WO2010032377A1 - Elastic wave filter device - Google Patents

Abstract

A 5-IDT type longitudinally-coupled resonator type elastic wave filter device with narrowly-pitched electrode finger sections improves steepness of the filter characteristics. It is a 5-IDT type longitudinally-coupled resonator type elastic wave filter device (1) having first through a fifth IDTs (11a-11e) wherein, when the total numbers of the electrode fingers provided at the narrowly-pitched electrode finger sections in a first region (R1) and a fourth region (R4) are denoted respectively as Nx, and the total numbers of the electrode fingers provided at the narrowly-pitched electrode finger sections in a second region (R2) and a third region (R3) are denoted respectively as Ny, the average value of the cycles of the electrode fingers is set greater for the narrowly-pitched electrode finger sections in the regions with the greater total numbers between the total numbers Nx of the electrode fingers and the total numbers Ny of the electrode fingers than the narrowly-pitched electrode finger sections in the regions with the smaller total numbers, and cycles of the electrode fingers are set narrower for the IDT electrodes that are included in the regions with the greater total numbers out of the first, the third, and the fifth IDT electrodes (11a, 11c, 11e) than the IDT electrodes that are included in the regions with the smaller total numbers of electrode fingers, except at the parts where the narrowly-pitched electrode finger sections are provided.

Description

Elastic wave filter device

The present invention relates to an elastic wave filter device used, for example, in an RF stage band filter of a mobile phone, and more particularly to a longitudinally coupled resonator type elastic wave filter device having first to fifth IDT electrodes.

In band filters, it is strongly required to increase the steepness of the filter characteristics in the region between the pass band and the stop band. The following Patent Document 1 discloses a surface acoustic wave filter device that can enhance the steepness of filter characteristics. In the surface acoustic wave filter device described in Patent Document 1, an acoustic wave resonator is connected in series or in parallel to a 3IDT type longitudinally coupled resonator type surface acoustic wave filter section. By controlling the position of the resonance frequency and anti-resonance frequency of the elastic wave resonators connected in series or in parallel, the steepness of the filter characteristics on the low passband and high passband sides is enhanced.

However, in such a method using the frequency characteristics of the elastic wave resonator, the effect of improving the steepness depends on the Q value of the elastic wave resonator. Here, the Q value of the acoustic wave resonator is substantially determined by the piezoelectric substrate material and the electrode material. Therefore, there is a limit to further increase the steepness of the filter characteristics by increasing the Q value of the acoustic wave resonator.

On the other hand, Patent Document 2 below discloses a 5IDT type longitudinally coupled resonator type surface acoustic wave filter device having a balance-unbalance conversion function. FIG. 26 is a schematic plan view showing the surface acoustic wave filter device described in Patent Document 2. As shown in FIG. The surface acoustic wave filter device 1001 includes a piezoelectric substrate 1002. The illustrated electrode structure is formed on the piezoelectric substrate 1002. This electrode structure is connected between the unbalanced terminal 1003 and the first and second balanced terminals 1004 and 1005. A 5IDT type longitudinally coupled resonator type acoustic wave filter unit 1010 is connected to the unbalanced terminal 1003. The longitudinally coupled resonator type acoustic wave filter unit 1010 includes first to fifth IDT electrodes 1011 to 1015 and reflectors 1016 and 1017. Here, the first to fifth IDT electrodes 1011 to 1015 are provided at the end portions on the side adjacent to the other IDT electrodes, respectively, of narrow pitch electrode finger portions N1011, N1012a, N1012b, N1013a, N1013b, N1014a, N1014b and N1015.

The surface acoustic wave resonators 1021 and 1022 are connected to the subsequent stage of the longitudinally coupled resonator type acoustic wave filter unit 1010, respectively.

Here, the narrow pitch electrode finger portions N1011 and N1015 of the first IDT electrode 1011 connected to the first balanced terminal 1004 and the fifth IDT electrode 1015 connected to the second balanced terminal 1005; In the narrow pitch electrode finger portions N1013a and N1013b of the third IDT electrode 1013, the electrode finger pitch of the narrow pitch electrode finger portion on the side where the number of electrode fingers in the narrow pitch electrode finger portion is large is the electrode finger in the narrow pitch electrode finger portion. The electrode pitch is made larger than the electrode pitch of the narrow pitch electrode fingers of the smaller number. Thereby, the ripple in the pass band can be reduced. However, with such a configuration, the steepness of the filter characteristics cannot be sufficiently increased.

Also, the following Patent Document 3 discloses a 5IDT type longitudinally coupled resonator type surface acoustic wave filter device that does not have a narrow pitch electrode finger. Here, the number of electrode fingers and the electrode finger pitch in the IDT electrode located in the center are set smaller than the number of electrode fingers and the electrode finger pitch in the IDT electrodes on both sides of the IDT electrode located in the center. Accordingly, it is said that the attenuation amount of the stop band on the low pass band side can be increased, and the steepness of the filter characteristics can be enhanced.

Japanese Patent Laid-Open No. 4-54011 WO2006 / 068086A1 WO2007 / 083503A1

As described above, the surface acoustic wave filter device described in Patent Document 1 has a limit in increasing the steepness of the filter characteristics. Therefore, it has not been possible to realize the high steepness of filter characteristics that has been required in recent years.

On the other hand, in the longitudinally coupled resonator type surface acoustic wave filter device described in Patent Document 2, it appears in the passband by controlling the electrode finger pitch and the number of electrode fingers in the narrow pitch electrode finger portion as described above. The ripple was only suppressed. In Patent Document 2, there is no particular mention of a configuration that increases the steepness of the filter characteristics.

In the surface acoustic wave filter device described in Patent Document 3, in the longitudinally coupled resonator type surface acoustic wave filter device that does not have a narrow pitch electrode finger portion, the number of electrode fingers and the electrode finger pitch in the center IDT electrode It is shown that the steepness of the filter characteristics can be improved by adjusting the number of electrode fingers and the electrode finger pitch in the IDT electrodes on both sides. However, the steepness of the filter characteristics is not sufficiently high, and further improvement has been demanded.

An object of the present invention is to further enhance the steepness of filter characteristics in a 5IDT type longitudinally coupled resonator type acoustic wave filter device having a narrow pitch electrode finger portion in view of the current state of the prior art described above.

The acoustic wave filter device according to the present invention includes a piezoelectric substrate, first to fifth IDT electrodes sequentially disposed along the acoustic wave propagation direction on the piezoelectric substrate, and the first to fifth IDT electrodes. Are provided on both sides of the region in which the elastic wave is propagated, and the first to fifth IDT electrodes and the first and second reflectors vertically A coupled resonator type acoustic wave filter unit is configured, and the first to fifth IDT electrodes are arranged at the ends adjacent to the other IDT electrodes, and the period of the electrode finger in the remaining part of the electrode finger is left. A narrow-pitch electrode finger that is smaller than the period. Here, a region including the first IDT electrode and a central portion of the second IDT electrode in the elastic wave propagation direction to the first IDT electrode side portion is defined as a first region, and the second IDT electrode. The region formed by the third IDT electrode side portion from the central portion in the elastic wave propagation direction and the second IDT electrode side portion from the central portion in the elastic wave propagation direction of the third IDT electrode 2 region, a portion on the fourth IDT electrode side from the central portion of the third IDT electrode in the elastic wave propagation direction, and a third IDT from the central portion of the fourth IDT electrode in the elastic wave propagation direction. A region formed by the electrode side portion is a third region, and a region formed by the fifth IDT electrode side portion from the central portion in the elastic wave propagation direction of the fourth IDT electrode and the fifth IDT electrode With the fourth region That. In the present invention, the total number of electrode fingers of the narrow pitch electrode finger portion in the first region and the total number of electrode fingers in the narrow pitch electrode finger portion of the fourth region are Nx and the narrow pitch electrode in the second region, respectively. When the total number of electrode fingers in the finger portion and the total number of electrode fingers in the narrow pitch electrode finger portion in the third region is Ny, the total number Nx of electrode fingers and the total number Ny of electrode fingers are different. The narrow pitch electrode finger portion in the region where the total number of electrode fingers is larger among the total number Nx of electrode electrodes and the total number Ny of electrode fingers is more electrode electrode than the narrow pitch electrode finger portion in the region where the total number of electrode fingers is small. Of the first IDT electrode, the third IDT electrode, and the fifth IDT electrode, the IDT electrode included in the region having the larger total number of electrode fingers But the electrode Than IDT electrodes total is included in the area of the lesser, the period of the electrode fingers is smaller in the portion other than the narrow pitch electrode finger portion.

In the first specific aspect of the acoustic wave filter device according to the present invention, the number of electrode fingers in the narrow pitch electrode finger portion in the first region is smaller than that in the narrow pitch electrode finger portion in the second region. The number of electrode fingers in the narrow pitch electrode finger portion in the third region is larger than that in the narrow pitch electrode finger portion in the fourth region.

In an embodiment according to the first specific aspect, the number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the second IDT electrode is the second IDT electrode. Less than the number of electrode fingers in the narrow pitch electrode finger portion in the region, and the number of electrode fingers in the narrow pitch electrode finger portion on the third region side of the fourth IDT electrode is the fourth IDT. The number of electrode fingers in the narrow pitch electrode finger portion in the fourth region of the electrode is larger than the number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the second IDT electrode, The electrode in the narrow pitch electrode finger portion on the third region side of the fourth IDT electrode, which is smaller than the period of the electrode finger in the narrow pitch electrode finger portion in the second region of the second IDT electrode. Finger cycle is The period of the electrode finger in the portion other than the narrow pitch electrode finger portion of the third IDT electrode is larger than the cycle of the electrode finger in the narrow pitch electrode finger portion in the fourth region of the fourth IDT electrode. The period of the electrode fingers in the portions other than the narrow pitch electrode finger portions of the first and fifth IDT electrodes is made smaller.

In another embodiment of the first specific aspect described above, the number of electrode fingers in the narrow-pitch electrode finger portion on the first region side of the second IDT electrode is the second IDT electrode second. Less than the number of electrode fingers in the narrow pitch electrode finger portion in the region, and the number of electrode fingers in the narrow pitch electrode finger portion on the third region side of the fourth IDT electrode is the fourth IDT. The number of electrode fingers in the narrow pitch electrode finger portion in the fourth region of the electrode is larger than the number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the first IDT electrode, The electrode in the narrow pitch electrode finger portion on the third region side of the third IDT electrode, which is smaller than the period of the electrode finger in the narrow pitch electrode finger portion in the second region of the third IDT electrode. The finger cycle is Note that the period of the electrode finger in the portion other than the narrow pitch electrode finger part of the third IDT electrode is larger than the period of the electrode finger in the narrow pitch electrode finger part in the fourth region of the fifth IDT electrode. The period of the electrode fingers in the portions other than the narrow pitch electrode finger portions of the first and fifth IDT electrodes is made smaller.

In another embodiment of the first specific aspect described above, the number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the first IDT electrode is the second of the third IDT electrode. The number of electrode fingers in the narrow pitch electrode finger portion of the third area of the third IDT electrode is less than the number of electrode fingers in the narrow pitch electrode finger section of the third IDT electrode. The number of electrode fingers in the narrow pitch electrode finger portion in the fourth region of the electrode is larger than the number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the second IDT electrode, The electrode in the narrow pitch electrode finger portion on the third region side of the fourth IDT electrode, which is smaller than the period of the electrode finger in the narrow pitch electrode finger portion in the second region of the second IDT electrode. The finger cycle is Note that the period of the electrode finger in the portion other than the narrow pitch electrode finger part of the third IDT electrode is larger than the period of the electrode finger in the narrow pitch electrode finger part in the fourth region of the fourth IDT electrode. The period of the electrode fingers in the portions other than the narrow pitch electrode finger portions of the first and fifth IDT electrodes is made smaller.

In still another embodiment of the first specific aspect described above, the number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the first IDT electrode is the number of the electrode fingers of the third IDT electrode. The number of electrode fingers in the narrow pitch electrode finger portion in the second region is smaller than the number of electrode fingers in the narrow pitch electrode finger portion in the second region, and the number of electrode fingers in the narrow pitch electrode finger portion on the third region side of the third IDT electrode is The number of electrode fingers in the narrow pitch electrode finger portion in the fourth region of the IDT electrode is larger than the number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the first IDT electrode. The period of the electrode finger in the narrow pitch electrode finger portion in the second region of the third IDT electrode is smaller than the period of the electrode finger in the third region side of the third IDT electrode. Around electrode fingers Is larger than the period of the electrode finger in the narrow pitch electrode finger portion in the fourth region of the fifth IDT electrode, and the electrode finger in the portion other than the narrow pitch electrode finger portion of the third IDT electrode The period is made smaller than the period of the electrode fingers in the portions other than the narrow pitch electrode finger parts of the first and fifth IDT electrodes.

In still another embodiment of the first aspect of the present invention, the number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the first IDT electrode is the number of the electrode fingers of the third IDT electrode. The number of electrode fingers in the narrow pitch electrode finger portion in the second region is smaller than the number of electrode fingers in the narrow pitch electrode finger portion in the second region, and the number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the second IDT electrode is The number of electrode fingers in the narrow pitch electrode finger portion in the second region of the IDT electrode is smaller than the number of electrode fingers in the narrow pitch electrode finger portion on the third region side of the fourth IDT electrode. The number of electrode fingers in the narrow pitch electrode finger portion in the fourth region of the fourth IDT electrode is larger than that in the narrow pitch electrode finger portion on the third region side of the third IDT electrode. Number of electrode fingers The number of electrode fingers in the narrow pitch electrode finger portion in the fourth region of the fifth IDT electrode is larger than that in the narrow pitch electrode finger portion on the first region side of the first IDT electrode. The cycle of the electrode fingers is smaller than the cycle of the electrode fingers in the narrow pitch electrode finger portion in the second region of the third IDT electrode, and the narrower side of the second IDT electrode on the first region side. The period of the electrode fingers in the pitch electrode finger part is smaller than the period of the electrode fingers in the narrow pitch electrode finger part in the second region of the second IDT electrode, and the third of the fourth IDT electrode. The electrode finger period in the narrow pitch electrode finger part on the region side of the fourth IDT electrode is larger than the period of the electrode finger in the narrow pitch electrode finger part in the fourth area of the fourth IDT electrode, and the third IDT The period of the electrode fingers in the narrow pitch electrode finger portion on the third region side of the pole is larger than the cycle of the electrode fingers in the narrow pitch electrode finger portion in the fourth region of the fifth IDT electrode, The period of the electrode finger in the portion other than the narrow pitch electrode finger portion of the third IDT electrode is made smaller than the cycle of the electrode finger in the portion other than the narrow pitch electrode finger portion of the first and fifth IDT electrodes. Yes.

