Elastic wave device and electronic module

Abstract

The invention discloses an elastic wave device and an electronic module. The elastic wave device includes: a piezoelectric substrate; a plurality of parallel resonators and a plurality of series resonators which are formed on the piezoelectric substrate and serve as band-pass filters; wherein when the pass band high-frequency end of the band-pass filter is arranged from near to far according to the anti-resonant frequency, the plurality of series resonators sequentially comprise a first series resonator, a second series resonator and a third series resonator; a duty ratio of the first series resonator is smaller than duty ratios of the second series resonator and the third series resonator. According to the elastic wave device, the frequency temperature characteristic can be improved while the chip size is not increased.

Description

Technical Field

[0001] The present invention relates to the field of electronic devices, and particularly to an elastic wave device and a module including the elastic wave device. Background Art

[0002] Patent Document 1 (International Publication No. WO2017 / 006742) discloses an elastic wave device. In this elastic wave device, the IDT electrode is covered with a silicon dioxide film, and through this silicon dioxide film, the frequency-temperature characteristics of the elastic wave device can be improved.

[0003] However, in the elastic wave device disclosed in Patent Document 1, since the IDT electrode is covered with a silicon dioxide film, many problems have arisen. For example, the chip size of the elastic wave device becomes larger. Summary of the Invention

[0004] An object of the present invention is to provide an elastic wave device and a module including the elastic wave device, which can improve the frequency-temperature characteristics without increasing the chip size.

[0005] The elastic wave device according to the present invention includes: a piezoelectric substrate; a plurality of parallel resonators and a plurality of series resonators formed on the piezoelectric substrate and serving as a band-pass filter; when arranged in the order from near to far at the high-frequency end of the passband of the band-pass filter according to the anti-resonant frequency, the plurality of series resonators sequentially include a first series resonator, a second series resonator, and a third series resonator, and the duty ratio of the first series resonator is smaller than the duty ratios of the second series resonator and the third series resonator.

[0006] In some embodiments, the duty ratio of the second series resonator is smaller than the duty ratio of the third series resonator.

[0007] In some embodiments, the difference between the duty ratio of the first series resonator and the duty ratio of the second series resonator is greater than the difference between the duty ratio of the second series resonator and the duty ratio of the third series resonator.

[0008] In some embodiments, the plurality of series resonators include four or more series resonators. When arranged in the order from near to far at the high-frequency end of the passband of the band-pass filter according to the anti-resonant frequency, the plurality of series resonators at least sequentially include a first series resonator, a second series resonator, a third series resonator, and a fourth series resonator, and the duty ratio of the third series resonator is smaller than the duty ratio of the fourth series resonator.

[0009] In some embodiments, the difference between the duty ratio of the first series resonator and the duty ratio of the second series resonator is greater than the difference between the duty ratio of the third series resonator and the duty ratio of the fourth series resonator.

[0010] In some embodiments, the difference between the duty cycle of the first series resonator and the duty cycle of the second series resonator is greater than the difference between the duty cycle of the second series resonator and the duty cycle of the fourth series resonator.

[0011] In some embodiments, the plurality of parallel resonators and the plurality of series resonators function as a transmit filter.

[0012] In some embodiments, the duty cycles of the plurality of series resonators increase in order from the lowest anti-resonant frequency to the highest anti-resonant frequency.

[0013] In some embodiments, a module including the surface acoustic wave device is also disclosed.

[0014] According to the present disclosure, a surface acoustic wave device and a module including the surface acoustic wave device can be provided, and the device can improve the frequency-temperature characteristics while preventing an increase in chip size.

[0015] Other features and advantages of the present invention will be set forth in the following description, and in part will be obvious from the description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments and descriptions thereof are used to explain the present application and do not constitute an improper limitation of the present application.

[0017] Figure 1 is a cross-sectional view of the surface acoustic wave device in Embodiment 1.

[0018] Figure 2 is an exemplary view of the surface acoustic wave element of the surface acoustic wave device in Embodiment 1.

