JP2022026850A - Filter and multiplexer - Google Patents

Abstract

To provide a filter capable of reducing an insertion loss.SOLUTION: A filter includes: one or a plurality of serial resonators connected to a path between an input terminal and an output terminal in serial; a plurality of electrode fingers 31a and 31b in which one end is connected to the path, the other end is connected to a ground, and which is arranged in a first arrangement direction; and bus bars 32a and 32b to which the plurality of electrode fingers 31a and 31b. The plurality of electrode fingers 31a and 31b contains a pair of comb-type electrodes 34a and 34b which is differently faced each other in at least one part, respectively. In a first parallel resonator of which an average interval of the plurality of electrode fingers 31a and 31b is the minimum, virtual straight liners 50ba and 50bb connecting a tip of the plurality of electrode fingers 31a of one comb-type electrode 34a of the pair of comb-type electrodes are inclined and extended to a first arrangement direction. At least one parallel resonator other than the first parallel resonator, comprises a plurality of parallel resonators in which straight liners 60a and 60b are extended so as to be nearly matched to the first arrangement direction.SELECTED DRAWING: Figure 2

Description

The present invention relates to filters and multiplexers.

In wireless communication devices such as smartphones, elastic wave resonators are used for filters and multiplexers. The elastic wave resonator has a pair of comb-shaped electrodes and a pair of reflectors on a piezoelectric substrate. The comb-shaped electrode has a plurality of electrode fingers and a bus bar to which the plurality of electrode fingers are connected. The reflector reflects elastic waves excited by the pair of comb-shaped electrodes and confine them in the pair of comb-shaped electrodes. It is known that the crossing region where the electrode fingers of the comb-shaped electrode intersect is inclined from the propagation direction of the elastic wave excited by the electrode fingers (for example, Patent Document 1).

International Publication No. 2015/064238

According to the elastic wave resonator described in Patent Document 1, transverse mode spurious is suppressed by inclining the crossing region where the electrode fingers of the comb-shaped electrode intersect from the propagation direction of the elastic wave. However, when a filter is formed by using such an elastic wave resonator for a series resonator and a parallel resonator, spurious emission is suppressed, but insertion loss may increase.

The present invention has been made in view of the above problems, and an object of the present invention is to reduce insertion loss.

The present invention comprises one or more series resonators connected in series in the path between the input and output terminals, one end connected to the path and the other end connected to the ground, in the first array direction. A pair of first combs having a plurality of first electrode fingers arranged and a first bus bar to which the plurality of first electrode fingers are connected, and the plurality of first electrode fingers alternately facing each other at least in a part thereof. The first parallel resonator containing each type electrode and having the smallest average distance between the plurality of first electrode fingers is the plurality of first electrodes of the first comb type electrode of one of the pair of first comb type electrodes. A virtual first straight line connecting the tips of the fingers is inclined and extended with respect to the first arrangement direction, and in at least one parallel resonator other than the first parallel resonator, the first straight line is the first. It is a filter including a plurality of parallel resonators extending substantially in line with each other in the arrangement direction.

In the above configuration, in the second parallel resonator having the largest average spacing of at least the plurality of first electrode fingers among the plurality of parallel resonators, the first straight line extends substantially in agreement with the first arrangement direction. It can be configured.

In the above configuration, all of the parallel resonators other than the second parallel resonator among the plurality of parallel resonators can be configured such that the first straight line is inclined and extended with respect to the first arrangement direction. ..

In the above configuration, all of the parallel resonators other than the first parallel resonator among the plurality of parallel resonators can be configured such that the first straight line substantially coincides with the first arrangement direction and extends.

In the above configuration, in the parallel resonator having a resonance frequency higher than the reference, the first straight line is the first, with respect to the portion having the largest interval among the intervals of the adjacent resonance frequencies of the plurality of parallel resonators. A parallel resonator that is inclined with respect to the arrangement direction and has a resonance frequency lower than that of the reference can be configured such that the first straight line substantially coincides with the first arrangement direction and extends.

In the above configuration, the first parallel resonator may be configured to be connected between the input terminal and the output terminal other than the first stage closest to the input terminal and the final stage closest to the output terminal. ..

In the above configuration, the pair of first comb-shaped electrodes may have no dummy electrode finger connected to the first bus bar.

In the above configuration, the pair of first comb-shaped electrodes may have a dummy electrode finger connected to the first bus bar.

In the above configuration, the one or more series resonators each have a plurality of second electrode fingers arranged in the second arrangement direction and a second bus bar to which the plurality of second electrode fingers are connected, and at least a part thereof. Includes a pair of second comb-shaped electrodes in which the plurality of second electrode fingers are alternately opposed to each other, and the plurality of second electrode fingers of the second comb-shaped electrode of one of the pair of second comb-shaped electrodes. The virtual second straight line connecting the tips of the above can be configured to be inclined and extended with respect to the second arrangement direction.

The present invention is a multiplexer including the filters described above.

According to the present invention, the insertion loss can be reduced.

