WO2019170339A1 - Acoustic wave devices with improved spurious mode suppression - Google Patents

Acoustic wave devices with improved spurious mode suppression Download PDF

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Publication number
WO2019170339A1
WO2019170339A1 PCT/EP2019/052741 EP2019052741W WO2019170339A1 WO 2019170339 A1 WO2019170339 A1 WO 2019170339A1 EP 2019052741 W EP2019052741 W EP 2019052741W WO 2019170339 A1 WO2019170339 A1 WO 2019170339A1
Authority
WO
WIPO (PCT)
Prior art keywords
circuit
resonant circuit
resonator
series
filter circuit
Prior art date
Application number
PCT/EP2019/052741
Other languages
French (fr)
Inventor
Simone Colasanti
Franz Kubat
Original Assignee
RF360 Europe GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by RF360 Europe GmbH filed Critical RF360 Europe GmbH
Publication of WO2019170339A1 publication Critical patent/WO2019170339A1/en

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
    • H03H9/56—Monolithic crystal filters
    • H03H9/566—Electric coupling means therefor
    • H03H9/568—Electric coupling means therefor consisting of a ladder configuration
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
    • H03H9/542—Filters comprising resonators of piezoelectric or electrostrictive material including passive elements
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
    • H03H9/58—Multiple crystal filters
    • H03H9/60—Electric coupling means therefor
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
    • H03H9/58—Multiple crystal filters
    • H03H9/60—Electric coupling means therefor
    • H03H9/605—Electric coupling means therefor consisting of a ladder configuration
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/64—Filters using surface acoustic waves
    • H03H9/6423—Means for obtaining a particular transfer characteristic
    • H03H9/6433—Coupled resonator filters
    • H03H9/6483—Ladder SAW filters

