WO2019131530A1 - 弾性波フィルタ - Google Patents
弾性波フィルタ Download PDFInfo
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- WO2019131530A1 WO2019131530A1 PCT/JP2018/047302 JP2018047302W WO2019131530A1 WO 2019131530 A1 WO2019131530 A1 WO 2019131530A1 JP 2018047302 W JP2018047302 W JP 2018047302W WO 2019131530 A1 WO2019131530 A1 WO 2019131530A1
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- electrode
- thinning
- elastic wave
- idt
- arm resonators
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Images
Classifications
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- 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
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- 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
- H03H9/6406—Filters characterised by a particular frequency characteristic
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/02535—Details of surface acoustic wave devices
- H03H9/02637—Details concerning reflective or coupling arrays
- H03H9/02685—Grating lines having particular arrangements
- H03H9/0274—Intra-transducers grating lines
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/125—Driving means, e.g. electrodes, coils
- H03H9/145—Driving means, e.g. electrodes, coils for networks using surface acoustic waves
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/125—Driving means, e.g. electrodes, coils
- H03H9/145—Driving means, e.g. electrodes, coils for networks using surface acoustic waves
- H03H9/14502—Surface acoustic wave [SAW] transducers for a particular purpose
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/125—Driving means, e.g. electrodes, coils
- H03H9/145—Driving means, e.g. electrodes, coils for networks using surface acoustic waves
- H03H9/14517—Means for weighting
- H03H9/14526—Finger withdrawal
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/125—Driving means, e.g. electrodes, coils
- H03H9/145—Driving means, e.g. electrodes, coils for networks using surface acoustic waves
- H03H9/14544—Transducers of particular shape or position
- H03H9/1457—Transducers having different finger widths
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/25—Constructional features of resonators using surface acoustic waves
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- 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 present invention relates to an elastic wave filter having a thinning electrode.
- Patent Document 1 discloses that, in a surface acoustic wave device including a series arm surface acoustic wave resonator and a parallel arm surface acoustic wave resonator, the shoulder of the low frequency end of the pass band and the steepness of the high frequency end are improved.
- at least one of the series arm surface acoustic wave resonator and the parallel arm surface acoustic wave resonator is weighted by the thinning method.
- the steepness at the low frequency end and the high frequency end of the elastic wave filter largely depends on the Q characteristics of the series arm resonator and the parallel arm resonator constituting the elastic wave filter.
- the thinning electrode is applied to the elastic wave resonator, the shape of the thinning electrode and the Q characteristic of the elastic wave resonator to which the thinning electrode is applied The relationship between is not considered. That is, since the thinning-out electrode disclosed in Patent Document 1 does not take into account the Q characteristics attributed to the shape of the thinning-out electrode, the sharpness of the high frequency end and the low frequency end of the passband is effective according to the required specification. Can not improve.
- the present invention has been made to solve the above-mentioned problems, and in the elastic wave filter constituted by a series arm resonator and a parallel arm resonator, the steepness of the low frequency end and the high frequency end of the pass band. Aims to provide an elastic wave filter that is effectively improved.
- a multiplexer includes a first input / output terminal and a second input / output terminal, and a path connecting the first input / output terminal and the second input / output terminal.
- the one or more series arm resonators and the one or more parallel arm resonances comprising: one or more series arm resonators arranged; and one or more parallel arm resonators arranged between the path and the ground.
- Each of the daughters is an elastic wave resonator having IDT (Inter Digital Transducer) electrodes formed on a substrate having piezoelectricity, and the IDT electrodes extend in a direction intersecting the elastic wave propagation direction and are parallel to each other.
- IDT Inter Digital Transducer
- a pair of comb-shaped electrodes constituted of a plurality of arranged electrode fingers and a bus bar electrode connecting one ends of the electrode fingers constituting the plurality of electrode fingers.
- An electrode finger not connected to any of the bus bar electrodes constituting the pair of comb-shaped electrodes is defined as a first thinning electrode, and an electrode finger having the largest electrode finger width among the plurality of electrode fingers, When an electrode finger having an electrode finger width twice or more the average electrode finger width of the electrode fingers excluding the electrode finger is defined as a second thinning electrode, the IDT electrode of at least one of the one or more series arm resonators is And an IDT electrode included in at least one of the one or more parallel arm resonators including the first thinning electrode includes the second thinning electrode.
- the IDT electrodes are weighted using a so-called decimation method. Is valid.
- the steepness at the low frequency end of the pass band is improved as the Q characteristic near the resonance frequency of the parallel arm resonator improves
- the steepness of the high frequency end of the pass band is the series arm It improves as the Q characteristics near the antiresonant frequency of the resonator improve.
- the inventors compared the Q values of the elastic wave resonator including the first thinning electrode and the elastic wave resonator including the second thinning electrode, and the elastic wave including the second thinning electrode on the low frequency side near the resonance frequency It has been found that the resonator has a higher Q value, and the elastic wave resonator including the first thinning electrode has a higher Q value on the high frequency side near the antiresonance frequency.
- the IDT electrode including the second thinning electrode is applied to the parallel arm resonator, and the IDT electrode including the first thinning electrode is applied to the series arm resonator. This can effectively improve the steepness at both the low frequency end and the high frequency end of the passband.
- the IDT electrode of each of the one or more series arm resonators may include the first thinning electrode.