[0019] Figure 3 is a circuit diagram corresponding to the chip substrate of the surface acoustic wave device in Embodiment 1.

[0020] Figure 4 is a schematic diagram of the frequency characteristics of the surface acoustic wave device near the high-frequency end of the passband in Embodiment 1.

[0021] Figure 5 is a circuit diagram corresponding to a modified example of the chip substrate of the surface acoustic wave device in Embodiment 1.

[0022] Figure 6 is a cross-sectional view of the module to which the surface acoustic wave device is applied in Embodiment 2.

[0023]

REFERENCE SIGNS

[0024] The embodiments will be described below with reference to the accompanying drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals. The repeated description of the corresponding parts is appropriately simplified or omitted.

[0025] Embodiment 1 Figure 1 is a cross-sectional view of the elastic wave device in Embodiment 1.

[0026] As Figure 1 shown, the elastic wave device 1 includes a wiring substrate 2, a chip substrate 3, a plurality of bumps 4, and a sealing portion 5.

[0027] For example, the wiring substrate 2 is a multi-layer substrate containing resin. For example, the wiring substrate 2 is a Low Temperature Co-fired Ceramics (LTCC) multi-layer substrate composed of a plurality of dielectric layers. For example, the wiring substrate 2 is a High Temperature Co-fired Ceramics (HTCC) multi-layer substrate composed of a plurality of dielectric layers. For example, passive components such as capacitors or inductors (not shown) are built in the wiring substrate 2.

[0028] In Figure 1In this case, the upper surface of the wiring substrate 2 is the component mounting surface. A plurality of conductive pads 2A are formed on the upper surface of the wiring substrate 2. For example, the plurality of conductive pads 2A are made of copper. The lower surface of the wiring substrate 2 is the mounting surface for mounting to a mother board or the like. A plurality of conductive pads 2B are formed on the lower surface of the wiring substrate 2. For example, the plurality of conductive pads 2B are made of copper. A plurality of internal conductors 2C are built in the wiring substrate 2. For example, the plurality of internal conductors 2C are made of copper. Each internal conductor 2C is electrically connected to the corresponding conductive pad 2A and conductive pad 2B.

[0029] The chip substrate 3 faces the wiring substrate 2. For example, the chip substrate 3 at least includes a piezoelectric substrate 3A. For example, the piezoelectric substrate 3A is formed of a piezoelectric single crystal such as lithium tantalate, lithium niobate, or quartz. For example, the piezoelectric substrate 3A is formed of a piezoelectric ceramic.

[0030] The chip substrate 3 may also include a support substrate 3B. For example, the support substrate 3B is made of sapphire, silicon, alumina, spinel, quartz, or glass. For example, the support substrate 3B is joined to the piezoelectric substrate 3A through an adhesive layer (not shown).

[0031] For example, a band-pass filter is formed on the main surface of the chip substrate 3 (the lower surface in Figure 1 this case). For example, a receiving filter and a transmitting filter are formed. The receiving filter and the transmitting filter constitute a duplexer.

[0032] The receiving filter is designed to allow an electrical signal in a desired frequency band to pass through. For example, the receiving filter includes a ladder filter composed of a plurality of series resonators and a plurality of parallel resonators.

[0033] The transmitting filter is designed to allow an electrical signal in a desired frequency band to pass through. For example, the transmitting filter includes a ladder filter composed of a plurality of series resonators and a plurality of parallel resonators.

[0034] For example, the chip substrate 3 includes a wiring pattern 6 and a plurality of surface acoustic wave elements 7. For example, the wiring pattern 6 is formed of a metal or alloy such as silver, aluminum, copper, titanium, palladium, etc. For example, the wiring pattern 6 is formed by stacking a plurality of metal layers. For example, the thickness of the wiring pattern 6 is 150 nm to 400 nm. For example, the plurality of surface acoustic wave elements 7 receive a high-frequency electric field through the wiring pattern 6 to excite surface acoustic waves, and convert the surface acoustic waves into a high-frequency electric field through the piezoelectric effect, thereby obtaining the desired filtering characteristics.