Definitions

  • the invention refers to an acoustic wave devices such as a resonator or a filter made in SAW and BAW technology with improved suppression of a spurious mode like a plate-modes.
  • spurious modes i.e. plate modes, bulk waves etc.
  • a layer stack with such a structure causes another spurious mode to propagate.
  • This secondary mode also known as plate mode, has an excitation that depends on the properties of the dielectric layer. In some cases, to fulfill specifications on the temperature
  • solution 1 modifying the resonator itself
  • the displacement of disturbing modes impairs the performance of that resonator causing that modes.
  • the excitation of disturbing modes is related to the quality factor of a resonator. Reducing the excitation of these modes leads to reduced quality factors and, consequently, to reduced performance. Unwanted mode is only shifted up, but not suppressed.
  • Disadvantage of solution 2 is that it is not possible to create an efficient pole in a frequency range of the unwanted mode of the corresponding resonator that normally has a frequency above the main frequency and hence above the pass band of the filter device. Moreover it causes degradation of performance at the band edges, loss of selectivity and reduction of bandwidth. Further, it works only for unwanted modes caused by parallel resonators.
  • Basic idea of the invention is to couple a shunt line to the signal line of a filter circuit and to include a resonant circuit therein.
  • the resonant circuit is to produce a pole in the transfer curve of the filter.
  • the pole is set to a frequency of a spurious mode. In effect, the signal of the spurious mode can be attenuated or deleted such that a disturbance in a neighbored band can be avoided.
  • a possible solution for such a resonant circuit is a parallel resonance circuit of a capacity and an inductance or coil.
  • the resonant circuit is a series resonance circuit of a capacity and an inductance or coil.
  • the resonant circuit can be coupled to an arbitrary band pass filter of any pass band realized in any filter technique.
  • An impedance element for such a filter may be chosen from capacitor, inductance or
  • the resonator may be a series or a parallel circuit of a discrete capacitance and an inductance.
  • the resonator may operate with acoustic waves and comprises a SAW or a BAW resonator.
  • the band pass filter (without resonant circuit) may produce a spurious mode having a spurious frequency located above the pass band.
  • the spurious mode may be facilitated by the construction of the band filter and preferably by the
  • the resonance of the resonant circuit can be set to a desired frequency by properly dimensioning size and value of the elements of the resonant circuit.
  • the series resonant circuit is a series connection of a resonator and an inductance.
  • the band pass filter comprises resonators too that can use the same technology.
  • the resonator of the resonant circuit is made in SAW
  • the finger pitch of this resonator can easily be made greater that the finger pitch of the resonators in the band pass filter such that has a resonance frequency of the resonator is lower than and outside of the pass band of the filter. Then the achieved resonance of the resonant circuit can be located at frequency above the pass band .
  • the resonator and the inductance of the resonant circuit in the shunt line may be additional elements that are coupled to the signal line. This means that the band pass filter can be optimized independently from the resonant circuit to achieve a desired pass band. Then the additional shunt line has no critical impact on the pass-band performance.
  • the shunt line may be connected to a node between two series impedance elements of the ladder type circuit.
  • the shunt line can be coupled to the filter circuits signal line separate and possibly distant to the band pass filter.
  • the series resonant circuit is a series connection of a coil and a modified resonator that, before modifying, has been part of the ladder type circuit used to create the band pass but that has a resonance
  • Figure 1 shows an admittance curve of a common filter circuit of the art showing a spurious signal that is due to a plate mode
  • FIG. 2 shows a general filter circuit according to the
  • Figure 3 shows different examples of creating a resonant
  • Figure 4 shows a specified embodiment with a filter realized in ladder type structure and a resonant circuit comprising a series connection of a resonator and a coil ;
  • Figure 5 shows transfer function of a resonator compared with the transfer function of the same resonator coupled with a coil and with a resonator according to the invention .
  • Fig. 1 represents the admittance of a band pass filter according to the art.
  • a resonator that is designed to have its main mode in Band 3 (uplink) has its plate mode in Band 1 (downlink) . If such a resonator would be used in a
  • FIG. 2 shows a general filter circuit according to the invention.
  • a signal line SIL couples a first terminal T1 to a second terminal T2, one of them may be an antenna terminal.
  • a shunt line SHL couples a node N in the signal line SIL to ground.
  • a resonant circuit RC is arranged creating a resonance at a desired frequency.
  • a resonant circuit is characterized by a resonant frequency which inversely depends on the product of the inductance and capacity of the two reactive elements. The frequency thereof is set to a frequency of a spurious mode that is excited by the band pass filter BF.
  • Figure 3 shows three different examples of how such a
  • a parallel resonance circuit RCp of a capacitance CRC and an inductance LRC is referenced by a) .
  • Capacitance and inductance may be realized as discrete elements that may be mounted on a board together with the filter circuit. Moreover these elements may be elements that integrated within the filter circuit may be in a multi-layer carrier of the chip bearing the filter circuit. Further, capacitance CRC may be an interdigital comb
  • Inductance may be a metallization on a chip, a board or a discrete coil of copper for example.
  • a series resonant circuit RCs of a capacitance CRC and an inductance LRC is referenced by b) .
  • the elements CRC and L RC may be embodied as described above.
  • a series resonant circuit RCs of a resonator R R C and an inductance L R C is referenced by c) .
  • the resonator may be a LC resonator or a resonator formed as a SAW or BAW resonator .
  • the resonant circuit RC is introduced in a ladder-type structure of a band pass filter BF as shown in Figure 4. If properly dimensioned this resonant circuit RC introduces a pole in the transfer
  • a shunt coil L R C is circuited in series to a parallel
  • fr' of the resonator R R C forming the resonant circuit RC is much lower than the resonance frequency fr of the other resonators: fr' ⁇ fr. This not only avoids a degradation of the pass-band due to the coil, but guarantees the suppression of any unwanted mode generated by the other parallel resonators as well as by the series resonators.
  • This proposed solution does not simply offer an alternative way of creating a resonant circuit RC .
  • the performance of the filter BF in the pass-band does not suffer as it does in the case of the traditional solutions.
  • the key feature is that the resonator used to create the resonance circuit does not contribute to the selectivity of the filter.
  • the pole-zero distance of the resonator greatly changes (see curve 2 in Fig. 5) . This will negatively affect selectivity of the filter at the right skirt.
  • resonator can be modeled as a capacitor only in regions of the filter spectrum far from its main-mode and far from its plate-mode. In these regions, an electromagnetic pole for the suppression of the plate mode can be created. If a resonance is already present, a second order singularity in the
  • Figure 5 shows transfer function of a resonator (see curve 1) compared with the transfer function of the same resonator coupled with a coil (see curve 2) and with a resonator according to the invention (see curve 3)
  • the proposed approach can successfully create the electromagnetic pole where it is needed (curve 3 in Fig. 5) . Furthermore, due to its distance from the pass- band, the overall performance in the pass-band itself it is not degraded as in the case of the traditional tank circuit.