- the IDT electrode including the first thinning electrode is applied to all series arm resonators constituting the elastic wave filter. This makes it possible to maximize the steepness at the high frequency end of the pass band.
- the IDT electrode of each of the one or more parallel arm resonators may include the second thinning electrode.
- the IDT electrode including the second thinning electrode is applied to all parallel arm resonators constituting the elastic wave filter. This makes it possible to maximize the steepness at the low frequency end of the passband.
- a ratio of the number of the first thinning electrodes to the total number of the plurality of electrode fingers is defined as a first thinning ratio of the IDT electrodes.
- the first thinning rate of the IDT electrode including the first thinning electrode may be 30% or less.
- the Q value is improved, but when the first thinning rate is higher than 30%, the Q value of the IDT electrode is degraded.
- a high Q value can be maintained in the vicinity of the antiresonance frequency of the series arm resonator including the first thinning electrode. Therefore, it is possible to improve the sharpness at the high frequency end of the pass band as compared to the elastic wave filter having the same bandwidth and to which the first thinning electrode is not applied to the series arm resonator.
- the ratio of the number of the second thinning electrodes to the total number of the plurality of electrode fingers is defined as the second thinning ratio of the IDT electrodes.
- the second thinning rate of the IDT electrode including the second thinning electrode may be 30% or less.
- the Q value is improved.
- the second thinning ratio is higher than 30%, the Q value of the IDT electrode is degraded.
- a high Q value can be maintained in the vicinity of the resonance frequency of the parallel arm resonator including the second thinning electrode. Therefore, compared with the elastic wave filter which has the same bandwidth and to which the 2nd thinning electrode is not applied to the parallel arm resonator, it is possible to enhance the sharpness at the low frequency end of the pass band.
- the substrate may be a piezoelectric film on which the IDT electrode is formed on one surface, and a high sound velocity support substrate in which the bulk wave velocity of propagation is faster than the acoustic wave velocity of propagation of the elastic film.
- a low sound velocity film may be provided, which is disposed between a high sound velocity support substrate and the piezoelectric film, and the bulk wave velocity of propagation is slower than the bulk wave velocity of sound propagating through the piezoelectric film.
- the Q value of the elastic wave resonator in addition to the improvement of the Q value of the elastic wave resonator by providing the thinning electrode, the Q value of the elastic wave resonator can be maintained at a high value. Therefore, it is possible to form an elastic wave filter having low loss within the passband.
- the elastic wave filter of the present invention it is possible to effectively improve the sharpness of the low frequency end and the high frequency end of the pass band.
- FIG. 1 is a circuit diagram of an elastic wave filter according to an embodiment.
- FIG. 2A is a plan view and a sectional view schematically showing an example of the elastic wave resonator according to the embodiment.
- FIG. 2B is a cross-sectional view schematically showing an elastic wave resonator according to a modification of the embodiment.
- FIG. 3 is a circuit diagram illustrating the operation principle of a ladder-type elastic wave filter and a graph showing frequency characteristics.
- FIG. 4A is a schematic plan view showing an example of the configuration of the IDT electrode of the series arm resonator that constitutes the elastic wave filter according to the embodiment.
- FIG. 4B is a schematic plan view showing an example of the configuration of IDT electrodes of parallel arm resonators constituting the elastic wave filter according to the embodiment.
- FIG. 5 is a graph comparing impedance characteristics and Q characteristics of the elastic wave resonator to which the first thinning electrode is applied and the elastic wave resonator to which the second thinning electrode is applied.
- FIG. 6A is a graph comparing Q characteristics when the thinning rate is 5% for the elastic wave resonator to which the first thinning electrode is applied and the elastic wave resonator to which the second thinning electrode is applied.
- FIG. 6B is a graph comparing Q characteristics of the elastic wave resonator to which the first thinning electrode is applied and the elastic wave resonator to which the second thinning electrode is applied when the thinning ratio is 15%.
- FIG. 6A is a graph comparing Q characteristics when the thinning rate is 5% for the elastic wave resonator to which the first thinning electrode is applied and the elastic wave resonator to which the second thinning electrode is applied.
- FIG. 6B is a graph comparing Q characteristics of the elastic wave resonator
- FIG. 6C is a graph comparing Q characteristics of the elastic wave resonator to which the first thinning electrode is applied and the elastic wave resonator to which the second thinning electrode is applied when the thinning ratio is 20%.
- FIG. 7 is a graph showing the pass characteristic of the elastic wave filter according to the embodiment, the pass characteristic of the series arm resonator, and the reflection characteristic of the parallel arm resonator.
- FIG. 8 is a graph comparing the insertion loss around the passbands of the elastic wave filters according to the embodiment, the comparative example 1 and the comparative example 2.
- FIG. 9 is a graph comparing the insertion loss around the pass band of the elastic wave filter according to the embodiment and the comparative example 3.
- FIG. 1 is a circuit diagram of an elastic wave filter 10 according to an embodiment.
- the elastic wave filter 10 includes series arm resonators 101, 102, 103, 104 and 105, parallel arm resonators 201, 202, 203 and 204, and input / output terminals 310 and 320. Prepare.
- the series arm resonators 101 to 105 are disposed on a path connecting the input / output terminal 310 (first input / output terminal) and the input / output terminal 320 (second input / output terminal), and are connected in series with each other.