[0035] For example, each of the plurality of bumps 4 can be made of a material such as gold, conductive adhesive, solder, etc. For example, the height of the bump 4 is 20 μm to 50 μm. Each of the plurality of bumps 4 electrically connects the conductive pad 2A and the wiring pattern 6 at the corresponding position.

[0036] While the sealing portion 5 forms a space 8 between the wiring substrate 2 and the chip substrate 3, it hermetically seals the chip substrate 3 together with the wiring substrate 2. For example, the sealing portion 5 is made of an insulating material such as a synthetic resin. The synthetic resin may be a material such as epoxy resin or polyimide.

[0037] Next, refer to Figure 2 to illustrate an example of the elastic wave element 7.

[0038] Figure 2 FIG. is an example diagram of the elastic wave element of the elastic wave device in Embodiment 1.

[0039] In Figure 2 , the elastic wave element 7 is a surface acoustic wave (SAW) resonator. As Figure 2 shown, a pair of IDT electrodes 7A and a pair of reflectors 7B are formed on the main surface of the chip substrate 3. The pair of IDT electrodes 7A and the pair of reflectors 7B are arranged so as to be able to excite surface elastic waves.

[0040] For example, the pair of IDT electrodes 7A and the pair of reflectors 7B are made of an alloy of aluminum and copper. For example, the pair of IDT electrodes 7A and the pair of reflectors 7B are made of a suitable metal such as titanium, palladium, silver or an alloy of these metals. For example, the pair of IDT electrodes 7A and the pair of reflectors 7B are made of a laminated metal film formed by stacking multiple metal films.

[0041] The IDT electrode 7A includes a plurality of electrode fingers 7C and a bus bar 7D. The plurality of electrode fingers 7C are arranged in the long side direction. The bus bar 7D connects the plurality of electrode fingers 7C to each other. One of the pair of reflectors 7B is adjacent to one side of the pair of IDT electrodes 7A. The other of the pair of reflectors 7B is adjacent to the other side of the pair of IDT electrodes 7A. For example, the pair of IDT electrodes 7A and the pair of reflectors 7B are formed and patterned in the same process as the wiring pattern 6 ( Figure 2 not shown in the figure).

[0042] Next, refer to Figure 3 to illustrate the connection relationship of the resonators.

[0043] Figure 3 FIG. is a circuit diagram corresponding to the chip substrate of the elastic wave device in Embodiment 1.

[0044] Figure 3 FIG. is a circuit example that functions as a duplexer as a whole. In Figure 3 , the wiring pattern 6 includes a plurality of ground bump pads GND, receive bump pads RX, transmit bump pads TX, and antenna bump pads ANT. These bump pads are parts that are electrically connected to the bumps 4 ( Figure 3 not shown in the figure).

[0045] The plurality of elastic wave elements 7 include four or more series resonators and a plurality of parallel resonators. For example, the plurality of elastic wave elements 7 include a plurality of series resonators TS1, TS2, TS3, TS4, etc., a plurality of parallel resonators TP1, TP2, TP3, TP4, etc., and a multimode resonator DMS. The plurality of series resonators TS1, TS2, TS3, TS4, etc., the plurality of parallel resonators TP1, TP2, TP3, TP4, etc., and the multimode resonator DMS are electrically connected through a wiring pattern 6.

[0046] The plurality of series resonators (series resonators other than TS1, TS2, TS3, TS4), the plurality of parallel resonators (parallel resonators other than TP1, TP2, TP3, TP4), and the multimode resonator DMS together constitute the function of a receiving filter. Specifically, when a high-frequency electrical signal is input to the antenna bump pad ANT, the electrical signal passes through the series resonators other than the plurality of series resonators TS1, TS2, TS3, TS4, the parallel resonators other than the plurality of parallel resonators TP1, TP2, TP3, TP4, and the multimode resonator DMS. At this time, only the electrical signal of the desired frequency band reaches the receiving bump pad RX. As a result, only the electrical signal of the desired frequency band is output from the receiving bump pad RX.