FIG. 1 is a circuit diagram of a filter. FIG. 2 is a plan view of the first elastic wave resonator used in the filter. FIG. 3 is a cross-sectional view of the first elastic wave resonator. FIG. 4 is a plan view of the second elastic wave resonator used in the filter. 5 (a) is a diagram showing the passing characteristics of the filters of Example 1, Comparative Example 1, and Comparative Example 2, and FIG. 5 (b) is an enlarged view of the region A of FIG. 5 (a). FIG. 6 is a diagram showing the frequency characteristics of Real (Y) of the first elastic wave resonator and the second elastic wave resonator. FIG. 7A is a diagram showing the passage characteristics of the parallel resonators P1 to P4 in the filter of the first embodiment, and FIG. 7B is a diagram showing the passage characteristics of the series resonators S1 to S3. FIG. 8A is a plan view of the third elastic wave resonator used for the filter, and FIG. 8B is a plan view of the fourth elastic wave resonator. 9 (a) is a plan view of the fifth elastic wave resonator used for the filter, and FIG. 9 (b) is a plan view of the sixth elastic wave resonator. 10 (a) to 10 (e) are cross-sectional views showing another example of the substrate. 11 (a) is a diagram showing the passing characteristics of the filters of Example 2 and Comparative Example 3, and FIG. 11 (b) is an enlarged view of the region A of FIG. 11 (a). FIG. 12A is a diagram showing the passage characteristics of the parallel resonators P1 to P4 in the filter of the second embodiment, and FIG. 12B is a diagram showing the passage characteristics of the series resonators S1 to S3. FIG. 13 is a diagram showing the pass characteristics of the filters of Example 3 and Comparative Example 4 and the pass characteristics of the parallel resonators P1 to P4 and the series resonators S1 to S3 in the filter of Example 3. FIG. 14 is a circuit diagram of the duplexer according to the fourth embodiment.

Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of a filter. As shown in FIG. 1, in the filter 100, one or a plurality of series resonators S1 to S3 are connected in series in the path between the input terminal Tin and the output terminal Tout. A plurality of parallel resonators P1 to P4 are connected in parallel between the input terminal Tin and the output terminal Tout. One end of the parallel resonators P1 to P4 is connected to the path between the input terminal Tin and the output terminal Tout, and the other end is connected to the ground terminal.

FIG. 2 is a plan view of the first elastic wave resonator used in the filter. The arrangement direction of the electrode fingers is the X direction, the extension direction of the electrode fingers is the Y direction, and the normal direction of the piezoelectric substrate is the Z direction. The X-direction, Y-direction, and Z-direction are not necessarily the crystal orientations of the piezoelectric substrate, but when the piezoelectric substrate is a rotating Y-cut X-propagation substrate, the X-direction is the X-axis orientation of the crystal orientation.

As shown in FIG. 2, the first surface acoustic wave resonator 11 is a 1-port surface acoustic wave resonator, and an IDT (InterDigital Transducer) 30 and a reflector 40 are provided on the substrate 20. Reflectors 40 are provided on both sides of the IDT 30 in the X direction.

The IDT 30 includes a pair of opposed comb-shaped electrodes 34a and 34b. The comb-shaped electrode 34a includes a plurality of electrode fingers 31a and a bus bar 32a. The plurality of electrode fingers 31a are connected to the bus bar 32a. Similarly, the comb-shaped electrode 34b also includes a plurality of electrode fingers 31b and a bus bar 32b. The plurality of electrode fingers 31b are connected to the bus bar 32b. The electrode finger 31a and the electrode finger 31b are provided so as to be staggered in at least a part in the X direction. The electrode finger 31a and the bus bar 32b face each other in the Y direction. There is a gap 35b between the tip of the electrode finger 31a and the bus bar 32b. The same applies to the electrode finger 31b and the bus bar 32a, the electrode finger 31b and the bus bar 32a face each other in the Y direction, and there is a gap 35a between the tip of the electrode finger 31b and the bus bar 32a. The region where the electrode finger 31a and the electrode finger 31b overlap in the Y direction is the intersection region 36.

The elastic waves excited by the electrode finger 31a of the comb-shaped electrode 34a and the electrode finger 31b of the comb-shaped electrode 34b propagate mainly in the X direction. The distance D between the electrode fingers 31a or 31b of one of the pair of comb-shaped electrodes 34a and 34b is approximately the wavelength λ of the elastic wave. The distance D between the electrode fingers 31a or 31b is approximately twice the pitch P of the electrode fingers 31a and 31b. The reflector 40 includes a plurality of electrode fingers 41 and a bus bar 42 to which the plurality of electrode fingers 41 are connected. The reflector 40 reflects elastic waves. As a result, the energy of the elastic wave is confined in the intersection region 36.

IDT30 includes two regions 37a and 37b. A virtual straight line 50a connecting the tips of the plurality of electrode fingers 31b in the region 37a and a virtual straight line 50ba connecting the tips of the plurality of electrode fingers 31a are defined. Similarly, a virtual straight line 50ab connecting the tips of the plurality of electrode fingers 31b in the region 37b and a virtual straight line 50bb connecting the tips of the plurality of electrode fingers 31a are defined. The straight lines 50a and 50ab connecting the tips of the plurality of electrode fingers 31b and the virtual straight lines 50ba and 50bb connecting the tips of the plurality of electrode fingers 31a are inclined and extended in the X direction. In other words, the virtual straight line connecting the plurality of gaps 35a and the virtual straight line connecting the plurality of gaps 35b are inclined and extended in the X direction. The straight line 50aa and the straight line 50ba in the region 37a are substantially parallel to each other, and the area between the straight line 50aa and the straight line 50ba is substantially an intersecting region 36. The straight line 50ab and the straight line 50bb in the region 37b are substantially parallel to each other, and the area between the straight line 50ab and the straight line 50bb is substantially an intersecting region 36.

It defines virtual straight lines 60a and 60b parallel to the X direction. Let θaa and θab be the angles formed by the straight line 60a and the straight line 50aa and the straight line 50ab. The angles formed by the straight line 60b and the straight line 50ba and the straight line 50bb are defined as θba and θbb. Here, θaa, θab, θba, and θbb are positive in the counterclockwise direction with respect to the straight lines 60a and 60b. In FIG. 2, θaa and θba are positive, and θab and θbb are negative. Further, θaa and θba are substantially equal, and θab and θbb are substantially equal.

FIG. 3 is a cross-sectional view of the first elastic wave resonator. As shown in FIG. 3, the substrate 20 includes a support substrate 20a, a damping layer 20b and a temperature compensation layer 20c provided on the support substrate 20a, and a piezoelectric substrate 20e bonded on the support substrate 20a by a bonding layer 20d. To prepare for. The IDT 30 and the reflector 40 are formed by a metal film 21 formed on the substrate 20.