In the second specific aspect of the present invention, the narrow pitch electrode finger portion in the first region has a larger total number of electrode fingers than the narrow pitch electrode finger portion in the second region, The narrow pitch electrode finger portion in the region has a smaller total number of electrode fingers than the narrow pitch electrode finger portion in the fourth region.

In an embodiment of the second specific aspect of the present invention, the number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the second IDT electrode is the number of the electrode fingers of the second IDT electrode. The number of electrode fingers in the narrow pitch electrode finger portion in the second region is larger than the number of electrode fingers in the narrow pitch electrode finger portion in the second region, and the number of electrode fingers in the narrow pitch electrode finger portion on the third region side of the fourth IDT electrode is The number of electrode fingers in the narrow pitch electrode finger portion in the fourth region of the IDT electrode is smaller than the number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the second IDT electrode. The period of the electrode finger in the narrow pitch electrode finger portion in the second region of the second IDT electrode is larger than the period of the electrode finger in the third region side of the fourth IDT electrode. Electrode finger cycle The period of the electrode finger in a portion other than the narrow pitch electrode finger part of the third IDT electrode, which is smaller than the period of the electrode finger in the narrow pitch electrode finger part in the fourth region of the fourth IDT electrode. Is larger than the period of the electrode fingers in the portions other than the narrow pitch electrode finger portions of the first and fifth IDT electrodes.

In another embodiment of the second specific aspect, the number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the second IDT electrode is the second IDT electrode of the second IDT electrode. More than the number of electrode fingers in the narrow pitch electrode finger portion in the region, the number of electrode fingers in the narrow pitch electrode finger portion on the third region side of the fourth IDT electrode is the fourth IDT electrode Less than the number of electrode fingers in the narrow pitch electrode fingers in the fourth region, and the period of the electrode fingers in the narrow pitch electrode fingers on the first region side of the first IDT electrode is The electrode finger in the narrow pitch electrode finger portion on the third region side of the third IDT electrode is larger than the period of the electrode finger in the narrow pitch electrode finger portion in the second region of the third IDT electrode. The period of 5 of the IDT electrode is smaller than the period of the electrode finger in the narrow pitch electrode finger part in the fourth region, and the period of the electrode finger in the portion other than the narrow pitch electrode finger part of the third IDT electrode is It is made larger than the period of the electrode finger in parts other than the narrow pitch electrode finger part of the 1st and 5th IDT electrodes.

In another embodiment of the second specific aspect of the present invention, the number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the first IDT electrode is the number of the electrode fingers of the third IDT electrode. The number of electrode fingers in the narrow pitch electrode finger portion in the second region is larger than the number of electrode fingers in the narrow pitch electrode finger portion in the second region, and the number of electrode fingers in the narrow pitch electrode finger portion on the third region side of the third IDT electrode is The number of electrode fingers in the narrow pitch electrode finger portion in the fourth region of the IDT electrode is smaller than the number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the second IDT electrode. Is larger than the period of the electrode finger in the narrow pitch electrode finger portion in the second region of the second IDT electrode, and the narrow pitch electrode finger portion on the third region side of the fourth IDT electrode Electrode finger period The period of the electrode finger in a portion other than the narrow pitch electrode finger part of the third IDT electrode, which is smaller than the period of the electrode finger in the narrow pitch electrode finger part in the fourth region of the fourth IDT electrode. Is larger than the period of the electrode fingers in the portions other than the narrow pitch electrode finger portions of the first and fifth IDT electrodes.

In still another specific embodiment of the second specific aspect of the present invention, the number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the first IDT electrode is the third IDT. The number of electrode fingers in the narrow pitch electrode fingers in the second region of the electrode is larger than the number of electrode fingers in the narrow pitch electrode fingers in the third region side of the third IDT electrode. The number of electrode fingers in the narrow pitch electrode finger portion in the fourth region of the fifth IDT electrode is less than the number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the first IDT electrode. The period of the finger is larger than the period of the electrode finger in the narrow pitch electrode finger portion in the second area of the third IDT electrode, and the narrow pitch on the third area side of the third IDT electrode. In the electrode finger The period of the polar finger is smaller than the period of the electrode finger in the narrow pitch electrode finger part in the fourth region of the fifth IDT electrode, and the part other than the narrow pitch electrode finger part of the third IDT electrode The period of the electrode fingers is larger than the period of the electrode fingers in the portions other than the narrow pitch electrode fingers of the first and fifth IDT electrodes.

According to still another embodiment of the second specific aspect of the present invention, the number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the first IDT electrode is the third IDT. More than the number of electrode fingers in the narrow pitch electrode finger portion in the second region of the electrode, the number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the second IDT electrode is: The number of electrode fingers in the narrow pitch electrode finger portion in the second region of the second IDT electrode is larger than the number of electrode fingers in the narrow pitch electrode finger portion on the third region side of the fourth IDT electrode. The number of fingers is less than the number of electrode fingers in the narrow pitch electrode finger portion in the fourth region of the fourth IDT electrode, and the narrow pitch on the third region side of the third IDT electrode. Electrodes in electrode fingers Is smaller than the number of electrode fingers in the narrow pitch electrode finger portion in the fourth region of the fifth IDT electrode, and the narrow pitch electrode on the first region side of the first IDT electrode. The period of the electrode finger in the finger part is larger than the period of the electrode finger in the narrow pitch electrode finger part in the second region of the third IDT electrode, and the first region of the second IDT electrode. The electrode finger period in the narrow pitch electrode finger part on the side is larger than the electrode finger period in the narrow pitch electrode finger part in the second region of the second IDT electrode, and the fourth IDT electrode The period of the electrode fingers in the narrow pitch electrode finger portion on the third region side is smaller than the cycle of the electrode fingers in the narrow pitch electrode finger portion in the fourth region of the fourth IDT electrode, The period of the electrode finger in the narrow pitch electrode finger portion on the third region side of the IDT electrode is made smaller than the cycle of the electrode finger in the narrow pitch electrode finger portion in the fourth region of the fifth IDT electrode. And the period of the electrode finger in the portion other than the narrow pitch electrode finger portion of the third IDT electrode is larger than the cycle of the electrode finger in the portion other than the narrow pitch electrode finger portion of the first and fifth IDT electrodes. Has been.

According to the present invention, in the 5IDT type acoustic wave device having the first to fifth IDT electrodes, the total number Nx of the electrode fingers and the total number Ny of the electrode fingers are different. It is possible to effectively increase the steepness.

Further, the narrow pitch electrode finger portion in the region where the total number of electrode fingers is larger among the total number Nx of electrode fingers and the total number Ny of electrode fingers is a narrow pitch electrode finger portion in the region where the total number of electrode fingers is small Since the average value of the period of the electrode finger is made larger than that, it is possible to reduce the spike ripple in the pass band.

Furthermore, among the first, third, and fifth IDT electrodes, the IDT electrode included in the region with the larger total number of electrode fingers is narrower than the IDT electrode included in the region with the smaller total number of electrode fingers. Since the period of the electrode finger in the portion other than the pitch electrode finger portion is reduced, the steepness of the filter characteristic on the low pass band side can be more effectively increased.

FIG. 1 is a schematic plan view showing an acoustic wave filter device according to a first embodiment of the present invention. FIG. 2 is a diagram showing a schematic configuration of a 5IDT type longitudinally coupled resonator type acoustic wave filter unit for specifying the position of a narrow pitch electrode finger unit in the present invention. FIG. 3 is a schematic plan view for explaining the structure of the narrow pitch electrode finger portion of the first longitudinally coupled resonator type acoustic wave filter portion in the first embodiment of the present invention. FIG. 4 is a diagram showing the filter characteristics of the elastic wave filter devices of the first embodiment and the comparative example of the present invention. FIG. 5 is a diagram for explaining resonance points of the 0th-order mode, the second-order mode, and the IDT electrode-IDT electrode mode of the 5IDT type longitudinally coupled resonator type acoustic wave filter section. FIG. 6 shows ripples Y and ripples Z in the case where the number of electrode fingers in the narrow pitch electrode finger portion B and the number of electrode fingers in the narrow pitch electrode finger portion C are different from each other in the first embodiment of the present invention. It is a figure which shows the change of. FIG. 7 shows the change of the resonance mode when the period of the electrode finger in the narrow pitch electrode finger part B and the period of the electrode finger in the narrow pitch electrode finger part C are changed in the first embodiment of the present invention. FIG. FIG. 8 shows the change of the resonance mode when the period of the electrode finger in the narrow pitch electrode finger part A and the period of the electrode finger in the narrow pitch electrode finger part D are changed in the first embodiment of the present invention. In particular, FIG. FIG. 9 shows the period of electrode fingers in electrode finger portions other than the narrow pitch electrode finger portions of the first and fifth IDT electrodes and the narrow pitch electrode finger of the third IDT electrode in the first embodiment of the present invention. It is a figure which shows the change of the ripple Y and the ripple Z at the time of changing the period of the electrode finger in electrode finger parts other than a part. FIG. 10 is a schematic plan view for explaining the structure of a narrow pitch electrode finger portion of a 5IDT type longitudinally coupled resonator type acoustic wave filter portion in a modification of the first embodiment of the present invention. FIG. 11 shows a ripple Y in the case where the number of electrode fingers in the narrow pitch electrode finger portion B is different from the number of electrode fingers in the narrow pitch electrode finger portion C in the modification of the first embodiment of the present invention. It is a figure which shows the change of the ripple Z. FIG. 12 shows a resonance mode when the period of the electrode finger in the narrow pitch electrode finger part B and the period of the electrode finger in the narrow pitch electrode finger part C are changed in the modification of the first embodiment of the present invention. It is a figure which shows the change of. FIG. 13 shows a resonance mode when the period of the electrode finger in the narrow pitch electrode finger part A and the period of the electrode finger in the narrow pitch electrode finger part D are changed in the modification of the first embodiment of the present invention. It is a figure which shows the change of this and shows the change of the ripple Z especially. FIG. 14 shows a modification of the first embodiment of the present invention, in which the electrode finger period in the electrode finger portions other than the narrow pitch electrode finger portions of the first and fifth IDT electrodes and the narrowness of the third IDT electrode. It is a figure which shows the change of the ripple Y at the time of changing the period of the electrode finger in electrode finger parts other than a pitch electrode finger part, and the ripple Z. FIG. FIG. 15 is a schematic plan view for explaining the structure of the narrow pitch electrode finger portion of the first longitudinally coupled resonator type acoustic wave filter portion according to the second embodiment of the present invention. FIG. 16 is a diagram illustrating filter characteristics of the elastic wave filter devices of the second embodiment and the comparative example of the present invention. FIG. 17 shows ripples Y and ripples Z when the number of electrode fingers in the narrow pitch electrode finger portion A and the number of electrode fingers in the narrow pitch electrode finger portion D are different in the second embodiment of the present invention. It is a figure which shows the change of. FIG. 18 shows the change of the resonance mode when the period of the electrode finger in the narrow pitch electrode finger part B and the period of the electrode finger in the narrow pitch electrode finger part C are changed in the second embodiment of the present invention. FIG. FIG. 19 shows the change of the resonance mode when the period of the electrode finger in the narrow pitch electrode finger part A and the period of the electrode finger in the narrow pitch electrode finger part D are changed in the second embodiment of the present invention. In particular, FIG. FIG. 20 shows a period of electrode fingers in a portion other than the narrow pitch electrode finger portion of the first and fifth IDT electrodes and a portion other than the narrow pitch electrode finger portion of the third IDT electrode in the second embodiment of the present invention. It is a figure which shows the change of the ripple Y at the time of changing the period of the electrode finger in this part, and the ripple Z. FIG. FIG. 21 is a schematic plan view for explaining the structure of a narrow pitch electrode finger portion of a 5IDT type longitudinally coupled resonator type acoustic wave filter portion in a modification of the second embodiment of the present invention. FIG. 22 shows a ripple Y in the case where the number of electrode fingers in the narrow pitch electrode finger portion A is different from the number of electrode fingers in the narrow pitch electrode finger portion D in the modification of the second embodiment of the present invention. It is a figure which shows the change of the ripple Z. FIG. 23 shows a resonance mode when the period of the electrode finger in the narrow-pitch electrode finger part B and the period of the electrode finger in the narrow-pitch electrode finger part C are changed in the modification of the second embodiment of the present invention. It is a figure which shows the change of. FIG. 24 shows a resonance mode when the period of the electrode finger in the narrow pitch electrode finger part A and the period of the electrode finger in the narrow pitch electrode finger part D are changed in the modification of the second embodiment of the present invention. It is a figure which shows the change of this and shows the change of the ripple Z especially. FIG. 25 shows an electrode finger period in a portion other than the narrow pitch electrode finger portion of the first and fifth IDT electrodes and a narrow pitch electrode of the third IDT electrode in a modification of the second embodiment of the present invention. It is a figure which shows the change of the ripple Y at the time of changing the period of the electrode finger in parts other than a finger part, and the ripple Z. FIG. FIG. 26 is a schematic plan view for explaining an example of a conventional acoustic wave filter device. FIG. 27 is a schematic plan view for explaining the structure of the narrow pitch electrode finger part of the first longitudinally coupled resonator type acoustic wave filter part in the third embodiment of the present invention. FIG. 28 is a diagram illustrating filter characteristics of the elastic wave filter devices of the third embodiment and the comparative example of the present invention. FIG. 29 is a schematic plan view for explaining the structure of the narrow pitch electrode finger portion of the first longitudinally coupled resonator type acoustic wave filter portion in the modification of the third embodiment of the present invention.

Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

[Elastic wave filter device according to first embodiment of the present invention]
FIG. 1 is a schematic plan view showing an acoustic wave filter device according to a first embodiment of the present invention. The elastic wave filter device 1 of the present embodiment has a piezoelectric substrate 2. The illustrated electrode structure is formed on the piezoelectric substrate 2, thereby forming a surface acoustic wave filter device having a balance-unbalance conversion function.