[0047] The plurality of series resonators TS1, TS2, TS3, TS4 and the plurality of parallel resonators TP1, TP2, TP3, TP4 together constitute the function of a transmitting filter. Specifically, when a high-frequency electrical signal is input to the transmitting bump pad TX, the electrical signal passes through the plurality of series resonators TS1, TS2, TS3, TS4 and the plurality of parallel resonators TP1, TP2, TP3, TP4. At this time, only the electrical signal of the desired frequency band reaches the antenna bump pad ANT. As a result, only the electrical signal of the desired frequency band is output from the antenna bump pad ANT.

[0048] In recent years, the sizes of filters and duplexers have become smaller and smaller, and the required power to be carried has become larger and larger. Therefore, it has become very important to improve the power resistance.

[0049] In terms of power resistance, the most stringent test occurs when the transmitting filter (including the transmitting part of the duplexer and the transmit / receive filter) adds a frequency on the high-frequency side of the transmitting frequency band.

[0050] Here, Table 1 shows an example of the relationship between the duty ratio (the ratio of the pitch of the electrode fingers to the width of the electrode fingers) and the frequency-temperature characteristics.

[0051] Table 1

[0052] In Table 1, "TxIL L-side" represents the position of the transmit filter in Band 28 on the low-frequency side of the transmit band. "TxIL R-side" represents the position of the transmit filter in Band 28 on the high-frequency side of the transmit band. "Duty65" represents a duty cycle of 65%, "Duty60" represents a duty cycle of 60%, "Duty55" represents a duty cycle of 55%, and "Duty50" represents a duty cycle of 50%. Each value represents the frequency-temperature characteristic value when the insertion loss is -5 dB.

[0053] For example, on the low-frequency side of the passband of the transmit filter in Band 28, when the position where the insertion loss of the transmit filter is -5 dB, the frequency-temperature characteristic of the resonator with a duty cycle of 65% is -17.5 ppm / °C. The frequency-temperature characteristic of the resonator with a duty cycle of 60% is -16.4 ppm / °C. The frequency-temperature characteristic of the resonator with a duty cycle of 55% is -15.4 ppm / °C. The frequency-temperature characteristic of the resonator with a duty cycle of 50% is -14.1 ppm / °C.

[0054] For example, at the high-frequency end of the passband of the transmit filter in Band 28, when the position where the insertion loss of the transmit filter is -5 dB, the frequency-temperature characteristic of the resonator with a duty cycle of 65% is -36.1 ppm / °C. The frequency-temperature characteristic of the resonator with a duty cycle of 60% is -33.4 ppm / °C. The frequency-temperature characteristic of the resonator with a duty cycle of 55% is -32.2 ppm / °C. The frequency-temperature characteristic of the resonator with a duty cycle of 50% is -30.8 ppm / °C.

[0055] As shown in Table 1, the frequency-temperature characteristic is negative. Therefore, when the temperature rises due to power application, the resonance frequency and the anti-resonance frequency will shift in the decreasing direction. This will cause an increase in the insertion loss at the shoulder on the high-frequency side of the transmit filter, which may further cause a temperature rise and even may cause damage to the transmit filter. Therefore, improving the frequency-temperature characteristic on the high-frequency side of the transmit filter can improve its power resistance.

[0056] As shown in Table 1, reducing the duty cycle can improve the frequency-temperature characteristic. However, a smaller duty cycle will result in a decrease in the capacitance per unit area. Therefore, the area of the resonator will increase. Therefore, it is not a wise choice to reduce the duty cycle of all series resonators of the transmit filter.

[0057] Regarding this, as a measure, it can be considered to only reduce the duty cycle of the series resonator that has the greatest impact on the shoulder on the high-frequency side of the transmit band of the transmit filter. However, in reality, the series resonator with the second lowest anti-resonance frequency and the series resonator with the third lowest anti-resonance frequency, although the impact gradually decreases, is not completely without impact.

