JP5581859B2 - Elastic wave filter - Google Patents

Description

  The present invention relates to an acoustic wave filter, for example, a (SAW: Surface Acoustic Wave) filter.

  The SAW device uses surface acoustic waves, and an electrode called IDT (interdigital transducer) is disposed on a piezoelectric substrate as an input side electrode and an output side electrode along the propagation direction of the elastic wave. An electrical-mechanical mutual conversion between an electric signal and an elastic wave is performed between two electrodes to give a frequency selection (band filter) characteristic. A SAW filter, which is one of SAW devices, is used as a panda-pass filter for various communication devices such as mobile phones that have been improved in function and size. As a result of this trend, a wider pass frequency band is required.

  As a technique for widening the pass frequency band as described above, for example, a method using the following filter is known. As shown in FIG. 24, this filter is configured so that the width dimension and the distance dimension of the electrode finger 102 and the reflective electrode 107 are widened from the bus bar 101 on one side (front side) toward the bus bar 101 on the other side (back side). The arranged tapered IDT electrode 103 is arranged on the piezoelectric substrate 100 along the propagation direction of the elastic wave as the input side IDT electrode 104 and the output side IDT electrode 105, and, for example, a shield electrode 106 is interposed between these electrodes 104, 105. It is the composition which arranged. In FIG. 24, reference numeral 108 denotes an absorber for absorbing unnecessary elastic waves that propagate to the end region of the piezoelectric substrate 100 via the electrodes 104 and 105.

  In this filter, in the propagation direction of the elastic wave, the connection angle of the electrode finger 102 to the bus bar 101 (taper angle θ described later) approaches a right angle, that is, the number of electrode fingers 102 is not so large. In addition, in the direction orthogonal to the propagation direction of the elastic wave, the electrodes 104 and 105 are arranged in the longitudinal direction of the piezoelectric substrate 100 in order to increase the separation distance between the pair of bus bars 101 and 101 and increase the opening length. In the region between the shield electrode 106 and the absorber 108, a blank region 110 in which no electrode or the like is formed is provided.

  In this filter, λ in FIG. 24 is a periodic unit that is repeated at a predetermined interval according to the width dimension and the interval dimension of the electrode finger 102 and the reflective electrode 107 so as to correspond to the wavelength of the propagating elastic wave. Propagating from the elastic wave of the short wavelength wavelength track (propagation path) to the elastic wave of the long wavelength wavelength wave from the bus bar 101 on one side to the bus bar 101 on the other side so as to have a constant period along the direction. In other words, the pass frequency band is widened. For this reason, in this filter, the electrode fingers 102 are inclined and connected to the bus bar 101 at the ends (both sides in the propagation direction of the elastic wave) of the electrodes 104 and 105, that is, with the electrode fingers 102 at the ends. Since the taper angle θ, which is an angle formed with the bus bar 101, is smaller than 90 °, for example, when an elastic wave is output from the input-side IDT electrode 104, the elastic wave is diffracted.

  In this filter, as a method of further widening the pass frequency band, for example, there is a method of obtaining a large difference in the cycle unit λ between the low frequency and the high frequency. However, in this case, the taper angle θ is further reduced. For this reason, if the elastic wave propagates to a region outside the region between the bus bars 101 and 101 by diffraction, for example, energy loss occurs and good characteristics cannot be obtained in the pass frequency band.

  Further, as a method of widening the pass frequency band in such a filter, a method of increasing the crossing width (opening length) D of the electrode fingers 102 alternately extending from the pair of bus bars 101 and 101 can be mentioned. However, in this case, the size of the piezoelectric substrate 100 in the length direction (opening length direction) of the electrode finger 102 needs to be formed large, so that the chip size increases.

  Patent Documents 1 and 2 describe a technique of connecting two filters in a resonator-type filter, but do not describe the above-described tapered filter. Patent Document 3 describes a technique of arranging two filters in the direction of propagation of elastic waves in a tapered filter, but it has not been studied for widening the pass frequency band.

JP-A-6-334476 (FIG. 1) JP 2004-343637 (FIG. 1) Japanese Patent Laid-Open No. 2001-237667 (FIG. 3)

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an elastic wave filter in which an input-side IDT electrode and an output-side IDT electrode are arranged in a tapered shape on a piezoelectric substrate. It is an object of the present invention to provide an elastic wave filter having a wide pass frequency band while keeping the size in the opening length direction small.

The elastic wave filter of the present invention is
A taper type IDT electrode as an input side IDT electrode and an output side IDT electrode separated from each other in the elastic wave propagation direction and arranged on a piezoelectric substrate to constitute a filter unit;
The taper-type IDT electrodes are arranged in a comb-teeth shape with a pair of bus bars formed to be spaced apart from each other in a direction perpendicular to the propagation direction of the elastic wave and alternately extending from each of the pair of bus bars. An electrode finger group, and a period unit consisting of the width dimension of the electrode finger and the spacing dimension of the electrode finger corresponding to the wavelength of the propagating elastic wave is directed from the bus bar on one side to the bus bar on the other side. That it was formed to spread,
The filter unit is arranged so that periodic units having the same length in the input-side IDT electrode and the output-side IDT electrode are spaced apart from each other in the elastic wave propagation direction;
The filter unit is arranged so that one side bus bars and the other side bus bars of the input-side IDT electrode and the output-side IDT electrode are arranged in a line along the propagation direction of the elastic wave. and the aligned plurality along the propagation direction of,
An input port commonly connected to one side bus bar or the other side bus bar in each input side IDT electrode of the filter unit ;
An output port commonly connected to one side bus bar or the other side bus bar in each output side IDT electrode of the filter unit;
The periodic unit is smaller in order in the plurality of filter units, the region adjacent to the bus bar on one side of one filter unit, and the other side of the filter unit having the next smallest periodic unit after the one filter unit It is characterized by being set to be equal in the area close to the bus bar.
One filter unit of the plurality of filter units is configured so that a cycle unit having the same length as a cycle unit in the other filter unit is not aligned in a line along the propagation direction of the elastic wave. Thus, they may be arranged at positions that are separated in the direction of propagation of the elastic wave and are displaced in the direction orthogonal to the direction of propagation of the elastic wave.