The support substrate 20a is a single crystal sapphire substrate, a silicon substrate, a spinel substrate, a crystal substrate, a quartz substrate, an alumina substrate, a silicon carbide substrate, or the like. For example, a single crystal sapphire substrate having a thickness of 50 μm to 500 μm may be used for the support substrate 20a. The damping layer 20b is an aluminum oxide film, an aluminum nitride film, a silicon film, a silicon nitride film, a silicon carbide film, or the like. For example, an aluminum oxide film having a thickness of 0.1 μm to 10 μm may be used for the damping layer 20b. The temperature compensation layer 20c is a film formed of a material whose elastic constant has a temperature coefficient opposite to that of the piezoelectric substrate 20e, and is, for example, a silicon oxide film. For example, a silicon oxide film having a thickness of 0.1 μm to 10 μm may be used for the temperature compensation layer 20c. The bonding layer 20d is, for example, an aluminum oxide film. For example, an aluminum oxide film having a thickness of 1 nm to 20 nm may be used for the bonding layer 20d. The support substrate 20a, the damping layer 20b, the temperature compensation layer 20c, and the bonding layer 20d may not be provided.

The piezoelectric substrate 20e is, for example, a lithium tantalate substrate or a lithium niobate substrate, and is, for example, a lithium tantalate substrate or a lithium niobate substrate for rotating Y-cut X propagation. For example, a lithium tantalate substrate having a thickness of 0.5 μm to 20 μm and having a Y-cut X propagation of 36 ° to 48 ° may be used for the piezoelectric substrate 20e. The metal film 21 is, for example, an aluminum film, a copper film, or a molybdenum film. A metal film such as a titanium film or a chromium film may be provided between the aluminum film, the copper film, or the molybdenum film and the piezoelectric substrate 20e. For example, a laminated film of a titanium film having a thickness of 10 nm to 50 nm and an aluminum-copper alloy (copper: 1% by weight) film having a thickness of 70 nm to 150 nm may be used for the metal film 21. A protective film made of a silicon oxide film having a thickness of 5 nm to 30 nm may be provided so as to cover the metal film 21.

The logarithm of the electrode fingers 31a and 31b of the IDT 30 may be 20 to 300 pairs. The pitch P of the electrode fingers 31a and 31b of the IDT 30 may be 1 μm to 6 μm. The opening length (the length of the intersection region 36 in the Y direction) may be 10λ to 50λ. The duty ratio of the electrode fingers 31a and 31b of the IDT 30 may be 30% to 80%. The logarithm of the electrode fingers 41 of the reflector 40 may be 5 to 20 pairs. The pitch of the electrode fingers 41 of the reflector 40 may be 1 μm to 6 μm. The duty ratio of the electrode finger 41 of the reflector 40 may be 30% to 80%. In the first elastic wave resonator 11, θaa and θba: may be larger than 0 ° and 7 ° or less, and θab and θbb may be smaller than 0 ° and −7 ° or more.

FIG. 4 is a plan view of the second elastic wave resonator used in the filter. As shown in FIG. 4, in the second elastic wave resonator 12, the virtual straight line 50a connecting the tips of the plurality of electrode fingers 31b and the virtual straight line 50b connecting the tips of the plurality of electrode fingers 31a are substantially parallel to the X direction. Is. In other words, the virtual straight line connecting the plurality of gaps 35a and the virtual straight line connecting the plurality of gaps 35b are substantially parallel to the X direction. Since other configurations are the same as those of the first elastic wave resonator 11, the description thereof will be omitted.

[experiment]
Experiments on the passing characteristics of the filters of Example 1, Comparative Example 1, and Comparative Example 2 were performed. The filter of the first embodiment uses the first elastic wave resonator 11 of FIG. 2 for the series resonators S1 to S3 and the parallel resonator P4 in FIG. 1, and the second elastic wave resonance of FIG. 4 for the parallel resonators P1 to P3. A vessel 12 was used. As the filter of Comparative Example 1, the first elastic wave resonator 11 of FIG. 2 was used for the series resonators S1 to S3 and the parallel resonators P1 to P4. As the filter of Comparative Example 2, the first elastic wave resonator 11 of FIG. 2 was used for the series resonators S1 to S3, and the second elastic wave resonator 12 of FIG. 4 was used for the parallel resonators P1 to P4. It is summarized in Table 1.

Table 2 shows the resonance frequencies of the series resonators S1 to S3 and the parallel resonators P1 to P4 in the filters of Example 1, Comparative Example 1, and Comparative Example 2. As shown in Table 2, the resonance frequency of the series resonator S1 is 2703.6 MHz, the resonance frequency of the series resonator S2 is 2708.6 MHz, and the resonance frequency of the series resonator S3 is 2683.6 MHz. The resonance frequency of the parallel resonator P1 was 2513.5 MHz, the resonance frequency of the parallel resonator P2 was 2518.5 MHz, the resonance frequency of the parallel resonator P3 was 2523.5 MHz, and the resonance frequency of the parallel resonator P4 was 2548.5 MHz. Since the resonance frequency correlates with the average distance D of the electrode fingers, the average distance D of the electrode fingers differs between the series resonators S1 and S3, and the series resonator S3, the series resonator S1 and the series resonator S2 are averaged in this order. The interval D is small. The parallel resonators P1 to P4 also have different average distances D between the electrode fingers, and the average distance D decreases in the order of the parallel resonator P1, the parallel resonator P2, the parallel resonator P3, and the parallel resonator P4.

