CN211046886U - Elastic wave device and multiplexer - Google Patents
Elastic wave device and multiplexer Download PDFInfo
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- CN211046886U CN211046886U CN201922375659.6U CN201922375659U CN211046886U CN 211046886 U CN211046886 U CN 211046886U CN 201922375659 U CN201922375659 U CN 201922375659U CN 211046886 U CN211046886 U CN 211046886U
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Abstract
Provided are an elastic wave device and a multiplexer. An elastic wave device comprising a piezoelectric substrate and a longitudinally coupled resonator-type elastic wave filter unit formed on the piezoelectric substrate, wherein the longitudinally coupled resonator-type elastic wave filter unit comprises: and at least first, second, and third IDT electrodes arranged adjacently with a gap in the elastic wave propagation direction, wherein each of the first, second, and third IDT electrodes has a main-pitch electrode finger portion and a narrow-pitch electrode finger portion having an electrode finger pitch smaller than that of the main-pitch electrode finger portion, the narrow-pitch electrode finger portion is a portion from an end of another IDT electrode arranged adjacently in the elastic wave propagation direction, and the total number of electrode fingers of the pair of narrow-pitch electrode finger portions facing the gap between the first IDT electrode and the second IDT electrode is different from the total number of electrode fingers of the pair of narrow-pitch electrode finger portions facing the gap between the second IDT electrode and the third IDT electrode. This improves the insertion loss in the passband.
Description
Technical Field
The present invention relates to an acoustic wave device and a multiplexer, and more particularly, to an acoustic wave device including a longitudinally coupled resonator type acoustic wave filter unit and a multiplexer including the same.
Background
Conventionally, when a terminal 1 transmits a transmission signal, as shown in fig. 8, the transmission signal enters the terminal 2 even in the terminals 1 and 2 having the same frequency BAND (for example, BAND 3). The passband of the transmission antenna Tx differs for each terminal according to the standard. Therefore, as shown in fig. 9, the transmission signal of the terminal 1 may enter the reception antenna Rx attenuation band of the terminal 2. At this time, if a load is applied to the longitudinally coupled resonator of the Rx filter of the reception antenna of the terminal 2, a malfunction may occur.
For this reason, various schemes have been proposed for the longitudinally coupled resonators in the reception antenna Rx.
In the longitudinally coupled resonator type elastic wave filter, the continuity of the propagation characteristics of the elastic surface wave in the portion where the IDT electrodes are adjacent to each other can be improved by providing the narrow pitch electrode finger portions, but there is room for further improvement in terms of low loss, high attenuation, wide band, and the like.
Prior art documents
Patent document
Patent document 1: international publication WO2010/119745
SUMMERY OF THE UTILITY MODEL
The present invention has been made in view of the above problems occurring in the prior art, and an object of the present invention is to provide an elastic wave device capable of improving insertion loss in a passband, and a multiplexer including the elastic wave device.
In order to solve the above problem, according to one aspect of the present invention, there is provided an acoustic wave device including a piezoelectric substrate and a longitudinally coupled resonator type acoustic wave filter unit formed on the piezoelectric substrate, the longitudinally coupled resonator type acoustic wave filter unit including: and at least first, second, and third IDT electrodes arranged adjacently with a gap in an elastic wave propagation direction, the first, second, and third IDT electrodes each having a main-pitch electrode finger portion and a narrow-pitch electrode finger portion having an electrode finger pitch smaller than that of the main-pitch electrode finger portion, the narrow-pitch electrode finger portion being a portion from an end of another IDT electrode arranged adjacently in the elastic wave propagation direction, a total number of electrode fingers of a pair of the narrow-pitch electrode finger portions facing the gap between the first IDT electrode and the second IDT electrode being different from a total number of electrode fingers of a pair of the narrow-pitch electrode finger portions facing the gap between the second IDT electrode and the third IDT electrode.
