JP2012182529A - Acoustic wave filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adjust a frequency characteristic of a certain bandwidth separately from the other bandwidth in an acoustic wave filter where IDT electrodes on the input side and IDT electrodes on the output side are each arranged in a taper shape on a piezoelectric substrate.SOLUTION: Filter parts 31, 32 (the filter part 31: λ1 to λ2 (λ1<λ2), the filter part 32: λ3 to λ4 (λ3<λ4)) each comprise tapered IDT electrodes 12 on the input side and IDT electrodes 13 on the output side formed in such a manner that a cycle unit λ becomes wider from a bus bar 14a on one side toward a bus bar 14b on the other side. These filter parts 31, 32 are arranged in such a direction that they mutually intersect the propagating direction of acoustic waves, and a cycle unit λ2 of the first filter part 31 and a cycle unit λ3 of the second filter part 32 are arranged in a same length.

Description

  The present invention relates to an acoustic wave filter in which an arrangement region of electrode finger groups is formed in a tapered shape.

  As a filter (bandpass filter) using an elastic wave, for example, a surface acoustic wave, for example, a pair of bus bars arranged so as to be parallel to each other and alternately comb-shaped from one side of the bus bar to the other side There is known a configuration in which an IDT (Inter Digital Transducer) electrode including a plurality of electrode fingers arranged to extend is formed on a piezoelectric substrate as an input side electrode and an output side electrode. In this filter, the period unit λ composed of the width dimension of the electrode fingers and the separation dimension between the electrode fingers adjacent to each other is adjusted so that an elastic wave having a wavelength corresponding to the pass frequency band propagates. Such a filter is required to have a wide pass frequency band, and has a flatness within the pass frequency band, and steepness in the low frequency (low frequency) side and the high frequency (high frequency) side of the pass frequency band. Damping characteristics and high selectivity (a large amount of attenuation is required on the low frequency side and the high frequency side of the pass frequency band). Further, in order to suppress the insertion loss of the filter, for example, a reflective electrode is disposed adjacent to the electrode finger.

  As a method of widening the pass frequency band of the filter, the periodic unit λ gradually spreads from one bus bar to the other bus bar, that is, the arrangement region of the electrode finger group is a tapered type (inclined type). , A method of forming each of the aforementioned IDT electrodes so as to be a slant type) is known. Then, frequency characteristics such as attenuation characteristics can be obtained by adjusting the number of pairs of IDT electrodes (the number of sets of electrode fingers arranged so as to cross each other) or by weighting the electrode fingers and reflectors. Is adjusted.

  At this time, it may be required to individually adjust the frequency characteristics of a certain band independently of other bands. Specifically, in order to improve the selectivity of the filter, for example, the IDT electrode is weighted so that the attenuation characteristic of the low frequency side is good on the low frequency side of the pass frequency band, while the high frequency of the pass frequency band is set. On the band side, it is desirable to weight the IDT electrodes independently from the low band side so that the attenuation characteristic on the high band side is good. However, as described above, electrode fingers and reflectors are arranged in a straight line between the bus bar on one side and the bus bar on the other side, and the electrodes extend from the low-frequency track to the high-frequency track. Since the number of pairs of fingers and the number of reflectors are uniform, it is difficult to individually perform weighting on the low frequency side and the high frequency side.

  Patent Document 1 describes that both the input-side IDT 12 divided into four blocks 12a to 12d, the input-side IDT 12, and the output-side IDT 13 may be divided, but a specific filter configuration and each IDT 12 , 13 is not described. Patent Document 2 describes a dual-track transversal filter type filter, but does not describe the above-described tapered type filter. Furthermore, Patent Document 3 does not describe the above-described problem.

JP 2009-60412 (paragraph 0033, FIG. 1, etc.) JP-A-2005-102119 (FIG. 1) JP 62-120115 A

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an acoustic wave filter in which an input-side IDT electrode and an output-side IDT electrode are each arranged in a tapered shape on a piezoelectric substrate. It is an object of the present invention to provide an elastic wave filter that can be adjusted independently of the frequency band.