The elastic wave filter device 1 of the present embodiment is used as a reception-side filter of a UMTS-Band 2 of a cellular phone. The transmission frequency band of UMTS-Band2 is 1.850 to 1.910 GHz, and the reception side frequency band is 1.930 to 1.990 GHz.

The acoustic wave filter device 1 includes an unbalanced terminal 3 and first and second balanced terminals 4 and 5. The impedance on the unbalanced terminal 3 side is 50Ω, and the impedance on the first and second balanced terminals 4 and 5 side is 100Ω. That is, the elastic wave filter device 1 has not only a balanced-unbalanced conversion function but also an impedance conversion function.

The piezoelectric substrate 2 is made of an appropriate piezoelectric single crystal or piezoelectric ceramic, but in the present embodiment, is made of a 40 ° ± 5 ° Y-cut X-propagation LiTaO ₃ substrate.

The electrode structure formed on the piezoelectric substrate 2 is made of Al in the present embodiment, but can be formed of various metals or alloys such as Au, Cu, Pt, W, and Ta. These electrode structures may be formed of a single metal film, or may be formed of a laminated metal film formed by laminating a plurality of metal films.

A first longitudinally coupled resonator type elastic wave filter unit 11 is connected between the unbalanced terminal 3 and the first balanced terminal 4. Further, a 5IDT type second longitudinally coupled resonator type acoustic wave filter unit 12 is connected between the unbalanced terminal 3 and the second balanced terminal 5.

An elastic wave resonator 13 is connected in series with the first longitudinally coupled resonator type elastic wave filter unit 11 between the first longitudinally coupled resonator type elastic wave filter unit 11 and the unbalanced terminal 3. . The acoustic wave resonator 13 is provided to form a series trap.

In order to form a parallel trap between the connection point between the first balanced terminal 4 on the output side of the first longitudinally coupled resonator type acoustic wave filter unit 11 and the ground potential, the acoustic wave resonator 14 is formed. Is connected.

Between the second longitudinally coupled resonator type acoustic wave filter unit 12 and the unbalanced terminal 3, an acoustic wave resonator 15 is connected in series to the second longitudinally coupled resonator type acoustic wave filter unit 12. . The acoustic wave resonator 15 is provided to form a series trap.

In order to form a parallel trap between the connection point between the second balanced terminal 5 on the output side of the second longitudinally coupled resonator type acoustic wave filter unit 12 and the ground potential, the acoustic wave resonator 16 is formed. Is connected.

The first longitudinally coupled resonator type acoustic wave filter unit 11 includes first to fifth IDT electrodes 11a to 11e arranged in order along the acoustic wave propagation direction. First and second reflectors 11f and 11g are formed on both sides of the region where the IDT electrodes 11a to 11e are provided in the elastic wave propagation direction.

Similarly to the first longitudinally coupled resonator type acoustic wave filter unit 11, the second longitudinally coupled resonator type acoustic wave filter unit 12 also includes the first to fifth IDT electrodes 12a to 12e, the first and second IDT electrodes. Reflectors 12f and 12g. However, the first to fifth IDT electrodes 11a to 11e and the first to fifth so that the phase of the signal extracted from the first balanced terminal 4 and the signal extracted from the second balanced terminal 5 are 180 degrees different from each other. IDT electrodes 12a to 12e. Specifically, the phases of the second and fourth 12b and 12e are inverted with respect to the phases of the second and fourth IDT electrodes 11b and 11d, whereby the first and second balanced terminals 4 are reversed. , 5 are different in phase by 180 degrees.

In the first longitudinally coupled resonator type elastic wave filter unit 11, one ends of the first, third, and fifth IDT electrodes 11 a, 11 c, and 11 e are connected in common, and the unbalanced terminal is connected via the elastic wave resonator 13. 3 is connected. The other ends of the first, third and fifth IDT electrodes 11a, 11c and 11e are connected to the ground potential.

One end of each of the second and fourth IDT electrodes 11b and 11d is connected to the ground potential, and the other ends are connected in common and connected to the first balanced terminal 4.

The second longitudinally coupled resonator type acoustic wave filter unit 12 is also configured in the same manner, and one end of each of the first, third and fifth IDT electrodes 12a, 12c and 12e is connected in common to form a series trap. It is connected to the unbalanced terminal 3 through an elastic wave resonator 15 for the purpose. The other ends of the IDT electrodes 12a, 12c and 12e are connected to the ground potential.

One end of each of the second and fourth IDT electrodes 12b and 12d is connected to the ground potential, and the other ends are connected in common and connected to the second balanced terminal 5.

Each of the elastic wave resonators 13 to 16 is a 1-port elastic wave resonator, and includes an IDT electrode and first and second reflectors disposed on both sides of the IDT electrode in the elastic wave propagation direction. .

Elastic wave resonators 13 to 16 are provided to increase the attenuation outside the passband. More specifically, the resonance supply frequency of the elastic wave resonators 13 and 15 is located in the pass band of the elastic wave filter device 1, and the anti-resonance frequency is arranged in the attenuation region near the end on the high band side of the pass band. Has been. As a result, the amount of attenuation in the attenuation region on the high passband side is increased.

On the other hand, the resonance frequencies of the acoustic wave resonators 14 and 16 are arranged in the attenuation region near the low frequency side end of the pass band, and the anti-resonance frequencies are arranged in the pass band. Therefore, the amount of attenuation is expanded in the attenuation region on the lower frequency side than the passband of the elastic wave filter device 1.

The elastic wave filter device 1 of the present embodiment is characterized by the structure of the first to fifth IDT electrodes 11a to 11e and 12a to 12e of the first and second longitudinally coupled resonator type elastic wave filter portions 11 and 12. is there. This will be described with reference to FIGS.

In FIG. 1, the pitches between the electrode fingers of the first to fifth IDT electrodes 11a to 11e and 12a to 12e of the first and second longitudinally coupled resonator type acoustic wave filter units 11 and 12 are all equal. In the acoustic wave filter device of this embodiment, the first longitudinally coupled resonator type acoustic wave filter unit 11 actually has the structure shown in FIG.

As shown in FIG. 3, the first to fifth IDT electrodes 11a to 11e are narrow-pitch electrode finger portions whose electrode finger pitch is relatively narrower than the remaining portions at the end portions where the IDT electrodes are adjacent to each other. Have In order to explain this in more detail, a virtual 5IDT type longitudinally coupled resonator type acoustic wave filter unit 10 not provided with such narrow pitch electrode fingers is shown in FIG. The structure of FIG. 3 will be described based on the 5IDT type longitudinally coupled resonator type acoustic wave filter unit 10.

In FIG. 2, in order to specify the position where the narrow pitch electrode finger portion is provided, the end portions of the first to fifth IDT electrodes 10a to 10e where the narrow pitch electrode finger portion can be provided are indicated by A to D portions, respectively. It is said. Specifically, the end portion on the second IDT electrode side of the first IDT electrode is defined as A part. Similarly, a portion near the end of the fifth IDT electrode 10e on the fourth IDT electrode 10d side is defined as an A portion. The outer end portions of the second and fourth IDT electrodes 10b and 10d, that is, the end portions adjacent to the first and fifth IDT electrodes 10a or 10e are defined as a B portion. The inner end portions of the second and fourth IDT electrodes 10b and 10d, that is, the end portions on the side adjacent to the third IDT electrode 10c are set as C portions. And the part near the edge part of the both sides of the 3rd IDT electrode located in the center is made into D part.

In this embodiment, as shown in FIG. 3, narrow pitch electrode finger portions are provided in the A portion to the D portion. In the following description, the narrow pitch electrode finger portions provided in each of the A portion, the B portion, the C portion, and the D portion are referred to as a narrow pitch electrode finger portion A, a narrow pitch electrode finger portion B, and a narrow pitch electrode finger portion C, respectively. And a narrow pitch electrode finger D.

In the present specification, the narrow pitch electrode finger means an electrode finger having a relatively narrow pitch between the electrode fingers relative to the pitch of the remaining electrode finger in the IDT electrode other than the narrow pitch electrode finger. Shall.

As shown in FIG. 3, the narrow pitch electrode fingers are provided in a portion where the IDT electrodes are adjacent to each other, and the second and fourth IDT electrodes 11b, 11d where the IDT electrodes are located on both sides, In the third IDT electrode 11c, narrow pitch electrode fingers are provided at both ends of the IDT electrode.

The feature of this embodiment is that the first IDF electrode 11b and the fourth IDT electrode 11d on the first or fifth IDT electrode 11a, 11e side in the first longitudinally coupled resonator type acoustic wave filter unit 11 Narrow pitch electrode fingers, that is, the number of electrode fingers in the narrow pitch electrode fingers B is narrow pitch electrode fingers on the third IDT electrode 11c side of the second and fourth IDT electrodes 11b and 11d, that is, narrow pitch. The number of electrode fingers in the electrode finger C is less than the number of electrode fingers in the narrow pitch electrode finger B, and the period of the electrode fingers in the narrow pitch electrode finger C is smaller than the number of electrode fingers in the third. The period of the electrode finger in the part other than the narrow pitch electrode finger part of the IDT electrode 11c is longer than the period of the electrode finger in the part other than the narrow pitch electrode finger part of the first and fifth IDT electrodes 11a and 11e. Some that have been fence. The second longitudinally coupled resonator type acoustic wave filter unit 12 is configured similarly to the first longitudinally coupled resonator type acoustic wave filter unit 11. Thereby, in the acoustic wave filter device 1, the steepness of the filter characteristic on the low pass band side is effectively enhanced. This will be described with reference to FIGS. FIG. 4 is a diagram showing the filter characteristics of the elastic wave filter device of the present embodiment, where the solid line shows the results of the present embodiment, and the broken line shows the filter properties of the elastic wave filter device prepared as a comparative example. . The details of the electrode structure in the embodiment and the comparative example are as follows.

Specifications of the first longitudinally coupled resonator type acoustic wave filter unit 11:
In the following, the wavelength determined by the pitch of the electrode fingers of the IDT electrode is λI.

Electrode finger crossing width = 15.2λI
1st and 5th IDT electrodes 11a, 11e: 40 electrode fingers each, provided that 5 out of 40 are electrode fingers of narrow pitch electrode finger part A. Third IDT electrode 11c: 79 electrode fingers However, a narrow pitch electrode finger portion D having five electrode fingers at both ends is provided.

Second and fourth IDT electrodes 11b and 11d: 43 electrode fingers, provided that the number of electrode fingers in the narrow pitch electrode finger portion B is 3, and the number of electrode fingers in the narrow pitch electrode finger portion C is The number of electrode fingers in the remaining part is 33 each.

Number of electrode fingers in first and second reflectors 11f and 11g: 65 each Metallization ratio: 0.68
Electrode film thickness: 0.091λI

In addition, the period of the electrode fingers in the narrow pitch electrode finger part B of the second and fourth IDT electrodes 11b and 11d is 0.13 μm smaller than the period of the electrode fingers in the narrow pitch electrode finger part C.

The period of the electrode finger in the part other than the narrow pitch electrode finger part D of the third IDT electrode 11c is more than the period of the electrode finger in the part other than the narrow pitch electrode finger part A of the first and fifth IDT electrodes 11a and 11e. Is also reduced by 0.01 μm.

The period of the electrode fingers in the narrow pitch electrode finger part B is 0.13 μm smaller than the period of the electrode fingers in the narrow pitch electrode finger part C.

As described above, the second longitudinally coupled resonator type acoustic wave filter unit 12 is the first longitudinally coupled resonator type acoustic wave filter unit, except that the phases of some IDT electrodes are inverted. 11 is configured in the same manner.

Specifications of acoustic wave resonators 13 and 15:
In the following, the wavelength determined by the pitch of the electrode fingers of the IDT electrode is λII.
Electrode finger crossing width: 11.0λII
Number of electrode fingers in IDT electrode: 71 Number of electrode fingers in reflector: 18 each Metallization ratio: 0.60
Electrode film thickness: 0.095λII
Specifications of acoustic wave resonators 14 and 16:
In the following, the wavelength determined by the pitch of the electrode fingers of the IDT electrode is λIII.
Electrode finger crossing width: 15.0λIII
Number of electrode fingers in IDT electrode: 111 Number of electrode fingers in reflector: 18 Metallization ratio: 0.60
Electrode film thickness: 0.091λIII
As a comparative example, the number of electrode fingers in each of the narrow pitch electrode finger portion D and the narrow pitch electrode finger portion C is four, and the period of the electrode fingers in the narrow pitch electrode finger portion B and the narrow pitch electrode finger An elastic wave filter device configured in the same manner as in the above embodiment was prepared except that the period of the finger C was the same.

As can be seen from FIG. 4, according to the present embodiment, the steepness in the vicinity of the low-frequency side end of 1.930 to 1.990 GHz, which is the passband, is enhanced compared to the comparative example. That is, the steepness is enhanced in the stop band near 1.930 GHz, more specifically in the frequency band of 1.900 to 1.930 GHz, and the loss is from 3.5 dB to 47.47 with respect to the through level of the filter characteristics. According to the embodiment, the frequency interval reaching 0 dB is narrower by 2.5 MHz than the comparative example. When this frequency interval is narrowed, the intersection with respect to the frequency variation due to the manufacturing variation becomes large. Furthermore, even if the ambient temperature changes, it is possible to provide the elastic wave filter device 1 with little insertion loss or attenuation deterioration.

As described above, in the present embodiment, the number of electrode fingers and the cycle of the electrode fingers in the narrow pitch electrode finger portion B are less or smaller than the number and cycle of the electrode fingers in the narrow pitch electrode finger portion C. The reason why the steepness of the filter characteristic in the vicinity of the low passband side as described above is enhanced will be described.

