut X propagation lithium tantalate single crystal, 64 ° ± 3 ° Y Cut X Propagation Lithium Niobate Single Crystal, 41 ° ± 3 ° Y Cut X Propagation Lithium Single Crystal, 45 ° ± 3 ° X Cut Z Propagation Lithium Tetraborate Single Crystal has a large electromechanical coupling coefficient and frequency temperature coefficient Is preferable as a piezoelectric substrate. Of these pyroelectric piezoelectric single crystals, if the substrate has a significantly reduced pyroelectric property due to solid solution of oxygen defects or Fe, the reliability of the device is good. The thickness of the piezoelectric substrate is preferably about 0.1 mm to 0.5 mm. If the thickness is less than 0.1 mm, the piezoelectric substrate becomes brittle, and if it exceeds 0.5 mm, the material cost and component dimensions increase, and the piezoelectric substrate cannot be used.

  The IDT electrode and the reflector electrode are made of Al or an Al alloy (Al—Cu system, Al—Ti system), and are formed by a thin film formation method such as a vapor deposition method, a sputtering method, or a CVD method. An electrode thickness of about 0.1 μm to 0.5 μm is suitable for obtaining characteristics as a surface acoustic wave filter.

Further, the surface acoustic wave propagation part on the surface of the surface acoustic wave filter according to the present invention and the piezoelectric substrate is formed with SiO ₂ , SiN _x , Si, Al ₂ O ₃ as a protective film to prevent electrical conduction due to conductive foreign matter. It is also possible to improve power durability.

  The surface acoustic wave filter of the present invention can be applied to a communication device. That is, at least one of the reception circuit and the transmission circuit is provided and used as a bandpass filter included in these circuits. For example, the transmission signal output from the transmission circuit is put on the carrier frequency by the mixer, the unnecessary signal is attenuated by the band pass filter, and then the transmission signal is amplified by the power amplifier and transmitted from the antenna through the duplexer. Communication device equipped with a transmission circuit capable of receiving the received signal with an antenna, the received signal that passed through the duplexer is amplified with a low noise amplifier, and then the unnecessary signal is attenuated with a band-pass filter, and then the carrier frequency is detected with a mixer. The present invention is applicable to a communication device having a receiving circuit that separates a signal and transmits the signal to a receiving circuit that extracts the signal. By adopting the surface acoustic wave device of the present invention, an excellent communication device with improved sensitivity can be obtained. Can be provided.

Thus, according to the surface acoustic wave device of the present invention, in the electrode group composed of the IDT electrode group and the separation electrode, by providing the separation electrode composed of at least one of the IDT electrode and the reflector electrode, the resonance mode The degree of freedom of selection increases, and the degree of freedom of control of the surface acoustic wave amplitude distribution increases. As a result, it is possible to control the filter characteristics such as widening the bandwidth while reducing the ripple. Further, by adopting a non-connected configuration in which the separation electrodes (non-adjacent IDT electrodes, etc.) of other IDT electrode groups are electrically connected or not connected, the degree of freedom of resonance mode selection is further increased. Can be increased. Also, when you widen the spacing between the forcibly resonant mode trying broadband tends to S ₂₁ is a transmission characteristic between the resonance peak and the resonance peak is reduced. As described above, it is possible to arrange the resonance frequencies with a certain degree of interval when the degree of freedom of selection of the possible resonance modes is large (resonance frequencies suitable for wideband characteristics can be easily arranged). This is advantageous for widening the bandwidth. In addition, the electrode finger pitch of one or more IDT electrodes in the IDT electrode group is constant, and the average electrode finger pitch of IDT electrodes located at one or both ends of the IDT electrode group is the remaining electrode finger pitch in one electrode group. Since it is narrower than the average electrode finger pitch of all the electrodes, it becomes possible to prevent the radiation loss of the surface acoustic wave to the bulk wave, and as a result, the pass band width of the filter characteristic can be widened.

  In addition, since two adjacent IDT electrodes or adjacent IDT electrodes and reflector electrodes have different average electrode finger pitches and are not electrically connected to each other, the degree of freedom in selecting a resonance mode is increased. In addition, since the electrical coupling is disconnected while the surface acoustic wave coupling is kept as it is, ripples can be reduced and, in particular, the shoulder characteristics can be improved. As a result, a wide band can be realized.