The present invention in another aspect relates to an acoustic wave device including a piezoelectric substrate and a longitudinally coupled resonator type acoustic wave filter unit formed on the piezoelectric substrate, the acoustic wave device including: at least a first IDT electrode, a second IDT electrode and a third IDT electrode which are adjacently arranged in an elastic wave propagation direction, wherein the first IDT electrode, the second IDT electrode and the third IDT electrode respectively comprise a main pitch electrode finger part and a narrow pitch electrode finger part with an electrode finger pitch smaller than that of the main pitch electrode finger part, the narrow pitch electrode finger part is a part from the end part of other IDT electrode which is adjacently arranged in the elastic wave propagation direction, the total number of electrode fingers of the narrow pitch electrode finger part which is a part from the end part of the second IDT electrode and the narrow pitch electrode finger part which is a part from the end part of the first IDT electrode, the electrode finger part which is a part from the end part of the third IDT electrode and the electrode finger part which is a part from the end part of the second IDT electrode and the narrow pitch electrode finger part which is a part from the end part of the second IDT electrode The total number of (2) is different.
Further, according to the acoustic wave device of the present invention, it is preferable that parallel resonators are connected to one side and the other side of the longitudinally coupled resonator type acoustic wave filter unit, respectively, and an electrode finger pitch of the parallel resonator on the one side is different from an electrode finger pitch of the parallel resonator on the other side.
Further, according to the acoustic wave device of the present invention, it is preferable that the one side of the longitudinally coupled resonator type acoustic wave filter portion is an input side, and the other side is an output side.
Further, according to the elastic wave device of the present invention, it is preferable that the electrode finger pitch of the parallel resonator on the input side is smaller than the electrode finger pitch of the parallel resonator on the output side.
Further, according to the elastic wave device of the present invention, it is preferable that the electrode finger pitch of the input-side parallel resonator is formed so that the resonance frequency of the input-side parallel resonator coincides with the peak frequency of the secondary mode ripple.
Further, according to the elastic wave device of the present invention, it is preferable that the parallel resonator on the input side and the parallel resonator on the output side have a fixed electrode finger pitch, respectively.
Further, according to the elastic wave device of the present invention, it is preferable that the number of electrode fingers of a pair of the narrow-pitch electrode finger portions facing one gap is different from each other.
A multiplexer according to another aspect of the present invention is provided with a plurality of band pass filters, and the multiplexer is provided with any one of the elastic wave devices described above as at least one of the plurality of band pass filters.
Furthermore, according to the present invention, it is preferable that the pass band of the at least one band pass filter among the plurality of band pass filters is a high frequency side compared to the pass band of the other at least one band pass filter.
Effect of the utility model
According to the present invention, the insertion loss in the passband can be improved, and in addition, the load on the longitudinal coupling resonator type elastic wave filter can be reduced, and the occurrence of a failure can be suppressed, and the steep deterioration of the passband can be suppressed.
Drawings
The above objects, advantages and features of the present invention will become more apparent by describing in detail preferred embodiments thereof with reference to the following drawings, in which:
fig. 1 is a schematic diagram showing a circuit configuration of an elastic wave device according to an embodiment of the present invention.
Fig. 2A is a schematic diagram showing a circuit configuration of a longitudinally coupled resonator type elastic wave filter unit according to an embodiment of the present invention.
Fig. 2B is a schematic diagram showing a circuit configuration of a longitudinally coupled resonator type elastic wave filter unit according to an embodiment of the present invention.
Fig. 3 is a schematic diagram showing a circuit configuration of a parallel resonator according to an embodiment of the present invention.
Fig. 4 is a diagram showing the filter characteristics and the longitudinal coupling filter resonance modes of the longitudinal coupling resonator type elastic wave filter unit according to the embodiment of the present invention.
Fig. 5A is a diagram showing the passing characteristics of an elastic wave device according to an embodiment of the present invention.
Fig. 5B is a diagram showing the transmission characteristics from the input side of the acoustic wave device according to the embodiment of the present invention to the longitudinally coupled resonator type acoustic wave filter unit.
Fig. 6 is a diagram showing a technical effect of an elastic wave device according to embodiment 1 of the present invention.
Fig. 7 is a diagram showing a technical effect of an elastic wave device according to embodiment 2 of the present invention.
Fig. 8 is a diagram for explaining a technical problem in the related art.