Landscapes

  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
  • Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)

Abstract

It is proposed to couple a shunt line (SHL) to the signal line (SIL) of a filter circuit (BF) with series impedance elements (IES) and parallel impedance elements (IEP) arranged in a ladder type structure and to include a resonant circuit (RCS) in shunt thereto. The resonant circuit serves to produce a pole in the transfer curve of the filter. The pole is set to a frequency of a spurious mode. In effect, the signal of the spurious mode can be attenuated or deleted such that a disturbance in a neighbored band can be avoided.

Description

Description
Acoustic wave devices with improved spurious mode suppression
The invention refers to an acoustic wave devices such as a resonator or a filter made in SAW and BAW technology with improved suppression of a spurious mode like a plate-modes.
In multi-layer stacked acoustic wave filters and resonators (SAW/BAW) spurious modes (i.e. plate modes, bulk waves etc.) can be regarded. These modes, which are excited at
frequencies far from the main mode frequency of the
resonator, negatively affect the reflectivity and the
selectivity of the filter. Their effect is particularly severe in case of multiplexer applications.
In the so-called TC-SAW filters (temperature compensated SAW) , to improve the insensitivity of the filters with respect to temperature variations, the resonators are
commonly covered with a dielectric layer. In addition to the main propagating mode, a layer stack with such a structure causes another spurious mode to propagate. This secondary mode, also known as plate mode, has an excitation that depends on the properties of the dielectric layer. In some cases, to fulfill specifications on the temperature
coefficient of the filter, it is necessary to deposit an amount of dielectric that causes a strong excitation of the plate mode.
Similar problems arise at BAW devices where a spurious mode is caused by the layered construction of the BAW resonators. Increasingly more often, the position of these disturbing modes collides with other LTE bands. More and more
applications demand new band combinations and, consequently, more strict requirements for the selectivity and reflectivity of the single filters. Therefore, rather than trying to move the spurious modes out of the main bands, the real challenge is to find a way to completely suppress them.
In recent years, lot of efforts have been done trying to suppress these modes. Two fundamental solutions have been proposed :
1. Modifying the resonator itself by reducing its Q-factor or by moving up the resonance of the resonator that causes an up-shift of the unwanted mode and introducing a shunt coil to compensate the loss of bandwidth.
2. Circuiting a coil in parallel to series resonator to achieve a "tank circuit" that creates a pole with its anti resonance .
Disadvantage of solution 1 (modifying the resonator itself) is that the displacement of disturbing modes impairs the performance of that resonator causing that modes. Moreover, the excitation of disturbing modes is related to the quality factor of a resonator. Reducing the excitation of these modes leads to reduced quality factors and, consequently, to reduced performance. Unwanted mode is only shifted up, but not suppressed. With increasing carrier-aggregation
combinations this could represent a problem. Moreover this solution is applicable only to parallel resonators. If the unwanted mode is caused by a series resonator, the compensating-coil cannot be introduced because of causing a negative impact on the bandwidth.
Disadvantage of solution 2 is that it is not possible to create an efficient pole in a frequency range of the unwanted mode of the corresponding resonator that normally has a frequency above the main frequency and hence above the pass band of the filter device. Moreover it causes degradation of performance at the band edges, loss of selectivity and reduction of bandwidth. Further, it works only for unwanted modes caused by parallel resonators.
It is an object of the invention to provide a filter circuit that can suppress a spurious mode above the pass band
frequency without affecting the filter performance.
This and other objects are met by a filter circuit according to claim 1. Further embodiments including advantageous features are given by dependent claims.
Basic idea of the invention is to couple a shunt line to the signal line of a filter circuit and to include a resonant circuit therein. The resonant circuit is to produce a pole in the transfer curve of the filter. The pole is set to a frequency of a spurious mode. In effect, the signal of the spurious mode can be attenuated or deleted such that a disturbance in a neighbored band can be avoided.