An experiment was conducted with the configurations of the first elastic wave resonator 11 and the second elastic wave resonator 12 as follows.
Board 20
Support substrate 20a: Sapphire substrate with a thickness of 500 μm Damping layer 20b: Aluminum oxide film with a thickness of 450 nm Temperature compensation layer 20c: Silicon oxide film with a thickness of 450 nm Bonding layer 20d: Aluminum oxide film with a thickness of 10 nm piezoelectric substrate 20e: 42 ° Y-cut X-propagated lithium tartrate substrate IDT30 and reflector 40 with a thickness of 750 nm
Metal film 21: Titanium film with a thickness of 50 nm from the piezoelectric substrate 20e side, aluminum-copper alloy (copper: 1% by weight) film with a thickness of 104 nm Protective film on the metal film 21: Silicon oxide film with a thickness of 15 nm 1 The elastic wave resonator 11 θaa and θba: 7 °, θab and θbb: −7 °

5 (a) is a diagram showing the passing characteristics of the filters of Example 1, Comparative Example 1, and Comparative Example 2, and FIG. 5 (b) is an enlarged view of the region A of FIG. 5 (a). The horizontal axis of FIGS. 5A and 5B is the frequency [MHz], and the vertical axis is the attenuation amount [dB]. The amount of attenuation is the magnitude of S21. As shown in FIGS. 5A and 5B, in Comparative Example 2, spurious is generated at the position of the arrow on the low frequency side of the pass band. This spurious is considered to correspond to a transverse mode spurious caused by an elastic wave propagating in the Y direction. It is considered that the spurious was generated in Comparative Example 2 because the second elastic wave resonator 12 in which the straight lines 50a and 50b are substantially parallel in the X direction was used for the parallel resonators P1 to P4 in Comparative Example 2. Be done. On the other hand, in Example 1 and Comparative Example 1, the generation of spurious on the low frequency side of the pass band is suppressed. This is because the first elastic wave resonator 11 in which the straight lines 50aa, 50ab, 50ba, and 50bb are inclined from the X direction is used for the parallel resonator P4 in the first embodiment and for the parallel resonators P1 to P4 in the comparative example 1. Is considered to be.

In both Example 1 and Comparative Example 1, the generation of spurious is suppressed, but in Comparative Example 1, the insertion loss on the high frequency side in the pass band is large, whereas in Example 1, the insertion loss is reduced.

FIG. 6 is a diagram showing the frequency characteristics of Real (Y) of the first elastic wave resonator and the second elastic wave resonator. The horizontal axis of FIG. 6 is the frequency [MHz], and the vertical axis is Real (Y) [S]. Real (Y) is the real part of S11's admittance. An experiment was conducted with the configurations of the first elastic wave resonator 11 and the second elastic wave resonator 12 as follows.
Board 20
Support substrate 20a: Sapphire substrate with a thickness of 500 μm Damping layer 20b: Aluminum oxide film with a thickness of 450 nm Temperature compensation layer 20c: Silicon oxide film with a thickness of 450 nm Bonding layer 20d: Aluminum oxide film with a thickness of 10 nm piezoelectric substrate 20e: 42 ° Y-cut X-propagated lithium tartrate substrate IDT30 and reflector 40 with a thickness of 750 nm
Metal film 21: Titanium film with a thickness of 50 nm from the piezoelectric substrate 20e side, aluminum-copper alloy (copper: 1% by weight) film with a thickness of 104 nm Protective film on the metal film 21: Silicon oxide film with a thickness of 15 nm IDT30 Log: 120 vs IDT30 pitch P: 1.48 μm
Aperture length (Y direction length of intersection region 36): 41.82λ
IDT30 duty ratio: 55%
Logarithm of reflector 40: 11 pairs Pitch of reflector 40: 1.48 μm
Duty ratio of reflector 40: 55%
Θaa and θba: 7 °, θab and θbb: −7 ° of the first elastic wave resonator 11.

As shown in FIG. 6, spurious is generated in the second elastic wave resonator 12 at a frequency from the resonance frequency to the antiresonance frequency. Therefore, in FIGS. 5 (a) and 5 (b), in the filter of Comparative Example 2 in which the second elastic wave resonator 12 is used for the parallel resonators P1 to P4, spurious is generated on the low frequency side of the pass band. It is believed that it was done. On the other hand, in the first elastic wave resonator 11, spurious generation is suppressed at a frequency from the resonance frequency to the antiresonance frequency. Therefore, in FIGS. 5 (a) and 5 (b), the filter of Example 1 in which the first elastic wave resonator 11 is used for the parallel resonator P4 and the first elastic wave resonator for the parallel resonators P1 to P4. It is considered that the filter of Comparative Example 1 using 11 suppressed the generation of spurious on the low frequency side of the passing band.

As shown in FIG. 6, the first elastic wave resonator 11 has a larger loss at a frequency higher than the antiresonance frequency as compared with the second elastic wave resonator 12. This is because the piezoelectric substrate 20e is an anisotropic substance, so that the straight lines 50aa, 50ab, 50ba, and 50bb are inclined from the X direction, that is, the intersecting region 36 is inclined from the propagation direction of the elastic wave. Conceivable. Therefore, in FIGS. 5 (a) and 5 (b), the filter of Comparative Example 1 in which the first elastic wave resonator 11 is used for the parallel resonators P1 to P4 suppresses the generation of spurious, but passes through. It is considered that the insertion loss on the high frequency side in the band increased.

FIG. 7A is a diagram showing the passage characteristics of the parallel resonators P1 to P4 in the filter of the first embodiment, and FIG. 7B is a diagram showing the passage characteristics of the series resonators S1 to S3. The horizontal axis of FIGS. 7A and 7B is the frequency [MHz], and the vertical axis is the attenuation amount [dB]. In FIGS. 7 (a) and 7 (b), the passing characteristics of the filter of the first embodiment are shown by dotted lines.