The elastic wave filter of the present invention is
A tapered IDT electrode formed such that a period unit comprising a width dimension of electrode fingers and a spacing dimension between adjacent electrode fingers spreads from one bus bar to the other bus bar is defined as an input side electrode and an output side electrode. As a first filter part and a second filter part respectively arranged along the propagation direction of the elastic wave,
An input port connected in common to any bus bar of the input side electrode of the first filter section and any bus bar of the input side electrode of the second filter section;
An output port connected in common to any bus bar of the output side electrode of the first filter unit and any bus bar of the output side electrode of the second filter unit;
The cycle unit on the other bus bar side in the first filter unit and the cycle unit on the one bus bar side in the second filter unit are set to the same length,
When a region between each of the one side bus bar and the other side bus bar in the input side electrode and the output side electrode is referred to as a propagation region, the first filter unit includes the propagation region of the first filter unit and the first filter unit. A position spaced apart in a direction orthogonal to the propagation direction of the elastic wave when viewed from the second filter unit so that the propagation region of the second filter unit is not aligned in a line in the propagation direction of the elastic wave; Or it is separated in the propagation direction of an elastic wave, and is formed in the position away in the orthogonal direction.

The filter may be configured as follows.
The first filter unit and the second filter unit are arranged in a direction orthogonal to the propagation direction of the elastic wave. The first filter part and the second filter part are respectively arranged so that the one side bus bar in the second filter part faces the other side bus bar in the first filter part,
The other side bus bar in the first filter part and the one side bus bar in the second filter part are commonly used as floating electrodes.

In the first filter unit, the arrangement pattern of the electrode fingers is set so that the attenuation amount on the high frequency side is larger than the low frequency side outside the pass frequency band of the first filter unit,
The second filter unit is configured such that the arrangement pattern of the electrode fingers is set so that the attenuation amount on the low frequency side is larger than the high frequency side outside the pass frequency band of the second filter unit.
The first filter portion and the second filter portion each include a reflective electrode extending from one of the one side bus bar and the other side bus bar along the length direction of the electrode finger,
In the first filter unit, the arrangement pattern of the reflective electrodes is set so that the attenuation amount on the high frequency side is larger than the low frequency side outside the pass frequency band of the first filter unit,
The second filter unit is configured such that the arrangement pattern of the reflective electrodes is set so that the attenuation amount on the low frequency side is larger than the high frequency side outside the pass frequency band of the second filter unit.

  The present invention provides a first filter section and a second filter section in which tapered IDT electrodes formed so that a period unit is widened from one bus bar to the other bus bar are arranged as an input electrode and an output electrode, respectively. In the filter unit, the cycle unit on the other bus bar side in the first filter unit and the cycle unit on the one bus bar side in the second filter unit are set to the same length. A common input port and output port are provided for the first filter unit and the second filter unit. Therefore, in one of these two filter units, the weight of the IDT electrode and the adjustment of the logarithm of the electrode finger can be adjusted independently of the other filter units, so that it corresponds to one filter unit. The frequency characteristics of the band can be adjusted independently from the characteristics of the bands corresponding to the other filter units.

It is a top view which shows an example of the elastic wave filter of this invention. It is the top view which expanded a part of said filter. It is a schematic diagram which shows the outline of the said filter. It is a schematic diagram which shows the outline of the said filter. It is a top view which shows the other example of the said filter. It is a top view which shows the other example of the said filter. It is a top view which shows the other example of the said filter. It is a top view which shows the other example of the said filter. It is a top view which shows the other example of the said filter. It is a top view which shows the other example of the said filter. It is a top view which shows the other example of the said filter. It is a top view which shows the other example of the said filter. It is a top view which shows the other example of the said filter. It is a top view which shows the other example of the said filter. It is a top view which shows the other example of the said filter.