[0058] Therefore, in the elastic wave device 1 disclosed in this embodiment, the duty cycle of the series resonator increases in order from the lowest anti-resonant frequency to the highest anti-resonant frequency. In addition, since the influence degree decreases as the anti-resonant frequency increases, the difference in duty cycle between the series resonator with the first low anti-resonant frequency and the series resonator with the second low anti-resonant frequency is set to be greater than the difference in duty cycle between any two series resonators from the series resonator with the second low anti-resonant frequency to the series resonator with the fourth low anti-resonant frequency.

[0059] Specifically, among the multiple series resonators disclosed in this embodiment, the anti-resonant frequencies are sequentially defined as the 1st series resonator, the 2nd series resonator, the 3rd series resonator, and the 4th series resonator in the order from near to far from the high-frequency end of the passband of the band-pass filter. This definition has nothing to do with the layout and connection relationship of the series resonators. The magnitude order of the duty cycle is set among the 1st series resonator, the 2nd series resonator, the 3rd series resonator, and the 4th series resonator.

[0060] For example, the duty cycle of the 1st series resonator is set to be less than the duty cycles of the 2nd series resonator and the 3rd series resonator. For another example, the duty cycle of the 2nd series resonator is set to be less than the duty cycle of the 3rd series resonator. For still another example, the duty cycle of the 3rd series resonator is set to be less than the duty cycle of the 4th series resonator.

[0061] For example, the difference between the duty cycle of the 1st series resonator and the duty cycle of the 2nd series resonator is set to be greater than the difference between the duty cycle of the 2nd series resonator and the duty cycle of the 3rd series resonator. For another example, the difference between the duty cycle of the 1st series resonator and the duty cycle of the 2nd series resonator is set to be greater than the difference between the duty cycle of the 3rd series resonator and the duty cycle of the 4th series resonator. For still another example, the difference between the duty cycle of the 1st series resonator and the duty cycle of the 2nd series resonator is set to be greater than the difference between the duty cycle of the 2nd series resonator and the duty cycle of the 4th series resonator.

[0062] Next, refer to Figure 4 to illustrate the frequency characteristics of the elastic wave device 1.

[0063] Figure 4 is a schematic diagram of the frequency characteristics of the elastic wave device in Embodiment 1 near the high-frequency end of the passband.

[0064] In Figure 4 , F represents the frequency characteristics of the elastic wave device 1 as a transmit filter corresponding to the frequency band 28. W is the passband of the transmit filter. A represents the frequency characteristics of the 1st series resonator alone. B represents the frequency characteristics of the 2nd series resonator alone. C represents the frequency characteristics of the 3rd series resonator alone. D represents the frequency characteristics of the 4th series resonator alone.

[0065] In this example, the duty ratio of the first series resonator is set to 45%. The duty ratio of the second series resonator is set to 50%. The duty ratio of the third series resonator is set to 52%. The duty ratio of the fourth series resonator is set to 54%.

[0066] As Figure 4 shown, the anti-resonant frequency of the first series resonator is closer to the high-frequency end of the passband than that of the second series resonator. The anti-resonant frequency of the second series resonator is closer to the high-frequency end of the passband than that of the third series resonator. The anti-resonant frequency of the third series resonator is closer to the high-frequency end of the passband than that of the fourth series resonator.

[0067] By setting the anti-resonant frequency positions and duty ratios of multiple series resonators in this way, it is possible to prevent the size of the chip substrate 3 including multiple series resonators from increasing, while improving the frequency temperature characteristics. As a result, the power resistance is also improved.

[0068] According to the above Embodiment 1, the anti-resonant frequencies of multiple series resonators are the first series resonator, the second series resonator, the third series resonator, and the fourth series resonator in order from the closest to the high-frequency end of the passband of the band-pass filter. The duty ratio of the first series resonator is smaller than those of the second series resonator and the third series resonator. Therefore, in the surface acoustic wave device 1, it is possible to prevent the chip size from increasing while improving the frequency temperature characteristics. As a result, the power resistance is also improved.