A possible solution for such a resonant circuit is a parallel resonance circuit of a capacity and an inductance or coil.
Preferably the resonant circuit is a series resonance circuit of a capacity and an inductance or coil. The resonant circuit can be coupled to an arbitrary band pass filter of any pass band realized in any filter technique.
A preferred filter technique uses a ladder type structure comprising series impedance elements and parallel impedance elements arranged in the series branch (=signal line) and in a number of parallel branches. An impedance element for such a filter may be chosen from capacitor, inductance or
resonator. The resonator may be a series or a parallel circuit of a discrete capacitance and an inductance.
Alternatively, the resonator may operate with acoustic waves and comprises a SAW or a BAW resonator.
The band pass filter (without resonant circuit) may produce a spurious mode having a spurious frequency located above the pass band. The spurious mode may be facilitated by the construction of the band filter and preferably by the
construction of the ladder type structure.
The resonance of the resonant circuit can be set to a desired frequency by properly dimensioning size and value of the elements of the resonant circuit. A resonance at the
frequency of a spurious mode of the band pass filter is preferred .
According to an embodiment the series resonant circuit is a series connection of a resonator and an inductance. Such a solution is preferred when the band pass filter comprises resonators too that can use the same technology. Preferably the resonator of the resonant circuit is made in SAW
technology. Then the finger pitch of this resonator can easily be made greater that the finger pitch of the resonators in the band pass filter such that has a resonance frequency of the resonator is lower than and outside of the pass band of the filter. Then the achieved resonance of the resonant circuit can be located at frequency above the pass band .
The resonator and the inductance of the resonant circuit in the shunt line may be additional elements that are coupled to the signal line. This means that the band pass filter can be optimized independently from the resonant circuit to achieve a desired pass band. Then the additional shunt line has no critical impact on the pass-band performance.
The shunt line may be connected to a node between two series impedance elements of the ladder type circuit. Alternatively, the shunt line can be coupled to the filter circuits signal line separate and possibly distant to the band pass filter.
According to an embodiment the series resonant circuit is a series connection of a coil and a modified resonator that, before modifying, has been part of the ladder type circuit used to create the band pass but that has a resonance
frequency greater than the resonance frequency of the
remaining resonators used as parallel impedance elements.
In the following the filter circuit is explained in more detail by reference to specific embodiments and the
accompanied figures. The figures are schematically only and not to scale. Elements that are identical in form or function are referenced with the same reference symbols. Figure 1 shows an admittance curve of a common filter circuit of the art showing a spurious signal that is due to a plate mode;
Figure 2 shows a general filter circuit according to the
invention;
Figure 3 shows different examples of creating a resonant
circuit in the shunt line;
Figure 4 shows a specified embodiment with a filter realized in ladder type structure and a resonant circuit comprising a series connection of a resonator and a coil ;
Figure 5 shows transfer function of a resonator compared with the transfer function of the same resonator coupled with a coil and with a resonator according to the invention .
Fig. 1 represents the admittance of a band pass filter according to the art. A resonator that is designed to have its main mode in Band 3 (uplink) has its plate mode in Band 1 (downlink) . If such a resonator would be used in a
multiplexed application (Band 1 + Band 3) , the overall performance would suffer considerably due to a mediocre cross-isolation between the two operating bands. Once again, one could try to move the plate mode in frequency, but this will result in violations of other constraints e.g. in case of carrier aggregation with Band 40. The invention aims to suppress these unwanted modes including but not limited to plate modes far from the pass-band without any significant collateral effect on the pass-band itself.
Figure 2 shows a general filter circuit according to the invention. A signal line SIL couples a first terminal T1 to a second terminal T2, one of them may be an antenna terminal.