FIG. 5 shows the electrical characteristics of only the first longitudinally coupled resonator type acoustic wave filter section in the acoustic wave filter device 1 of the comparative example described above, terminating at 1Ω, removing the characteristic impedance, It represents a resonance point. In FIG. 5, the resonance characteristics of the resonance mode in which X1 is the zero-order mode, X2 is the second-order mode, and X3 is the peak of the energy distribution of the elastic wave between the IDT electrode and the IDT electrode, that is, the IDT electrode-IDT electrode mode It is a broken part. The resonance point of the secondary mode is arranged outside the pass band and does not contribute to the formation of the pass band. That is, in the 5IDT type longitudinally coupled resonator type acoustic wave filter section, a pass band is formed by the resonance point of the 0th-order mode and the resonance point of the IDT electrode-IDT electrode mode.

For this comparative example, FIG. 6 shows the change in the resonance mode when the number of electrode fingers in the narrow pitch electrode finger portion B and the number of electrode fingers in the narrow pitch electrode finger portion C are different. In FIG. 6, the solid line shows the result when the number of electrode fingers in the narrow-pitch electrode finger part B and the narrow-pitch electrode finger part C is four as in the comparative example. On the other hand, the broken line shows the result when the number of electrode fingers in the narrow pitch electrode finger portion B is three and the number of electrode fingers in the narrow pitch electrode finger portion C is five. An alternate long and short dash line indicates a result when the number of electrode fingers in the narrow pitch electrode finger portion B is three and the number of electrode fingers in the narrow pitch electrode finger portion C is seven. It can be seen that as the difference between the number of electrode fingers in the narrow pitch electrode finger portion B and the number of electrode fingers in the narrow pitch electrode finger portion C increases, a large ripple Y is generated in the vicinity of the passband low band side end portion. . The ripple Y is generated between the resonance point of the 0th-order mode and the resonance point of the secondary mode. Therefore, by adjusting the design parameters and adjusting the frequency position of the ripple Y, the ripple Y can be positioned in the slope portion on the low pass band side. In other words, the ripple Y can be used to increase the steepness of the filter characteristics on the low pass band side.

However, at the same time, a ripple Z is also generated between the resonance point of the 0th-order mode and the resonance point of the IDT electrode-IDT electrode mode. When the ripple Z is generated, a large spike-like ripple appears in the passband. Therefore, it is required to reduce the ripple Z.

Therefore, as a result of examining the technique for reducing the ripple Z, it was found that it is effective to make the period of the electrode fingers in the narrow pitch electrode finger part B different from the period of the electrode fingers in the narrow pitch electrode finger part C.

FIG. 7 is a diagram showing a change in the resonance mode when the period of the electrode finger in the narrow pitch electrode finger part B and the period of the narrow pitch electrode finger part C are made different.

In FIG. 7, the solid line indicates the result when the period of the narrow pitch electrode finger portion B is the same as the narrow pitch electrode finger portion of the narrow pitch electrode finger portion C, and the broken line indicates the electrode in the narrow pitch electrode finger portion B. The result when the period of the finger is 0.04 μm smaller than the period of the electrode finger in the narrow pitch electrode finger part C is shown, and the alternate long and short dash line indicates that the period of the electrode finger in the narrow pitch electrode finger part B is a narrow pitch electrode The result when 0.08 μm is smaller than the finger C is shown.

As is apparent from FIG. 7, it can be seen that the ripple Z can be reduced by making the period of the electrode fingers in the narrow pitch electrode finger part B smaller than the period of the narrow pitch electrode finger part C. In particular, it can be seen that the ripple Z can be further reduced by increasing the difference between the periods of the two electrode fingers.

In FIG. 7, the cycle of the electrode fingers in the narrow pitch electrode finger portion B is made smaller than the cycle of the electrode fingers in the narrow pitch electrode finger portion C, but conversely, the cycle of the electrode fingers in the narrow pitch electrode finger portion B. Is increased with respect to the period of the electrode fingers in the narrow pitch electrode finger portion C, the ripple Z increases. That is, of the narrow pitch electrode finger portion B and the narrow pitch electrode finger portion C, the cycle of the electrode finger in the narrow pitch electrode finger portion on the side where the number of electrode fingers in the narrow pitch electrode finger portion is reduced is relatively reduced. As a result, it is possible to effectively increase the steepness of the filter characteristics by using the ripple Y while reducing the ripple Z.

Therefore, contrary to the above embodiment, when the number of electrode fingers in the narrow pitch electrode finger portion B is larger than the number of electrode fingers in the narrow pitch electrode finger portion C, the narrow pitch electrode finger portion B The cycle of the electrode fingers in the above may be made larger than the cycle of the electrode fingers in the narrow pitch electrode finger portion C. In this case as well, the same effect as in the above embodiment can be obtained.

Further, even if the period of the electrode finger in the narrow pitch electrode finger part B is equal to the period of the electrode finger in the narrow pitch electrode finger part C, the period of the electrode finger in the narrow pitch electrode finger part A and the narrow pitch electrode finger part D Similar effects can be obtained by varying the period of the electrode fingers in. This will be described with reference to FIG.

FIG. 8 is a diagram showing a change in ripple Y when the period of the electrode fingers in the narrow pitch electrode finger part A is made different from the period of the electrode fingers in the narrow pitch electrode finger part D. Here, the period and pitch of the electrode fingers in the narrow pitch electrode finger portion B and the narrow pitch electrode finger portion C are equal.

In FIG. 8, the solid line indicates the result when the period of the electrode fingers in the narrow pitch electrode finger part A and the narrow pitch electrode finger part D is the same, and the broken line indicates the period of the electrode finger in the narrow pitch electrode finger part D. The results when the electrode finger period in the narrow-pitch electrode finger part A is reduced by 0.04 μm, the one-dot broken line indicates that the period of the electrode finger in the narrow-pitch electrode finger part A is 0. 0 compared to the narrow-pitch electrode finger part D. The results when the size is reduced by 08 μm are shown. As apparent from FIG. 8, the ripple Z becomes smaller as the period of the narrow pitch electrode finger part A becomes smaller, that is, as the period difference increases, as compared with the narrow pitch electrode finger part D. I understand.

In FIG. 8, the cycle of the narrow pitch electrode finger portion A is made smaller than that of the narrow pitch electrode finger portion D, but conversely, the cycle of the electrode finger in the narrow pitch electrode finger portion A is made smaller than the narrow pitch electrode finger portion D. If it is relatively large, the ripple Z becomes large. That is, in the narrow-pitch electrode finger part A and the narrow-pitch electrode finger part D, the part of the narrow-pitch electrode finger part B and the narrow-pitch electrode finger part C that faces the smaller number of electrode fingers It is necessary to reduce the period of the electrode fingers.

As apparent from FIGS. 7 and 8, the period of the electrode fingers in the narrow pitch electrode finger part B is made smaller than the period of the electrode fingers in the narrow pitch electrode finger part C, or the electrode in the narrow pitch electrode finger part A Although the ripple Z can be reduced by making the period of the finger smaller than the period of the electrode finger in the narrow pitch electrode finger part D, in this case, the ripple Y also tends to be small. When the ripple Y is reduced, the effect of improving the steepness on the low side of the passband is reduced.

Therefore, as a result of further investigation, in order to increase the ripple Y, the frequency of the remaining electrode fingers other than the narrow pitch electrode fingers of the first, third and fifth IDT electrodes 11a, 11c, 11e, that is, the filter is determined. It has been found that it is effective to adjust the period of the electrode fingers in the main electrode finger portion.

FIG. 9 shows changes in ripple Y and ripple Z when the period of the electrode fingers in the first IDT electrode 11a and the fifth IDT electrode 11e is different from the period of the electrode fingers in the third IDT electrode 11c. FIG. More specifically, in FIG. 9, the solid line indicates the electrode fingers in the third IDT electrode 11c and the first and fifth IDT electrodes 11a and 11e other than the narrow pitch electrode finger portions (main electrode finger portions). The results when the periods are equal are shown, and the broken line indicates that the period of the electrode fingers in the third IDT electrode 11c, which is the center IDT electrode, is set to be 0. 0 than the period of the electrode fingers in the first and fifth IDT electrodes 11a and 11e. When the result is 03 μm smaller, the alternate long and short dash line shows that the period of the electrode finger in the center third IDT electrode 11c is longer than the period of the electrode finger in the main electrode finger part of the first and fifth IDT electrodes 11a and 11e. The result when 0.06 μm is reduced is shown.

As is apparent from FIG. 9, it can be seen that the ripple Y increases as the difference between the periods of the electrode fingers in the first and fifth IDT electrodes 11a and 11e and the third IDT electrode 11c increases. In this case, the ripple Z hardly changes. Therefore, the period of the electrode finger in the portion other than the narrow pitch electrode finger portion of the third IDT electrode 11c is defined as the cycle of the electrode finger in the portion other than the narrow pitch electrode finger portion of the first and fifth IDT electrodes 11a and 11e. It can be seen that it is desirable to make them different.

In FIG. 9, the period of the electrode fingers in the portions other than the narrow pitch electrode fingers of the third IDT electrode 11c is relatively small with respect to the first and fifth IDT electrodes 11a and 11e. When the period of the electrode fingers in the portions other than the narrow pitch electrode finger portions of the first and fifth IDT electrodes 11a and 11e is relatively increased, the ripple Y is reduced. That is, in order to increase the ripple Y, the main part other than the narrow pitch electrode finger portion of the IDT electrode facing the portion of the narrow pitch electrode finger portion B and the narrow pitch electrode finger portion C which has the smaller number of electrode fingers. It is necessary to relatively increase the period of the electrode fingers in the electrode finger portion. Therefore, when the number of electrode fingers in the narrow pitch electrode finger portion B is larger than the number of electrode fingers in the narrow pitch electrode finger portion C, other than the narrow pitch electrode finger portions of the first and fifth IDT electrodes 11a and 11e. It is desirable that the period of the electrode fingers in the main electrode finger part is smaller than the period of the electrode fingers in the main electrode finger part other than the narrow pitch electrode finger part of the third IDT electrode 11c.

Next, modifications of the above embodiment will be described with reference to FIGS. FIG. 10 is a schematic plan view for explaining the structure of the narrow pitch electrode finger portion of the first longitudinally coupled resonator type elastic wave filter portion 11 in the elastic wave filter device according to the modification of the embodiment.

In this modification, the relationship between the number of electrodes and the period of the electrode fingers in the narrow pitch electrode fingers is reversed. That is, as shown in FIG. 10, the number of electrode fingers in the narrow pitch electrode finger portion B is larger than the number of electrode fingers in the narrow pitch electrode finger portion C, and the period of the electrode fingers in the narrow pitch electrode finger portion B Is made larger than the period of the electrode fingers in the narrow pitch electrode finger portion C. And the period of the electrode finger in parts other than the narrow pitch electrode finger part of the 1st, 5th IDT electrodes 11a and 11e is from the period of the electrode finger in the part other than the narrow pitch electrode finger part of the third IDT electrode 11c. It is also small. As a result, the ripple Y can be increased to increase the steepness of the filter characteristics on the low frequency side, and the ripple Z can be reduced as in the above embodiment. This is shown in FIGS.

FIG. 11 is a diagram showing changes in the ripple Y and the ripple Z when the number of electrode fingers in the narrow pitch electrode finger portion B and the narrow pitch electrode finger portion C is different. In FIG. 11, the solid line indicates the result when the number of electrode fingers in the narrow pitch electrode finger portion B and the narrow pitch electrode finger portion C is four, and the broken line indicates the electrode finger in the narrow pitch electrode finger portion B. The result when the number is 5 and the number of electrode fingers in the narrow pitch electrode finger part C is 3 is shown, and the alternate long and short dash line indicates the number of electrode fingers in the narrow pitch electrode finger part B is 7, The result when the number of electrode fingers in part C is three is shown.

As apparent from FIG. 11, the ripple Y can be increased as the number of electrode fingers in the narrow pitch electrode finger portion B is relatively increased with respect to the number of electrode fingers in the narrow pitch electrode finger portion C. I understand.

However, the ripple Z increases as the number of electrode fingers in the narrow pitch electrode finger portion B is relatively increased with respect to the number of electrode fingers in the narrow pitch electrode finger portion C.

FIG. 12 is a diagram showing the relationship between the period of the electrode finger in the narrow pitch electrode finger part B, the period of the electrode finger in the narrow pitch electrode finger part C, and the ripple Y and ripple Z. In FIG. 12, the solid line indicates the result when the period of the electrode finger in the narrow pitch electrode finger part B and the narrow pitch electrode finger part C is the same, and the broken line indicates the period of the electrode finger in the narrow pitch electrode finger part B. The result in the case of relatively widening 0.04 μm is shown, and the alternate long and short dash line shows the result in the case where the period of the electrode finger in the narrow pitch electrode finger portion B is relatively increased by 0.08 μm.

As is apparent from FIG. 12, as the period of the electrode fingers in the narrow-pitch electrode finger portion B is relatively increased, the undesired ripple Z can be reduced, in which case the magnitude of the ripple Y changes greatly. You can see that they are not.

FIG. 13 is a diagram showing a change in ripple Z when the pitch of the electrode fingers of the narrow pitch electrode finger portion A and the narrow pitch electrode finger portion D is changed in the present modification, and the solid line indicates the narrow pitch electrode finger portion A. And the result when the period of the electrode finger in the narrow pitch electrode finger part D is the same is shown, and the broken line shows the period of the electrode finger in the narrow pitch electrode finger part A with respect to the period of the electrode finger in the narrow pitch electrode finger part B The result in the case of relatively larger 0.04 μm is shown, and the alternate long and short dash line indicates that the period of the electrode finger in the narrow pitch electrode finger part A is 0.08 μm relatively larger than the period of the electrode finger in the narrow pitch electrode finger part B The result of the case is shown.

As is apparent from FIG. 13, as the period of the electrode fingers in the narrow pitch electrode finger portion A is increased, that is, the number of electrode fingers in the narrow pitch electrode finger portion is relatively larger than that in the narrow pitch electrode finger portion C. The ripple Z is reduced by making the period of the electrode fingers in the narrow pitch electrode finger part A facing the many narrow pitch electrode finger parts B larger than the period of the electrode fingers in the narrow pitch electrode finger part D. You can see that

FIG. 14 shows the relationship between the period of the electrode finger and the ripple Y in a portion other than the narrow pitch electrode finger portion of the third IDT electrode 11c and the first and fifth IDT electrodes 11a and 11e in this modification. FIG.