  An example of an embodiment of an elastic wave filter of the present invention will be described with reference to FIGS. This elastic wave filter includes a tapered input side IDT electrode 12 and an output side IDT electrode 13 which are arranged so as to be separated from each other along the propagation direction of the elastic wave. Has been placed. As shown in FIG. 1, these IDT electrodes 12 and 13 are orthogonal to the propagation direction of the elastic wave by the floating electrode 10 extending along the propagation direction of the elastic wave at the center of each IDT electrode 12 and 13. A plurality of areas in this direction are divided into two areas in this example. When the region is labeled with “1”, the frequency characteristics of the two regions 1 and 1 are individually adjusted in each of the IDT electrodes 12 and 13 as described in detail below. 1 and 2 are connected in parallel between the signal port 20 (input port 21 or output port 22) and the ground port 23. Between the IDT electrodes 12 and 13, for example, a shield electrode 5, which is a rectangular metal film, is disposed, and a region on the short side 3 and 3 side of the piezoelectric substrate 11 with respect to the IDT electrodes 12 and 13 in the propagation direction of the elastic wave. Are disposed with dampers 6 and 6 made of, for example, resin for absorbing elastic waves.

  The IDT electrodes 12 and 13 are provided with a pair of bus bars 14 and 14, respectively. The bus bars 14 and 14 are separated from each other in the direction perpendicular to the propagation direction of the elastic wave, and the length of the piezoelectric substrate 11 is long. They are respectively arranged in the regions on the sides 4 and 4 side. And the electrode finger 15 and the reflective electrode 16 are each arrange | positioned so that it may cross | intersect alternately at one side and the other side of these bus bars 14 and 14. As shown in FIG. 2, the electrode fingers 15 and the reflective electrodes 16 are tapered between the bus bars 14, 14, that is, the width dimensions of the electrode fingers 15 and the reflective electrodes 16, and the electrode fingers 15 and the reflective electrodes 16. A periodic unit λ consisting of a separation dimension between the electrodes 16 is arranged so as to spread from one side of the bus bars 14, 14 toward the other side. In the electrode finger 15 and the reflective electrode 16, “14a” is applied to one side of the bus bar 14 on the narrow region side (high frequency side) of the cycle unit λ, and the other side bus bar 14 on the wide region side (low frequency side) of the cycle unit λ. In this example, the bus bars 14a and 14b are arranged on the front side and the back side of the piezoelectric substrate 11, respectively. The periodic unit λ in the region close to the bus bar 14a and the periodic unit λ in the region close to the bus bar 14b are λ1 and λ4 (λ1 <λ4), respectively. In FIG. 1, the dimensions of the electrode fingers 15 and the reflective electrodes 16 are schematically drawn.

・・・（１）
即ち、各波長ｘで与えられる開口長ｗを
ｗ＝ａｘとすると、
λ１〜λ４の全開口長は、以下の式（２）のようになる。

・・・（２）
従って、開口長方向において浮き電極１０がバスバー１４ａ、１４ｂ間の中間位置となるためには、以下の式（３）が満たされるようにすれば良い。

・・・（３）
これを解くと、既述の式（１）となる。 Here, in each of the IDT electrodes 12 and 13, the floating electrodes 10 and 10 described above formed so as to extend in the propagation direction of the elastic wave are arranged in the region between the bus bars 14a and 14b. The floating electrodes 10 and 10 of the IDT electrodes 12 and 13 are arranged in a line in the propagation direction of the elastic wave. That is, in each IDT electrode 12 and 13, each floating electrode 10 and 10 is arrange | positioned so that the separation dimension between the bus-bar 14a and the floating electrode 10 may align, for example. In FIG. 1, the floating electrodes 10 and 10 are drawn so as to be arranged at the approximate center of each IDT electrode 12 and 13, but the floating electrodes 10 and 10 are arranged so as to satisfy the following formula (1). ing.