- the parallel arm resonators 201 to 204 are arranged between the node on the above path and the ground terminal.
- the ground terminals to which parallel arm resonators 201, 202 and 203 are connected are made common.
- the elastic wave filter 10 constitutes a ladder type band pass filter by the above-described connection configuration of the series arm resonators 101 to 105 and the parallel arm resonators 201 to 204.
- the commonization and individualization of the ground terminals to which parallel arm resonators 201, 202, 203 and 204 are connected are not limited to the connection mode shown in FIG. 1, and the attenuation pole of elastic wave filter 10 It may be set arbitrarily from the viewpoint of adjusting.
- the number of series arm resonators constituting the elastic wave filter 10 is not limited to five as shown in FIG. 1 and may be one or more. Further, the number of parallel arm resonators constituting the elastic wave filter 10 is not limited to four as shown in FIG. 1 and may be one or more.
- circuit elements such as an inductor and a capacitor, a longitudinally coupled resonator, and the like are inserted between series arm resonators 101 to 105, parallel arm resonators 201 to 204, and input / output terminals 310 and 320. It is also good.
- FIG. 2A is a schematic view schematically showing an example of the elastic wave resonator according to the present embodiment, wherein (a) is a plan view and (b) and (c) are one-dot chain lines shown in (a).
- FIG. FIG. 2A exemplifies an elastic wave resonator 100 having the basic structure of the series arm resonators 101 to 105 and the parallel arm resonators 201 to 204 constituting the elastic wave filter 10.
- the elastic wave resonator 100 shown in FIG. 2A is for explaining a typical structure of the elastic wave resonator, and the number and the length of the electrode fingers constituting the electrode, etc. It is not limited.
- the elastic wave resonator 100 is composed of a substrate 5 having piezoelectricity and comb electrodes 100a and 100b.
- the comb-shaped electrode 100a includes a plurality of parallel electrode fingers 150a and a bus bar electrode 160a connecting the plurality of electrode fingers 150a.
- the comb-shaped electrode 100b is configured of a plurality of parallel electrode fingers 150b and a bus bar electrode 160b connecting the plurality of electrode fingers 150b.
- the plurality of electrode fingers 150 a and 150 b are formed along a direction orthogonal to the elastic wave propagation direction (X-axis direction).
- the IDT (InterDigital Transducer) electrode 54 configured of the plurality of electrode fingers 150a and 150b and the bus bar electrodes 160a and 160b includes the adhesion layer 541 and the main electrode layer 542. Has a laminated structure.
- the adhesion layer 541 is a layer for improving the adhesion between the substrate 5 and the main electrode layer 542, and, for example, Ti is used as a material.
- the film thickness of the adhesion layer 541 is 12 nm, for example.
- the material of the main electrode layer 542 for example, Al containing 1% of Cu is used.
- the film thickness of the main electrode layer 542 is, for example, 162 nm.
- the protective layer 55 is formed to cover the comb electrodes 100a and 100b.
- the protective layer 55 is a layer for protecting the main electrode layer 542 from the external environment, adjusting the frequency temperature characteristic, enhancing the moisture resistance, etc.
- a dielectric film mainly composed of silicon dioxide It is.
- the thickness of the protective layer 55 is, for example, 25 nm.
- glue layer 541, the main electrode layer 542, and the protective layer 55 is not limited to the material mentioned above.
- the IDT electrode 54 may not have the above-described laminated structure.
- the IDT electrode 54 may be made of, for example, a metal or alloy such as Ti, Al, Cu, Pt, Au, Ag, Pd or the like, and is made of a plurality of laminates made of the above metals or alloys May be
- the protective layer 55 may not be formed.
- the substrate 5 includes a high sound velocity support substrate 51, a low sound velocity film 52, and a piezoelectric film 53, and the high sound velocity support substrate 51, the low sound velocity film 52 and the piezoelectric film 53 are It has a stacked structure in this order.
- the piezoelectric film 53 is a 50 ° Y-cut X-propagation LiTaO 3 piezoelectric single crystal or a piezoelectric ceramic (lithium tantalate single crystal cut at a plane whose normal axis is rotated by 50 ° from the Y axis with the X axis as the central axis, or It is a ceramic, and is made of a single crystal or ceramic in which a surface acoustic wave propagates in the X-axis direction.
- the piezoelectric film 53 has, for example, a thickness of 600 nm.
- the material and cut angle of the piezoelectric single crystal used as the piezoelectric film 53 are appropriately selected according to the required specifications of each filter.
- the high sound velocity support substrate 51 is a substrate for supporting the low sound velocity film 52, the piezoelectric film 53 and the IDT electrode 54. Further, the high sound velocity support substrate 51 is a substrate in which the sound velocity of the bulk wave in the high sound velocity support substrate 51 is higher than that of the surface waves propagating through the piezoelectric film 53 and the elastic waves such as boundary waves. It is confined in the portion where the piezoelectric film 53 and the low sound velocity film 52 are stacked, and functions so as not to leak below the high sound velocity support substrate 51.
- the high sound velocity support substrate 51 is, for example, a silicon substrate and has a thickness of, for example, 200 ⁇ m.