In FIG. 14, the result when the period of the electrode fingers in the portions other than the narrow pitch electrode finger portions of the third IDT electrode 11c and the first and fifth IDT electrodes 11a, 11e are all equal is shown. The result when the period of the electrode finger in the third IDT electrode 11c is relatively increased by 0.03 μm is shown, and the alternate long and short dash line indicates the period of the electrode finger in a portion other than the narrow pitch electrode finger part of the third IDT electrode 11c. The results are shown for a relatively large 0.06 μm.

As is apparent from FIG. 14, as in the case of FIG. 9, the period of the electrode fingers in the portions other than the narrow-pitch electrode finger portions is changed to the first IDT electrode 11a, the fifth IDT electrode 11e, and the third IDT electrode. It can be seen that the magnitude of the ripple Y can be controlled by making it different from 11c. Even in this case, other than the narrow pitch electrode finger portions of the first and fifth IDT electrodes on the side of the portion facing the narrow pitch electrode finger portion B where the number of electrode fingers in the narrow pitch electrode finger portion is relatively large. The period of the electrode finger in the portion is set to a portion other than the narrow pitch electrode finger portion of the third IDT electrode 11c facing the narrow pitch electrode finger portion C where the number of electrode fingers in the narrow pitch electrode finger portion is relatively small. It can be seen that the ripple Y can be increased by making it smaller than the cycle of the electrode fingers. Thereby, the steepness of the filter characteristics can be effectively enhanced.

In the above modification, the example in which the period of the electrode fingers in the narrow pitch electrode finger part B is set larger than the period of the electrode fingers in the narrow pitch electrode finger part C has been described. The period of the electrode finger in the narrow pitch electrode finger part A is set larger than the period of the electrode finger in the narrow pitch electrode finger part D Also good.

In the present invention, the case where the period of the electrode fingers in the narrow pitch electrode finger portion is constant has been described. However, the period of the electrode fingers in the narrow pitch electrode finger portion is not necessarily constant. For example, the electrode finger period in the narrow pitch electrode finger portion may be gradually changed as described in JP-A-2002-528987, or narrow as described in JP-A-2003-243965. A plurality of portions having different electrode finger cycles may be provided in the pitch electrode finger portion. Thus, when the period of the electrode finger in the narrow pitch electrode finger part is not constant, if the average value of the period of the electrode finger in the narrow pitch electrode finger part satisfies the magnitude relationship described in the above embodiment, The effect of the present invention can be obtained. That is, in the present invention, the period of the electrode fingers in the narrow-pitch electrode fingers is the average value of the periods of the electrode fingers in the narrow-pitch electrode fingers when the period of the electrode fingers in the narrow-pitch electrode fingers is not constant. means.

In the embodiment and the modification, the surface acoustic wave filter device using the surface acoustic wave has been described. However, since the present invention has a feature in the electrode structure, not only the surface acoustic wave but also the elastic boundary The present invention can be similarly applied to a boundary acoustic wave filter device using a wave, and the steepness of the filter characteristics can be similarly improved.

[Elastic wave filter device according to second embodiment of the present invention]
The second embodiment of the present invention will be described below. Since the second embodiment has the structure shown in FIG. 1 as in the first embodiment, the same reference numerals are used for the parts common to the first embodiment, and the description will be omitted. Omitted.

As shown in FIG. 15, the feature of this embodiment is that the first longitudinally coupled resonator type acoustic wave filter unit 11 has narrow pitch electrodes provided at the ends of the first and fifth IDT electrodes 11a and 11e. The number of electrode fingers in the finger portion, that is, the narrow pitch electrode finger portion A is smaller than the number of electrode fingers in the narrow pitch electrode finger portion, that is, the narrow pitch electrode finger portion D provided at both ends of the third IDT electrode 11c. Narrow pitch electrode fingers provided at the ends of the second and fourth IDT electrodes 11b, 11d on the first and fifth IDT electrodes 11a, 11e side, that is, electrodes in the narrow pitch electrode fingers B The period of the finger is a narrow pitch electrode finger provided at the end of the second and fourth IDT electrodes 11b, 11d on the third IDT electrode 11c side, that is, the period of the electrode finger in the narrow pitch electrode finger C Smaller than The period of the electrode fingers in the portions other than the narrow pitch electrode finger portions B and C of the third IDT electrode 11c is the same as that of the electrode fingers in the portions other than the narrow pitch electrode finger portions A of the first and fifth IDT electrodes 11a and 11e. It is smaller than the period. The second longitudinally coupled resonator type acoustic wave filter unit 12 is configured similarly to the first longitudinally coupled resonator type acoustic wave filter unit 11. Thereby, in the acoustic wave filter device 1, the steepness of the filter characteristics on the low pass band side is effectively enhanced. This will be described with reference to FIGS.

FIG. 16 is a diagram illustrating the filter characteristics of the elastic wave filter device of the present embodiment, where the solid line indicates the result of the present embodiment, and the dashed line indicates the filter characteristic of the elastic wave filter device prepared as a comparative example. is there. The details of the electrode structure in the embodiment and the comparative example are as follows. In the following, λI is a wavelength determined by the period of the electrode fingers of the IDT electrode.

Specifications of the first longitudinally coupled resonator type acoustic wave filter unit 11:
Electrode finger crossing width = 14.9λI
First and fifth IDT electrodes 11a and 11e: 37 electrode fingers, each of which 37 are electrode fingers of narrow pitch electrode finger part A. Third IDT electrode 11c: Number of electrode fingers 85 However, narrow pitch electrode finger portions D each having seven electrode fingers at both ends are provided.

Second and fourth IDT electrodes 11b and 11d: 41 electrode fingers, provided that the number of electrode fingers in the narrow pitch electrode finger portion B is four, and the number of electrode fingers in the narrow pitch electrode finger portion C is There are four, and the number of electrode fingers in the remaining portion is 33.

Number of electrode fingers in first and second reflectors 11f and 11g: 65 each Metallization ratio: 0.68
Electrode film thickness: 0.091λI
The period of the electrode fingers in the narrow pitch electrode finger part B of the second and fourth IDT electrodes 11b and 11d is 0.14 μm smaller than the period of the electrode fingers in the narrow pitch electrode finger part C.

The period of the electrode finger in the part other than the narrow pitch electrode finger part D of the third IDT electrode 11c is more than the period of the electrode finger in the part other than the narrow pitch electrode finger part A of the first and fifth IDT electrodes 11a and 11e. Is also reduced by 0.01 μm.

As described above, the second longitudinally coupled resonator type acoustic wave filter unit 12 is the first longitudinally coupled resonator type acoustic wave filter unit, except that the phases of some IDT electrodes are inverted. 11 is configured in the same manner.

As a comparative example, the number of electrode fingers in each of the narrow pitch electrode finger part D and the narrow pitch electrode finger part A is four, and the period of the electrode finger in the narrow pitch electrode finger part B and the narrow pitch electrode An elastic wave filter device configured in the same manner as in the above embodiment was prepared except that the period of the finger C was the same.

As can be seen from FIG. 16, according to the present embodiment, the steepness in the vicinity of the low band side end of 1.930 to 1.990 GHz, which is the pass band, is enhanced as compared with the comparative example. That is, the steepness is enhanced in the stop band near 1.930 GHz, more specifically in the frequency band of 1.900 to 1.930 GHz, and the loss is from 3.5 dB to 47.47 with respect to the through level of the filter characteristics. According to the embodiment, the frequency interval reaching 0 dB is narrower by 2.1 MHz than the comparative example. When this frequency interval is narrowed, the intersection with respect to the frequency variation due to the manufacturing variation becomes large. Furthermore, even if the ambient temperature changes, it is possible to provide the elastic wave filter device 1 with little insertion loss or attenuation deterioration.

FIG. 17 shows the change in the resonance mode when the number of electrode fingers in the narrow pitch electrode finger portion A is different from the number of electrode fingers in the narrow pitch electrode finger portion D for this comparative example. In FIG. 17, the solid line shows the result when the number of electrode fingers in the narrow pitch electrode finger portion B and the narrow pitch electrode finger portion C is four as in the comparative example. The broken line shows the result when the number of electrode fingers in the narrow pitch electrode finger portion A is three and the number of electrode fingers in the narrow pitch electrode finger portion D is five. An alternate long and short dash line indicates a result when the number of electrode fingers in the narrow pitch electrode finger portion A is three and the number of electrode fingers in the narrow pitch electrode finger portion D is seven.

From the results shown in FIG. 17, as the difference between the number of electrode fingers in the narrow pitch electrode finger portion A and the number of electrode fingers in the narrow pitch electrode finger portion D increases, a large ripple in the vicinity of the passband low band side end portion. It can be seen that Y occurs. The ripple Y is generated between the resonance point of the 0th-order mode and the resonance point of the secondary mode. Therefore, by adjusting the design parameters and adjusting the frequency position of the ripple Y, the ripple Y can be positioned in the slope portion on the low pass band side. In other words, the ripple Y can be used to increase the steepness of the filter characteristics on the low pass band side.

However, at the same time, a ripple Z is also generated between the resonance point of the 0th-order mode and the resonance point of the IDT electrode-IDT electrode mode. When the ripple Z is generated, a large spike-like ripple appears in the passband. Therefore, it is required to reduce the ripple Z.

Therefore, as a result of examining the technique for reducing the ripple Z, it was found that it is effective to make the period of the electrode fingers in the narrow pitch electrode finger part B different from the period of the electrode fingers in the narrow pitch electrode finger part C.

FIG. 18 is a diagram showing a change in the resonance mode when the period of the electrode finger in the narrow pitch electrode finger part B is different from the period of the narrow pitch electrode finger part C.

In FIG. 18, the solid line indicates the result when the period of the narrow pitch electrode finger portion B is the same as the narrow pitch electrode finger portion of the narrow pitch electrode finger portion C, and the broken line indicates the electrode in the narrow pitch electrode finger portion B. The result in the case where the period of the finger is 0.04 μm smaller than the period of the electrode finger in the narrow pitch electrode finger part C is shown, and the alternate long and short dash line indicates the period of the electrode finger in the narrow pitch electrode finger part B The result when 0.08 μm is smaller than is shown.

As is apparent from FIG. 18, it can be seen that the ripple Z can be reduced by making the period of the electrode fingers in the narrow pitch electrode finger part B smaller than the period of the narrow pitch electrode finger part C. In particular, it can be seen that the ripple Z can be further reduced by increasing the difference between the periods of the two electrode fingers.

In FIG. 18, the cycle of the electrode fingers in the narrow pitch electrode finger B is made smaller than the cycle of the electrode fingers in the narrow pitch electrode finger C, but conversely, the cycle of the electrode fingers in the narrow pitch electrode finger B Is increased with respect to the period of the electrode fingers in the narrow pitch electrode finger portion C, the ripple Z increases. That is, of the narrow pitch electrode finger part B and the narrow pitch electrode finger part C, the narrow pitch electrode finger part that faces the smaller one of the narrow pitch electrode finger part A and the narrow pitch electrode finger part D. By relatively reducing the period, the steepness of the filter characteristics can be effectively increased by using the ripple Y while reducing the ripple Z.

Therefore, contrary to the above-described embodiment, when the number of electrode fingers in the narrow pitch electrode finger portion A is larger than the number of electrode fingers in the narrow pitch electrode finger portion D, the narrow pitch electrode finger portion B In this case, the ripple Z is reduced and the ripple Y is used in the same manner as in the above embodiment. The steepness of the filter characteristics can be effectively increased.

Further, even if the period of the electrode finger in the narrow pitch electrode finger part B is equal to the period of the electrode finger in the narrow pitch electrode finger part C, the period of the electrode finger in the narrow pitch electrode finger part A and the narrow pitch electrode finger part D Similarly, the ripple Z can be reduced by making the periods of the electrode fingers different. This will be described with reference to FIG.

FIG. 19 is a diagram showing a change in ripple Y when the period of the electrode fingers in the narrow pitch electrode finger part A is made different from the period of the electrode fingers in the narrow pitch electrode finger part D. Here, the period and pitch of the electrode fingers in the narrow pitch electrode finger portion B and the narrow pitch electrode finger portion C are equal.

In FIG. 19, the solid line indicates the result when the period of the electrode fingers in the narrow pitch electrode finger part A and the narrow pitch electrode finger part D is the same, and the broken line indicates the period of the electrode finger in the narrow pitch electrode finger part D. The results when the electrode finger period in the narrow-pitch electrode finger part A is reduced by 0.04 μm, the one-dot broken line indicates that the period of the electrode finger in the narrow-pitch electrode finger part A is 0. 0 compared to the narrow-pitch electrode finger part D. The results when the size is reduced by 08 μm are shown. As can be seen from FIG. 19, the ripple Z becomes smaller as the period of the narrow pitch electrode finger part A becomes smaller, that is, as the period difference becomes larger, as compared with the narrow pitch electrode finger part D. I understand.

In FIG. 19, the period of the narrow pitch electrode finger part A is made smaller than that of the narrow pitch electrode finger part D. If it is relatively large, the ripple Z becomes large. That is, it is necessary to reduce the period of the electrode finger in the narrow pitch electrode finger portion having the smaller number of electrode fingers among the narrow pitch electrode finger portion A and the narrow pitch electrode finger portion D.

As apparent from FIGS. 18 and 19, the period of the electrode fingers in the narrow pitch electrode finger part B is made smaller than the period of the electrode fingers in the narrow pitch electrode finger part C, or the electrode in the narrow pitch electrode finger part A Although the ripple Z can be reduced by making the period of the finger smaller than the period of the electrode finger in the narrow pitch electrode finger part D, in this case, the ripple Y also tends to be small. When the ripple Y is reduced, the effect of improving the steepness on the low side of the passband is reduced.

Therefore, as a result of further investigation, in order to increase the ripple Y without reducing the ripple Z, the remaining electrodes other than the narrow pitch electrode fingers of the first, third, and fifth IDT electrodes 11a, 11c, and 11e. It has been found effective to adjust the period of the electrode fingers in the main electrode finger that determines the frequency of the finger, i.e. the filter.