  In addition, the electrode group composed of the IDT electrode group and the separation electrode includes a narrow pitch electrode group composed of one or more electrodes having a narrow average electrode finger pitch from one end of the IDT electrode group to the other end; In addition to the effects of the surface acoustic wave device described above, the Q of the entire surface acoustic wave filter is added to the adjacent region of the wide pitch electrode group composed of one or more electrodes having a wide average electrode finger pitch. It is possible to increase the value and prevent the radiation loss of the surface acoustic wave to the bulk wave, and finely adjust the resonance frequency between the first-order mode, the third-order mode and their harmonic modes in the narrow-pitch electrode group. Therefore, it is possible to realize a surface acoustic wave device with excellent electrical characteristics in a wider band while preventing deterioration of insertion loss.

  In addition, an electrode group composed of an IDT electrode group and a separation electrode is arranged in a plurality of stages in a direction orthogonal to the propagation direction of the surface acoustic wave, and the electrode groups of the plurality of stages are electrically connected to each other. Yes. As a result, for example, the number of paths connected from the first stage to the second stage can be increased, the degree of freedom in designing the passband is increased, and the passband width can be more effectively widened.

  Further, by connecting and adding surface acoustic wave resonators in series, parallel or series-parallel to the IDT electrodes constituting the IDT electrode group, impedance matching can be achieved and the surface acoustic wave resonators are connected. Thus, an attenuation pole can be formed, and the characteristics can be controlled so that the out-of-band attenuation amount satisfies the specifications required for high attenuation.

  Further, for example, one of the plurality of opposing comb-like electrodes constituting at least one IDT electrode is divided, and the divided comb-like electrode is connected to the input and output balanced signals. By using the electrodes, it is possible to provide a surface acoustic wave device having the function of an unbalanced-balanced signal converter.

  Also, for example, in the first and second electrode groups (for example, composed of a plurality of IDT electrodes and reflector electrodes) arranged along the propagation direction of the surface acoustic wave, one electrode group is connected to the other. When the electrode group is moved in parallel, if it is arranged so that both electrode groups substantially coincide with each other, a surface acoustic wave device that is remarkably excellent in insertion loss, amplitude balance, and phase balance can be provided. Furthermore, it is possible to realize a surface acoustic wave device excellent in quality by widening the pass bandwidth of the filter characteristics.

  As described above, it is possible to provide a communication device such as an excellent communication device having a reception circuit and a transmission circuit each having an excellent surface acoustic wave device and having extremely good sensitivity.

  In the above description of the embodiment, a surface acoustic wave filter has been described as an example of a surface acoustic wave device, but the present invention can also be suitably applied to a surface acoustic wave resonator. In addition, for the sake of simplicity, a gap between at least two IDT electrodes in the IDT electrode group is long in a direction perpendicular to the propagation direction of the other IDT electrodes and the surface acoustic wave, which is not electrically connected to the IDT electrode group. Although an example in which one of the separation electrodes among the reflector electrodes having a plurality of electrode fingers is disposed has been shown, the present invention is not limited to this, and other IDT electrodes and reflector electrodes 2 A plurality of seeds may be arranged, and other configurations can be appropriately changed without departing from the gist of the present invention.

  Next, an embodiment that further embodies the present invention will be described.

An embodiment in which the surface acoustic wave filter shown in FIG. A fine electrode pattern of Al (99% by mass) -Cu (1% by mass) was formed on a LiTaO ₃ single crystal piezoelectric substrate having a 38.7 ° Y-cut in the X direction. The average electrode finger pitch of the IDT electrodes 71, 74, 77, 78, 81, 82, 85 (the average center distance between adjacent electrode fingers) was 2.28 μm. The logarithms of the IDT electrodes 71, 74, 78, 81, 82, and 85 were 10 pairs, 14 pairs, 10 pairs, 7 pairs, 7 pairs, and 10 pairs. Also, the number of electrode fingers of the IDT electrodes 72, 73, 75, 76, 79, 80, 83 and 84 is 1 pair, 2 pairs, 2 pairs, 1 pair, 1 pair, 2 pairs, 2 pairs and 1 pair, respectively. The average electrode finger pitch of IDT electrodes 72, 73, 75, 76, 79, 80, 83 and 84 is 1.42 μm, 1.71 μm, 1.71 μm, 1.42 μm, 1.42 μm, 1.71 μm, 1.71 μm and 1.42 μm, respectively. It was. The electrode finger pitch was gradually shortened in the direction toward both ends of the electrode group 27. The average electrode finger pitch of the reflector electrodes 2, 3, 4, and 5 disposed on both sides of the surface acoustic wave resonator was 2.33 μm. The number of reflector electrodes was 70. For pattern production, photolithography was performed using a sputtering apparatus, a reduction projection exposure machine (stepper), and an RIE (Reactive Ion Etching) apparatus.