It is preferable that the arrangement pattern of the electrode fingers is set to be equal between the filter portions.
A reflective electrode extending from one of the pair of bus bars along the length direction of the electrode fingers;
It is preferable that the arrangement pattern of the reflective electrodes is set to be equal between the filter portions.

Among the plurality of filter units, a filter unit in which a cycle unit corresponding to the lowest frequency in the pass frequency band is formed is a low frequency filter, and a cycle unit corresponding to the highest frequency in the pass frequency band is formed. If the filtered filter is a high-pass filter,
In the low-pass filter, the arrangement pattern of the electrode fingers is set so that the attenuation on the low-frequency side is larger than the high-frequency side outside the pass frequency band of the low-frequency filter,
It is preferable that the arrangement pattern of the electrode fingers is set in the high frequency filter so that the attenuation amount on the high frequency side is larger than that on the low frequency side outside the pass frequency band of the high frequency filter.
A reflective electrode extending from one of the pair of bus bars along the length direction of the electrode fingers;
Among the plurality of filter units, a filter unit in which a cycle unit corresponding to the lowest frequency side in the pass frequency band is formed is a low frequency filter, and a cycle unit corresponding to the highest frequency side in the pass frequency band is formed. If the filter part is a high-pass filter,
In the low-pass filter, the arrangement pattern of the reflective electrodes is set so that the attenuation amount on the low-pass side is larger than the high-pass side outside the pass frequency band of the low-pass filter,
In the high-pass filter, the reflective electrode array pattern is preferably set so that the attenuation amount on the high-frequency side is larger than that on the low-frequency side outside the pass frequency band of the high-frequency filter.
Between each said filter part, the absorber for absorbing an elastic wave may be arrange | positioned.

Between the input-side IDT electrode and the output-side IDT electrode of one filter unit among the plurality of filter units, at least one of the input-side IDT electrode and the output-side IDT electrode of a filter unit different from the one filter unit In this case, two filter parts are provided, and a tapered IDT electrode of the filter part on one side of these filter parts and a tapered IDT electrode of the filter part on the other side are provided. Are preferably arranged alternately along the propagation direction of the elastic wave.
A bus bar on one side and a bus bar on the other side in another filter unit in which a tapered IDT electrode is interposed between the input-side IDT electrode and the output-side IDT electrode of one filter unit are the other side of the one filter unit The bus bar and the bus bar on one side are provided separately in the propagation direction of the elastic wave,
These filter sections are arranged in a state where they are displaced from each other in the orthogonal direction so that the regions in which periodic units of equal length are formed are separated from each other in the direction orthogonal to the propagation direction of the elastic wave. May be.

  According to the present invention, a filter unit including a tapered input side IDT electrode and an output side IDT electrode formed so that the width dimension and the interval dimension of the electrode fingers spread from one bus bar to the other bus bar is provided with an elastic wave. A plurality of input ports are arranged on the piezoelectric substrate along the propagation direction of the filter, and the input ports are commonly connected to one bus bar or the other bus bar of each input side IDT electrode of the filter unit, and each output side IDT of the filter unit is connected. The output port is connected in common to the bus bar on one side or the bus bar on the other side of the electrode, and the unit of period corresponding to the wavelength of the propagating elastic wave, the width dimension of the electrode finger and the spacing dimension of the electrode finger, The area close to the bus bar on one side of one of the plurality of filter sections so as to sequentially decrease in the plurality of filter sections. When is set to be equal in the region close to the bus bar on the other side in the next cycle unit is small filter portion of the filter portion of the one. For this reason, a set of tapered IDT electrodes and output IDT electrodes having a long opening length are divided into a plurality of filter sections, arranged in the elastic wave propagation direction, and these filter sections are connected in parallel. Since it has almost the same characteristics as the original IDT electrode set with a long opening length, the taper angle between the end electrode finger of each IDT electrode and the bus bar is made close to a right angle to suppress the diffraction loss small. In addition, an elastic wave filter having a wide pass frequency band can be obtained while keeping the size of the piezoelectric substrate in the opening length direction small.

It is a top view which shows an example of the elastic wave filter which concerns on the 1st Embodiment of this invention. It is the top view which expanded a part of above-mentioned elastic wave filter. It is a top view which shows typically the method of designing said filter. It is a top view which shows the other example of said elastic wave filter. It is a top view which shows the other example of said elastic wave filter. It is a top view which shows the other example of said elastic wave filter. It is a top view which shows the other example of said elastic wave filter. It is a top view which shows the other example of said elastic wave filter. It is a top view which shows an example of the elastic wave filter of the 2nd Embodiment of this invention. It is a characteristic view which shows the attenuation | damping characteristic obtained in the Example of this invention. It is a characteristic view which shows the attenuation | damping characteristic obtained in the Example of this invention. It is a characteristic view which shows the attenuation | damping characteristic obtained in the Example of this invention. It is a characteristic view which shows the attenuation | damping characteristic obtained in the Example of this invention. It is a top view which shows the other example of said elastic wave filter. It is a top view which expands and shows a part of said elastic wave filter. It is a top view which shows the other example of said elastic wave filter. It is a top view which shows the other example of said elastic wave filter. It is a top view which shows the other example of said elastic wave filter. It is a top view which shows the other example of said elastic wave filter. It is a top view which shows the other example of said elastic wave filter. It is a top view which shows the other example of said elastic wave filter. It is a top view which shows the other example of said elastic wave filter. It is a top view which shows the other example of said elastic wave filter. It is the schematic which shows the structure of the conventional elastic wave filter.