In FIG. 20, the cycle of the electrode fingers in the main electrode finger portion of the first IDT electrode 11a and the fifth IDT electrode 11e is different from the cycle of the electrode fingers in the main electrode finger portion of the third IDT electrode 11c. It is a figure which shows the change of the ripple Y at the time of a case, and the ripple Z. More specifically, in FIG. 20, the solid line shows the result when the periods of the electrode fingers in the portions other than the narrow pitch electrode finger portions of the third IDT electrode 11c and the first and fifth IDT electrodes 11a, 11e are equal. The broken line shows the result when the period of the electrode finger in the third IDT electrode 11c which is the center IDT electrode is 0.03 μm smaller than the period of the electrode finger in the first and fifth IDT electrodes 11a and 11e. The one-dot chain line shows a case where the period of the electrode finger in the center third IDT electrode 11c is 0.06 μm smaller than the period of the electrode finger in the main electrode finger part of the first and fifth IDT electrodes 11a and 11e. Results are shown.

As is clear from FIG. 20, it can be seen that the ripple Y increases as the difference between the periods of the electrode fingers in the first and fifth IDT electrodes 11a and 11e and the third IDT electrode 11c increases. In this case, the ripple Z hardly changes. Therefore, the period of the electrode finger in the portion other than the narrow pitch electrode finger portion of the third IDT electrode 11c is defined as the cycle of the electrode finger in the portion other than the narrow pitch electrode finger portion of the first and fifth IDT electrodes 11a and 11e. It can be seen that it is desirable to make them different.

In FIG. 20, the period of the electrode finger in the portion other than the narrow pitch electrode finger portion of the third IDT electrode 11c is relatively small with respect to the first and fifth IDT electrodes 11a and 11e. When the period of the electrode fingers in the portions other than the narrow pitch electrode finger portions of the first and fifth IDT electrodes 11a and 11e is relatively increased, the ripple Y is reduced. In other words, in order to increase the ripple Y, the main other than the narrow pitch electrode finger portion of the IDT electrode having the larger number of electrode fingers of the narrow pitch electrode finger portion among the first and third IDT electrodes 11a and 11c. It is necessary to relatively reduce the period of the electrode fingers in the electrode finger portion. Therefore, when the number of electrode fingers in the narrow pitch electrode finger portion A is larger than the number of electrode fingers in the narrow pitch electrode finger portion D, other than the narrow pitch electrode finger portions of the first and fifth IDT electrodes 11a and 11e. It is desirable that the period of the electrode fingers in the main electrode finger part is smaller than the period of the electrode fingers in the main electrode finger part other than the narrow pitch electrode finger part of the third IDT electrode 11c.

Next, a modification of the above embodiment will be described with reference to FIGS. FIG. 21 is a schematic plan view for explaining the structure of the narrow pitch electrode finger portion of the first longitudinally coupled resonator type elastic wave filter portion 11 in the elastic wave filter device according to the modification of the embodiment.

In this modification, the relationship between the number of electrodes and the period of the electrode fingers in the narrow pitch electrode fingers is reversed. That is, as shown in FIG. 21, in this modification, the number of electrode fingers in the narrow pitch electrode finger part A is larger than the number of electrode fingers in the narrow pitch electrode finger part D, and the electrode in the narrow pitch electrode finger part B The period of the finger is larger than the period of the electrode finger in the narrow pitch electrode finger part C, and the period of the electrode finger in the part other than the narrow pitch electrode finger parts B and C of the third IDT electrode 11c is the first and fifth. The period of the electrode fingers in the portions other than the narrow pitch electrode finger portion A of the IDT electrodes 11a and 11e is larger. As a result, the ripple Y can be increased to increase the steepness of the filter characteristics on the low frequency side as in the above embodiment, and the ripple Z can be reduced. This is shown in FIGS.

FIG. 22 is a diagram showing changes in the ripple Y and the ripple Z when the number of electrode fingers in the narrow pitch electrode finger portion A and the narrow pitch electrode finger portion D is varied. In FIG. 22, the solid line indicates the result when the number of electrode fingers in the narrow pitch electrode finger part A and the narrow pitch electrode finger part D is four, and the broken line indicates the electrode finger in the narrow pitch electrode finger part A. 7 shows the result when the number of electrode fingers in the narrow pitch electrode finger portion D is three, and the alternate long and short dash line indicates the number of electrode fingers in the narrow pitch electrode finger portion A is nine, and the narrow pitch electrode finger The result when the number of electrode fingers in part D is three is shown.

As apparent from FIG. 22, the ripple Y can be increased as the number of electrode fingers in the narrow pitch electrode finger portion A is relatively increased with respect to the number of electrode fingers in the narrow pitch electrode finger portion D. I understand.

However, the ripple Z increases as the number of electrode fingers in the narrow pitch electrode finger portion A is relatively increased with respect to the number of electrode fingers in the narrow pitch electrode finger portion D.

FIG. 23 is a diagram showing the relationship between the period of the electrode finger in the narrow pitch electrode finger part B, the period of the electrode finger in the narrow pitch electrode finger part C, and the ripple Y and ripple Z. In FIG. 23, the solid line indicates the result when the period of the electrode fingers in the narrow pitch electrode finger part B and the narrow pitch electrode finger part C is the same, and the broken line indicates the period of the electrode finger in the narrow pitch electrode finger part B. The result in the case of relatively widening 0.02 μm is shown, and the alternate long and short dash line shows the result in the case where the period of the electrode finger in the narrow pitch electrode finger portion B is relatively increased by 0.04 μm.

As is apparent from FIG. 23, as the period of the electrode fingers in the narrow-pitch electrode finger portion B is relatively increased, the undesired ripple Z can be reduced, in which case the magnitude of the ripple Y changes greatly. You can see that they are not.

FIG. 24 is a diagram showing a change in the ripple Z when the period of the electrode fingers of the narrow pitch electrode finger portion A and the narrow pitch electrode finger portion D is changed in the present modification, and the solid line indicates the narrow pitch electrode finger portion A. And the result when the period of the electrode finger in the narrow pitch electrode finger part D is the same is shown, and the broken line shows the period of the electrode finger in the narrow pitch electrode finger part A with respect to the period of the electrode finger in the narrow pitch electrode finger part B The result in the case of relatively larger 0.02 μm is shown, and the alternate long and short dash line indicates that the period of the electrode finger in the narrow pitch electrode finger part A is 0.04 μm relatively larger than the period of the electrode finger in the narrow pitch electrode finger part B The result of the case is shown.

As is clear from FIG. 24, it can be seen that the ripple Z decreases as the period of the electrode fingers in the narrow pitch electrode finger portion A is relatively increased. That is, it can be seen that the ripple Z decreases as the period of the electrode finger in the narrow pitch electrode finger portion of the narrow pitch electrode finger portion A and the narrow pitch electrode finger portion D which has the larger number of electrode fingers is increased.

FIG. 25 shows the relationship between the period of the electrode finger and the ripple Y in a portion other than the narrow pitch electrode finger portion of the third IDT electrode 11c and the first and fifth IDT electrodes 11a and 11e in this modification. FIG.

In FIG. 25, the period of the electrode finger in the portion other than the narrow pitch electrode finger portion of the third IDT electrode 11c and the electrode finger in the portion other than the narrow pitch electrode finger portion of the first and fifth IDT electrodes 11a and 11e. The result when the period is made equal is shown, and the broken line indicates the period of the electrode finger in the portion other than the narrow pitch electrode finger part of the third IDT electrode 11c, and the narrow pitch of the first and fifth IDT electrodes 11a and 11e. The result when 0.03 μm larger than the period of the electrode finger in the part other than the electrode finger part is shown, and the alternate long and short dash line indicates the period of the electrode finger in the part other than the narrow pitch electrode finger part of the third IDT electrode 11c. The result in the case where it is larger than the period of the electrode fingers in the portions other than the narrow pitch electrode finger portions of the first and fifth IDT electrodes 11a and 11e is shown.

As is clear from FIG. 25, as in the case of FIG. 20, the period of the electrode finger in the portion other than the narrow pitch electrode finger portion is changed to the first IDT electrode 11a, the fifth IDT electrode 11e, and the third IDT electrode. It can be seen that the magnitude of the ripple Y can also be controlled by making it different from 11c. Specifically, of the first and fifth IDT electrodes 11a and 11e and the third IDT electrode 11c, the number of electrode fingers in the narrow pitch electrode finger portion is larger than that of the narrow pitch electrode finger portion of the IDT electrode. It can be seen that the ripple Y can be increased by making the period of the electrode finger in the part smaller than the period of the electrode finger in the part other than the narrow pitch electrode finger part of the other IDT electrode. Thereby, the steepness of the filter characteristics can be effectively enhanced.

In the above modification, the example in which the period of the electrode fingers in the narrow pitch electrode finger part B is set larger than the period of the electrode fingers in the narrow pitch electrode finger part C has been described. The period of the electrode finger in the narrow pitch electrode finger part A is set larger than the period of the electrode finger in the narrow pitch electrode finger part D Also good.

[Elastic wave filter device according to third embodiment of the present invention]
The third embodiment of the present invention will be described below. Since the third embodiment also has the structure shown in FIG. 1 as in the first embodiment, the same reference numerals are used for the parts common to the first embodiment, and the description will be omitted. Omitted.

As shown in FIG. 27, the present embodiment is characterized in that, in the first longitudinally coupled resonator type acoustic wave filter unit 11, the first or fifth IDT of the second IDT electrode 11b and the fourth IDT electrode 11d. The number of electrode fingers in the narrow pitch electrode finger portion at the end on the electrode 11a, 11e side, that is, the narrow pitch electrode finger portion B, is narrower on the third IDT electrode 11c side of the second and fourth IDT electrodes 11b and 11d. The number of electrode fingers in the pitch electrode finger portion, that is, the narrow pitch electrode finger portion C is reduced, and the cycle of the electrode finger in the narrow pitch electrode finger portion B is smaller than the cycle of the electrode finger in the narrow pitch electrode finger portion C. The number of electrode fingers in the narrow pitch electrode finger portions provided at the end portions of the first and fifth IDT electrodes 11a and 11e, that is, in the narrow pitch electrode finger portion A is equal to both the third IDT electrodes 11c. The number of electrode fingers in the narrow pitch electrode finger portion D is smaller than the number of electrode fingers in the narrow pitch electrode finger portion D. The period of the electrode fingers in the portion other than the narrow pitch electrode finger portions B and C of the third IDT electrode 11c is smaller than that of the narrow pitch electrode finger portion A of the first and fifth IDT electrodes 11a and 11e. This is because it is smaller than the period of the electrode fingers in the portion. The second longitudinally coupled resonator type acoustic wave filter unit 12 is configured similarly to the first longitudinally coupled resonator type acoustic wave filter unit 11. Thereby, in the acoustic wave filter device 1, the steepness of the filter characteristics on the low pass band side is effectively enhanced. This will be described with reference to FIG.

FIG. 28 is a diagram showing the filter characteristics of the elastic wave filter device of the present embodiment, the solid line shows the result of the present embodiment, and the one-dot broken line shows the filter characteristic of the elastic wave filter device prepared as a comparative example. is there. The details of the electrode structure in the embodiment and the comparative example are as follows. In the following, λI is a wavelength determined by the period of the electrode fingers of the IDT electrode.

Specifications of the first longitudinally coupled resonator type acoustic wave filter unit 11:
Electrode finger crossing width = 16.9λI
First and fifth IDT electrodes 11a and 11e: 42 electrode fingers, each of which 42 are electrode fingers of narrow pitch electrode finger portion A. Third IDT electrode 11c: Number of electrode fingers 55 However, a narrow pitch electrode finger portion D having five electrode fingers at both ends is provided.
Second and fourth IDT electrodes 11b and 11d: 43 electrode fingers, provided that the number of electrode fingers in the narrow pitch electrode finger portion B is 3, and the number of electrode fingers in the narrow pitch electrode finger portion C is The number of electrode fingers in the remaining part is 33.
Number of electrode fingers in first and second reflectors 11f and 11g: 65 each Metallization ratio: 0.68
Electrode film thickness: 0.091λI

The cycle of the electrode fingers in the narrow pitch electrode finger portion B of the second and fourth IDT electrodes 11b and 11d is 0.177 μm smaller than the cycle of the electrode fingers in the narrow pitch electrode finger portion C.
The period of the electrode fingers in the narrow pitch electrode finger part A of the first and fifth IDT electrodes 11a and 11e is 0.076 μm smaller than the period of the electrode fingers in the narrow pitch electrode finger part D of the third IDT electrode 11c.

The period of the electrode finger in the part other than the narrow pitch electrode finger part D of the third IDT electrode 11c is more than the period of the electrode finger in the part other than the narrow pitch electrode finger part A of the first and fifth IDT electrodes 11a and 11e. Is also reduced by 0.01 μm.

As described above, the second longitudinally coupled resonator type acoustic wave filter unit 12 is the first longitudinally coupled resonator type acoustic wave filter unit, except that the phases of some IDT electrodes are inverted. 11 is configured in the same manner.
As a comparative example, the number of electrode fingers in each of the narrow pitch electrode finger portions A to D is four, and the period of the electrode fingers in the narrow pitch electrode finger portions A to D is the above. An elastic wave filter device configured in the same manner as in the embodiment was prepared.

As is apparent from FIG. 28, according to the present embodiment, it is understood that the steepness in the vicinity of the low band side end portion of 1.930 to 1.990 GHz, which is the pass band, is enhanced as compared with the comparative example. That is, the steepness is enhanced in the stop band near 1.930 GHz, more specifically in the frequency band of 1.900 to 1.930 GHz, and the loss is from 3.5 dB to 47.47 with respect to the through level of the filter characteristics. According to the embodiment, the frequency interval reaching 0 dB is narrower by 3.8 MHz than the comparative example. When this frequency interval is narrowed, the intersection with respect to the frequency variation due to the manufacturing variation becomes large. Furthermore, even if the ambient temperature varies and changes, it is possible to provide the elastic wave filter device 1 with small insertion loss and attenuation.