Fig. 9 is a diagram for explaining a technical problem in the related art.
Description of the reference numerals
11 input terminal
12 output terminal
101. 105 series resonator
103 longitudinally coupled resonator type elastic wave filter unit
102. 104 parallel resonator
201. 202, 203, 211, 212, 213, 214, 215, 301 IDT electrodes
2001. 2002, 302, 303 reflectors.
Detailed Description
The present application will be described in further detail with reference to the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and are not limiting of the invention. It should be noted that, for convenience of description, only the relevant portions of the related inventions are shown in the drawings.
Fig. 1 is a schematic diagram showing a circuit configuration of an elastic wave device according to an embodiment of the present invention.
The acoustic wave device of the present embodiment includes an input terminal 11 and an output terminal 12. Series resonator 101, longitudinally coupled resonator type elastic wave filter unit 103, and series resonator 105 are connected in series to a series arm connecting input terminal 11 and output terminal 12. Parallel resonator 102 is connected to the input side of longitudinally coupled resonator type elastic wave filter unit 103. That is, parallel resonator 102 is disposed in a parallel arm connecting a connection point between series resonator 101 and longitudinally coupled resonator type elastic wave filter unit 103 and a ground potential. Parallel resonators 104 are connected to the output side of longitudinally coupled resonator type elastic wave filter unit 103. That is, parallel resonator 104 is disposed in a parallel arm connecting a connection point between longitudinally coupled resonator type elastic wave filter unit 103 and series resonator 105 and a ground potential. In the present embodiment, the series resonator and the parallel resonator may be each formed of an elastic wave resonator.
Fig. 2A is a schematic diagram showing a circuit configuration of a longitudinally coupled resonator type elastic wave filter unit according to an embodiment of the present invention.
Fig. 2A shows an example of a circuit configuration of longitudinal coupled resonator type elastic wave filter unit 103 according to the present embodiment, and longitudinal coupled resonator type elastic wave filter unit 103 having three IDT electrodes is formed by forming the electrode structure shown in fig. 2A on a piezoelectric substrate.
The longitudinally coupled resonator type elastic wave filter unit 103 includes at least three IDT electrodes 201, 202, and 203 arranged adjacently with a gap in the elastic wave propagation direction, and hereinafter, for convenience, the IDT electrodes are also referred to as a first IDT electrode 201, a second IDT electrode 202, and a third IDT electrode 203. The reflectors 2001 and 2002, hereinafter also referred to as a first reflector 2001 and a second reflector 2002 for convenience, may be disposed on both sides in the elastic wave propagation direction of the region where the first IDT electrode 201, the second IDT electrode 202, and the third IDT electrode 203 are disposed. That is, the first reflector 2001 and the second reflector 2002 are arranged along the elastic wave propagation direction so as to sandwich the region where the first IDT electrode 201, the second IDT electrode 202, and the third IDT electrode 203 are arranged. The first reflector 2001 and the second reflector 2002 may be grating reflectors in which a plurality of electrode fingers are short-circuited at both ends. Wherein, the propagation direction of the elastic wave is approximately vertical to the extending direction of the electrode fingers.
The structure of the IDT electrode will be described by taking the first IDT electrode 201 as an example. The first IDT electrode 201 has a pair of comb-shaped electrodes, each of which has a bus bar and a plurality of electrode fingers having one end connected to the bus bar. A pair of comb-teeth-shaped electrodes are opposed such that respective electrode fingers are interposed between each other. The plurality of electrode fingers extend in a direction substantially perpendicular to the propagation direction of the elastic wave. The basic structure of the other IDT electrodes is also the same.
As shown in fig. 2A, two of the first IDT electrode 201, the second IDT electrode 202, and the third IDT electrode 203, which are adjacent to each other, include a portion where the electrode finger pitch of the plurality of electrode fingers located on the outermost side of the end of the IDT electrode is smaller than the electrode finger pitch of the other portion of the IDT electrode. The portion of the electrode fingers having a relatively small pitch is referred to as a narrow-pitch electrode finger. That is, the narrow-pitch electrode finger portions are portions from the side ends of the other IDT electrodes arranged adjacent to each other in the elastic wave propagation direction. In fig. 2A, the narrow-pitch electrode fingers are schematically indicated by N. The portion of the IDT electrode other than the narrow-pitch electrode finger portions is referred to as a main-pitch electrode finger portion. Here, the electrode finger pitch is a distance between centers of adjacent electrode fingers.