[0069] In this process, adjusting the duty ratio can be easily achieved during the patterning of the IDT electrode 7A. Therefore, the frequency temperature characteristics can be improved by a simple manufacturing method.

[0070] In addition, the duty ratio of the second series resonator is smaller than that of the third series resonator. Therefore, in the surface acoustic wave device 1, it is possible to prevent the chip size from increasing while more reliably improving the frequency temperature characteristics.

[0071] In addition, the duty ratio of the third series resonator is smaller than that of the fourth series resonator. Therefore, in the surface acoustic wave device 1, it is possible to prevent the chip size from increasing while more reliably improving the frequency temperature characteristics.

[0072] In addition, the difference between the duty ratio of the first series resonator and that of the second series resonator is greater than the difference between the duty ratio of the second series resonator and that of the third series resonator. Therefore, in the surface acoustic wave device 1, it is possible to prevent the chip size from increasing while more reliably improving the frequency temperature characteristics.

[0073] In addition, the difference between the duty ratio of the first series resonator and the duty ratio of the second series resonator is greater than the difference between the duty ratio of the third series resonator and the duty ratio of the fourth series resonator. Therefore, in the elastic wave device 1, an increase in chip size can be prevented, and the frequency-temperature characteristics can be improved more reliably.

[0074] In addition, the difference between the duty ratio of the first series resonator and the duty ratio of the second series resonator is greater than the difference between the duty ratio of the second series resonator and the duty ratio of the fourth series resonator. Therefore, in the elastic wave device 1, an increase in chip size can be prevented, and the frequency-temperature characteristics can be improved more reliably.

[0075] In addition, the plurality of parallel resonators and the plurality of series resonators function as a transmission filter. Therefore, even for a transmission filter that generates a large amount of heat, an increase in chip size can be prevented, and the frequency-temperature characteristics can be improved more reliably.

[0076] Next, a modified example of the chip substrate 3 will be described with reference to Figure 5 a modified example of the chip substrate of the elastic wave device in Embodiment 1 will be described.

[0077] Figure 5 is a circuit diagram corresponding to a modified example of the chip substrate of the elastic wave device in Embodiment 1.

[0078] Figure 5 is a circuit example whose overall function is a transmission filter. As Figure 5 shown, the wiring pattern 6 includes a plurality of ground bump pads GND, an input bump pad IN, and an output bump pad OUT.

[0079] The plurality of elastic wave elements 7 include a plurality of series resonators TS1, TS2, TS3, TS4 and a plurality of parallel resonators TP1, TP2, TP3, TP4. The plurality of series resonators TS1, TS2, TS3, TS4 and the plurality of parallel resonators TP1, TP2, TP3, TP4 are electrically connected through the wiring pattern 6.

[0080] The plurality of series resonators TS1, TS2, TS3, TS4 and the plurality of parallel resonators TP1, TP2, TP3, TP4 function as a transmission filter. Specifically, when a high-frequency electrical signal is input to the input bump pad IN, the electrical signal passes through the plurality of series resonators TS1, TS2, TS3, TS4 and the plurality of parallel resonators TP1, TP2, TP3, TP4. At this time, only the electrical signal in the desired frequency band reaches the output bump pad OUT. As a result, only the electrical signal in the desired frequency band is output from the output bump pad OUT.

[0081] In this modified example, the anti-resonant frequency positions and duty ratios of the plurality of series resonators are also set in a similar manner to those in Example 1.

[0082] According to the description of the above modification example, similar to Embodiment 1, in the elastic wave device 1, an increase in chip size can be prevented while improving the frequency temperature characteristics.

[0083] Embodiment 2 Figure 6 FIG. is a cross-sectional view of a module in which the elastic wave device is applied in Embodiment 2. In addition, the same or corresponding parts in Embodiment 1 are denoted by the same reference numerals. The description of these parts will be omitted.

[0084] In Figure 6 , the module 100 includes a wiring substrate 101, an integrated circuit element 102, an elastic wave device 1, a coil 103, and a sealing portion 104.