... (1)
That is, if the aperture length w given by each wavelength x is w = ax,
The total opening length of λ1 to λ4 is expressed by the following equation (2).

... (2)
Therefore, in order for the floating electrode 10 to be in an intermediate position between the bus bars 14a and 14b in the opening length direction, the following equation (3) may be satisfied.

... (3)
When this is solved, the above-described equation (1) is obtained.

  The electrode fingers 15 and the reflective electrodes 16 described above are disposed so as to intersect each other between the bus bar 14 a and the floating electrode 10, and are disposed so as to intersect each other between the bus bar 14 b and the floating electrode 10. .

  When the periodic unit λ on the bus bar 14a side and the periodic unit λ on the bus bar 14b side in the floating electrode 10 are “λ2” and “λ3”, respectively, λ2 and λ3 have the same dimensions as shown in FIG. . Therefore, with the floating electrode 10 as a boundary, in the area on the front side (bus bar 14a side), a propagation area in which low-wavelength (high frequency) elastic waves from λ1 to λ2 propagate is arranged, and the back side (bus bar 14b side). In this region, a propagation region in which an elastic wave having a long wavelength (low frequency) from λ3 to λ4 is disposed. FIG. 2 is an enlarged view of the left end of the input-side IDT electrode 12.

  In the input-side IDT electrode 12, bus bars 14 a and 14 b are connected to a common input port 21, and the floating electrode 10 is grounded via a ground port 23. In the output-side IDT electrode 13, the bus bars 14 a and 14 b are connected to the common output port 22, and the floating electrode 10 is grounded via the ground port 23. Therefore, as schematically shown in FIG. 3, the filter of the present invention includes a first filter unit 31 that propagates wavelengths from λ1 to λ2 and a second filter unit 32 that propagates wavelengths from λ3 to λ4. Are arranged in a direction orthogonal to the propagation direction of the elastic wave, and the floating electrodes 10 are formed by sharing the bus bars 14 and 14 facing each other. The two filter units 31 and 32 are arranged in parallel between the signal port 20 and the ground port 23 so as to be a filter through which an elastic wave having a wavelength from λ1 to λ4 (frequency from f1 to f4) propagates. A connected configuration is adopted. Accordingly, when an electric signal is input from the input port 21 in this filter, an elastic wave is generated at the input-side IDT electrode 12 of each of the filter units 31 and 32, and an electric signal is again generated at the output-side IDT electrode 13 of the respective filter units 31 and 32. The signal is converted into a signal, and a signal having a frequency corresponding to the cycle units λ <b> 1 to λ <b> 4 is extracted from the output port 22. In the following description, the region 1 of the input IDT electrode 12 and the region 1 of the output IDT electrode 13 in the first filter unit 31 are respectively referred to as “input IDT electrode 12” and “output IDT electrode 13”. Terminology will be used. The same applies to the second filter unit 32.

  Here, as shown in FIG. 1, the first filter unit 31 on the high frequency side of the two filter units 31 and 32 has a higher frequency side (from λ <b> 1) than the pass frequency band of the first filter unit 31. The number and arrangement pattern (thinning amount) of the electrode fingers 15 and the reflective electrodes 16 described above are set and weighted so that the attenuation amount increases on the higher wavelength side. Further, in the second filter unit 32 on the low frequency side of the two filter units 31 and 32, the amount of attenuation is on the lower frequency side (lower wavelength side than λ4) than the pass frequency band of the second filter unit 32. Is set and weighted so that the quantity and arrangement pattern of the electrode fingers 15 and the reflective electrodes 16 are set. Therefore, the first filter unit 31 has a frequency lower than the pass frequency band of the first filter unit 31, and the second filter unit 32 has a frequency lower than the pass frequency band of the second filter unit 32. On the high frequency side, attenuation characteristics may be deteriorated as compared with the case where weighting is not performed as described above.