  A first embodiment of an elastic wave filter of the present invention will be described with reference to FIGS. The elastic wave filter includes a tapered input side IDT electrode 12 and an output side IDT electrode 13 provided at intervals along the propagation direction of the elastic wave. For example, on a piezoelectric substrate 11 such as a crystal, Filter sections 30 including these IDT electrodes 12 and 13 are arranged at a plurality of places, for example, two places along the propagation direction of the elastic wave. Here, if the left filter unit 30 in FIG. 1 is the first filter unit 31, and the right filter unit 30 is the second filter unit 32, the output IDT electrode 13 is disposed on the left side in the first filter unit 31, The input side IDT electrode 12 is disposed on the right side. In the second filter unit 32, the input-side IDT electrode 12 is disposed on the left side, and the output-side IDT electrode 13 is disposed on the right side. In FIG. 1, reference numeral 26 denotes an absorber (damper) for absorbing unnecessary elastic waves propagating to the end region of the piezoelectric substrate 11 through the filter units 30.

  Next, the first filter unit 31 will be described. When the input-side IDT electrode 12 and the output-side IDT electrode 13 in the first filter unit 31 are respectively referred to as a first input-side IDT electrode 12a and a first output-side IDT electrode 13a, the first input-side IDT electrode 12a is elastic to each other. Bus bar 14a on one side and bus bar 14b on the other side formed on the front side and the back side so as to be parallel to each other along the propagation direction, and each of these bus bars 14a, 14b are alternately comb-shaped. The electrode finger 15 and the reflective electrode 16 are provided so as to extend. The other side bus bar 14b is connected to the input port 21, and the one side bus bar 14a is grounded. In FIG. 1, the electrodes 12 and 13 and the absorber 26 are hatched so as to be easily distinguished from the region of the piezoelectric substrate 11. The same applies to the following figures.

  The electrode fingers 15 and the reflective electrodes 16 are formed so that the width dimension and the interval dimension of each of the electrode fingers 15 and the reflective electrode 16 increase from the bus bar 14a on one side to the bus bar 14b on the other side. A pair of electrode fingers 15, 15 formed adjacent to each other from each of 14 a, 14 b and one reflective electrode 16 extending from the bus bar 14 a so as to be adjacent to these electrode fingers 15, 15 make one set. Thus, they are arranged so as to be repeated periodically along the propagation direction of the elastic wave at a predetermined cycle unit λ. In this example, the width dimension of the electrode finger 15 and the reflection electrode 16 is λ / 8 and 3 / 8λ, respectively, and the separation dimension of the electrode finger 15 and the reflection electrode 16 is λ / 8, respectively. The taper angle θ (θ ≦ 90 °), which is the angle formed by the electrode finger 15 and the bus bar 14a at the end portion (both sides in the elastic wave propagation direction) of the first input side IDT electrode 12a, is an angle close to 90 °, for example, 85 The angle is 90 °. In FIG. 2, a part of the piezoelectric substrate 11 is notched and drawn.

  In this filter, an elastic wave having the same length as the period unit λ propagates. Therefore, when the track that is the propagation path of the elastic wave is Tr, the period unit λ is narrow (the frequency is high) from the front bus bar 14a to the back bus bar 14b in the direction orthogonal to the propagation direction of the elastic wave. ) Tr1 to wide (low frequency) Tr2 are formed. In FIG. 1 described above, the width dimensions of the electrode fingers 15 and the reflective electrodes 16 are drawn as being constant for the sake of simplicity of illustration.

  The output-side IDT electrode 13 (first output-side IDT electrode 13a) in the first filter unit 31 is configured in the same manner as the first input-side IDT electrode 12a, and as shown in FIG. The side bus bar 14c and the other side bus bar 14d are provided. The bus bar 14c on one side is disposed on the front side in FIG. 1 and connected to the output port 22, and the bus bar 14d on the other side is disposed on the back side and grounded. Similarly to the first input side IDT electrode 12a, the first output side IDT electrode 13a has a constant period unit λ along the propagation direction of the elastic wave, and from the one side bus bar 14c to the other side bus bar 14d. The electrode finger 15 and the reflective electrode 16 are provided so that the period unit λ extends from Tr1 to Tr2. In the first output-side tapered IDT electrode 13a, the reflective electrode 16 is connected to the other bus bar 14d.

  Next, the second filter unit 32 will be described. The second filter unit 32 is configured in substantially the same manner as the first filter unit 31 described above. When the input-side IDT electrode 12 and the output-side IDT electrode 13 in the second filter unit 32 are respectively referred to as a second input-side IDT electrode 12b and a second output-side IDT electrode 13b, the second input-side IDT electrode 12b and the second output-side IDT The electrode 13b is provided between one bus bar 14a, 14c arranged on the front side in FIG. 1 and the other bus bar 14b, 14d arranged on the back side, and between these bus bars 14a (14c), 14b (14d). Are provided with electrode fingers 15 and reflection electrodes 16 which alternately extend in a comb-like shape.

  The bus bar 14b on the back side of the second input side IDT electrode 12b is connected to the input port 21, and the bus bar 14a on the near side is grounded. Further, the bus bar 14c on the front side of the second output side IDT electrode 13b is connected to the output port 22, and the bus bar 14d on the back side is grounded. That is, when viewed from the input port 21 and the output port 22, the first input-side IDT electrode 12a and the second input-side IDT electrode 12b, and the first output-side IDT electrode 13a and the second output-side IDT electrode 13b are parallel to each other. Will be connected to.

  Further, in the second input side IDT electrode 12b and the second output side IDT electrode 13b, when the second output side IDT electrode 13b is viewed from the second input side IDT electrode 12b and from the second output side IDT electrode 13b, the second input is input. The arrangement pattern (arrangement order) of the electrode finger 15 and the reflection electrode 16 when the side IDT electrode 12b is viewed is as follows. In the first filter unit 31, the first output side IDT electrode 13a is changed from the first input side IDT electrode 12a. The electrode fingers 15 and the reflective electrodes 16 are arranged so as to be equal to the arrangement pattern when viewed and when the first input-side IDT electrode 12a is viewed from the first output-side IDT electrode 13a. Therefore, the taper angle θ in the second filter portion 32 is set similarly to the taper angle θ of the first filter portion 31.