In the present embodiment, the provision of the narrow-pitch electrode finger portions N can improve the continuity of the propagation characteristics of the elastic wave in the portion where the IDT electrodes are adjacent to each other, and can reduce the transmission loss of the elastic wave.
In the present embodiment, the total number of electrode fingers of the pair of narrow-pitch electrode finger portions N facing the gap between the first IDT electrode 201 and the second IDT electrode 202 is different from the total number of electrode fingers of the pair of narrow-pitch electrode finger portions N facing the gap between the second IDT electrode 202 and the third IDT electrode 203.
In the present embodiment, the number of electrode fingers of the pair of narrow-pitch electrode finger portions N facing one IDT inter-electrode gap is preferably different from each other.
The elastic wave device of the present embodiment includes a piezoelectric substrate and longitudinally coupled resonator type elastic wave filter unit 103 formed on the piezoelectric substrate, and thereby can significantly improve the insertion loss in the passband and obtain an elastic wave device having a sufficient passband width.
In the present embodiment, the number of IDT electrodes in longitudinally coupled resonator type elastic wave filter unit 103 is not particularly limited. For example, fig. 2B shows a configuration example of a longitudinally coupled resonator type elastic wave filter unit having 5 IDT electrodes.
Fig. 2B is a schematic diagram showing a circuit configuration of a longitudinally coupled resonator type elastic wave filter unit according to an embodiment of the present invention.
As shown in fig. 2B, longitudinally coupled resonator type elastic wave filter unit 103' includes: five IDT electrodes 211, 212, 213, 214, 215, hereinafter also referred to as a first IDT electrode 211, a second IDT electrode 212, a third IDT electrode 213, a fourth IDT electrode 214, and a fifth IDT electrode 215, which are disposed adjacent to each other along the elastic wave propagation direction, for convenience; and a first reflector 2001 and a second reflector 2002 which are arranged along the elastic wave propagation direction so as to sandwich a region where the first IDT electrode 211, the second IDT electrode 212, the third IDT electrode 213, the fourth IDT electrode 214, and the fifth IDT electrode 215 are arranged.
As shown in fig. 2B, each of the first IDT electrode 211, the second IDT electrode 212, the third IDT electrode 213, the fourth IDT electrode 214 and the fifth IDT electrode 215 has a main-pitch electrode finger portion and a narrow-pitch electrode finger portion N having an electrode finger pitch smaller than that of the main-pitch electrode finger portion, and the narrow-pitch electrode finger portion N is a portion from the end of the other IDT electrode disposed adjacent to the end in the elastic wave propagation direction. The total number of electrode fingers of the narrow-pitch electrode finger portions N adjacent to each other in the first IDT electrode 211 and the second IDT electrode 212 is different from the total number of electrode fingers of the narrow-pitch electrode finger portions N adjacent to each other in the second IDT electrode 212 and the third IDT electrode 213. The total number of electrode fingers of the narrow-pitch electrode finger portions N adjacent to each other in the third IDT electrode 213 and the fourth IDT electrode 214 is different from the total number of electrode fingers of the narrow-pitch electrode finger portions N adjacent to each other in the fourth IDT electrode 214 and the fifth IDT electrode 215. That is, the total number of electrode fingers of the narrow-pitch electrode finger portion that is a portion from the side end of the second IDT electrode 212 of the first IDT electrode 211 and the narrow-pitch electrode finger portion that is a portion from the side end of the first IDT electrode 211 of the second IDT electrode 212 is different from the total number of electrode fingers of the narrow-pitch electrode finger portion that is a portion from the side end of the third IDT electrode 213 of the second IDT electrode 212 and the narrow-pitch electrode finger portion that is a portion from the side end of the second IDT electrode 212 of the third IDT electrode 213. The total number of electrode fingers of the narrow-pitch electrode finger portion that is a portion from the end of the fourth IDT electrode 214 of the third IDT electrode 213 and the narrow-pitch electrode finger portion that is a portion from the end of the third IDT electrode 213 of the fourth IDT electrode 214 is different from the total number of electrode fingers of the narrow-pitch electrode finger portion that is a portion from the end of the fifth IDT electrode 215 of the fourth IDT electrode 214 and the narrow-pitch electrode finger portion that is a portion from the end of the fourth IDT electrode 214 of the fifth IDT electrode 215.