  However, the pass frequency band of the second filter unit 32 is located on the lower frequency side than the pass frequency band of the first filter unit 31, and accordingly, on the higher frequency side than the pass frequency band of the second filter unit 32. Is the pass frequency band of the first filter unit 31. Therefore, when these two filter units 31 and 32 are connected in parallel, as schematically shown in FIG. 4, in one filter unit 31 (32), the band where the characteristic may be deteriorated is another filter unit. 32 (31) pass frequency band. Therefore, the filter of the present invention is more effective than the conventional filter (indicated by a broken line in FIG. 4) in which the elastic waves of the period units λ1 to λ4 propagate without the floating electrode 10 being disposed. Also, good (large) attenuation can be obtained on the low frequency side and the high frequency side. 3, illustration of the electrode finger 15, the reflective electrode 16, and the bus bar 14 is omitted, and FIG. 4 schematically shows the frequency characteristics. Further, in the lower gram of FIG. 3 and each graph of FIG. 4, the horizontal axis represents frequency and the vertical axis represents attenuation.

  According to the above-described embodiment, the tapered input-side IDT electrode 12 and the output-side IDT electrode 13 formed so that the cycle unit λ increases from the one side bus bar 14a side toward the other side bus bar 14b side. About each filter part 31 and 32 with which each was provided, while arrange | positioning in the direction orthogonal to the propagation direction of an elastic wave, period unit (lambda) 2 of the 1st filter part 31 and period unit (lambda) 3 of the 2nd filter part 32 are set. The same length is set. Therefore, the weighting of each IDT electrode 12, 13 and the adjustment of the number of pairs of electrode fingers 15 (the number of electrode fingers 15, 15 intersecting each other) can be adjusted independently for each of the filter units 31, 32. One frequency characteristic of the two filter units 31 and 32 can be adjusted independently of the other frequency characteristic. Therefore, the logarithm of the electrode finger 15 is set and weighted so that the frequency characteristic (attenuation amount) on the high frequency side is good for the first filter unit 31 on the high frequency side, while the second filter on the low frequency side. For the filter unit 32, the logarithm of the electrode fingers 15 can be set and weighted so that the frequency characteristics on the low frequency side are good. Therefore, for example, a filter with good selectivity (a good attenuation can be obtained on the low frequency side and the high frequency side of the pass frequency band) can be obtained.

  In FIG. 1, the bus bars 14 a and 14 b are connected to the signal port 20 and the floating electrode 10 is connected to the ground port 23, but in the present invention, the two filter units 31 and 32 are connected to each other between the signal port 20 and the ground port 23. As long as they are connected in parallel, a specific configuration example of the filter of the present invention other than that shown in FIG. FIG. 5 shows an example in which the IDT electrodes 12 and 13 are arranged in the same manner as in FIG. 1, the bus bars 14 a and 14 b are connected to the ground port 23, and the floating electrode 10 is connected to the signal port 20. In this case, the input-side IDT electrode 12 may have the same configuration as that of FIG. 1 described above, that is, the bus bars 14a and 14b may be connected to the input port 21 and the floating electrode 10 may be grounded.

  In FIG. 6, the first filter unit 31 is arranged in the same layout as in FIG. 1, while the second filter unit 32 is arranged such that the period unit λ increases from the bus bar 14 b side to the floating electrode 10 side. An example of arrangement is shown. Accordingly, in the second filter section 32, the cycle unit λ3 is set on the bus bar 14b side, and the cycle unit λ4 is set on the floating electrode 10 side. In FIG. 6, the bus bars 14 a and 14 b are connected to the common signal port 20, and the floating electrode 10 is connected to the ground port 23.