  First, the substrate material was subjected to ultrasonic cleaning with acetone / IPA (isopropyl alcohol) or the like to remove organic components. Next, the substrate was sufficiently dried by a clean oven, and then an electrode was formed. A sputtering apparatus was used for film formation of the electrode, and a material composed of an Al (99 mass%)-Cu (1 mass%) alloy was used. The electrode film thickness at this time was about 0.30 μm.

  Next, a photoresist is spin-coated to a thickness of about 0.5 μm, patterned into a desired shape by a reduction projection exposure apparatus (stepper), and an unnecessary portion of the photoresist is dissolved with an alkaline developer by a developing device. After the pattern was exposed, the electrode film was etched by the RIE apparatus, the patterning was finished, and the electrode pattern of the surface acoustic wave resonator constituting the surface acoustic wave filter was obtained.

Thereafter, a protective film was formed on a predetermined region of the electrode. That is, SiO ₂ was formed to a thickness of about 0.02 μm on the electrode pattern and the piezoelectric substrate by a CVD (Chemical Vapor Deposition) apparatus. Thereafter, the photoresist was patterned by photolithography, and the flip-chip window opening was etched by an RIE apparatus or the like. Thereafter, an electrode mainly composed of Al was formed using a sputtering apparatus. The electrode film thickness at this time was about 1.0 μm. Thereafter, the photoresist and unnecessary portions of Al were simultaneously removed by a lift-off method to complete a pad for forming a flip chip bump.

  Next, a flip-chip bump made of Au was formed on the pad using a bump bonding apparatus. The bump had a diameter of about 80 μm and a height of about 30 μm.

Next, the substrate was diced along dicing lines and divided into chips. Thereafter, each chip was bonded to the inside of the package with the flip chip mounting apparatus with the electrode forming surface on the bottom surface. Thereafter, baking was performed in an N ₂ atmosphere to complete a surface acoustic wave filter. The package used was a 2.5 × 2.0 mm square laminate structure. As a comparative sample, a fine electrode pattern as shown in FIG. 19 was produced in the same process as described above. There are 19 pairs of IDT electrodes 204, and 10 pairs of IDT electrodes 203, 205, 206, 207, 208. The average electrode finger pitch (average distance between adjacent electrode fingers) of the IDT electrodes 203, 204, 205, 206, 207 and 208 is 2.28 μm, 2.10 μm, 2.28 μm, 2.28 μm, 2.10 μm and 2.10 μm, respectively. did. The average period length of the reflector electrodes 210, 211, 212, and 213 provided on both sides of the IDT electrode was 2.33 μm.

  Next, the characteristics of the surface acoustic wave filter in this example were measured. A signal of 0 dBm was input, and measurement was performed under the conditions of a frequency of 780 MHz to 960 MHz and a measurement point of 800 points. The number of samples is 30, and the measuring instrument is a multiport network analyzer E5071A manufactured by Agilent Technologies.

  A frequency characteristic graph near the passband is shown in FIG. Here, FIG. 16 is a graph showing the frequency dependence of the insertion loss representing the transmission characteristics of the filter. The filter characteristics of the product of the present invention were very good. The specific bandwidth of this example was 4.9% as shown by the solid line in FIG. On the other hand, the specific bandwidth of the comparative example was 4.2% as shown by the broken line in FIG. Thus, in this example, it was possible to realize a wide band.