Accordingly, according to the configuration of the longitudinally coupled resonator type elastic wave filter unit of the present embodiment, it is possible to reduce the transmission loss of the elastic wave, to significantly improve the insertion loss in the passband, and to obtain an elastic wave device having a sufficient passband width.
In the acoustic wave device according to the present embodiment, as shown in fig. 1, parallel resonators 102 and 104 are preferably connected to one side and the other side of longitudinally coupled resonator-type acoustic wave filter unit 103, respectively. Further, it is preferable that the one side is an input side and the other side is an output side.
The input-side parallel resonator 102 and the output-side parallel resonator 104 may have fixed electrode finger pitches, respectively.
Fig. 3 is a schematic diagram showing a circuit configuration of a parallel resonator according to an embodiment of the present invention. As shown in fig. 3, the parallel resonators 102 and 104 each have a structure in which the parallel resonator 102 includes an IDT electrode 301, and reflectors 302 and 303 arranged along the elastic wave propagation direction so as to sandwich a region in which the IDT electrode 301 is arranged. The parallel resonator 104 may have the same structure as the parallel resonator 102. Fig. 3 is merely an example, and the configuration of the parallel resonators 102 and 104 is not particularly limited.
Fig. 4 is a diagram showing the filter characteristics and the longitudinal coupling filter resonance modes of the longitudinal coupling resonator type elastic wave filter unit according to the embodiment of the present invention, and in fig. 4, the curve with ○ shows the longitudinal coupling filter resonance modes, and the curve without ○ shows the filter characteristics.
The inventors of the present invention have found that, as shown in fig. 2A and 2B, the advantageous technical effects described above can be obtained by making the total number of electrode fingers of the narrow-pitch electrode finger portion N in which the left two IDT electrodes are adjacent to each other among the adjacent 3 IDT electrodes among the plurality of IDT electrodes arranged adjacently along the elastic wave propagation direction of the longitudinally-coupled resonator type elastic wave filter portion different from the total number of electrode fingers of the narrow-pitch electrode finger portion N in which the right two IDT electrodes are adjacent to each other, but on the other hand, when the total number of electrode fingers of the narrow-pitch electrode finger portion N in which the left two IDT electrodes are adjacent to each other among the 3 IDT electrodes arranged adjacently along the elastic wave propagation direction is made different from the total number of electrode fingers of the narrow-pitch electrode finger portion N in which the right two IDT electrodes are adjacent to each other, 1-order mode ripple occurs between the 0-order mode and the 2-order mode, as shown in fig. 4, the peak of the 2 nd order mode ripple is two, and the peak of the 2 nd order mode ripple on the low frequency side exists outside the band on the low frequency side of the pass band. If a strong electric power is applied near the peak of the 2 nd order mode ripple, the longitudinally coupled resonator may malfunction.
For this reason, in the present embodiment, the electrode finger pitch of the input-side parallel resonator 102 may be made different from the electrode finger pitch of the output-side parallel resonator 104.
Fig. 5A is a diagram showing the pass characteristics of an elastic wave device according to an embodiment of the present invention, fig. 5A shows an input-side parallel notch with a curve of ○, an output-side parallel notch with a curve of □, and filter characteristics with no curves of ○ and □, and fig. 5B is a diagram showing the pass characteristics of an input side of an elastic wave device according to an embodiment of the present invention to a longitudinally coupled resonator type elastic wave filter unit.