  Further, in FIG. 7, the filter units 31 and 32 are arranged in the same manner as in FIG. 6, and the floating electrode 10 is not shared in the filter units 31 and 32. , 14b are provided individually. Therefore, in each filter part 31 and 32, each area | region 1 is arrange | positioned between bus-bar 14a, 14b, the bus-bar 14b of the back side of the 1st filter part 31, and the bus-bar 14a of the near side of the 2nd filter part 32, Are opposed to each other through the gap region 40 along the direction of propagation of the elastic wave at the approximate center of the piezoelectric substrate 11. In addition, the bus bars 14a and 14a on the front side of the filter sections 31 and 32 are connected to the common signal port 20, respectively, and the bus bars 14b and 14b on the back side are connected to the ground port 23, respectively. 5 to 7 can provide the same effects as those of FIG.

  Here, it has already been described that the weighting of the filter units 31 and 32 may be performed individually, but another specific example of such a weighting method will be described. First, in FIG. 8, for example, with respect to the input-side IDT electrode 12, the electrode fingers 15 and the reflective electrodes 16 are arranged from the bus bar 14a on one side to the bus bar 14b on the other side without being divided into a plurality of filter portions 31 and 32. A conventional configuration example will be shown.

  For example, as described above, the input-side IDT electrode 12 is divided into two filter parts 31 and 32 in a direction orthogonal to the propagation direction of the elastic wave, and for each of these two filter parts 31 and 32. An example in which excitation thinning (logarithm of electrode fingers 15) is performed individually is shown in FIG. As shown in FIG. 9, in this example, by providing a plurality of electrode fingers 15 extending from the floating electrode 10 toward the bus bars 14a and 14b so as to be adjacent to each other along the propagation direction of the elastic wave, the logarithm of the electrode fingers 15 is provided. In the first filter unit 31, the logarithm is provided in four places, and in the second filter part 32, the logarithm is provided in three places. In FIG. 9, the regions of the electrode fingers 15, 15 arranged so as to cross each other are marked with a circle.

  Further, in FIG. 10, for example, for the input-side IDT electrode 12, the two filter parts 31 and 32 are arranged, and the arrangement position and quantity of the reflective electrode 16 are changed in each filter part 31 and 32 (the reflective electrode 16 An example is shown in which the thinning amount is changed. In FIG. 10, the reflective electrode 16 is formed at two locations in the first filter portion 31, and the reflective electrode 16 is formed at four locations in the second filter portion 32.

  As shown in FIGS. 9 and 10, when weighting is individually performed in each of the filter units 31 and 32, the first filter unit 31 in FIG. 1 described above has a higher frequency than the band of the first filter unit 31. On the other hand, the second filter unit 32 is set so that the attenuation on the lower frequency side is better than the band of the second filter unit 32. The portions 31 and 32 may be weighted so that the slope of the attenuation curve on the high frequency side and the low frequency side becomes steep. In addition, either or both of the filter units 31 and 32 are weighted so that the attenuation amount and the inclination of the attenuation are good, or together with the weighting, the flatness in the pass frequency band is good. You may weight.

  Further, in each of the above examples, when each of the IDT electrodes 12 and 13 is partitioned into a plurality of filter portions 31 and 32, the floating electrodes 10 and 10 are arranged at the approximate center of each of the IDT electrodes 12 and 13, Depending on the required frequency characteristics, the floating electrode 10 may be arranged so as to be shifted to a higher frequency side or a lower frequency side than the central portion. Specifically, the floating electrodes 10 and 10 may be arranged so that λ2 (λ3) = (λ1 + (λ4−λ1) × 0.1) to (λ1 + (λ4−λ1) × 0.9). good. Even in such a case, the floating electrodes 10 and 10 that partition the IDT electrodes 12 and 13 in the filter units 31 and 32 are arranged in a line along the propagation direction of the elastic wave.