Next, an example of the surface acoustic wave filter shown in FIG. 6 will be described. A fine electrode pattern made of Al (99 mass%)-Cu (1 mass%) as shown in FIG. 6 was formed on the piezoelectric substrate 1 made of a LiTaO ₃ single crystal having a 38.7 ° Y-cut propagation in the X direction. The average electrode finger pitch of the IDT electrodes 71, 74, 77, 78, 81, 82, 85 (the average center distance between adjacent electrode fingers) was 2.28 μm. The logarithm of the IDT electrode 71 is 10 pairs, the logarithm of 74 is 14 pairs, the logarithm of 78 is 10 pairs, the logarithm of 81 is 7 pairs, the logarithm of 82 is 7 pairs, and the logarithm of 85 is 10 pairs. The number of electrode fingers of the IDT electrodes 72, 73, 75, 76, 79, 80, 83 and 84 is 1 pair, 2 pairs, 2 pairs, 1 pair, 1 pair, 2 pairs, 2 pairs, 1 pair, respectively. The average electrode finger pitch of IDT electrodes 72, 73, 75, 76, 79, 80, 83 and 84 is 1.42 μm, 1.71 μm, 1.71 μm, 1.42 μm, 1.42 μm, 1.71 μm, 1.71 μm and 1.42 μm, respectively. It was. The electrode finger pitch gradually decreased in the direction toward both ends of the electrode group 27. The average electrode finger pitch of the reflector electrodes 2, 3, 4, and 5 disposed on both sides of the surface acoustic wave resonator was 2.33 μm. The number of reflector electrodes was 70. For pattern production, photolithography was performed using a sputtering apparatus, a reduction projection exposure machine (stepper), and an RIE (Reactive Ion Etching) apparatus.

  First, the substrate material was subjected to ultrasonic cleaning with acetone / IPA or the like to remove organic components. Next, the substrate was sufficiently dried by a clean oven, and then an electrode was formed. A sputtering apparatus was used for film formation of the electrode, and a material composed of an Al (99 mass%)-Cu (1 mass%) alloy was used. The electrode film thickness at this time was about 0.30 μm.

  Next, a photoresist is spin-coated to a thickness of about 0.5 μm, patterned into a desired shape by a reduction projection exposure apparatus (stepper), and an unnecessary portion of the photoresist is dissolved with an alkaline developer by a developing device. After the pattern was exposed, the electrode film was etched by the RIE apparatus, the patterning was finished, and the electrode pattern of the surface acoustic wave resonator constituting the ladder type surface acoustic wave filter was obtained.

Thereafter, a protective film was formed on a predetermined region of the electrode. That is, SiO ₂ was formed to a thickness of about 0.02 μm on the electrode pattern and the piezoelectric substrate by a CVD apparatus. Thereafter, the photoresist was patterned by photolithography, and the flip-chip window opening was etched by an RIE apparatus or the like. Thereafter, an electrode mainly composed of Al was formed using a sputtering apparatus. The electrode film thickness at this time was about 1.0 μm. Thereafter, the photoresist and unnecessary portions of Al were simultaneously removed by a lift-off method to complete a pad for forming a flip chip bump.

  Next, a flip-chip bump made of Au was formed on the pad using a bump bonding apparatus. The bump had a diameter of about 80 μm and a height of about 30 μm.

  Next, the substrate was diced along dicing lines and divided into chips. Thereafter, each chip was bonded to the inside of the package with the flip chip mounting apparatus with the electrode forming surface on the bottom surface. Thereafter, baking was performed in a nitrogen atmosphere to complete a surface acoustic wave filter. The package used was a 2.5 × 2.0 mm square laminate structure.

  As a comparative sample, a fine electrode pattern as shown in FIG. 19 was produced in the same process as described above. There are 19 pairs of IDT electrodes 204, and 10 pairs of IDT electrodes 203, 205, 206, 207, 208. The average electrode finger pitch (average distance between adjacent electrode fingers) of the IDT electrodes 203, 204, 205, 206, 207, 208 is 2.28 μm, 2.10 μm, 2.28 μm, 2.28 μm, 2.10 μm, 2.10 μm, respectively. did. The average period length of the reflector electrodes 210, 211, 212, and 213 provided on both sides of the IDT electrode was 2.33 μm.