As is apparent from fig. 5A and 5B, parallel resonators are connected to the input side and the output side of longitudinal coupling resonator type elastic wave filter unit 103, respectively, and the electrode finger pitch of parallel resonator 102 on the input side is made different from the electrode finger pitch of parallel resonator 104 on the output side, whereby the attenuation (attenuation) on the low frequency side of the passband can be increased, and a signal flows into the parallel resonators, so that a signal when a filter voltage having a low passband is applied can be caused to flow into the ground through the parallel resonators. Accordingly, the load on the longitudinally coupled resonator is reduced, and the occurrence of a failure can be suppressed.
In other words, by matching the resonance frequency of the parallel resonator with the peak frequency of the 2 nd order mode ripple, a signal when a filter voltage having a low pass band is applied flows into the ground through the parallel resonator. Accordingly, the load on the longitudinally coupled resonator is reduced, and the occurrence of a failure can be suppressed.
In addition, of the parallel resonators connected to the input and output sides of the longitudinally coupled resonator for the purpose of improving the attenuation, it is preferable to use the input side parallel resonator for the resolution of the 2-order mode ripple. That is, it is preferable that the electrode finger pitch of the parallel resonator on the input side of the longitudinally coupled resonator type elastic wave filter unit is set so that the resonance frequency of the parallel resonator on the input side coincides with the peak frequency of the secondary mode ripple.
The technical effects of the elastic wave device according to the embodiment of the present invention were tested. The following is a detailed description.
(example 1)
In example 1, the case where the electrode finger pitch of the parallel resonator on the input side is larger than the electrode finger pitch of the parallel resonator on the output side is shown for the elastic wave device of the present embodiment.
[ Structure ]
The acoustic wave device of example 1 includes a piezoelectric substrate and a longitudinally coupled resonator-type acoustic wave filter unit formed on the piezoelectric substrate, and the longitudinally coupled resonator-type acoustic wave filter unit includes: a first IDT electrode, a second IDT electrode and a third IDT electrode which are adjacently arranged along the propagation direction of the elastic wave; and a first reflector and a second reflector arranged along the elastic wave propagation direction so as to sandwich a region where the first, second, and third IDT electrodes are arranged, wherein the first, second, and third IDT electrodes respectively have a main-pitch electrode finger portion and a narrow-pitch electrode finger portion having an electrode finger pitch smaller than that of the main-pitch electrode finger portion, the narrow-pitch electrode finger portion is a portion from an end portion of another IDT electrode adjacent in the elastic wave propagation direction, and a total number of electrode fingers of the narrow-pitch electrode finger portions adjacent to each other of the first and second IDT electrodes is different from a total number of electrode fingers of the narrow-pitch electrode finger portions adjacent to each other of the second and third IDT electrodes.
Parallel resonators are connected to the input side and the output side of the longitudinally coupled resonator type elastic wave filter unit, respectively, and the electrode finger pitch of the parallel resonator on the input side is larger than the electrode finger pitch of the parallel resonator on the output side.
[ test conditions ]
The elastic wave device of embodiment 1 is applied to a filter of a reception antenna Rx of a communication terminal having Band 3.
Test frequency: tx band
Modulation L TE 1.4MHz FullRB
Temperature: 85 deg.C
Time of application of power: 30 seconds
Fig. 6 is a graph showing the technical effect of the elastic wave device according to example 1 of the present invention, and in fig. 6, a curve without ○ shows the initial characteristic, and a curve with ○ shows the characteristic after 150mW application.
As is clear from fig. 6, in the elastic wave device according to example 1, the longitudinally coupled resonator was destroyed 30 seconds after applying 150mW of electric power, that is, the blowing electric power was 150 mW.
(example 2)
In example 2, the case where the electrode finger pitch of the input-side parallel resonator is smaller than the electrode finger pitch of the output-side parallel resonator is shown for the elastic wave device of the present embodiment.
[ Structure ]
The structure of the elastic wave device according to example 2 is the same as that of example 1 except that the electrode finger pitch of the input-side parallel resonator is smaller than that of the output-side parallel resonator, and therefore, detailed description thereof is omitted.
[ test conditions ]
The elastic wave device of embodiment 2 is applied to a filter of a reception antenna Rx of a communication terminal having Band 3.