  Further, in the second input side IDT electrode 12b and the second output side IDT electrode 13b, the electrode fingers 15 and the reflective electrodes 16 are cycled from the front bus bar 14a (14c) toward the back bus bar 14b (14d). The unit λ is formed so as to expand. Here, assuming that the track in the area close to the bus bars 14a and 14c on the front side in the second filter section 32 is Tr3 and the track in the area close to the bus bars 14b and 14d on the back side is Tr4, the track Tr3 is described above. As shown in FIG. 2, it is equal to the track Tr <b> 2 in a region close to the bus bar 14 a on the back side of the first filter portion 31. That is, as shown in FIG. 3, this filter is a filter (input side IDT electrode 12 and output side IDT electrode 13) having a long aperture length D in which the cycle unit λ is formed from the track Tr 1 to the track Tr 4. The track Tr2 (track Tr3) between the track Tr1 and the track Tr4 is divided into two filter units 30 (31, 32), and the filter units 30, 30 are arranged along the elastic wave propagation direction. It can be said that it is composed. Then, the bus bar 14b on the longer side of the cycle unit λ in each of the filter units 31 and 32 so that the input-side IDT electrodes 12a and 12b and the output-side IDT electrodes 13a and 13b in each filter unit 30 are connected in parallel. , 14b (14d, 14d) are connected to a common input port 21 and a common output port 22, respectively. In FIG. 3, the electrode fingers 15, the reflective electrodes 16, and the bus bars 14 are not shown.

  Here, in this filter, in the propagation direction of the elastic wave, the connection angle (taper angle θ) of the electrode finger 15 to the bus bar 14 approaches a right angle, that is, the number of the electrode fingers 15 is not so large. Therefore, in the direction orthogonal to the propagation direction of the elastic wave, in order to increase the separation distance between the pair of bus bars 14 and 14 and increase the opening length D, the electrodes 12 are arranged in the longitudinal direction of the piezoelectric substrate 11. , 13 and an area between the absorber 26 is provided with a blank area 40 in which no electrode or the like is formed.

  In such an acoustic wave filter, when a frequency signal is input to the input-side IDT electrode 12 via the input port 21, a surface acoustic wave (SAW) is generated. This elastic wave is generated in the track Tr in which the period unit λ corresponding to the wavelength length is formed in the input-side IDT electrodes 12a and 12b, that is, the elastic wave having the wavelength from the tracks Tr1 to Tr2 is the first input. The elastic wave having a wavelength from the track Tr3 to the track Tr4 propagates from the side IDT electrode 12a toward the first output side IDT electrode 13a, and propagates from the second input side IDT electrode 12b toward the second output side IDT electrode 13b. I will do it. And since the electrode finger 15 is inclined and connected to the bus bar 14 at the end of the input side IDT electrode 12, an elastic wave is generated when being output from the input side IDT electrode 12 toward the output side IDT electrode 13. Try to diffract. However, since the taper angle θ is close to 90 ° as described above, the diffraction of the elastic wave is suppressed to be small, and almost the entire amount of the elastic wave propagates toward the output-side IDT electrode 13. become. In this way, the output-side IDT electrode 13 performs the mechanical-electrical mutual conversion of the elastic wave on the track Tr corresponding to the wavelength of the elastic wave propagating from the input-side IDT electrode 12, as shown in the examples described later. The electric signal corresponding to the elastic wave having the wavelength from the tracks Tr1 to Tr4 is taken out via the output port 22.

  According to the above-mentioned embodiment, the taper formed so that the width dimension and space | interval dimension of the electrode finger 15 and the reflective electrode 16 may spread so that it may go to the bus bar 14b (14d) of the other side from the bus bar 14a (14c) of the other side. Two filter portions 30 of the input side IDT electrode 12 and the output side IDT electrode 13 are arranged on the piezoelectric substrate 11 along the propagation direction of the elastic wave, and the input side IDT electrode 12 and the output side IDT electrode 13 are respectively provided. The other side bus bars 14b, 14b (14d, 14d) are connected to the input port 21 (output port 22), and the track Tr2 in the area adjacent to the other side bus bar 14b (14d) of the first filter section 31 is connected. And the track Tr3 in the area close to the bus bar 14a (14c) on one side of the second filter portion 32 are equal to each other. There. Therefore, as shown in FIG. 3 described above, this filter includes the electrode fingers 15 and the reflective electrodes 16 of the input side IDT electrodes 12a and 12b in the two filter units 31 and 32, and the output side IDT electrodes 13a and 13b. The characteristics are comparable to those of a filter having a long aperture length D in which the electrode fingers 15 and the reflective electrodes 16 are connected in the vertical direction (direction perpendicular to the propagation direction of elastic waves). Accordingly, since the opening length D can be made longer than the apparent dimension of the piezoelectric substrate 11 in the opening length D direction (the length direction of the electrode finger 15), the taper angle θ is kept close to a right angle and elastic. It is possible to widen the pass frequency band while suppressing wave diffraction. At this time, as described above, there is almost no extra space in the direction orthogonal to the propagation direction of the elastic wave on the piezoelectric substrate 11, but there is an extra space (blank region 40) in the propagation direction of the elastic wave. Since the two filter portions 31 and 32 are arranged in the horizontal direction, the gap on the piezoelectric substrate 11 can be used, so that the opening length D direction (the length direction of the electrode finger 15) can be used. The size of the piezoelectric substrate 11 can be suppressed smaller than when the filter having the long opening length D is arranged by extending the piezoelectric substrate 11.