  Next, the characteristics of the surface acoustic wave filter in this example were measured. FIG. 17 shows a frequency characteristic graph near the passband. Here, FIG. 17 is a graph showing the frequency dependence of the insertion loss representing the transmission characteristics of the filter. A signal of 0 dBm was input, and measurement was performed under conditions of a frequency of 780 MHz to 960 MHz and the number of measurement points: 800 points. The number of samples is 30, and an example of the electrical characteristics is shown in FIG. A multi-port network analyzer E5071A manufactured by Agilent Technologies was used as a measuring instrument.

  A frequency characteristic graph near the passband is shown in FIG. Here, FIG. 17 is a graph showing the frequency dependence of the insertion loss representing the transmission characteristics of the filter. The filter characteristics of the product of the present invention were very good. The specific bandwidth of this example was 4.6% as shown by the solid line in FIG. On the other hand, the specific bandwidth of the comparative example was 4.2% as shown by the broken line in FIG. Thus, in this example, it was possible to realize a wide band.

Next, an example of the surface acoustic wave filter shown in FIG. 7 will be described. A fine electrode pattern made of Al (99 mass%)-Cu (1 mass%) as shown in FIG. 6 was formed on the piezoelectric substrate 1 made of a LiTaO ₃ single crystal having a 38.7 ° Y-cut propagation in the X direction. The average electrode finger pitch (average distance between adjacent electrode fingers) of the IDT electrodes 71, 74, 77, 78, 81, 82, 85 was 2.28 μm. The logarithm of the IDT electrode 71 is 10 pairs, the logarithm of 74 is 14 pairs, the logarithm of 78 is 10 pairs, the logarithm of 81 is 7 pairs, the logarithm of 82 is 7 pairs, and the logarithm of 85 is 10 pairs. Further, the number of pairs of electrode fingers of the IDT electrodes 72, 76, 79 and 84 is one pair, and the average electrode finger pitch of the IDT electrodes 72, 76, 79 and 84 is 1.42 μm. The number of reflector electrodes 91, 92, 93 and 94 was all four, and the average electrode finger pitch of the reflector electrodes 91, 92, 93 and 94 was 1.71 μm. The electrode finger pitch of IDT electrodes or reflector electrodes other than the IDT electrode having a constant electrode finger pitch gradually decreased in the direction toward both ends of the electrode group 27. The average electrode finger pitch of the reflector electrodes 2, 3, 4, and 5 disposed on both sides of the surface acoustic wave resonator was 2.33 μm. The number of reflector electrodes was 70. For pattern production, photolithography was performed using a sputtering apparatus, a reduction projection exposure machine (stepper), and an RIE (Reactive Ion Etching) apparatus.

  First, the substrate material was subjected to ultrasonic cleaning with acetone / IPA or the like to remove organic components. Next, the substrate was sufficiently dried by a clean oven, and then an electrode was formed. A sputtering apparatus was used for film formation of the electrode, and a material composed of an Al (99 mass%)-Cu (1 mass%) alloy was used. The electrode film thickness at this time was about 0.30 μm.

  Next, a photoresist is spin-coated to a thickness of about 0.5 μm, patterned into a desired shape by a reduction projection exposure apparatus (stepper), and an unnecessary portion of the photoresist is dissolved with an alkaline developer by a developing device. After the pattern was exposed, the electrode film was etched by the RIE apparatus, the patterning was finished, and the electrode pattern of the surface acoustic wave resonator constituting the ladder type surface acoustic wave filter was obtained.

Thereafter, a protective film was formed on a predetermined region of the electrode. That is, SiO ₂ was formed to a thickness of about 0.02 μm on the electrode pattern and the piezoelectric substrate by a CVD apparatus. Thereafter, the photoresist was patterned by photolithography, and the flip-chip window opening was etched by an RIE apparatus or the like. Thereafter, an electrode mainly composed of Al was formed using a sputtering apparatus. The electrode film thickness at this time was about 1.0 μm. Thereafter, the photoresist and unnecessary portions of Al were simultaneously removed by a lift-off method to complete a pad for forming a flip chip bump.

  Next, a flip-chip bump made of Au was formed on the pad using a bump bonding apparatus. The bump had a diameter of about 80 μm and a height of about 30 μm.

  Next, the substrate was diced along dicing lines and divided into chips. Thereafter, each chip was bonded to the inside of the package with the flip chip mounting apparatus with the electrode forming surface on the bottom surface. Thereafter, baking was performed in a nitrogen atmosphere to complete a surface acoustic wave filter. The package used was a 2.5 × 2.0 mm square laminate structure.