As shown in FIGS. 7A and 2 in the parallel resonators P1 to P4, the resonance frequency is on the lower frequency side of the pass band of the filter, and the loss on the higher frequency side than near the anti-resonance frequency is within the pass band of the filter. Affects the insertion loss on the high frequency side of. Here, the resonance frequencies of the parallel resonators P1 to P4 are higher in the order of P1, P2, P3, and P4, and the parallel resonator P4 having the highest resonance frequency is anti-resonant as compared with the other parallel resonators P1 to P3. The effect of the loss on the high frequency side of the frequency on the insertion loss on the high frequency side in the pass band of the filter is small. Further, since the pass characteristic of the parallel resonator P4 having the highest resonance frequency is located near the shoulder on the low frequency side of the pass band of the filter, the low frequency of the pass band of the filter when spurious occurs in the parallel resonator P4. Spurious is likely to be generated on the side. Therefore, in FIGS. 5 (a) and 5 (b), in the filter of the first embodiment, the second elastic wave resonance occurs from the parallel resonators P1 to P3, which have a large influence on the insertion loss on the high frequency side in the pass band. It is considered that the instrument 12 was used, and the insertion loss on the high frequency side in the pass band was suppressed by this. Further, it is considered that the first elastic wave resonator 11 is used for the parallel resonator P4, which has a large influence on the spirit on the low frequency side of the pass band, and that this suppresses the generation of spurious on the low frequency side of the pass band. Be done.

As shown in FIGS. 7 (b) and Table 2, in the series resonators S1 to S3, the resonance frequency is in the pass band of the filter, and the antiresonance frequency is on the high frequency side of the pass band of the filter. Therefore, in the series resonators S1 to S3, even if the loss becomes large at a frequency higher than the antiresonance frequency, there is almost no influence on the insertion loss in the pass band of the filter. Therefore, it is preferable to use a first elastic wave resonator 11 for the series resonators S1 to S3 to suppress the generation of spurious.

[Other examples of elastic wave resonators used in filters]
FIG. 8A is a plan view of the third elastic wave resonator used for the filter, and FIG. 8B is a plan view of the fourth elastic wave resonator. 9 (a) is a plan view of the fifth elastic wave resonator used for the filter, and FIG. 9 (b) is a plan view of the sixth elastic wave resonator.

As shown in FIG. 8A, in the third elastic wave resonator 13, the bus bar 42 of the reflector 40 extends substantially in the X direction. Since other configurations are the same as those of the first elastic wave resonator 11, the description thereof will be omitted. In the first elastic wave resonator 11, the reflector 40 is provided so that the bus bar 42 is inclined and extends in the X direction. However, like the third elastic wave resonator 13, the reflector 40 is provided by the bus bar 42. By providing the third elastic wave resonator 13 so as to extend so as to substantially coincide with the X direction, the size of the third elastic wave resonator 13 in the Y direction can be made smaller than that of the first elastic wave resonator 11.

As shown in FIG. 8B, in the fourth elastic wave resonator 14, the straight line 50a connecting the tips of the plurality of electrode fingers 31b is inclined with respect to the straight line 60a, and the straight line 50b connecting the tips of the plurality of electrode fingers 31a is a straight line. It is inclined with respect to 60b. The angle θa formed by the straight line 50a and the straight line 60a and the angle θb formed by the straight line 50b and the straight line 60b are constant within the IDT 30. Since other configurations are the same as those of the first elastic wave resonator 11, the description thereof will be omitted. Similarly to the third elastic wave resonator 13, the fourth elastic wave resonator 14 may be provided with the reflector 40 so as to extend so that the bus bar 42 substantially coincides with the X direction.

As shown in FIG. 9A, in the fifth elastic wave resonator 15, the comb-shaped electrode 34a includes a plurality of electrode fingers 31a, a plurality of dummy electrode fingers 33a, and a bus bar 32a. The plurality of electrode fingers 31a and the plurality of dummy electrode fingers 33a are connected to the bus bar 32a. Similarly, the comb-shaped electrode 34b includes a plurality of electrode fingers 31b, a plurality of dummy electrode fingers 33b, and a bus bar 32b. The plurality of electrode fingers 31b and the plurality of dummy electrode fingers 33b are connected to the bus bar 32b. The electrode finger 31a and the dummy electrode finger 33b face each other in the Y direction. The gap 35b is between the tip of the electrode finger 31a and the tip of the dummy electrode finger 33b. The same applies to the electrode finger 31b and the dummy electrode finger 33a. The electrode finger 31b and the dummy electrode finger 33a face each other in the Y direction, and a gap 35a is provided between the tip of the electrode finger 31b and the tip of the dummy electrode finger 33a. Since other configurations are the same as those of the first elastic wave resonator 11, the description thereof will be omitted.

As shown in FIG. 9B, in the sixth elastic wave resonator 16, the straight line 50a connecting the tips of the plurality of electrode fingers 31b is inclined with respect to the straight line 60a, and the straight line 50b connecting the tips of the plurality of electrode fingers 31a is a straight line. It is inclined with respect to 60b. The angle θa formed by the straight line 50a and the straight line 60a and the angle θb formed by the straight line 50b and the straight line 60b are constant within the IDT 30. Since other configurations are the same as those of the fifth elastic wave resonator 15, the description thereof will be omitted.

In the fifth elastic wave resonator 15 and the sixth elastic wave resonator 16, similarly to the third elastic wave resonator 13, even if the reflector 40 is provided so that the bus bar 42 extends substantially in the X direction. good.

As the resonator for suppressing the transverse mode spurious, any one of the third elastic wave resonator 13 to the sixth elastic wave resonator 16 may be used instead of the first elastic wave resonator 11.