- the low sound velocity film 52 is a film in which the sound velocity of the bulk wave in the low sound velocity film 52 is lower than the bulk wave propagating through the piezoelectric film 53, and is disposed between the piezoelectric film 53 and the high sound velocity support substrate 51. Ru. This structure and the property that energy concentrates in a medium in which elastic waves are inherently low in sound velocity suppress leakage of surface acoustic wave energy to the outside of the IDT electrode.
- the low sound velocity film 52 is, for example, a film containing silicon dioxide as a main component, and has a thickness of, for example, 670 nm.
- the substrate 5 it is possible to significantly increase the Q value at the resonant frequency and the antiresonant frequency as compared with the conventional structure in which the piezoelectric substrate is used as a single layer. That is, since an elastic wave resonator having a high Q value can be configured, it is possible to configure a filter having a small insertion loss using the elastic wave resonator.
- the elastic wave resonator 100 can be maintained at a high value. Therefore, it is possible to form the elastic wave filter 10 in which the low loss in the pass band is maintained.
- the high sound velocity support substrate 51 has a structure in which a support substrate and a high sound velocity film in which the sound velocity of bulk waves propagating is faster than elastic waves such as surface waves and boundary waves propagating in the piezoelectric film 53 are stacked. May be included.
- the support substrate is lithium tantalate, lithium niobate, piezoelectric such as quartz, alumina, magnesia, silicon nitride, aluminum nitride, silicon carbide, zirconia, cordierite, mullite, steatite, forsterite, etc.
- a dielectric such as sapphire or glass or a semiconductor such as silicon or gallium nitride, a resin substrate, or the like can be used.
- the high sound velocity film may be various materials such as aluminum nitride, aluminum oxide, silicon carbide, silicon nitride, silicon oxynitride, DLC film or diamond, a medium containing the above material as a main component, a medium containing a mixture of the above materials as a main component, High sound speed materials can be used.
- FIG. 2B is a cross-sectional view schematically showing an elastic wave resonator according to a first modification of the embodiment.
- the IDT electrode 54 is formed on the substrate 5 having the piezoelectric film 53, but the substrate on which the IDT electrode 54 is formed is shown in FIG. 2B.
- it may be a piezoelectric single crystal substrate 57 formed of a single layer of a piezoelectric layer.
- Piezoelectric single crystal substrate 57 for example, is composed of a piezoelectric single crystal of LiNbO 3.
- the elastic wave resonator 100 includes a piezoelectric single crystal substrate 57 of LiNbO 3 , an IDT electrode 54, and a protective layer 55 formed on the piezoelectric single crystal substrate 57 and on the IDT electrode 54. ing.
- the laminated structure, the material, the cut angle, and the thickness of the piezoelectric film 53 and the piezoelectric single crystal substrate 57 described above may be changed as appropriate according to the required passage characteristics of the elastic wave filter device. Even in the elastic wave resonator 100 using a LiTaO 3 piezoelectric substrate or the like having a cut angle other than the cut angle described above, the same effect as the elastic wave resonator 100 using the piezoelectric film 53 described above can be exhibited. .
- the wavelength of the elastic wave resonator is defined by a wavelength ⁇ which is a repetition period of a plurality of electrode fingers 150a or 150b constituting the IDT electrode 54 shown in (b) of FIG. 2A.
- the electrode pitch is 1/2 of the wavelength ⁇
- the line width of the electrode fingers 150a and 150b forming the comb electrodes 100a and 100b is W
- the crossing width L of the pair of comb electrodes 100a and 100b is an overlap when viewed from the elastic wave propagation direction (X-axis direction) of the electrode finger 150a and the electrode finger 150b.
- Electrode finger length is a repetition period of a plurality of electrode fingers 150a or 150b constituting the IDT electrode 54 shown in (b) of FIG. 2A.
- the electrode pitch is 1/2 of the wavelength ⁇
- the line width of the electrode fingers 150a and 150b forming the comb electrodes 100a and 100b is
- the electrode duty of each elastic wave resonator is the line width occupancy rate of the plurality of electrode fingers 150a and 150b, and the ratio of the line width to the added value of the line width and the space width of the plurality of electrode fingers 150a and 150b. And defined by W / (W + S). Further, the height of the comb electrodes 100a and 100b is h.
- electrode parameters relating to the shape of the IDT electrode of the elastic wave resonator such as the wavelength ⁇ , the crossover width L, the electrode duty, the height h of the IDT electrode 54, and the like are referred to as electrode parameters.
- FIG. 3 is a circuit diagram illustrating the operation principle of a ladder-type elastic wave filter and a graph showing frequency characteristics.
- the elastic wave filter shown in (a) of FIG. 3 is a basic ladder type filter configured of one series arm resonator 301 and one parallel arm resonator 302.
- the parallel arm resonator 302 has a resonance frequency frp and an antiresonance frequency fap (> frp) in the resonance characteristic.
- the series arm resonator 301 has a resonance frequency frs and an antiresonance frequency fas (> frs> frp) in the resonance characteristic.
- the antiresonance frequency fap of the parallel arm resonator 302 and the resonance frequency frs of the series arm resonator 301 are made close to each other.
- the vicinity of the resonance frequency frp in which the impedance of the parallel arm resonator 302 approaches 0 becomes the low frequency side stop band.
- the impedance of the parallel arm resonator 302 increases near the antiresonance frequency fap, and the impedance of the series arm resonator 301 approaches zero near the resonance frequency frs.