  Further, since the arrangement patterns of the electrode fingers 15 and the reflective electrodes 16 in the respective filter portions 31 and 32 are made equal, by connecting the two filter portions 31 and 32 in parallel as described above, the upper side in FIG. The same characteristics as the filter having a long opening length D shown in FIG.

Here, for example, when an elastic wave interferes with each other between the two filter parts 31 and 32 and an adverse effect occurs, an auxiliary absorber that absorbs the elastic wave between the filter parts 31 and 32 as shown in FIG. 27 may be arranged.
Moreover, although each filter part 31 and 32 was arrange | positioned so that period unit (lambda) may spread as it goes to the back side from this side, you may arrange | position so that period unit (lambda) may spread as it goes to the near side from the back side. For example, as shown in FIG. 5, the cycle unit λ increases as one of the two filter units 31 and 32 moves from the near side to the far side, and the other unit goes from the far side to the near side. May be arranged to spread. Also in this case, the other bus bars 14b and 14b (14d and 14d) are connected in parallel, and the same operation and effect as the above example can be obtained. At this time, in the filter portions 31 and 32 in FIG. 5, the same periodic units λ (tracks Tr2 and Tr3) are not aligned in a line along the propagation direction of the elastic wave in the region close to the inner bus bar 14. Are arranged respectively. That is, as shown in FIG. 15 to be described later, the filter units 31 and 32 are arranged in a state of being displaced from each other in a direction orthogonal to the propagation direction of the elastic wave. The filter part 32 is formed slightly behind. In addition, when the filter parts 31 and 32 are arranged and the auxiliary absorber 27 is formed as described above, in order to connect the bus bars 14b and 14b on the other side of the input-side IDT electrodes 12a and 12b, For example, a wire or the like may be provided via an upper region of the piezoelectric substrate 11.

  Further, on the piezoelectric substrate 11, the first filter unit 31 is disposed on the left side and the second filter unit 32 is disposed on the right side. However, the first filter unit 31 may be disposed on the right side and the second filter unit 32 may be disposed on the left side. In each filter part 31 and 32, you may replace the arrangement | positioning of the input side IDT electrode 12 and the output side IDT electrode 13 with each right and left. Furthermore, the bus bars 14b and 14b (14d and 14d) on the other side are connected to the input port 21 (output port 22), but the bus bars 14a and 14a (14c and 14c) on the other side may be connected. Moreover, in each filter part 31 and 32, you may arrange | position a shield electrode between the input side IDT electrode 12 and the output side IDT electrode 13. FIG.

  Furthermore, as shown in FIG. 3 described above, the track Tr2 (Tr3) common to the two filter units 31 and 32 is set to a period unit λ substantially in the middle between the track Tr1 and the track Tr4. As shown in FIG. 6, the filter units 31 and 32 may share a track Tr that is close to one of the track Tr <b> 1 and the track Tr <b> 4. That is, you may make a difference in the pass frequency band in each filter part 31 and 32. FIG. In this case, for example, for the filter unit 30 having a narrow pass frequency band, the taper angle θ may be increased (closer to 90 °) so that the opening length D is approximately the same as that of the filter unit 30 having a wide pass frequency band. good. In FIG. 6, the electrode fingers 15, the reflective electrodes 16, and the bus bars 14 are not shown. The same applies to FIGS. 7 and 8 below.

  Further, as shown in FIGS. 7 and 8, a plurality of, for example, three filter portions 31, 32, 33 may be arranged along the elastic wave propagation direction. In this case, in the three filter units 31, 32, and 33, the period unit λ is formed so that the elastic waves of the tracks Tr1 to Tr2, the tracks Tr3 to Tr4, and the tracks Tr5 to Tr6 are propagated. The track Tr3, the track Tr4, and the track Tr5 are set to the same cycle unit λ. In this case, the same effect as the above example can be obtained. Further, in this filter, the auxiliary absorber 27 described above may be disposed.

  Next, a second embodiment of the present invention will be described with reference to FIG. In the first embodiment, the electrode fingers 15 and the reflective electrodes 16 are formed in the same arrangement pattern in each of the filter portions 31 and 32. In the second embodiment, each of the filter portions 31 and 32 is formed. The arrangement pattern of the electrode fingers 15 and the reflective electrodes 16 is changed. Specifically, in the filter unit 31 in which an elastic wave having a short cycle unit λ from the track Tr1 to the track Tr2 (high frequency side) propagates, the arrangement is made so that the attenuation amount on the high frequency side is larger than that of the track Tr1. In the filter unit 32 in which a pattern is set and an elastic wave having a long period unit λ from the track Tr3 to the track Tr4 (on the low frequency side) propagates, the arrangement is made so that the attenuation on the low frequency side is larger than that of the track Tr4. A pattern is set. In setting the band in which the attenuation amount increases in this way, in this embodiment, as shown in FIG. 9, for example, in the IDT electrodes 12 and 13 of the filter units 31 and 32, the electrode fingers 15 and 15 intersecting each other. By adjusting the position of the excitation point, the position of the attenuation pole is adjusted to the band where the amount of attenuation is desired to be increased.

Also in the filter of the second embodiment, the same effect as the first embodiment can be obtained. In addition, by adjusting the position of the attenuation pole in this way, the attenuation characteristics obtained in the respective filter units 31 and 32 are superimposed, and as shown in an embodiment described later, the low frequency side outside the pass frequency band and Since the attenuation amount on the high frequency side increases, a steep attenuation characteristic can be obtained.
In the filter shown in FIG. 9 as well, as shown in FIGS. 4 to 8, the auxiliary absorber 27 may be arranged, or three or more filter units 31, 32, and 33 may be arranged.