In the signal line SIL and band pass filter BF is arranged that spanning up a pass band. A shunt line SHL couples a node N in the signal line SIL to ground. In the shunt line a resonant circuit RC is arranged creating a resonance at a desired frequency. A resonant circuit is characterized by a resonant frequency which inversely depends on the product of the inductance and capacity of the two reactive elements. The frequency thereof is set to a frequency of a spurious mode that is excited by the band pass filter BF.
Figure 3 shows three different examples of how such a
resonant circuit can be produced. A parallel resonance circuit RCp of a capacitance CRC and an inductance LRC is referenced by a) . Capacitance and inductance may be realized as discrete elements that may be mounted on a board together with the filter circuit. Moreover these elements may be elements that integrated within the filter circuit may be in a multi-layer carrier of the chip bearing the filter circuit. Further, capacitance CRC may be an interdigital comb
structure. Inductance may be a metallization on a chip, a board or a discrete coil of copper for example.
A series resonant circuit RCs of a capacitance CRC and an inductance LRC is referenced by b) . Here too the elements CRC and LRC may be embodied as described above. A series resonant circuit RCs of a resonator RRC and an inductance LRC is referenced by c) . Here too, the resonator may be a LC resonator or a resonator formed as a SAW or BAW resonator .
According to a more detailed embodiment the resonant circuit RC is introduced in a ladder-type structure of a band pass filter BF as shown in Figure 4. If properly dimensioned this resonant circuit RC introduces a pole in the transfer
function of the filter itself.
A shunt coil LRC is circuited in series to a parallel
resonator RRC. The main aspect is that the resonance
frequency fr' of the resonator RRC forming the resonant circuit RC is much lower than the resonance frequency fr of the other resonators: fr' << fr. This not only avoids a degradation of the pass-band due to the coil, but guarantees the suppression of any unwanted mode generated by the other parallel resonators as well as by the series resonators.
This proposed solution does not simply offer an alternative way of creating a resonant circuit RC . With the proposed approach, the performance of the filter BF in the pass-band does not suffer as it does in the case of the traditional solutions. The key feature is that the resonator used to create the resonance circuit does not contribute to the selectivity of the filter. When a coil is added to form the resonant circuit, the pole-zero distance of the resonator greatly changes (see curve 2 in Fig. 5) . This will negatively affect selectivity of the filter at the right skirt.
The fact that the parallel resonator is at a very different frequency respect to all the other resonators is a crucial aspect for the invention. With good approximation, a
resonator can be modeled as a capacitor only in regions of the filter spectrum far from its main-mode and far from its plate-mode. In these regions, an electromagnetic pole for the suppression of the plate mode can be created. If a resonance is already present, a second order singularity in the
transfer function occurs, preventing the suppression of the unwanted mode (see curve 2 in Fig. 5) . This is basically the reason why it is not possible to suppress a plate-mode of a certain resonator by using the resonator itself (or in general resonators at the same frequency position) to create a resonant circuit. This is also the reason why a traditional tank circuit can only suppress plate-modes of parallel resonators .
Figure 5 shows transfer function of a resonator (see curve 1) compared with the transfer function of the same resonator coupled with a coil (see curve 2) and with a resonator according to the invention (see curve 3)
On the other hand, the proposed approach can successfully create the electromagnetic pole where it is needed (curve 3 in Fig. 5) . Furthermore, due to its distance from the pass- band, the overall performance in the pass-band itself it is not degraded as in the case of the traditional tank circuit.
Due to the limited number of embodiments the invention shall not be limited to these embodiments. A full scope of the invention is given by the claims. - lo
List of used reference symbols
1,2,3 admittance curves of different resonators
BF band pass filter
CRC capacitance in a resonant circuit
IEP parallel impedance element
IEs series impedance element
LRC inductance in a resonant circuit
N node
RC resonant circuit
RRC resonator in a resonant circuit
SHL shunt line
SIL signal line
Tl, T2 terminals