- the signal path from the input / output terminal 310 to the signal path 320 becomes a signal passing area. Furthermore, when the frequency becomes high and comes close to the antiresonance frequency fas, the impedance of the series arm resonator 301 becomes high, and it becomes the high frequency side stop band.
- the number of resonance stages formed by the parallel arm resonators and the series arm resonators is appropriately optimized according to the required specification.
- antiresonance frequencies fap of a plurality of parallel arm resonators are made to substantially coincide, and antiresonance frequencies fas of a plurality of series arm resonators are made to substantially coincide.
- the elastic wave filter having the above operation principle, when a high frequency signal is input from the input / output terminal 310, a potential difference occurs between the input / output terminal 310 and the reference terminal, thereby distorting the piezoelectric layer. Surface acoustic waves are generated.
- the wavelength ⁇ of the IDT electrode 54 with the wavelength of the passband, only the high frequency signal having the frequency component to be passed passes through the elastic wave filter.
- FIG. 4A is a schematic plan view showing an example of the configuration of the IDT electrodes of the series arm resonators 101 to 105 constituting the elastic wave filter 10 according to the embodiment.
- FIG. 4B is a schematic plan view showing an example of the configuration of the IDT electrodes of the parallel arm resonators 201 to 204 constituting the elastic wave filter 10 according to the embodiment.
- FIG. 4A exemplarily shows a planar schematic view showing the IDT electrode structure of the series arm resonator 101 as a representative of the series arm resonators 101 to 105.
- the series arm resonator 101 shown in FIG. 4A is for describing a typical structure of the series arm resonators 101 to 105, and the number and length of the electrode fingers constituting the electrode Not limited to this.
- the series arm resonator 101 is composed of a substrate 5 having piezoelectricity, comb electrodes 101 a and 101 b formed on the substrate 5, and a reflector 141.
- the comb-shaped electrode 101a is composed of a plurality of parallel electrode fingers 151a and a bus bar electrode 161a connecting one ends of the plurality of electrode fingers 151a.
- the comb-shaped electrode 101b is configured of a plurality of parallel electrode fingers 151b and a bus bar electrode 161b connecting one ends of the plurality of electrode fingers 151b.
- the plurality of electrode fingers 151a and 151b are formed along a direction orthogonal to the elastic wave propagation direction (X-axis direction).
- the comb-shaped electrodes 101a and 101b are disposed to face each other such that the plurality of electrode fingers 151a and 151b are inserted in each other. That is, the IDT electrode of the series arm resonator 101 has a pair of comb electrodes 101a and 101b.
- the comb-shaped electrode 101a has the dummy electrode arrange
- the comb-shaped electrode 101b has the dummy electrode arrange
- the reflector 141 includes a plurality of electrode fingers parallel to one another and bus bar electrodes connecting the plurality of electrode fingers, and is disposed at both ends of the pair of interdigital electrodes 101a and 101b.
- the IDT electrode constituted by the pair of comb electrodes 101a and 101b has a laminated structure of the adhesion layer 541 and the main electrode layer 542 as shown in (b) of FIG. 2A. It is not limited.
- electrode fingers 152 are discretely formed on the IDT electrodes of the series arm resonator 101.
- the electrode finger 152 is a first thinning electrode (floating electrode) which is not connected to any of the bus bar electrodes 161a and 161b, and is disposed in parallel with the plurality of electrode fingers 151a and 151b at the same pitch.
- a plurality of electrode fingers 151 a and 151 b are disposed between two adjacent electrode fingers 152. That is, the pitch of the electrode fingers 152 is larger than the pitch of the plurality of electrode fingers 151a and 151b.
- FIG. 4B exemplarily shows a plane schematic view showing an IDT electrode structure of the parallel arm resonator 201 as a representative of the parallel arm resonators 201 to 204.
- the parallel arm resonator 201 shown in FIG. 4B is for explaining a typical structure of the parallel arm resonators 201 to 204, and the number and length of the electrode fingers constituting the electrode, etc. Not limited to this.
- the parallel arm resonator 201 is composed of a substrate 5 having piezoelectricity, comb electrodes 201 a and 201 b formed on the substrate 5, and a reflector 241.
- the comb-shaped electrode 201a is composed of a plurality of parallel electrode fingers 251a and a bus bar electrode 261a connecting one ends of the plurality of electrode fingers 251a.
- the comb-shaped electrode 201b is configured of a plurality of parallel electrode fingers 251b and a bus bar electrode 261b connecting one ends of the plurality of electrode fingers 251b.
- the plurality of electrode fingers 251 a and 251 b are formed along a direction orthogonal to the elastic wave propagation direction (X-axis direction).
- the comb-shaped electrodes 201a and 201b are disposed to face each other such that the plurality of electrode fingers 251a and 251b are inserted in each other. That is, the IDT electrode of the parallel arm resonator 201 has a pair of comb electrodes 201a and 201b.
- the comb-shaped electrode 201a has the dummy electrode arrange
- the comb-shaped electrode 201b has the dummy electrode arrange
- the reflector 241 includes a plurality of parallel electrode fingers and bus bar electrodes connecting the plurality of electrode fingers, and is disposed at both ends of the pair of interdigital electrodes 201 a and 201 b.
- the IDT electrode composed of a pair of comb electrodes 201a and 201b has a laminated structure of the adhesion layer 541 and the main electrode layer 542 as shown in (b) of FIG. 2A. It is not limited.