  As a comparative sample, a fine electrode pattern as shown in FIG. 19 was produced in the same process as described above. The number of pairs of IDT electrodes 204 is 19 and the number of pairs of IDT electrodes 203, 205, 206, 207, 208 is 10 pairs. The average electrode finger pitch of the IDT electrodes 203, 204, 205, 206, 207, 208 (the average center distance between adjacent electrode fingers) is 2.28 μm, 2.10 μm, 2.28 μm, 2.28 μm, 2.10 μm, 2.10 μm, respectively. did. The average period length of the reflector electrodes 210, 211, 212, and 213 provided on both sides of the IDT electrode was 2.33 μm.

  Next, the characteristics of the surface acoustic wave filter in this example were measured. FIG. 17 shows a frequency characteristic graph near the passband. Here, FIG. 18 is a graph showing the frequency dependence of the insertion loss representing the transmission characteristics of the filter. A signal of 0 dBm was input, and measurement was performed under conditions of a frequency of 780 MHz to 960 MHz and the number of measurement points: 800 points. The number of samples is 30, and an example of the electrical characteristics is shown in FIG. A multi-port network analyzer E5071A manufactured by Agilent Technologies was used as a measuring instrument.

  FIG. 18 shows a frequency characteristic graph near the passband. Here, FIG. 18 is a graph showing the frequency dependence of the insertion loss representing the transmission characteristics of the filter. The filter characteristics of the product of the present invention were very good. The specific bandwidth of this example was 4.4% as shown by the solid line in FIG. On the other hand, the specific bandwidth of the comparative example was 4.2% as shown by the broken line in FIG. Thus, in this example, it was possible to realize a wide band.

It is a figure which shows typically an example of the electrode structure of the surface acoustic wave apparatus of this invention, and is the diagram and the top view of an electrode structure which explain typically the relationship between an electrode position and an electrode finger pitch. It is a figure which shows typically the other example of the electrode structure of the surface acoustic wave apparatus of this invention, and is the diagram which illustrates typically the relationship between an electrode position and an electrode finger pitch, and the top view of an electrode structure. It is a figure which shows typically the other example of the electrode structure of the surface acoustic wave apparatus of this invention, and is the diagram which illustrates typically the relationship between an electrode position and an electrode finger pitch, and the top view of an electrode structure. It is a figure which shows typically the other example of the electrode structure of the surface acoustic wave apparatus of this invention, and is the diagram which illustrates typically the relationship between an electrode position and an electrode finger pitch, and the top view of an electrode structure. It is a figure which shows typically the change of the electrode finger pitch of the IDT electrode of the surface acoustic wave apparatus of this invention, (a)-(e) is the line | wire which explains typically the relationship between an electrode position and an electrode finger pitch, respectively. It is a figure and a top view of an electrode structure. It is a figure which shows typically the other example of the electrode structure of the surface acoustic wave apparatus of this invention, and is the diagram which illustrates typically the relationship between an electrode position and an electrode finger pitch, and the top view of an electrode structure. It is a figure which shows typically the other example of the electrode structure of the surface acoustic wave apparatus of this invention, and is the diagram which illustrates typically the relationship between an electrode position and an electrode finger pitch, and the top view of an electrode structure. It is a top view which shows typically the other example of the electrode structure of the surface acoustic wave apparatus of this invention. It is a top view which shows typically the other example of the electrode structure of the surface acoustic wave apparatus of this invention. It is a top view which shows typically the other example of the electrode structure of the surface acoustic wave apparatus of this invention. It is a top view which shows typically the other example of the electrode structure of the surface acoustic wave apparatus of this invention. (A)-(c) is the diagram and the top view of an electrode structure which each explain typically the relationship between the electrode position of the surface acoustic wave apparatus of this invention, and an electrode finger pitch. It is a top view which shows typically the other example of the electrode structure of the surface acoustic wave apparatus of this invention. It is a top view which shows typically the other example of the electrode structure of the surface acoustic wave apparatus of this invention. (A), (b) is a top view which shows typically the other example of the electrode structure of the surface acoustic wave apparatus of this invention, respectively. It is a diagram which shows the frequency characteristic of the insertion loss in the pass band of a surface acoustic wave filter, and its vicinity. It is a diagram which shows the frequency characteristic of the insertion loss in the pass band of a surface acoustic wave filter, and its vicinity. It is a diagram which shows the frequency characteristic of the insertion loss in the pass band of a surface acoustic wave filter, and its vicinity. It is a figure which shows typically the example of an electrode structure of the conventional surface acoustic wave apparatus, and is the diagram and the top view of an electrode structure which explain typically the relationship between an electrode position and an electrode finger pitch.