Also in the third embodiment, similarly to the first and second embodiments, a modification example having the same effect can be obtained by reversing the magnitude relationship between the number of electrode fingers and the period. That is, in the modification of the third embodiment, as shown in FIG. 29, the number of electrode fingers in the narrow pitch electrode finger portion B is larger than the number of electrode fingers in the narrow pitch electrode finger portion C. The period of the electrode fingers in the pitch electrode finger part B is made larger than the period of the electrode fingers in the narrow pitch electrode finger part C. The number of electrode fingers in the narrow pitch electrode finger portion A is larger than the number of electrode fingers in the narrow pitch electrode finger portion D, and the period of the electrode fingers in the narrow pitch electrode finger portion A is the narrow pitch electrode finger portion. It is made larger than the period of the electrode finger in D. Further, the period of the electrode fingers in the portions other than the narrow pitch electrode finger portions of the first and fifth IDT electrodes 11a and 11e is greater than the cycle of the electrode fingers in the portions other than the narrow pitch electrode finger portions of the third IDT electrode 11c. It is also small. As a result, as in the third embodiment, the ripple Y can be increased to increase the steepness of the filter characteristics on the low frequency side, and the ripple Z can be reduced.

Specifically, a part of the specification of the first longitudinally coupled resonator type acoustic wave filter unit 11 may be changed as follows.
First and fifth IDT electrodes 11a and 11e: The number of electrode fingers is 42 each, provided that five of the 42 are electrode fingers of the narrow pitch electrode finger portion A.
Third IDT electrode 11c: The number of electrode fingers is 55, provided that narrow pitch electrode finger portions D each having three electrode fingers are provided at both ends.
Second and fourth IDT electrodes 11b and 11d: 43 electrode fingers, provided that the number of electrode fingers in the narrow pitch electrode finger portion B is 7, and the number of electrode fingers in the narrow pitch electrode finger portion C is There are three, and the number of electrode fingers in the remaining portion is 33.

The period of the electrode fingers in the narrow pitch electrode finger part B of the second and fourth IDT electrodes 11b and 11d is 0.177 μm larger than the period of the electrode fingers in the narrow pitch electrode finger part C.
The period of the electrode fingers in the narrow pitch electrode finger part A of the first and fifth IDT electrodes 11a, 11e is 0.076 μm larger than the period of the electrode fingers in the narrow pitch electrode finger part D of the third IDT electrode 11c.

The period of the electrode finger in the part other than the narrow pitch electrode finger part D of the third IDT electrode 11c is more than the period of the electrode finger in the part other than the narrow pitch electrode finger part A of the first and fifth IDT electrodes 11a and 11e. Is also increased by 0.01 μm.
The second longitudinally coupled resonator type acoustic wave filter unit 12 is configured in the same manner as the first longitudinally coupled resonator type acoustic wave filter unit 11 except that the phases of some IDT electrodes are inverted. do it.

Therefore, when the results of the first to third embodiments and the modified examples are summarized, the number and period of the electrode fingers in the narrow-pitch electrode finger portions A to D and the third IDT electrode 11c It can be seen that the period of the electrode fingers in the main electrode finger portions other than the narrow pitch electrode finger portions in the first and fifth IDT electrodes 11a and 11e may be designed.

Configuration 1 (corresponding to the first embodiment in the first specific aspect)
1) Number of electrode fingers in narrow pitch electrode finger portion B <Number of electrode fingers in narrow pitch electrode finger portion C 2) Period of electrode fingers in narrow pitch electrode finger portion B <Period of electrode fingers in narrow pitch electrode finger portion C Or cycle of electrode fingers in narrow pitch electrode finger portion A <cycle of electrode fingers in narrow pitch electrode finger portion D 3) cycle of electrode fingers in main electrode finger portions of first and fifth IDT electrodes 11a and 11e> Period of electrode fingers in the main electrode finger portion of the third IDT electrode 11c

Configuration 2 (corresponding to the second embodiment in the first specific aspect)
1) Number of electrode fingers in narrow pitch electrode finger portion A <Number of electrode fingers in narrow pitch electrode finger portion D 2) Period of electrode fingers in narrow pitch electrode finger portion B <Period of electrode fingers in narrow pitch electrode finger portion C Or cycle of electrode fingers in narrow pitch electrode finger portion A <cycle of electrode fingers in narrow pitch electrode finger portion D 3) cycle of electrode fingers in main electrode finger portions of first and fifth IDT electrodes 11a and 11e> Period of electrode fingers in the main electrode finger portion of the third IDT electrode 11c

Configuration 3 (corresponding to the third embodiment in the first specific aspect)
1) Number of electrode fingers in narrow pitch electrode finger portion B <Number of electrode fingers in narrow pitch electrode finger portion C 2) Number of electrode fingers in narrow pitch electrode finger portion A <Number of electrode fingers in narrow pitch electrode finger portion D 3) Period of electrode finger in narrow pitch electrode finger part B <Period of electrode finger in narrow pitch electrode finger part C 4) Period of electrode finger in narrow pitch electrode finger part A <Period of electrode finger in narrow pitch electrode finger part D 5) Period of electrode fingers in main electrode finger portions of first and fifth IDT electrodes 11a and 11e> Period of electrode fingers in main electrode finger portions of third IDT electrode 11c

Configuration 4 (corresponding to a modification of the first embodiment in the second specific aspect)
1) Number of electrode fingers in narrow pitch electrode finger portion B> Number of electrode fingers in narrow pitch electrode finger portion C 2) Period of electrode fingers in narrow pitch electrode finger portion B> Period of electrode fingers in narrow pitch electrode finger portion C Or cycle of electrode fingers in narrow pitch electrode finger portion A> cycle of electrode fingers in narrow pitch electrode finger portion D 3) cycle of electrode fingers in main electrode finger portions of first and fifth IDT electrodes 11a and 11e < Period of electrode fingers in the main electrode finger portion of the third IDT electrode 11c

Configuration 5 (corresponding to a modification of the second embodiment in the second specific aspect)
1) Number of electrode fingers in narrow pitch electrode finger portion A> Number of electrode fingers in narrow pitch electrode finger portion D 2) Period of electrode fingers in narrow pitch electrode finger portion B> Period of electrode fingers in narrow pitch electrode finger portion C Or cycle of electrode fingers in narrow pitch electrode finger portion A> cycle of electrode fingers in narrow pitch electrode finger portion D 3) cycle of electrode fingers in main electrode finger portions of first and fifth IDT electrodes 11a and 11e < Period of electrode fingers in the main electrode finger portion of the third IDT electrode 11c

Configuration 6 (corresponding to a modification of the third embodiment in the second specific aspect)
1) Number of electrode fingers in narrow pitch electrode finger portion B> Number of electrode fingers in narrow pitch electrode finger portion C 2) Number of electrode fingers in narrow pitch electrode finger portion A> Number of electrode fingers in narrow pitch electrode finger portion D 3) Period of electrode finger in narrow pitch electrode finger part B> Period of electrode finger in narrow pitch electrode finger part C 4) Period of electrode finger in narrow pitch electrode finger part A> Period of electrode finger in narrow pitch electrode finger part D 5) Period of electrode fingers in main electrode finger portions of first and fifth IDT electrodes 11a and 11e <Cycle of electrode fingers in main electrode finger portions of third IDT electrode 11c

The relationship between the number of electrode fingers and the period in the acoustic wave filter device according to the present invention will be summarized with reference to FIG. As shown in FIG. 3, a first IDT electrode 11a and a region formed from the central portion of the second IDT electrode 11b in the elastic wave propagation direction to the first IDT electrode 11a side portion are defined as a first region. A portion of the second IDT electrode 11b on the third IDT electrode 11c side from the central portion in the elastic wave propagation direction and a portion of the third IDT electrode 11c on the second IDT electrode 11b side from the central portion in the elastic wave propagation direction A region consisting of is defined as a second region. A portion of the third IDT electrode 11c on the fourth IDT electrode 11d side from the central portion in the elastic wave propagation direction, and a portion of the fourth IDT electrode 11d on the third IDT electrode 11c side from the central portion in the elastic wave propagation direction A region consisting of is defined as a third region. Further, the fourth IDT electrode 11d is defined as a fourth region which includes a portion on the fifth IDT electrode 11e side from the central portion in the elastic wave propagation direction and the fifth IDT electrode 11e.

Summarizing the above configurations 1 to 3, in the elastic wave filter device provided in the first specific aspect, the total number of electrode fingers of the narrow pitch electrode finger portions A and B in the first region is the same as that in the second region. The total number of electrode fingers of the narrow pitch electrode fingers C and D is smaller than the total number of electrode fingers of the narrow pitch electrode fingers C and D, and the total number of electrode fingers of the narrow pitch electrode fingers C and D in the third region is More than the total number of electrode fingers A and B. Here, the total number of electrode fingers of the narrow pitch electrode finger portion in the first region and the total number of electrode fingers in the narrow pitch electrode finger portion of the fourth region are Nx and the total number of electrode fingers in the narrow pitch electrode finger portion in the second region, respectively. When the total number of electrode fingers and the total number of electrode fingers of the narrow pitch electrode finger portion in the third region are Ny, the larger number of electrode fingers out of the total number Nx of electrode fingers and the total number Ny of electrode fingers The narrow pitch electrode finger portion in the region has a larger average value of the period of the electrode fingers than the narrow pitch electrode finger portion in the region where the total number of electrode fingers is smaller, and the first IDT electrode 11a, Among the three IDT electrodes 11c and the fifth IDT electrode 11e, the IDT electrodes included in the region having the larger total number of electrode fingers are narrower than the IDT electrodes included in the region having the smaller total number of electrode fingers. Other than electrode fingers So that the period of the electrode fingers is smaller in the portion.

Summarizing the configurations 4 to 6, the elastic wave filter device provided in the second specific aspect is such that the total number of electrode fingers of the narrow pitch electrode finger portions A and B in the first region is the second region. The total number of the electrode fingers of the narrow pitch electrode fingers C and D in the third region is smaller than the total number of the electrode fingers of the narrow pitch electrode fingers C and D in the third region. The total number of electrode fingers of the parts A and B is increased. Here, the total number of electrode fingers of the narrow pitch electrode finger portions A and B in the first region and the total number of electrode fingers in the narrow pitch electrode finger portion of the fourth region are Nx, respectively, and the narrow pitch electrode in the second region When the total number of electrode fingers in the finger portion and the total number of electrode fingers in the narrow pitch electrode finger portion in the third region are Ny, the total number of electrode fingers out of the total number Nx of electrode fingers and the total number Ny of electrode fingers is The narrow pitch electrode finger portion in the larger region has a larger average value of the period of the electrode fingers than the narrow pitch electrode finger portion in the region with the smaller total number of electrode fingers, and the first IDT electrode 11a, among the third IDT electrode 11c and the fifth IDT electrode 11e, the IDT electrode included in the region with the larger total number of electrode fingers is more than the IDT electrode included in the region with the smaller total number of electrode fingers. Narrow pitch electrode So that the period of the electrode fingers is smaller in the portion other than the part.

Further, by summing up the relationship between the number and period of electrode fingers in the surface acoustic wave device provided by the first specific aspect and the second specific aspect, the electrode fingers of the narrow-pitch electrode fingers in the first region Nx, the total number of electrode fingers in the narrow pitch electrode fingers in the fourth region, and the total number of electrode fingers in the narrow pitch electrode fingers in the second region and the narrow pitch electrode fingers in the third region, respectively. The total number of electrode fingers is different from the total number Nx of electrode fingers and the total number Ny of electrode fingers, where Ny is the total number of electrode fingers. The narrow pitch electrode finger portion in the region of the first electrode has an average period of electrode fingers larger than that of the narrow pitch electrode finger portion in the region where the total number of electrode fingers is smaller, and the first IDT electrode, Third Of the IDT electrode and the fifth IDT electrode, the IDT electrode included in the region having the larger total number of electrode fingers is narrower than the IDT electrode included in the region having the smaller total number of electrode fingers. It turns out that what is necessary is just the structure by which the period of the electrode finger in parts other than an electrode finger part is made small.

DESCRIPTION OF SYMBOLS 1 ... Elastic wave filter apparatus 2 ... Piezoelectric substrate 3 ... Unbalanced terminal 4 ... 1st balanced terminal 5 ... 2nd balanced terminal 10 ... Longitudinal coupled resonator type | mold elastic wave filter part 10a ... 1st IDT electrode 10b ... 1st 2nd IDT electrode 10c ... 3rd IDT electrode 10d ... 4th IDT electrode 10e ... 5th IDT electrode 11 ... 1st longitudinal coupling resonator type elastic wave filter part 11a ... 1st IDT electrode 11b ... 2nd IDT electrode 11c ... 3rd IDT electrode 11d ... 4th IDT electrode 11e ... 5th IDT electrode 11f ... 1st reflector 11g ... 2nd reflector 12 ... 2nd longitudinally coupled resonator type elastic wave Filter part 12a ... 1st IDT electrode 12b ... 2nd IDT electrode 12c ... 3rd IDT electrode 12d ... 4th IDT electrode 12e ... 5th IDT electrode 12f ... 1st reflector 12g ... 2nd reaction Vessel

Claims (13)