- electrode fingers 252 are discretely formed on the IDT electrodes of the parallel arm resonator 201.
- the electrode finger 252 is an electrode finger having the largest electrode finger width in the IDT electrodes of the parallel arm resonator 201, and has an electrode finger width twice or more the average electrode finger width in the electrode fingers excluding the electrode finger 252. 2 A thinning electrode (filled electrode).
- the adjacent electrode fingers 251a and 251b and the spaces between the plurality of adjacent electrode fingers 251a and 251b are combined to form one electrode finger, and the bus bar electrodes 261a and 261b are provided.
- the thinning rate of the IDT electrode is defined.
- the thinning-out rate (first thinning-out rate) of the IDT electrodes in the series arm resonators 101 to 105 is M, and the pair of adjacent electrode fingers 151a and 151b is a pair of electrode fingers.
- the thinning rate (second thinning rate) of the IDT electrodes in the parallel arm resonators 201 to 204 is M, and the number of electrode fingers 252 in the IDT electrode is M, and one pair of adjacent electrode fingers 251 a and 251 b is a pair.
- the logarithm of the IDT electrode in the case of being constituted by repetition of only the electrode fingers 251 a and 251 b without applying the electrode finger 252 is N, the following formula 1 is used.
- Table 1 shows an example of electrode parameters of the elastic wave filter 10 according to the embodiment.
- the first thinning electrode is applied to all IDT electrodes of series arm resonators 101 to 105, and the first thinning electrode is applied to all IDT electrodes of parallel arm resonators 201 to 204. 2 A thinning electrode is applied. This makes it possible to maximize the steepness at both the low frequency end and the high frequency end of the passband.
- a first thinning electrode may be applied to at least one of the IDT electrodes of the series arm resonators 101 to 105. Even in this case, the steepness can be enhanced at the high frequency end of the pass band.
- a second thinning electrode may be applied to at least one of the IDT electrodes of the parallel arm resonators 201 to 204. Even in this case, the steepness can be enhanced at the low frequency end of the pass band.
- FIG. 5 shows impedance characteristics ((a) of FIG. 5) and Q of an elastic wave resonator to which the first thinning electrode (floating electrode) is applied and an elastic wave resonator to which the second thinning electrode (filled electrode) is applied. It is the graph which compared the characteristic ((b) of Drawing 5). The first and second thinning rates of the elastic wave resonator shown in FIG. 5 are both 9%.
- the impedance which shows the resonance characteristic of an elastic wave resonator becomes a local minimum which approaches 0 in the resonant frequency fr, and becomes a local maximum which approaches infinity at antiresonance frequency fa.
- the impedance characteristics of the elastic wave resonator to which the first thinning electrode (floating electrode) is applied and the elastic wave resonator to which the second thinning electrode (filled electrode) is applied are substantially the same.
- the elastic wave resonator having the above-mentioned impedance characteristic is applied to either of the series arm resonator and the parallel arm resonator of the elastic wave filter, the frequency and amount of attenuation of the attenuation pole in the filter passage characteristic are substantially the same. .
- the second thinning electrode (filled electrode) is the second one in the frequency range BL on the low frequency side in the frequency range from the resonant frequency fr to the antiresonant frequency fa.
- the Q value is higher than that of the thinning electrode (floating electrode).
- the first thinning electrode (floating electrode) has a higher Q value than the second thinning electrode (filled electrode).
- weighting is applied to the IDT electrodes using a so-called decimation method. It is conventionally known to be effective.
- the steepness at the low frequency end of the passband is improved as the Q value near the resonance frequency of the parallel arm resonator improves
- the steepness of the high frequency end of the passband is the series arm It improves as the Q characteristics near the antiresonant frequency of the resonator improve.
- the inventors compared the Q values of an elastic wave resonator including a first thinning electrode (floating electrode) and an elastic wave resonator including a second thinning electrode (filled electrode) as shown in FIG.
- the elastic wave resonator including the second thinning electrode (filled electrode) has a higher Q value in the low frequency region (frequency range BL) near the frequency, and the first in the high frequency region (frequency range BH) near the antiresonance frequency. It has been found that the elastic wave resonator including the thinning electrode (floating electrode) has a higher Q value.
- the second thinned electrode has a low sound velocity as compared to a normal region not filled because the filled region is occupied by the electrode film.
- the first thinning electrode has a high sound velocity as compared with the filled area and the normal area. For this reason, the second thinning electrode (filled electrode) has a good Q value on the low frequency side corresponding to low sound velocity, and the first thinning electrode (floating electrode) has a good Q value on the high frequency side corresponding to high sound velocity.
- the IDT electrodes including the second thinning electrode are applied to the parallel arm resonators 201 to 204, and the IDT including the first thinning electrode (floating electrode) Electrodes are applied to the series arm resonators 101-105.
- the elastic wave filter 10 having high sharpness at both the low frequency end and the high frequency end of the pass band.
- FIG. 6A shows that the thinning rate (each of the first thinning rate and the second thinning rate) is 5% for the elastic wave resonator to which the first thinning electrode is applied and the elastic wave resonator to which the second thinning electrode is applied. It is the graph which compared the Q characteristic of the case.