[Other examples of boards]
10 (a) to 10 (e) are cross-sectional views showing another example of the substrate. As shown in FIG. 10A, the interface 70 between the support substrate 20a and the damping layer 20b may have irregularities. The unevenness may be formed regularly or may be irregular. The arithmetic mean roughness Ra of the interface 70 may be 10 nm or more and 1000 nm or less, 50 nm or more and 500 nm or less, or 100 nm or more and 300 nm or less. As shown in FIG. 10B, in addition to the interface 70 between the support substrate 20a and the damping layer 20b, the interface 71 between the damping layer 20b and the temperature compensation layer 20c may also have irregularities. As shown in FIG. 10C, the damping layer may not be provided between the support substrate 20a and the temperature compensation layer 20c. As shown in FIG. 10D, the interface 72 between the support substrate 20a and the temperature compensation layer 20c may have irregularities. As shown in FIG. 10 (e), the damping layer, the temperature compensation layer, and the bonding layer may not be provided between the support substrate 20a and the piezoelectric substrate 20e.

According to the filter of the first embodiment, the first elastic wave resonator 11, the third elastic wave resonator 13, and the fourth elastic wave resonance are added to the parallel resonator P4 having the highest resonance frequency among the plurality of parallel resonators P1 to P4. A device 14, a fifth elastic wave resonator 15, or a sixth elastic wave resonator 16 is used, and a second elastic wave resonator 12 is used for at least one parallel resonator other than the parallel resonator P4. In other words, among the plurality of parallel resonators P1 to P4, the parallel resonator P4 having the smallest average distance D of the plurality of electrode fingers 31a or 31b has the first elastic wave resonator 11, the third elastic wave resonator 13, and the fourth. An elastic wave resonator 14, a fifth elastic wave resonator 15, or a sixth elastic wave resonator 16 is used, and a second elastic wave resonator 12 is used for at least one parallel resonator other than the parallel resonator P4. The first elastic wave resonator 11, the third elastic wave resonator 13, the fourth elastic wave resonator 14, the fifth elastic wave resonator 15, or the sixth elastic wave resonator 16 are straight lines 50aa, 50ab, 50ba, 50bb, The 50a and 50b are resonators that are inclined and extended in the X direction, and the second elastic wave resonator 12 is a resonator in which the straight lines 50a and 50b are substantially aligned and extended in the X direction. As a result, as shown in FIGS. 5A and 5B, it is possible to reduce the insertion loss on the high frequency side in the pass band while suppressing the generation of spurious. The average distance D of the plurality of electrode fingers 31a or 31b may be calculated by dividing the length of the comb-shaped electrodes 34a or 34b in the X direction by the number of electrode fingers 31a or 31b. Further, the average distance D of the electrode fingers 31a or 31b may be obtained by dividing the length of the IDT 30 in the X direction by the logarithm of the electrode fingers 31a and 31b (1/2 of the total number of the electrode fingers 31a and 31b).

The parallel resonators P1 to P3 other than the parallel resonator P4 having the highest resonance frequency (the smallest average distance D of the electrode fingers) among the plurality of parallel resonators P1 to P4 may all be the second elastic wave resonator 12. .. As a result, the insertion loss on the high frequency side in the pass band can be effectively reduced.

As shown in Tables 1 and 2, the parallel resonator P4 having a resonance frequency higher than this reference is the first in reference to the location where the interval between the adjacent resonance frequencies of the plurality of parallel resonators P1 to P4 is the largest. The 1 elastic wave resonator 11 may be used, and the parallel resonators P1 to P3 having a resonance frequency lower than the reference may be the second elastic wave resonator 12. This makes it possible to effectively suppress spurious emissions and reduce insertion loss at the same time.

In the series resonators S1 to S3, even if the loss becomes large at a frequency higher than the antiresonance frequency, the influence on the insertion loss in the pass band of the filter is small. Therefore, in order to suppress the generation of spurious, all of the series resonators S1 to S3 have a first elastic wave resonator 11, a third elastic wave resonator 13, a fourth elastic wave resonator 14, and a fifth elastic wave resonance. The device 15 or the sixth elastic wave resonator 16 is preferable.

In the first embodiment, the first elastic wave resonator 11 is used for the parallel resonator P4 having the highest resonance frequency among the plurality of parallel resonators P1 to P4, and the remaining parallel resonators P1 to P3 other than the parallel resonator P4 are used. An example of using the second elastic wave resonator 12 is shown. In the second embodiment, the second elastic wave resonator 12 is used as the parallel resonator having the lowest resonance frequency among the plurality of parallel resonators, and the first is used for all the remaining parallel resonators including the parallel resonator having the highest resonance frequency. An example in the case of using the elastic wave resonator 11 will be described.

[experiment]
Experiments on the passing characteristics of the filters of Example 2 and Comparative Example 3 were performed. In the filters of Example 2 and Comparative Example 3, the resonance frequencies of the series resonators S1 to S3 and the parallel resonators P1 to P4 in FIG. 1 are as shown in Table 3. That is, the resonance frequency of the series resonator S1 was 2703.6 MHz, the resonance frequency of the series resonator S2 was 2683.6 MHz, and the resonance frequency of the series resonator S3 was 2708.6 MHz. The resonance frequency of the parallel resonator P1 was 2538.5 MHz, the resonance frequency of the parallel resonator P2 was 2548.5 MHz, the resonance frequency of the parallel resonator P3 was 2543.5 MHz, and the resonance frequency of the parallel resonator P4 was 2513.5 MHz. Therefore, among the parallel resonators P1 to P4, the resonator having the highest resonance frequency (the average distance D of the electrode fingers is the smallest) is the parallel resonator P2, and the resonance frequency is the lowest (the average distance D of the electrode fingers is the smallest). The large) resonator is the parallel resonator P4.

In the filter of the second embodiment, among the parallel resonators P1 to P4, the resonator having the highest resonance frequency is the parallel resonator P2, and the resonator having the lowest resonance frequency is the parallel resonator P4. The first elastic wave resonator 11 of FIG. 2 was used for the parallel resonators P1 to P3, and the second elastic wave resonator 12 of FIG. 4 was used for the parallel resonator P4. In the filter of Comparative Example 3, the first elastic wave resonator 11 of FIG. 2 was used for the series resonators S1 to S3 and the parallel resonators P1 to P4. It is summarized in Table 4.