Next, a simulation performed for confirming the filter characteristics obtained by connecting a plurality of, for example, two filter units 31 and 32 in parallel as described above will be described. First, regarding the characteristics of the filter after synthesis, the center frequency is set to 125 MHz, and the frequencies of the low-frequency side end and the high-frequency side end in the pass band are set to 100 MHz and 150 MHz, respectively. Therefore, the pass band is 50 MHz (150-100). Based on this filter, consider the case where the passband is equally divided by two filters. The frequency band to which the present invention is applied in this simulation is an example, and the present invention can be applied to any band.
10A and 10B show the characteristics of the low frequency side filter section 32 (center frequency: 112.5 MHz, bandwidth: 25 MHz) and the characteristics of the high frequency side filter section 31 (center frequency: 137. 5MHz, bandwidth: 25MHz), and by connecting these filter units 31 and 32 in parallel, the pass frequency bands of the two filter units 31 and 32 are synthesized as shown in FIG. It can be seen that the obtained broadband characteristics can be obtained.

  11 (a) and 11 (b) show the respective pass frequency bands in the low-frequency side filter unit 32 and the high-frequency side filter unit 31 as described in the second embodiment. The characteristic obtained when the arrangement pattern of the electrode finger 15 and the reflective electrode 16 is adjusted so that the attenuation amount on the low-frequency side and the high-frequency side outside becomes large is shown. As shown in FIG. 11A, in the low frequency side filter unit 32, when the low frequency side attenuation is increased, the high frequency side attenuation is smaller than the pass frequency band of the filter unit 32 ( It turns out that it has deteriorated). Further, in the high frequency side filter unit 31, as shown in FIG. 11B, when the high frequency side attenuation amount is increased, the low frequency side attenuation amount becomes smaller than the pass frequency band of the filter unit 31. You can see that However, when these filter units 31 and 32 are connected in parallel, as shown in FIG. 5C, a band in which attenuation is reduced (deteriorated) in one of the filter units 31 and 32 is obtained. Since it overlaps with the pass frequency band of the other filter sections 31 and 32, it can be seen that the deterioration of the characteristics is canceled out, and a steep attenuation characteristic having a large attenuation amount is obtained on both the low frequency side and the high frequency side.

Here, FIG. 12A shows characteristics obtained by connecting in parallel the filter units 31 and 32 adjusted so that the attenuation amount on the low frequency side is larger than the respective pass frequency bands. FIG. 6B shows the characteristics obtained in the second embodiment of the present invention. From FIG. 12, it can be seen that by adjusting the arrangement pattern of the filter units 31 and 32 as described above, the attenuation can be increased not only on the low frequency side but also on the high frequency side in the present invention.
Further, FIG. 13A shows characteristics obtained by connecting in parallel the filter units 31 and 32 adjusted so that the attenuation amount on the high frequency side is larger than the respective pass frequency bands. The characteristics obtained in the second embodiment of the invention are similarly shown in FIG. Even in this case, it can be seen that the present invention can increase the attenuation not only on the high frequency side but also on the low frequency side.

  In each of the examples described above, the plurality of filter units 30 (31, 32, 33) are arranged in order along the propagation direction of the elastic wave, but the IDT electrodes 12, 13 of these filter units 30 are alternately arranged. You may do it. Specifically, FIG. 14 shows such a filter from the left side to the right side along the propagation direction of the elastic wave, for example, the output side IDT electrode 13a, the input side IDT electrode 12b, the input side IDT electrode 12a, and the output side IDT. The electrodes 13b are arranged in this order. Further, the bus bars 14a and 14c on one side of the IDT electrodes 12a and 13a of the filter unit 31 are arranged on the front side in FIG. 14, and the bus bars 14b and 14d on the other side are arranged on the back side. The bus bars 14a and 14c on one side of the IDT electrodes 12b and 13b of the filter section 32 are arranged on the back side, and the bus bars 14b and 14d on the other side are arranged on the front side. Also in FIG. 14, the bus bars 14 b and 14 b are connected to the input port 21 in parallel, and the bus bars 14 c and 14 c are connected to the output port 22 in parallel, as in the example described above. That is, the filter shown in FIG. 14 has the IDT electrode 12b so that the back side and the near side of the first input side IDT electrode 12b and the second output side IDT electrode 13b are switched in the filter shown in FIG. , 13b are arranged so as to be turned upside down, and the input side IDT electrodes 12a, 12b are arranged in the opposite direction.

  Here, in these filter sections 31 and 32, the above-described tracks Tr2 and Tr3 are all arranged on the back side in FIG. 14, but in this embodiment, these tracks Tr2 and Tr3 are elastic waves. The filter units 31 and 32 are arranged so that the tracks Tr2 and Tr3 are separated from each other in a direction perpendicular to the propagation direction of the elastic wave (opening length D direction) so as not to line up in a line along the propagation direction. Has been.

  Specifically, a part of the vicinity of the boundary between the output-side IDT electrode 13a and the input-side IDT electrode 12b arranged on the left side in FIG. 14 is enlarged, and the input-side IDT electrode 12b is connected to this output as shown in FIG. The tracks Tr2 and Tr3 are spaced apart from each other in the direction of the opening length D by being disposed slightly behind the side IDT electrode 13a, for example. Further, since the output IDT electrode 13b and the input IDT electrode 12a on the right side in FIG. 14 are arranged to face the input IDT electrode 12b and the output IDT electrode 13a, respectively, along the propagation direction of the elastic wave. The tracks Tr2 and Tr3 on the output side IDT electrode 13b and the input side IDT electrode 12a are also arranged so as to be separated from each other in the opening length D direction.

  Accordingly, the filter units 31 and 32 are arranged so that the tracks Tr of the same cycle unit λ do not overlap each other in the propagation direction of the elastic wave over the opening length D direction (so as not to be in a line). become. In FIG. 14, the drawing of the electrode fingers 15 and the reflective electrodes 16 is omitted. However, in each of the filter units 31 and 32, the electrode fingers 15 and the reflective electrodes 16 are arranged in the same manner as in FIG. It is formed with a layout.