  Here, when the acoustic wave propagates through the IDT electrodes 12 and 13 and the dampers 6 and 6 to the short sides 3 and 3 of the piezoelectric substrate 11, the acoustic wave is transmitted to the IDT electrodes 12 and 13. In order to suppress the return to the side, for example, as schematically shown in FIG. 11, the short sides 3 and 3 are formed so as to have a rhombus shape so as to be inclined with respect to the long sides 4 and 4. There may be. In this case, when the filter units 31 and 32 are arranged in a direction perpendicular to the propagation direction of the elastic wave, the formation region of the damper 6 on the short side 3 side of the piezoelectric substrate 11 is, for example, on the left side in FIG. Since it becomes narrower on the side than on the back side, the dampers 6 and 6 are poorly accommodated (it is difficult to dispose the dampers 6 and 6). Therefore, as shown in FIG. 11, when the two filter portions 31 and 32 are arranged along the short side 3, for example, the application areas (formation areas) of the dampers 6 and 6 can be secured in a well-balanced manner. Specifically, on the left side in FIG. 11, the first filter portion 31 on the near side is arranged at a position farther from the short side 3 than the second filter portion 32 on the far side, and on the right side in FIG. The first filter part 31 is arranged at a position closer to the short side 3 than the second filter part 32 on the back side. Accordingly, the IDT electrodes 12 and 13 of the first filter unit 31 are separated in the propagation direction of the elastic wave when viewed from the IDT electrodes 12 and 13 of the second filter unit 32 and It is formed at a position separated in a direction orthogonal to the propagation direction. In this example, each of the IDT electrodes 12 and 13 of the filter units 31 and 32 has regions 1 and 1 partially overlapping each other when viewed from a direction orthogonal to the propagation direction of the elastic wave.

  FIG. 11 shows an example in which the floating electrode 10 is not shared by the two filter parts 31 and 32. However, as described above, the common floating electrode 10 may be disposed between the filter parts 31 and 32. . In FIG. 11, the electrode fingers 15 and the reflective electrodes 16 are not shown. The same applies to the subsequent FIGS.

  Further, FIG. 12 shows a configuration in which the filter units 31 and 32 are separated from each other in the elastic wave propagation direction as compared with the example of FIG. 13 further separates the filter units 31 and 32 from each other in the elastic wave propagation direction as compared with the example of FIG. 12, and the first filter unit 31 and the second filter unit 32 have an input side. An example in which the IDT electrode 12 and the output-side IDT electrode 13 are replaced is shown. Specifically, the first filter unit 31 is disposed in the same manner as in FIG. 1 described above, and the second filter unit 32 is disposed on the back side of the input-side IDT electrode 12 of the first filter unit 31. The output-side IDT electrode 13 is disposed. Further, the input-side IDT electrode 12 of the second filter unit 32 is disposed on the back side of the output-side IDT electrode 13 of the first filter unit 31.

  Further, FIG. 14 shows that the filter units 31 and 32 are arranged as in FIG. 12 described above, and the filter units 31 and 32 are arranged in the center of the piezoelectric substrate 11 in the direction orthogonal to the propagation direction of the elastic wave. An example in which it is arranged at a close position is shown. In FIG. 14, when viewed from the propagation direction of the elastic wave, the region 1 on the back side of the first filter portion 31 and the region 1 on the near side of the second filter portion 32 partially overlap each other.

  That is, in each example of FIGS. 11 to 14 described above, it can be said that the filter units 31 and 32 are arranged so as not to line up in a line along the propagation direction of the elastic wave. At this time, in FIGS. 11 to 14, as described above, the filter units 31 and 32 are connected in parallel between the signal port 20 and the ground port 23.