Test frequency: tx band
Modulation L TE 1.4MHz FullRB
Temperature: 85 deg.C
Time of application of power: 30 seconds
Fig. 7 is a graph showing the technical effect of the elastic wave device according to example 2 of the present invention, and in fig. 7, a curve without ○ shows the initial characteristic, and a curve with ○ shows the characteristic after 480mW application.
As is clear from fig. 7, in the elastic wave device according to example 2, the longitudinally coupled resonator was destroyed 30 seconds after 480mW of power was applied, that is, the blowing power was 150 mW.
As can be seen from comparison between embodiment 1 and embodiment 2, in the present invention, it is considered that the frequency on the input side is increased by reducing the pitch of the parallel resonators connected to the input side of the longitudinally coupled resonator, thereby increasing the power that can be input to the longitudinally coupled resonator.
Therefore, in the present invention, it is more preferable that the electrode finger pitch of the parallel resonator on the input side of the longitudinally coupled resonator type elastic wave filter unit is smaller than the electrode finger pitch of the parallel resonator on the output side.
In the present invention, the number of electrode fingers of the narrow pitch electrode finger portions N of each IDT electrode of the longitudinally coupled resonator type acoustic wave filter unit is not particularly limited, and may be zero.
Further, the present invention provides a multiplexer including a plurality of band pass filters. Preferably, the multiplexer includes any one of the elastic wave devices as at least one of the plurality of band pass filters. Preferably, at least one of the plurality of band pass filters using any one of the elastic wave devices has a higher frequency than the other at least one band pass filter.
The present invention is directed to an elastic wave device having a sufficient passband width, in which the total number of electrode fingers of a narrow-pitch electrode finger portion N in which two IDT electrodes on the left side among 3 adjacent IDT electrodes among a plurality of IDT electrodes arranged adjacently along the elastic wave propagation direction in a longitudinally-coupled resonator type elastic wave filter unit are adjacent is different from the total number of electrode fingers of a narrow-pitch electrode finger portion N in which two IDT electrodes on the right side are adjacent, thereby reducing the transmission loss of an elastic wave, greatly improving the insertion loss in the passband, and obtaining an elastic wave device having a sufficient passband width.
Further, by connecting the parallel resonators to both the input side and the output side of the longitudinally coupled resonator type elastic wave filter unit (longitudinally coupled resonator), the attenuation outside the low-frequency side band can be improved, and further, by making the pitch of the parallel resonators on the input side different from the pitch of the parallel resonators on the output side, it is preferable to make the pitch of the parallel resonators on the input side smaller than the pitch of the parallel resonators on the output side, that is, to make the resonance frequency of the parallel resonators on the input side larger than the resonance frequency of the parallel resonators on the output side, so that the resonance frequency of the parallel resonators on the input side can be made close to the peak frequency of the 2-order mode ripple. Accordingly, a signal when a filter voltage having a low pass band is applied flows into the ground through the parallel resonator. Accordingly, the load on the longitudinally coupled resonator is reduced, and the occurrence of a failure can be suppressed. Further, since the resonance frequency of the parallel resonator on the output side is low, the resonance point of the parallel resonator does not enter the passband, and the steepness of the passband does not deteriorate.
Although the present invention has been described with reference to preferred embodiments thereof, those skilled in the art will appreciate that various modifications, substitutions and changes can be made thereto without departing from the spirit and scope of the present invention. Accordingly, the present invention should not be limited by the above-described embodiments, but should be defined by the appended claims and their equivalents.
Claims (16)
1. An elastic wave device comprising a piezoelectric substrate and a longitudinally coupled resonator-type elastic wave filter unit formed on the piezoelectric substrate,
the longitudinally coupled resonator type elastic wave filter unit includes: at least a first IDT electrode, a second IDT electrode and a third IDT electrode which are adjacently arranged with a gap in the propagation direction of the elastic wave,
the first IDT electrode, the second IDT electrode and the third IDT electrode respectively have a main pitch electrode finger part and a narrow pitch electrode finger part with an electrode finger pitch smaller than that of the main pitch electrode finger part, the narrow pitch electrode finger part is a part from the end part of the side of the other IDT electrode adjacently arranged in the elastic wave propagation direction,
the total number of electrode fingers of the pair of narrow-pitch electrode finger portions facing the gap between the first IDT electrode and the second IDT electrode is different from the total number of electrode fingers of the pair of narrow-pitch electrode finger portions facing the gap between the second IDT electrode and the third IDT electrode.