The configurations of the first elastic wave resonator 11 and the second elastic wave resonator 12 were the same as those in the experiment shown in Example 1.

11 (a) is a diagram showing the passing characteristics of the filters of Example 2 and Comparative Example 3, and FIG. 11 (b) is an enlarged view of the region A of FIG. 11 (a). FIG. 12A is a diagram showing the passage characteristics of the parallel resonators P1 to P4 in the filter of the second embodiment, and FIG. 12B is a diagram showing the passage characteristics of the series resonators S1 to S3. The horizontal axis of FIGS. 11A to 12B is the frequency [MHz], and the vertical axis is the attenuation amount [dB]. In FIGS. 12 (a) and 12 (b), the passing characteristics of the filter of the second embodiment are shown by dotted lines.

As shown in FIGS. 11 (a) and 11 (b), in Example 2, the insertion loss on the high frequency side in the pass band is reduced as compared with Comparative Example 3. As shown in FIG. 12A, in the parallel resonator P4 having the lowest resonance frequency, a wide band on the high frequency side of the antiresonance frequency is within the pass band of the filter. Therefore, the parallel resonator P4 having the lowest resonance frequency has a greater influence on the insertion loss in the pass band of the filter than the other parallel resonators P1 to P3.

Therefore, it is preferable to use the second elastic wave resonator 12 for the parallel resonator P4 having at least the lowest resonance frequency (the largest average distance D of the electrode fingers) among the plurality of parallel resonators P1 to P4. As a result, as in the second embodiment of FIGS. 11 (a) and 11 (b), the insertion loss on the high frequency side in the pass band of the filter can be effectively reduced.

As shown in FIG. 12A, since the pass characteristics of the parallel resonators P1 to P3 are located near the shoulder on the low frequency side of the pass band of the filter, the filter is filtered when spurious is generated in the parallel resonators P1 to P3. Spurious is likely to be generated on the low frequency side of the passband. Therefore, the second elastic wave resonator 12 is used for the parallel resonator P4 having the lowest resonance frequency among the plurality of parallel resonators P1 to P4, and the parallel resonators other than the parallel resonator P4 including the parallel resonator P2 having the highest resonance frequency are used in parallel. The first elastic wave resonator 11 may be used for all of the resonators P1 to P3. As a result, spurious generation can be effectively suppressed while reducing the insertion loss on the high frequency side in the pass band of the filter.

[experiment]
An experiment of passage characteristics performed on the filters of Example 3 and Comparative Example 4 will be described. In the filters of Example 3 and Comparative Example 4, the resonance frequencies of the series resonators S1 to S3 and the parallel resonators P1 to P4 in FIG. 1 are as shown in Table 5. That is, the resonance frequency of the series resonator S1 was 2703.6 MHz, the resonance frequency of the series resonator S2 was 2683.6 MHz, and the resonance frequency of the series resonator S3 was 2708.6 MHz. The resonance frequency of the parallel resonator P1 was 2513.5 MHz, the resonance frequency of the parallel resonator P2 was 2518.5 MHz, the resonance frequency of the parallel resonator P3 was 2548.5 MHz, and the resonance frequency of the parallel resonator P4 was 2522.4 MHz. Therefore, the resonator having the lowest resonance frequency among the series resonators S1 to S3 (the average distance D between the electrode fingers is the largest) is the series resonator S2, and the resonance frequency is the highest among the parallel resonators P1 to P4 (there is the highest resonance frequency among the parallel resonators P1 to P4). The resonator (with the smallest average distance D between the electrode fingers) is the parallel resonator P3.

In the filter of the third embodiment, since the resonator having the highest resonance frequency among the parallel resonators P1 to P4 is the parallel resonator P3, the series resonators S1 to S3 and the parallel resonator P3 have the first elasticity of FIG. The wave resonator 11 was used, and the second elastic wave resonator 12 of FIG. 4 was used for the parallel resonators P1, P2, and P4. In the filter of Comparative Example 4, the first elastic wave resonator 11 of FIG. 2 was used for the series resonators S1 to S3 and the parallel resonators P1 to P4. It is summarized in Table 6.

The configurations of the first elastic wave resonator 11 and the second elastic wave resonator 12 were the same as those in the experiment shown in Example 1.

FIG. 13 is a diagram showing the pass characteristics of the filters of Example 3 and Comparative Example 4 and the pass characteristics of the parallel resonators P1 to P4 and the series resonators S1 to S3 in the filter of Example 3. The horizontal axis of FIG. 13 is the frequency [MHz], and the vertical axis is the attenuation amount [dB]. The passing characteristics of the parallel resonators P1 to P4 are shown by dotted lines, and the passing characteristics of the series resonators S1 to S3 are shown by the alternate long and short dashed line.

As shown in FIG. 13, in Example 3, the insertion loss on the high frequency side in the pass band is reduced as compared with Comparative Example 4. It is considered that this is because the second elastic wave resonator 12 was used for the parallel resonators P1, P2, and P4 in the third embodiment. Further, in Example 3, the first elastic wave resonator 11 is used for the parallel resonator P3, and in Comparative Example 4, the first elastic wave resonator 11 is used for the parallel resonators P1 to P4, so that the low frequency of the passing band is used. The generation of sprias on the side is suppressed.