Claims

We claim
1. A filter circuit comprising
series impedance elements and parallel impedance elements arranged in a ladder type structure,
a pass band created by the ladder type structure
a spurious mode having a spurious frequency above the pass band that is facilitated by the construction of the ladder type structure
wherein a shunt line is circuited in parallel to a signal line of the ladder type structure, comprising a resonant circuit that creates a shunt resonance at the spurious frequency thereby suppressing the spurious mode.
2. The filter circuit of the foregoing claim
wherein the series resonant circuit is a series connection of a capacitance and an inductance.
3. The filter circuit of claim 1
wherein the series resonant circuit is a parallel connection of a capacitance and an inductance.
4. The filter circuit of one of the foregoing claims, wherein the resonator has a resonance frequency that is lower than and outside of the pass band.
5. The filter circuit of one of the foregoing claims, wherein the series resonant circuit is a series connection of an additional resonator and a coil.
6. The filter circuit of one of the foregoing claims, wherein the shunt line is connected to a node between two series impedance elements of the ladder type circuit.
7. The filter circuit of one of the foregoing claims, wherein the series resonant circuit is a series connection of a coil and a resonator that has been part of the ladder type circuit used to create the band pass but that has a resonance frequency greater than the resonance frequency of the
remaining resonators used as parallel impedance elements.
8. The filter circuit of one of the foregoing claims, wherein the series resonant circuit comprises resonators operating with acoustic waves.
9. The filter circuit of one of the foregoing claims, wherein series and parallel impedance elements and the parallel resonant circuit comprise SAW or BAW resonators.
10. The filter circuit of one of the foregoing claims, wherein at least one of the impedance elements comprises a layer structure that facilitates exciting of a plate mode.
PCT/EP2019/052741 2018-03-05 2019-02-05 Acoustic wave devices with improved spurious mode suppression WO2019170339A1 (en)

Applications Claiming Priority (2)

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DE102018104955.2 2018-03-05
DE102018104955.2A DE102018104955A1 (en) 2018-03-05 2018-03-05 Sound wave devices with improved spurious mode suppression

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WO2019170339A1 true WO2019170339A1 (en) 2019-09-12

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Citations (5)

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Publication number Priority date Publication date Assignee Title
US20040124952A1 (en) * 2002-12-13 2004-07-01 Epcos Ag Component operating with bulk acoustic waves, and having coupled resonators
US20060267708A1 (en) * 2005-05-25 2006-11-30 Fujitsu Media Devices Limited Acoustic wave filter and acoustic wave duplexer
US20100109801A1 (en) * 2008-10-31 2010-05-06 Fujitsu Limited Acoustic wave filter, duplexer, communication module, and communication apparatus
JP2012049758A (en) * 2010-08-26 2012-03-08 Taiyo Yuden Co Ltd Filter and duplexer
DE102015114751A1 (en) * 2015-09-03 2017-03-09 Epcos Ag SAW filter

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Publication number Priority date Publication date Assignee Title
DE112011104653B4 (en) * 2010-12-29 2016-07-21 Murata Manufacturing Co., Ltd. Surface acoustic wave device
DE102015108511B3 (en) * 2015-05-29 2016-09-22 Epcos Ag multiplexer
DE102015116223B4 (en) * 2015-09-25 2019-05-09 Snaptrack, Inc. SAW filter with suppressed shear mode
DE102016112993B4 (en) * 2016-07-14 2018-06-28 Snaptrack, Inc. Notch filter as well as this comprehensive extractor arrangement

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040124952A1 (en) * 2002-12-13 2004-07-01 Epcos Ag Component operating with bulk acoustic waves, and having coupled resonators
US20060267708A1 (en) * 2005-05-25 2006-11-30 Fujitsu Media Devices Limited Acoustic wave filter and acoustic wave duplexer
US20100109801A1 (en) * 2008-10-31 2010-05-06 Fujitsu Limited Acoustic wave filter, duplexer, communication module, and communication apparatus
JP2012049758A (en) * 2010-08-26 2012-03-08 Taiyo Yuden Co Ltd Filter and duplexer
DE102015114751A1 (en) * 2015-09-03 2017-03-09 Epcos Ag SAW filter

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