2. The elastic wave device according to claim 1,
parallel resonators are connected to one side and the other side of the longitudinally coupled resonator type elastic wave filter unit,
the electrode finger pitch of the parallel resonator on one side is different from the electrode finger pitch of the parallel resonator on the other side.
3. The elastic wave device according to claim 2,
the one side of the longitudinally coupled resonator-type elastic wave filter section is an input side, and the other side is an output side.
4. The elastic wave device according to claim 3,
the electrode finger pitch of the parallel resonator on the input side is smaller than the electrode finger pitch of the parallel resonator on the output side.
5. The elastic wave device according to claim 3 or 4,
the electrode finger pitch of the input-side parallel resonator is formed such that the resonance frequency of the input-side parallel resonator coincides with the peak frequency of the secondary mode ripple.
6. The elastic wave device according to claim 3 or 4,
the input-side parallel resonator and the output-side parallel resonator each have a fixed electrode finger pitch.
7. The elastic wave device according to any one of claims 1 to 4,
the number of electrode fingers of a pair of the narrow-pitch electrode fingers facing one of the gaps is different from each other.
8. An elastic wave device comprising a piezoelectric substrate and a longitudinally coupled resonator-type elastic wave filter unit formed on the piezoelectric substrate,
the longitudinally coupled resonator type elastic wave filter unit includes: at least a first IDT electrode, a second IDT electrode and a third IDT electrode which are adjacently arranged in the propagation direction of the elastic wave,
the first IDT electrode, the second IDT electrode and the third IDT electrode respectively have a main pitch electrode finger part and a narrow pitch electrode finger part with an electrode finger pitch smaller than that of the main pitch electrode finger part, the narrow pitch electrode finger part is a part from the end part of the side of the other IDT electrode adjacently arranged in the elastic wave propagation direction,
the total number of electrode fingers of the narrow-pitch electrode finger portion that is a portion of the first IDT electrode from the side end of the second IDT electrode and the narrow-pitch electrode finger portion that is a portion of the second IDT electrode from the side end of the first IDT electrode is different from the total number of electrode fingers of the narrow-pitch electrode finger portion that is a portion of the second IDT electrode from the side end of the third IDT electrode and the narrow-pitch electrode finger portion that is a portion of the third IDT electrode from the side end of the second IDT electrode.
9. The elastic wave device according to claim 8,
parallel resonators are connected to one side and the other side of the longitudinally coupled resonator type elastic wave filter unit,
the electrode finger pitch of the parallel resonator on one side is different from the electrode finger pitch of the parallel resonator on the other side.
10. The elastic wave device according to claim 9,
the one side of the longitudinally coupled resonator-type elastic wave filter section is an input side, and the other side is an output side.
11. The elastic wave device according to claim 10,
the electrode finger pitch of the parallel resonator on the input side is smaller than the electrode finger pitch of the parallel resonator on the output side.
12. The elastic wave device according to claim 10 or 11,
the electrode finger pitch of the input-side parallel resonator is formed such that the resonance frequency of the input-side parallel resonator coincides with the peak frequency of the secondary mode ripple.
13. The elastic wave device according to claim 10 or 11,
the input-side parallel resonator and the output-side parallel resonator each have a fixed electrode finger pitch.
14. The elastic wave device according to any one of claims 8 to 11,
the number of electrode fingers of a pair of the narrow-pitch electrode finger portions adjacent to each other in the elastic wave propagation direction is different from each other.
15. A multiplexer having a plurality of band-pass filters, characterized in that,
the multiplexer is provided with the elastic wave device according to any one of claims 1 to 14 as at least one band-pass filter of the plurality of band-pass filters.
16. The multiplexer of claim 15,
the passband of at least one of the plurality of bandpass filters is a high frequency side compared to the passband of at least one other of the plurality of bandpass filters.
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