[0085] The wiring substrate 101 is the same as the wiring substrate 2 in Embodiment 1. The integrated circuit element 102 is mounted inside the wiring substrate 101 and includes a switching circuit and a low-noise amplifier. The elastic wave device 1 is mounted on the main surface of the wiring substrate 101. The coil 103 is also mounted on the main surface of the wiring substrate 101 for impedance matching. For example, the coil 103 is an integrated passive device (abbreviated as IPD). The sealing portion 104 encapsulates a plurality of electronic components including the elastic wave device 1.

[0086] According to the above Embodiment 2, the module 100 includes the elastic wave device 1. Therefore, it is possible to improve the frequency temperature characteristics on the module 100 without increasing the chip size.

[0087] Although multiple aspects of some embodiments have been described, it should be understood that various modifications, improvements, and enhancements can be readily conceived by those skilled in the art. These modifications, improvements, and enhancements are intended to be part of the present invention and are within the scope of the present disclosure.

[0088] It should be understood that the embodiments of the devices and modules described herein are not limited to the structural and arrangement details described in the above description or illustrated in the drawings. The devices and modules can be implemented in other embodiments and implemented or executed in various ways.

[0089] Specific implementation examples are provided for illustrative purposes only and are not intended to be limiting.

[0090] The expressions and terms used in this disclosure are for illustrative purposes and should not be regarded as limiting. Here, "comprising", "including", "having", "containing", and their variants are intended to include the items listed hereinafter, their equivalents, and additional items.

[0091] The reference to "or" is intended to be understood as any of the terms used, which can refer to one, more than one, or all of the terms.

[0092] References to directions such as front and back, left and right, top and bottom, horizontal and vertical, inside and outside, etc. are for the convenience of description. These references do not limit the components of the present invention to any particular position or spatial orientation. Therefore, the above description and illustration are only examples.

Claims

1. An elastic wave device, comprising: Piezoelectric substrate; A plurality of parallel resonators and a plurality of series resonators formed on the piezoelectric substrate and serving as a bandpass filter; It is characterized in that: when arranged in order from near to far at the high-frequency end of the passband of the bandpass filter according to the anti-resonance frequency, the multiple series resonators at least include a first series resonator, a second series resonator, and a third series resonator in sequence, and the duty cycle of the first series resonator is smaller than the duty cycles of the second series resonator and the third series resonator.

2. The elastic wave device according to claim 1, characterized in that: A duty cycle of the second series resonator is smaller than a duty cycle of the third series resonator.

3. The elastic wave device according to claim 1, characterized in that: A difference between a duty cycle of the first series resonator and a duty cycle of the second series resonator is greater than a difference between a duty cycle of the second series resonator and a duty cycle of the third series resonator.

4. The elastic wave device according to claim 1, characterized in that: The multiple series resonators include four or more series resonators. When arranged in order from near to far at the high-frequency end of the passband of the bandpass filter according to the anti-resonance frequency, the multiple series resonators at least include a first series resonator, a second series resonator, a third series resonator, and a fourth series resonator in sequence, and the duty cycle of the third series resonator is smaller than the duty cycle of the fourth series resonator.

5. The elastic wave device according to claim 4, characterized in that: A difference between a duty cycle of the first series resonator and a duty cycle of the second series resonator is greater than a difference between a duty cycle of the third series resonator and a duty cycle of the fourth series resonator.

6. The elastic wave device according to claim 4, characterized in that: A difference between a duty cycle of the first series resonator and a duty cycle of the second series resonator is greater than a difference between a duty cycle of the second series resonator and a duty cycle of the fourth series resonator.

7. The elastic wave device according to claim 1, characterized in that: The plurality of parallel resonators and the plurality of series resonators are used as a transmission filter.

8. The elastic wave device according to claim 1, characterized in that: Also included is a receive filter.

9. The elastic wave device according to claim 1, characterized in that: The duty ratios of the plurality of series resonators increase sequentially from low to high according to the anti-resonance frequency.

10. An electronic module, characterized in that: The elastic wave device comprises the elastic wave device according to any one of claims 1 to 9.

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