- FIG. 6B shows that the thinning rate (each of the first thinning rate and the second thinning rate) is 15 for the elastic wave resonator to which the first thinning electrode is applied and the elastic wave resonator to which the second thinning electrode is applied. It is the graph which compared the Q characteristic in the case of%. Further, FIG.
- FIG. 6C shows that the thinning rate (each of the first thinning rate and the second thinning rate) of the elastic wave resonator to which the first thinning electrode is applied and the elastic wave resonator to which the second thinning electrode is applied is 20. It is the graph which compared the Q characteristic in the case of%.
- the elastic wave resonators in FIGS. 6A to 6C are different from the elastic wave resonators in FIG. 5B in numerical values of electrode parameters other than the thinning rate.
- the second thinning electrode (filled electrode) is more effective in the frequency range BL on the low frequency side in the frequency range from the resonant frequency fr to the antiresonance frequency fa.
- the Q value is higher than that of the first thinning electrode (floating electrode), and in the frequency range BH on the high frequency side, the Q value of the first thinning electrode (floating electrode) is higher than that of the second thinning electrode (filled electrode).
- the Q value improves when the IDT electrode includes the thinning electrode, but the Q value of the IDT electrode is degraded when the thinning ratio is higher than 30%. For this reason, compared with the IDT electrode which does not apply a thinning-out electrode for ensuring the same bandwidth, the steepness in the high frequency end and low frequency end of a pass band may not be able to be improved more. Therefore, the first thinning ratio of the IDT electrode including the first thinning electrode (floating electrode) is desirably 30% or less.
- the second thinning ratio of the IDT electrode including the second thinning electrode (filled electrode) is preferably 30% or less.
- FIG. 7 is a graph showing the pass characteristics of the elastic wave filter 10 according to the embodiment, the pass characteristics of the series arm resonators 101 to 105, and the reflection characteristics of the parallel arm resonators 201 to 204.
- the pass characteristics (insertion loss) in the vicinity of the pass band of the elastic wave filter 10 in addition to the pass characteristics (insertion loss) in the vicinity of the pass band of the elastic wave filter 10, the pass characteristics (insertion loss) of one of the series arm resonators 101 to 105 and the parallel arm resonators 201 to 204.
- an IDT electrode including a second thinning electrode (filled electrode) is applied to parallel arm resonators 201 to 204, and an IDT electrode including a first thinning electrode (floating electrode) is a series arm
- the steepness is high at both the low frequency end and the high frequency end of the pass band.
- FIG. 8 is a graph comparing the insertion loss around the passbands of the elastic wave filters according to the embodiment, the comparative example 1 and the comparative example 2.
- the thinning rate of each of the IDT electrodes of the elastic wave filters according to the embodiment and the comparative examples 1 and 2 is 9%.
- the first thinning-out electrode is used for all the resonators of the series arm resonators 101 to 105 and the parallel arm resonators 201 to 204.
- the configuration differs in that (floating electrode) is applied, and the second thinning electrode (filled electrode) is not applied to the parallel arm resonators 201 to 204.
- the second thinning electrode is used for all the resonators of the series arm resonators 101 to 105 and the parallel arm resonators 201 to 204.
- the configuration differs in that (the filled-in electrode) is applied, and the first thinning-out electrode (floating electrode) is not applied to the series arm resonators 101 to 105.
- the comparative example 2 At the low frequency end of the pass band, the comparative example 2, the embodiment, and the comparative example 1 become the ascending order of the insertion loss.
- the elastic wave filter according to Comparative Example 1 since the first thinning electrode (floating electrode) having a high Q value in the frequency range BH on the high frequency side is applied to the parallel arm resonators 201 to 204, the frequency on the low frequency side In the range BL, the insertion loss increases.
- the embodiment, the comparative example 1, and the comparative example 2 are in ascending order of the insertion loss.
- the elastic wave filter according to Comparative Example 2 since the second thinning electrode (filled electrode) having a high Q value in the frequency range BL on the low frequency side is applied to the series arm resonators 101 to 105, the frequency on the high frequency side In the range BH, the insertion loss increases.
- the elastic wave filter according to the embodiment in which the first thinning electrode (floating electrode) having a high Q value in the frequency range BH on the high frequency side is applied to the series arm resonators 101 to 105 and the comparative example 1
- Insertion loss in the high frequency range BH is reduced.
- the steepness of the insertion loss at the high frequency end of the pass band is higher in the elastic wave filter according to the embodiment and the comparative example 1 than in the elastic wave filter according to the comparative example 2.
- the elastic wave filter 10 can improve the steepness of the insertion loss at both the low frequency end and the high frequency end of the pass band.
- FIG. 9 is a graph comparing the insertion loss around the pass band of the elastic wave filter according to the embodiment and the comparative example 3.
- the elastic wave filter according to comparative example 3 has thinning electrodes for any of the series arm resonators 101 to 105 and the parallel arm resonators 201 to 204 as compared with the elastic wave filter 10 according to the embodiment.
- the point which does not apply is different as composition.
- the electrode parameters of the IDT electrode of the elastic wave filter according to comparative example 3 such that the passband width of the elastic wave filter according to comparative example 3 and the passband width of elastic wave filter 10 according to the embodiment are the same. Is adjusted.
- the insertion loss of the elastic wave filter 10 according to the embodiment is lower than that of the elastic wave filter according to the third comparative example.