  By arranging the filter units 31 and 32 in this manner, the following effects can be obtained in addition to the effects described above. That is, when the region between the IDT electrodes 12 and 13 is called a propagation path 80, the same track Tr is not aligned in the propagation direction of the elastic wave in these filter portions 31 and 32 over the opening length D direction. Since the interference between the elastic waves on the same track Tr is suppressed, the IDT electrodes 12 and 13 of the filter units 31 and 32 are alternately arranged with each other while preventing the filter units 31 and 32 from affecting each other. Therefore, the propagation path 80 in one filter unit 30 can be used by another filter unit 30. Therefore, even when the IDT electrodes 12 and 13 are separated from each other in one filter unit 30 and the propagation path 80 is long, the propagation path 80 can be used effectively. The length dimension of the substrate 11 can be kept short.

  Also, the bus bar 14a (14c) on one side and the bus bar 14b (14d) on the other side of the filter part 31 are elastic with respect to the bus bar 14b (14d) on the other side and the bus bar 14a (14c) on one side of the filter part 32. They are arranged so as to be separated from each other in the wave propagation direction. That is, the bus bars 14a (14c) and the bus bars 14b (14d) are alternately arranged along the propagation direction of the elastic wave. Therefore, the IDT electrodes 12 and 13 can be arranged close to each other by using the aforementioned taper angle θ by alternately arranging the wide width regions and the narrow width regions in the IDT electrodes 12 and 13. Therefore, the length dimension of the piezoelectric substrate 11 in the propagation direction of the elastic wave can be further reduced.

  As an example in which the IDT electrodes 12 and 13 of the filter units 31 and 32 are alternately arranged as described above, the following may be performed. That is, as shown in FIG. 16, the output-side IDT electrode 13a, the output-side IDT electrode 13b, the input-side IDT electrode 12a, and the input-side IDT electrode 12b are arranged in this order from the left side to the right side along the propagation direction of the elastic wave. In other words, the input-side IDT electrode 12b and the output-side IDT electrode 13b of the filter unit 32 in FIG. 14 described above may be interchanged. Further, the IDT electrode 12a and the IDT electrode 13a may be interchanged with respect to the filter unit 31 as well. In FIG. 16, the same parts as those in FIG. The same applies to the following FIGS.

  In addition, as shown in FIG. 17, the bus bars 14a (14c) may be arranged in a line along the propagation direction of the elastic waves in the filter units 31 and 32, and the bus bars 14b (14d) may be arranged in a line. In this case, it is not necessary to form the routing electrode (labeled “50” in FIG. 17) connecting the port 21 (22) and the bus bar 14 between the IDT electrodes 12 and 13. The length dimension of the piezoelectric substrate 11 in the elastic wave propagation direction can be suppressed.

  Further, by alternately arranging the IDT electrodes 12 and 13 along the propagation direction of the elastic wave, the IDTs of the other filter units 32 and 31 between the IDT electrodes 12 and 13 are provided for both the filter units 31 and 32. Although the electrode 12 (13) is interposed, the IDT electrodes 12 and 13 of the other filter unit 30 may be interposed between the IDT electrodes 12 and 13 for one filter unit 30. Specifically, as shown in FIG. 18, for example, the output IDT electrode 13a, the input IDT electrode 12b, the output IDT electrode 13b, and the input IDT electrode 12a from the left to the right along the propagation direction of the elastic wave. Are arranged in this order, and the filter part 32 is arranged between the IDT electrodes 12 a and 13 a of the filter part 31. In this case, when the above-described propagation path 80 is formed by separating the IDT electrodes 12b and 13b of the filter unit 32, the above-described routing electrode 50 is formed in the propagation path 80 and the propagation path 80 is used. You may do it. That is, in at least one filter unit 30 among the plurality of filter units 30, at least one of the IDT electrodes 12 and 13 of another filter unit 30 is disposed between the IDT electrodes 12 and 13 of the filter unit 30. In such an embodiment, the same effect can be obtained.

  In addition, as shown in FIG. 19, the shield electrode 60 may be disposed in the region between the IDT electrodes 12 and 13 in each of the filter sections 31 and 32, that is, in the central position of the piezoelectric substrate 11 in the elastic wave propagation direction. Further, in each of the examples of FIGS. 14 to 19, by weighting the filter units 31 and 32 as shown in FIG. 9, the attenuation amount on the low frequency side and the high frequency side outside the pass frequency band is increased. Alternatively, the common track Tr2 (Tr3) in the two filter sections 31 and 32 may be shifted to the track Tr1 side or the track Tr4 side as shown in FIG.

  In each of the above examples, the two filter parts 31 and 32 are connected in parallel to form a filter having an apparently long opening length D as shown in FIG. 3 described above. May be configured in series by connecting them in series. Specifically, for example, when the filter units 31 and 32 are arranged in the same layout as that of FIG. 14 described above, the bus bars 14a and 14b of the input-side IDT electrodes 12 and 12 are shared as shown in FIG. Connected to the port 21, the bus bars 14 c and 14 d of the output-side IDT electrodes 13 and 13 are connected to the common output port 22.

  In this case, as shown in FIG. 21B, the tracks Tr1 and Tr2 in the filter unit 31 and the tracks Tr3 and Tr4 in the filter unit 32 satisfy Tr1 <Tr2 = Tr3 <Tr4 as described in the above examples. Alternatively, the period unit λ of the filter units 31 and 32 is set so that Tr1 <Tr2 <Tr3 <Tr4 or Tr1 <Tr3 <Tr2 <Tr4 as shown in FIGS. Also good. Even in this case, in FIGS. 21B and 21D, tracks Tr (period units λ) having the same length between the filter portions 31 and 32 are aligned in the propagation direction of the elastic wave over the opening length D direction. The positions of the IDT electrodes 12 and 13 are adjusted in the same manner as in FIG. 15 described above. FIG. 21A schematically shows an overview of the filter when the filter units 31 and 32 are connected in series and the track Tr in each IDT electrode 12 and 13. FIGS. 7B to 7D schematically show characteristics obtained in the filter units 31 and 32. FIG. In such a case, as shown in FIG. 22, even when the IDT electrodes 12 and 13 of the filter parts 31 and 32 are arranged as shown in FIG. 1, the filter parts 31 and 32 are connected in series. You may connect.