In the first embodiment, the resonator having the highest resonance frequency among the plurality of parallel resonators P1 to P4 is the final-stage parallel resonator P4 connected to the output terminal Tout closest to the output terminal Tout, and the parallel resonator P4 has the first elasticity. The case where the wave resonator 11 is used and the second elastic wave resonator 12 is used for the other parallel resonators P1 to P3 is shown as an example. However, this is not the case. As in the third embodiment, the resonator having the highest resonance frequency among the plurality of parallel resonators P1 to P4 is the parallel resonator P3, the first elastic wave resonator 11 is used for the parallel resonator P3, and other parallel resonances. The second elastic wave resonator 12 may be used for the instruments P1, P2, and P4. Even in this case, it is possible to reduce the insertion loss on the high frequency side in the pass band while suppressing the generation of spurious on the low frequency side of the pass band.

Of the plurality of parallel resonators P1 to P4, the resonator having the highest resonance frequency (the average distance D between the electrode fingers is the smallest) is the first-stage parallel resonator connected closest to the input terminal Tin and the output terminal Tout. It is preferable to use a parallel resonator other than the final stage parallel resonator connected nearby. The first-stage parallel resonator is likely to receive the largest power, and the final-stage parallel resonator may receive a large reflecting electrode due to a mismatch with the antenna, so the resonance frequency is the highest (average spacing D of the electrode fingers). This is because electrostatic breakdown may occur if the parallel resonator is placed in a stage other than the first stage or the final stage. Further, among the plurality of series resonators S1 to S3, the resonator having the lowest resonance frequency (the average distance D between the electrode fingers is the largest) is the first-stage series resonator connected to the input terminal Tin closest to the output terminal Tout. It is preferable to use a series resonator other than the final stage series resonator connected to the nearest one.

FIG. 14 is a circuit diagram of the duplexer according to the fourth embodiment. As shown in FIG. 14, in the duplexer 200, a transmission filter 80 is connected between the common terminal Ant and the transmission terminal Tx. A reception filter 81 is connected between the common terminal Ant and the reception terminal Rx. The transmission filter 80 passes a signal in the transmission band among the signals input from the transmission terminal Tx to the common terminal Ant as a transmission signal, and suppresses signals of other frequencies. The reception filter 81 passes a signal in the reception band among the signals input from the common terminal Ant to the reception terminal Rx as a reception signal, and suppresses signals of other frequencies. At least one of the transmission filter 80 and the reception filter 81 can be the filters of the first to third embodiments. Although the duplexer has been described as an example as the multiplexer, a triplexer or a quadplexer may be used.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such a specific embodiment, and various modifications and variations are made within the scope of the gist of the present invention described in the claims. It can be changed.

11 1st elastic wave resonator 12 2nd elastic wave resonator 13 3rd elastic wave resonator 14 4th elastic wave resonator 15 5th elastic wave resonator 16 6th elastic wave resonator 20 Board 20a Support board 20b Damping layer 20c Temperature compensation layer 20d Bonding layer 20e Resonant substrate 21 Metal film 30 IDT
31a, 31b Electrode finger 32a, 32b Bus bar 33a, 33b Dummy electrode finger 34a, 34b Comb-shaped electrode 35a, 35b Gap 36 Crossing area 37a, 37b Area 40 Reflector 41 Electrode finger 42 Bus bar 50a, 50b, 50aa, 50ab, 50ba, 50bb straight 60a, 60b straight 70-72 interface 80 transmit filter 81 receive filter 100 filter 200 duplexer

Claims (10)

One or more series resonators connected in series in the path between the input and output terminals,
One end is connected to the path, the other end is connected to the ground, and each has a plurality of first electrode fingers arranged in the first arrangement direction and a first bus bar to which the plurality of first electrode fingers are connected. The first parallel resonator, which includes a pair of first comb-shaped electrodes in which the plurality of first electrode fingers are alternately opposed to each other and the average distance between the plurality of first electrode fingers is the smallest, is the pair. A virtual first straight line connecting the tips of the plurality of first electrode fingers of one of the first comb-shaped electrodes is inclined and extended with respect to the first arrangement direction, and the first The at least one parallel resonator other than the parallel resonator is a filter including a plurality of parallel resonators in which the first straight line extends substantially in agreement with the first arrangement direction. Claim 1 of the second parallel resonator having at least the largest average spacing of the plurality of first electrode fingers among the plurality of parallel resonators, wherein the first straight line extends substantially in accordance with the first arrangement direction. The filter described in. The filter according to claim 2, wherein all of the parallel resonators other than the second parallel resonator among the plurality of parallel resonators have the first straight line inclined and extended with respect to the first arrangement direction. The filter according to claim 1 or 2, wherein in all the parallel resonators other than the first parallel resonator among the plurality of parallel resonators, the first straight line extends substantially in agreement with the first arrangement direction. In a parallel resonator having a resonance frequency higher than the reference, the first straight line is relative to the first arrangement direction, with reference to the portion having the largest interval among the intervals of adjacent resonance frequencies of the plurality of parallel resonators. The parallel resonator having a lower resonance frequency than the reference is the one according to any one of claims 1 to 4, wherein the first straight line extends substantially in agreement with the first arrangement direction. Filter. One of claims 1 to 5, wherein the first parallel resonator is connected between the input terminal and the output terminal other than the first stage closest to the input terminal and the final stage closest to the output terminal. The filter described in the section. The filter according to any one of claims 1 to 6, wherein the pair of first comb-shaped electrodes does not have a dummy electrode finger connected to the first bus bar. The filter according to any one of claims 1 to 6, wherein the pair of first comb-shaped electrodes has a dummy electrode finger connected to the first bus bar. The one or more series resonators each have a plurality of second electrode fingers arranged in the second arrangement direction and a second bus bar to which the plurality of second electrode fingers are connected, and at least a part of the plurality of second electrode fingers. Each includes a pair of second comb-shaped electrodes in which the second electrode fingers are staggered to face each other, and connects the tips of the plurality of second electrode fingers of one of the pair of second comb-shaped electrodes. The filter according to any one of claims 1 to 8, wherein the virtual second straight line is inclined and stretched with respect to the second arrangement direction. A multiplexer including the filter according to any one of claims 1 to 9.

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