1. A piezoelectric substrate;
   On the piezoelectric substrate, first to fifth IDT electrodes sequentially disposed along the elastic wave propagation direction;
   First and second reflectors disposed on both sides of the elastic wave propagation direction of the region where the first to fifth IDT electrodes are provided,
   The first to fifth IDT electrodes and the first and second reflectors constitute a longitudinally coupled resonator type acoustic wave filter unit,
   Each of the first to fifth IDT electrodes has a narrow pitch electrode finger portion having an electrode finger cycle smaller than the electrode finger cycle in the remaining portion at an end adjacent to another IDT electrode. Have
   A region composed of the first IDT electrode and a central portion of the second IDT electrode in the elastic wave propagation direction to the first IDT electrode side portion is a first region,
   The portion of the second IDT electrode on the side of the third IDT electrode from the central portion of the elastic wave propagation direction, and the portion of the third IDT electrode on the side of the second IDT electrode from the central portion of the elastic wave propagation direction The area consisting of the second area,
   The portion of the third IDT electrode on the fourth IDT electrode side from the central portion of the elastic wave propagation direction, and the portion of the fourth IDT electrode on the third IDT electrode side from the central portion of the elastic wave propagation direction A region consisting of the third region,
   When the fourth IDT electrode is a region formed by the fifth IDT electrode side portion from the center in the elastic wave propagation direction of the fourth IDT electrode and the fifth IDT electrode,
   The total number of electrode fingers of the narrow pitch electrode finger portion in the first region and the total number of electrode fingers of the narrow pitch electrode finger portion in the fourth region are Nx, respectively, and the electrode in the narrow pitch electrode finger portion in the second region When the total number of fingers and the total number of electrode fingers of the narrow pitch electrode fingers in the third region are Ny, the total number Nx of electrode fingers and the total number Ny of electrode fingers are different from each other,
   The narrow pitch electrode finger portion in the region where the total number of electrode fingers is larger among the total number Nx of electrode fingers and the total number Ny of electrode fingers, than the narrow pitch electrode finger portion in the region where the total number of electrode fingers is small, The average value of the electrode finger cycle has been increased,
   Of the first IDT electrode, the third IDT electrode, and the fifth IDT electrode, the IDT electrode included in the region where the total number of electrode fingers is larger is the smaller total number of the electrode fingers. An elastic wave filter device in which the period of the electrode fingers in a portion other than the narrow pitch electrode finger portions is made smaller than the IDT electrodes included in the region.
2. The narrow pitch electrode finger portion in the first region has a smaller total number of electrode fingers than the narrow pitch electrode finger portion in the second region,
   2. The acoustic wave filter device according to claim 1, wherein the number of electrode fingers of the narrow pitch electrode finger portion in the third region is larger than that of the narrow pitch electrode finger portion in the fourth region.
3. The number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the second IDT electrode is based on the number of electrode fingers in the narrow pitch electrode finger portion in the second region of the second IDT electrode. Has been reduced,
   The number of electrode fingers in the narrow pitch electrode finger portion on the third region side of the fourth IDT electrode is based on the number of electrode fingers in the narrow pitch electrode finger portion in the fourth region of the fourth IDT electrode. Has been a lot,
   The period of the electrode finger in the narrow pitch electrode finger portion on the first area side of the second IDT electrode is greater than the period of the electrode finger in the narrow pitch electrode finger section in the second area of the second IDT electrode. Have been made smaller,
   The period of the electrode finger in the narrow pitch electrode finger portion on the third region side of the fourth IDT electrode is greater than the cycle of the electrode finger in the narrow pitch electrode finger portion in the fourth region of the fourth IDT electrode. Has been enlarged,
   The period of the electrode finger in the portion other than the narrow pitch electrode finger portion of the third IDT electrode is made smaller than the cycle of the electrode finger in the portion other than the narrow pitch electrode finger portion of the first and fifth IDT electrodes. The elastic wave filter device according to claim 2.
4. The number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the second IDT electrode is based on the number of electrode fingers in the narrow pitch electrode finger portion in the second region of the second IDT electrode. Has been reduced,
   The number of electrode fingers in the narrow pitch electrode finger portion on the third region side of the fourth IDT electrode is based on the number of electrode fingers in the narrow pitch electrode finger portion in the fourth region of the fourth IDT electrode. Has been a lot,
   The period of the electrode finger in the narrow pitch electrode finger portion on the first region side of the first IDT electrode is greater than the cycle of the electrode finger in the narrow pitch electrode finger portion in the second region of the third IDT electrode. Have been made smaller,
   The period of the electrode finger in the narrow pitch electrode finger portion on the third region side of the third IDT electrode is greater than the cycle of the electrode finger in the narrow pitch electrode finger portion in the fourth region of the fifth IDT electrode. Has been enlarged,
   The period of the electrode finger in the portion other than the narrow pitch electrode finger portion of the third IDT electrode is made smaller than the cycle of the electrode finger in the portion other than the narrow pitch electrode finger portion of the first and fifth IDT electrodes. The elastic wave filter device according to claim 2.
5. The number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the first IDT electrode is greater than the number of electrode fingers in the narrow pitch electrode finger portion in the second region of the third IDT electrode. Has been reduced,
   The number of electrode fingers in the narrow pitch electrode finger portion on the third region side of the third IDT electrode is based on the number of electrode fingers in the narrow pitch electrode finger portion in the fourth region of the fifth IDT electrode. Has been a lot,
   The period of the electrode finger in the narrow pitch electrode finger portion on the first area side of the second IDT electrode is greater than the period of the electrode finger in the narrow pitch electrode finger section in the second area of the second IDT electrode. Have been made smaller,
   The period of the electrode finger in the narrow pitch electrode finger portion on the third region side of the fourth IDT electrode is greater than the cycle of the electrode finger in the narrow pitch electrode finger portion in the fourth region of the fourth IDT electrode. Has been enlarged,
   The period of the electrode finger in the portion other than the narrow pitch electrode finger portion of the third IDT electrode is made smaller than the cycle of the electrode finger in the portion other than the narrow pitch electrode finger portion of the first and fifth IDT electrodes. The elastic wave filter device according to claim 2.
6. The number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the first IDT electrode is greater than the number of electrode fingers in the narrow pitch electrode finger portion in the second region of the third IDT electrode. Has been reduced,
   The number of electrode fingers in the narrow pitch electrode finger portion on the third region side of the third IDT electrode is based on the number of electrode fingers in the narrow pitch electrode finger portion in the fourth region of the fifth IDT electrode. Has been a lot,
   The period of the electrode finger in the narrow pitch electrode finger portion on the first region side of the first IDT electrode is greater than the cycle of the electrode finger in the narrow pitch electrode finger portion in the second region of the third IDT electrode. Have been made smaller,
   The period of the electrode finger in the narrow pitch electrode finger portion on the third region side of the third IDT electrode is greater than the cycle of the electrode finger in the narrow pitch electrode finger portion in the fourth region of the fifth IDT electrode. Has been enlarged,
   The period of the electrode finger in the portion other than the narrow pitch electrode finger portion of the third IDT electrode is made smaller than the cycle of the electrode finger in the portion other than the narrow pitch electrode finger portion of the first and fifth IDT electrodes. The elastic wave filter device according to claim 2.
7. The number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the first IDT electrode is greater than the number of electrode fingers in the narrow pitch electrode finger portion in the second region of the third IDT electrode. Has been reduced,
   The number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the second IDT electrode is based on the number of electrode fingers in the narrow pitch electrode finger portion in the second region of the second IDT electrode. Has been reduced,
   The number of electrode fingers in the narrow pitch electrode finger portion on the third region side of the fourth IDT electrode is based on the number of electrode fingers in the narrow pitch electrode finger portion in the fourth region of the fourth IDT electrode. Has been a lot,
   The number of electrode fingers in the narrow pitch electrode finger portion on the third region side of the third IDT electrode is based on the number of electrode fingers in the narrow pitch electrode finger portion in the fourth region of the fifth IDT electrode. Has been a lot,
   The period of the electrode finger in the narrow pitch electrode finger portion on the first region side of the first IDT electrode is greater than the cycle of the electrode finger in the narrow pitch electrode finger portion in the second region of the third IDT electrode. Have been made smaller,
   The period of the electrode finger in the narrow pitch electrode finger portion on the first area side of the second IDT electrode is greater than the period of the electrode finger in the narrow pitch electrode finger section in the second area of the second IDT electrode. Have been made smaller,
   The period of the electrode finger in the narrow pitch electrode finger portion on the third region side of the fourth IDT electrode is greater than the cycle of the electrode finger in the narrow pitch electrode finger portion in the fourth region of the fourth IDT electrode. Has been enlarged,
   The period of the electrode finger in the narrow pitch electrode finger portion on the third region side of the third IDT electrode is greater than the cycle of the electrode finger in the narrow pitch electrode finger portion in the fourth region of the fifth IDT electrode. Has been enlarged,
   The period of the electrode finger in the portion other than the narrow pitch electrode finger portion of the third IDT electrode is made smaller than the cycle of the electrode finger in the portion other than the narrow pitch electrode finger portion of the first and fifth IDT electrodes. The elastic wave filter device according to claim 2.
8. The narrow pitch electrode fingers in the first region have a greater total number of electrode fingers than the narrow pitch electrode fingers in the second region,
   2. The acoustic wave filter device according to claim 1, wherein the narrow pitch electrode finger portion in the third region has a smaller total number of electrode fingers than the narrow pitch electrode finger portion in the fourth region.
9. The number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the second IDT electrode is based on the number of electrode fingers in the narrow pitch electrode finger portion in the second region of the second IDT electrode. Has been a lot,
   The number of electrode fingers in the narrow pitch electrode finger portion on the third region side of the fourth IDT electrode is based on the number of electrode fingers in the narrow pitch electrode finger portion in the fourth region of the fourth IDT electrode. Has been reduced,
   The period of the electrode finger in the narrow pitch electrode finger portion on the first area side of the second IDT electrode is greater than the period of the electrode finger in the narrow pitch electrode finger section in the second area of the second IDT electrode. Has been enlarged,
   The period of the electrode finger in the narrow pitch electrode finger portion on the third region side of the fourth IDT electrode is greater than the cycle of the electrode finger in the narrow pitch electrode finger portion in the fourth region of the fourth IDT electrode. Have been made smaller,
   The period of the electrode finger in the portion other than the narrow pitch electrode finger portion of the third IDT electrode is made larger than the cycle of the electrode finger in the portion other than the narrow pitch electrode finger portion of the first and fifth IDT electrodes. The elastic wave filter device according to claim 8.
10. The number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the second IDT electrode is based on the number of electrode fingers in the narrow pitch electrode finger portion in the second region of the second IDT electrode. Has been a lot,
    The number of electrode fingers in the narrow pitch electrode finger portion on the third region side of the fourth IDT electrode is based on the number of electrode fingers in the narrow pitch electrode finger portion in the fourth region of the fourth IDT electrode. Has been reduced,
    The period of the electrode finger in the narrow pitch electrode finger portion on the first region side of the first IDT electrode is greater than the cycle of the electrode finger in the narrow pitch electrode finger portion in the second region of the third IDT electrode. Has been enlarged,
    The period of the electrode finger in the narrow pitch electrode finger portion on the third region side of the third IDT electrode is greater than the cycle of the electrode finger in the narrow pitch electrode finger portion in the fourth region of the fifth IDT electrode. Have been made smaller,
    The period of the electrode finger in the portion other than the narrow pitch electrode finger portion of the third IDT electrode is made larger than the cycle of the electrode finger in the portion other than the narrow pitch electrode finger portion of the first and fifth IDT electrodes. The elastic wave filter device according to claim 8.
11. The number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the first IDT electrode is greater than the number of electrode fingers in the narrow pitch electrode finger portion in the second region of the third IDT electrode. Many have been
    The number of electrode fingers in the narrow pitch electrode finger portion on the third region side of the third IDT electrode is based on the number of electrode fingers in the narrow pitch electrode finger portion in the fourth region of the fifth IDT electrode. Has been reduced,
    The period of the electrode finger in the narrow pitch electrode finger portion on the first area side of the second IDT electrode is greater than the period of the electrode finger in the narrow pitch electrode finger section in the second area of the second IDT electrode. Has been enlarged,
    The period of the electrode finger in the narrow pitch electrode finger portion on the third region side of the fourth IDT electrode is greater than the cycle of the electrode finger in the narrow pitch electrode finger portion in the fourth region of the fourth IDT electrode. Have been made smaller,
    The period of the electrode finger in the portion other than the narrow pitch electrode finger portion of the third IDT electrode is made larger than the cycle of the electrode finger in the portion other than the narrow pitch electrode finger portion of the first and fifth IDT electrodes. The elastic wave filter device according to claim 8.
12. The number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the first IDT electrode is greater than the number of electrode fingers in the narrow pitch electrode finger portion in the second region of the third IDT electrode. Many have been
    The number of electrode fingers in the narrow pitch electrode finger portion on the third region side of the third IDT electrode is based on the number of electrode fingers in the narrow pitch electrode finger portion in the fourth region of the fifth IDT electrode. Has been reduced,
    The period of the electrode finger in the narrow pitch electrode finger portion on the first region side of the first IDT electrode is greater than the cycle of the electrode finger in the narrow pitch electrode finger portion in the second region of the third IDT electrode. Has been enlarged,
    The period of the electrode finger in the narrow pitch electrode finger portion on the third region side of the third IDT electrode is greater than the cycle of the electrode finger in the narrow pitch electrode finger portion in the fourth region of the fifth IDT electrode. Have been made smaller,
    The period of the electrode finger in the portion other than the narrow pitch electrode finger portion of the third IDT electrode is made larger than the cycle of the electrode finger in the portion other than the narrow pitch electrode finger portion of the first and fifth IDT electrodes. The elastic wave filter device according to claim 8.
13. The number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the first IDT electrode is greater than the number of electrode fingers in the narrow pitch electrode finger portion in the second region of the third IDT electrode. Many have been
    The number of electrode fingers in the narrow pitch electrode finger portion on the first region side of the second IDT electrode is based on the number of electrode fingers in the narrow pitch electrode finger portion in the second region of the second IDT electrode. Has been a lot,
    The number of electrode fingers in the narrow pitch electrode finger portion on the third region side of the fourth IDT electrode is based on the number of electrode fingers in the narrow pitch electrode finger portion in the fourth region of the fourth IDT electrode. Has been reduced,
    The number of electrode fingers in the narrow pitch electrode finger portion on the third region side of the third IDT electrode is based on the number of electrode fingers in the narrow pitch electrode finger portion in the fourth region of the fifth IDT electrode. Has been reduced,
    The period of the electrode finger in the narrow pitch electrode finger portion on the first region side of the first IDT electrode is greater than the cycle of the electrode finger in the narrow pitch electrode finger portion in the second region of the third IDT electrode. Has been enlarged,
    The period of the electrode finger in the narrow pitch electrode finger portion on the first area side of the second IDT electrode is greater than the period of the electrode finger in the narrow pitch electrode finger section in the second area of the second IDT electrode. Has been enlarged,
    The period of the electrode finger in the narrow pitch electrode finger portion on the third region side of the fourth IDT electrode is greater than the cycle of the electrode finger in the narrow pitch electrode finger portion in the fourth region of the fourth IDT electrode. Have been made smaller,
    The period of the electrode finger in the narrow pitch electrode finger portion on the third region side of the third IDT electrode is greater than the cycle of the electrode finger in the narrow pitch electrode finger portion in the fourth region of the fifth IDT electrode. Have been made smaller,
    The period of the electrode finger in the portion other than the narrow pitch electrode finger portion of the third IDT electrode is made larger than the cycle of the electrode finger in the portion other than the narrow pitch electrode finger portion of the first and fifth IDT electrodes. The elastic wave filter device according to claim 8.
    

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