Further, as shown in FIG. 23, the IDT electrodes 12 and 13 are individually connected to the ports 21 (21a and 21b) and 22 (22a and 22b) without connecting the filter units 31 and 32, respectively. May be. That is, the IDT electrodes 12 and 13 in the two filter units 30 of different types may be alternately arranged.
In each of the above examples, three or more filter units 30 may be arranged.

11 Piezoelectric substrate 12 Input side IDT electrode 13 Output side IDT electrode 14 Bus bar 15 Electrode finger 16 Reflective electrode 31 First filter part 32 Second filter part 40 Blank area Tr Track

Claims (10)

A taper type IDT electrode as an input side IDT electrode and an output side IDT electrode separated from each other in the elastic wave propagation direction and arranged on a piezoelectric substrate to constitute a filter unit;
The taper-type IDT electrodes are arranged in a comb-teeth shape with a pair of bus bars formed to be spaced apart from each other in a direction perpendicular to the propagation direction of the elastic wave and alternately extending from each of the pair of bus bars. An electrode finger group, and a period unit consisting of the width dimension of the electrode finger and the spacing dimension of the electrode finger corresponding to the wavelength of the propagating elastic wave is directed from the bus bar on one side to the bus bar on the other side. That it was formed to spread,
The filter unit is arranged so that periodic units having the same length in the input-side IDT electrode and the output-side IDT electrode are spaced apart from each other in the elastic wave propagation direction;
The filter unit is arranged so that one side bus bars and the other side bus bars of the input-side IDT electrode and the output-side IDT electrode are arranged in a line along the propagation direction of the elastic wave. and the aligned plurality along the propagation direction of,
An input port commonly connected to one side bus bar or the other side bus bar in each input side IDT electrode of the filter unit ;
An output port commonly connected to one side bus bar or the other side bus bar in each output side IDT electrode of the filter unit;
The periodic unit is smaller in order in the plurality of filter units, the region adjacent to the bus bar on one side of one filter unit, and the other side of the filter unit having the next smallest periodic unit after the one filter unit An elastic wave filter characterized by being set to be equal in a region close to the bus bar.   One filter unit of the plurality of filter units is configured so that a cycle unit having the same length as a cycle unit in the other filter unit is not aligned in a line along the propagation direction of the elastic wave. The elastic wave filter according to claim 1, wherein the elastic wave filter is disposed at a position spaced apart in a propagation direction of the elastic wave and shifted in a direction orthogonal to the propagation direction of the elastic wave. The arrangement pattern of the electrode fingers, the elastic wave filter according to claim 1 or 2, characterized in that it is set to be equal between each of the filter unit. A reflective electrode extending from one of the pair of bus bars along the length direction of the electrode fingers;
The arrangement pattern of the reflective electrode, the elastic wave filter according to any one of claims 1 to 3, characterized in that it is set to be equal between each of the filter unit. Among the plurality of filter units, a filter unit in which a cycle unit corresponding to the lowest frequency in the pass frequency band is formed is a low frequency filter, and a cycle unit corresponding to the highest frequency in the pass frequency band is formed. If the filtered filter is a high-pass filter,
In the low-pass filter, the arrangement pattern of the electrode fingers is set so that the attenuation on the low-frequency side is larger than the high-frequency side outside the pass frequency band of the low-frequency filter,
The high-frequency filter has an arrangement pattern of the electrode fingers so that the attenuation on the high-frequency side is larger than the low-frequency side outside the pass frequency band of the high-frequency filter. The elastic wave filter according to claim 1. A reflective electrode extending from one of the pair of bus bars along the length direction of the electrode fingers;
Among the plurality of filter units, a filter unit in which a cycle unit corresponding to the lowest frequency side in the pass frequency band is formed is a low frequency filter, and a cycle unit corresponding to the highest frequency side in the pass frequency band is formed. If the filter part is a high-pass filter,
In the low-pass filter, the arrangement pattern of the reflective electrodes is set so that the attenuation amount on the low-pass side is larger than the high-pass side outside the pass frequency band of the low-pass filter,
The high-pass filter has an arrangement pattern of the reflective electrodes so that the attenuation amount on the high-frequency side is larger than that on the low-frequency side outside the pass frequency band of the high-frequency filter. The elastic wave filter according to claim 1 or 5 . The elastic wave filter according to any one of claims 1 to 6 , wherein an absorber for absorbing an elastic wave is disposed between the filter units. Between the input-side IDT electrode and the output-side IDT electrode of one filter unit among the plurality of filter units, at least one of the input-side IDT electrode and the output-side IDT electrode of a filter unit different from the one filter unit acoustic wave filter according to any one of claims 1 to 7 but is characterized in that it is interposed. Two filter parts are provided,
The tapered IDT electrode of the filter part on one side of these filter parts and the tapered IDT electrode of the filter part on the other side are alternately arranged along the propagation direction of the elastic wave. Item 9. The acoustic wave filter according to Item 8 . A bus bar on one side and a bus bar on the other side in another filter unit in which a tapered IDT electrode is interposed between the input-side IDT electrode and the output-side IDT electrode of one filter unit are the other side of the one filter unit The bus bar and the bus bar on one side are provided separately in the propagation direction of the elastic wave,
These filter units are respectively arranged in a state where they are displaced from each other in the orthogonal direction so that the regions where the periodic units of the same length are formed are separated from each other in the direction orthogonal to the propagation direction of the elastic wave. acoustic wave filter according to claim 8 or 9, characterized in that there.

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