  In each of the above examples, the IDT electrodes 12 and 13 are divided into two filter units 31 and 32. However, the IDT electrodes 12 and 13 may be divided into three or more. FIG. 15 shows an example in which the IDT electrodes 12 and 13 are partitioned into three filter portions 31, 32, and 33 from the near side to the far side. In FIG. 15, the period units λ of the filter units 31, 32, and 33 are λ1 to λ2, λ3 to λ4, and λ5 to λ6 (λ1 <λ2 = λ3 <λ4 = λ5 <λ6), respectively. In FIG. 15, the filter units 31 to 33 are connected in parallel between the signal port 20 and the ground port 23, and specifically, the floating electrode 10 and the bus bar 14 b between the filter units 31 and 32 are common. The floating electrode 10 between the bus bar 14a and the filter portions 32 and 33 is connected to the ground port 23.

  When the three filter units 31 to 33 are arranged in this way, the high-frequency (high-frequency) side filter unit 31 has a higher attenuation amount on the high-frequency side than the band of the filter unit 31. The low frequency (low frequency) side filter unit 33 is weighted so that the attenuation amount on the low frequency side is better than the band of the filter unit 33. The center filter unit 32 is weighted so that, for example, the flatness is good in the band of the filter unit 32. Even when three or more filter units 31 to 33 are arranged as described above, the respective filter units 31 to 33 may be arranged as shown in FIGS.

DESCRIPTION OF SYMBOLS 10 Floating electrode 11 Piezoelectric substrate 12 Input side IDT electrode 13 Output side IDT electrode 20 Signal port 21 Input port 22 Output port 23 Grounding port 31 1st filter part 32 2nd filter part

Claims (5)

A tapered IDT electrode formed such that a period unit comprising a width dimension of electrode fingers and a spacing dimension between adjacent electrode fingers spreads from one bus bar to the other bus bar is defined as an input side electrode and an output side electrode. As a first filter part and a second filter part respectively arranged along the propagation direction of the elastic wave,
An input port connected in common to any bus bar of the input side electrode of the first filter section and any bus bar of the input side electrode of the second filter section;
An output port connected in common to any bus bar of the output side electrode of the first filter unit and any bus bar of the output side electrode of the second filter unit;
The cycle unit on the other bus bar side in the first filter unit and the cycle unit on the one bus bar side in the second filter unit are set to the same length,
When a region between each of the one side bus bar and the other side bus bar in the input side electrode and the output side electrode is referred to as a propagation region, the first filter unit includes the propagation region of the first filter unit and the first filter unit. A position spaced apart in a direction orthogonal to the propagation direction of the elastic wave when viewed from the second filter unit so that the propagation region of the second filter unit is not aligned in a line in the propagation direction of the elastic wave; Alternatively, the elastic wave filter is formed at a position that is separated along the propagation direction of the elastic wave and is separated in the orthogonal direction.   2. The acoustic wave filter according to claim 1, wherein the first filter unit and the second filter unit are arranged in a direction orthogonal to the propagation direction of the elastic wave. The first filter part and the second filter part are respectively arranged so that the one side bus bar in the second filter part faces the other side bus bar in the first filter part,
3. The acoustic wave filter according to claim 2, wherein the bus bar on the other side in the first filter part and the bus bar on the one side in the second filter part are shared as floating electrodes. . In the first filter unit, the arrangement pattern of the electrode fingers is set so that the attenuation amount on the high frequency side is larger than the low frequency side outside the pass frequency band of the first filter unit,
In the second filter unit, the arrangement pattern of the electrode fingers is set such that the attenuation amount on the low frequency side is larger than the high frequency side outside the pass frequency band of the second filter unit. The elastic wave filter according to any one of claims 1 to 3, wherein the elastic wave filter is provided. The first filter portion and the second filter portion each include a reflective electrode extending from one of the one side bus bar and the other side bus bar along the length direction of the electrode finger,
In the first filter unit, the arrangement pattern of the reflective electrodes is set so that the attenuation amount on the high frequency side is larger than the low frequency side outside the pass frequency band of the first filter unit,
In the second filter section, the arrangement pattern of the reflection electrodes is set so that the attenuation amount on the low frequency side is larger than the high frequency side outside the pass frequency band of the second filter section. The elastic wave filter according to any one of claims 1 to 4.

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