Explanation of symbols

1,202: Piezoelectric substrate
21-29: Electrode group
31 to 47, 50 to 52, 71 to 85, 203 to 209, 301 to 311: IDT electrodes 2 to 5, 61 to 68, 91 to 94, 210 to 213: reflector electrodes
12, 13: Resonator
6, 9, 215: Input terminals
7, 8, 10, 11, 216, 217: Output terminals

Claims (8)

A piezoelectric substrate ;
An input terminal disposed on the piezoelectric substrate;
First, second, and third IDT electrodes that are electrically connected to the input terminal and arranged in order along the propagation direction of the surface acoustic wave, and the first IDT electrode and the second IDT electrode. A first separation electrode comprising an IDT electrode or a grounded reflector electrode disposed between and electrically floating, and disposed between the second IDT electrode and the third IDT electrode. And a second separation electrode comprising an IDT electrode or a grounded reflector electrode that is in an electrically floating state, and the first separation electrode of the first IDT electrode A second electrode group including an IDT electrode disposed adjacent to the first IDT electrode on the side opposite to the side where the first IDT electrode is disposed and not connected to the first IDT electrode, and the third IDT On the opposite side of the electrode from the side where the second separation electrode is disposed. Comprising of disposed adjacent to the IDT electrode, a third electrode group including the IDT electrodes that are and are and the third IDT electrode and disconnected, and the first surface acoustic wave device having, a,
One or more conductive Gokuyubi pitch of the first to third IDT electrodes is constant,
Before SL average electrode finger pitch of the first IDT electrode, the first from the electrode group of the electrode group consisting of said first IDT electrode of another IDT electrodes and separation electrodes except average electrode fingers rather narrow than the pitch,
Said third average electrode finger pitch of the IDT electrode, said first from said electrode group third with other IDT electrode excluding the IDT electrode narrower than the average electrode finger pitch of the electrode group consisting of a separation electrode Ikoto A surface acoustic wave device. An output terminal disposed on the piezoelectric substrate;
A second surface acoustic wave device having a fourth electrode group including a fourth IDT electrode electrically connected to the output terminal,
The surface acoustic wave device according to claim 1, wherein the first surface acoustic wave element and the second surface acoustic wave element are cascade-connected . The first electrode group includes a narrow-pitch electrode group composed of one or more electrodes having a narrow average electrode finger pitch from one end of the first electrode group to the other end, and an average electrode finger 3. The surface acoustic wave device according to claim 1, wherein the surface acoustic wave device has a region adjacent to a wide pitch electrode group composed of one or more electrodes having a wide pitch. The second surface acoustic wave element includes: a fifth electrode group including an IDT electrode disposed adjacent to one side of the fourth electrode group along a propagation direction of the surface acoustic wave; The surface acoustic wave device according to claim 2, further comprising: a sixth electrode group including an IDT electrode disposed adjacent to the other side of the fourth electrode group along a propagation direction . A surface acoustic wave resonator that generates one or more mode resonances is electrically connected in series, in parallel, or in series-parallel to the IDT electrodes constituting the first electrode group. Item 5. The surface acoustic wave device according to any one of Items 1 to 4. 3. The surface acoustic wave device according to claim 2, wherein the fourth electrode group includes a third separation electrode including an IDT electrode that is electrically floated or a reflector electrode that is grounded . 4. The surface acoustic wave device according to claim 1, further comprising an output terminal electrically connected to the second IDT electrode. A reflector electrode having a constant electrode finger pitch is disposed on one end side of the electrode group including the first to third electrode groups, and the other end side of the electrode group including the first to third electrode groups. The surface acoustic wave device according to claim 1, wherein a reflector electrode having a constant electrode finger pitch and having the same electrode finger pitch as that of the reflector electrode is disposed.

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