- a region on the lower frequency side than the low frequency end of the passband a region where the steepness of the insertion loss is maximum on the low frequency side
- a region on the higher frequency side than the high frequency end of the passband insertion loss
- the elastic wave filter 10 according to the embodiment has a low frequency of the passband. It is possible to improve the steepness of the insertion loss at both the end and the high frequency end.
- elastic wave filter 10 concerning an embodiment of the present invention was mentioned and explained an embodiment, an elastic wave filter of the present invention is not limited to the above-mentioned embodiment.
- Other embodiments realized by combining arbitrary components in the above embodiments, and modifications obtained by applying various modifications to the above embodiments without departing from the scope of the present invention will occur to those skilled in the art Examples and various devices incorporating the elastic wave filter 10 according to the embodiment of the present invention are included in the present invention.
- the present invention can be widely used in communication devices such as mobile phones as high-elasticity elastic wave filters applicable to multi-band and multi-mode frequency standards.
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Abstract
Description
[1.弾性波フィルタの回路構成]
図1は、実施の形態に係る弾性波フィルタ10の回路構成図である。同図に示すように、弾性波フィルタ10は、直列腕共振子101、102、103、104および105と、並列腕共振子201、202、203および204と、入出力端子310および320と、を備える。
図2Aは、本実施の形態に係る弾性波共振子の一例を模式的に表す概略図であり、(a)は平面図、(b)および(c)は、(a)に示した一点鎖線における断面図である。図2Aには、弾性波フィルタ10を構成する直列腕共振子101~105および並列腕共振子201~204の基本構造を有する弾性波共振子100が例示されている。なお、図2Aに示された弾性波共振子100は、弾性波共振子の典型的な構造を説明するためのものであって、電極を構成する電極指の本数および長さなどは、これに限定されない。
次に、本実施の形態に係るラダー型の弾性波フィルタの動作原理について説明する。
次に、本実施の形態に係る弾性波フィルタ10の特徴的な構成である直列腕共振子および並列腕共振子のIDT電極の構成について説明する。
図5は、第1間引き電極(浮き電極)が適用された弾性波共振子および第2間引き電極(塗りつぶし電極)が適用された弾性波共振子のインピーダンス特性(図5の(a))およびQ特性(図5の(b))を比較したグラフである。なお、図5に示された弾性波共振子の第1間引き率および第2間引き率は、いずれも9%である。
図7は、実施の形態に係る弾性波フィルタ10の通過特性、直列腕共振子101~105の通過特性、および並列腕共振子201~204の反射特性を示すグラフである。同図には、弾性波フィルタ10の通過帯域近傍の通過特性(挿入損失)に加えて、直列腕共振子101~105のうちの1つの通過特性(挿入損失)および並列腕共振子201~204のうちの1つの反射特性(反射損失)が示されている。並列腕共振子の反射特性において、反射損失の極大値を有する周波数が、当該並列腕共振子の共振周波数frpを示している。また、直列腕共振子の通過特性において、挿入損失の極大値を有する周波数が、当該直列腕共振子の***振周波数fasを示している。
以上、本発明の実施の形態に係る弾性波フィルタ10について、実施の形態を挙げて説明したが、本発明の弾性波フィルタは、上記実施の形態に限定されるものではない。上記実施の形態における任意の構成要素を組み合わせて実現される別の実施の形態や、上記実施の形態に対して本発明の主旨を逸脱しない範囲で当業者が思いつく各種変形を施して得られる変形例や、本発明の実施の形態に係る弾性波フィルタ10を内蔵した各種機器も本発明に含まれる。
10 弾性波フィルタ
51 高音速支持基板
52 低音速膜
53 圧電膜
54 IDT電極
55 保護層
57 圧電単結晶基板
100 弾性波共振子
100a、100b、101a、101b、201a、201b 櫛形電極
101、102、103、104、105、301 直列腕共振子
141、241 反射器
150a、150b、151a、151b、152、251a、251b、252 電極指
160a、160b、161a、161b、261a、261b バスバー電極
201、202、203、204、302 並列腕共振子
310、320 入出力端子
541 密着層
542 主電極層
Claims (6)
- 第1入出力端子および第2入出力端子と、
前記第1入出力端子と前記第2入出力端子とを結ぶ経路上に配置された1以上の直列腕共振子と、
前記経路およびグランドの間に配置された1以上の並列腕共振子と、を備え、
前記1以上の直列腕共振子および前記1以上の並列腕共振子のそれぞれは、圧電性を有する基板上に形成されたIDT(InterDigital Transducer)電極を有する弾性波共振子であり、
前記IDT電極は、弾性波伝搬方向と交差する方向に延伸し、互いに平行に配置された複数の電極指と、当該複数の電極指を構成する電極指の一方端同士を接続するバスバー電極とで構成された櫛形電極を一対有し、
前記複数の電極指のうち、前記一対の櫛形電極を構成するいずれの前記バスバー電極とも接続されていない電極指を第1間引き電極と定義し、
前記複数の電極指のうち、最大の電極指幅を有する電極指であって、当該電極指を除く電極指における平均電極指幅の2倍以上の電極指幅を有する電極指を第2間引き電極と定義した場合、
前記1以上の直列腕共振子の少なくとも1つが有するIDT電極は、前記第1間引き電極を含み、
前記1以上の並列腕共振子の少なくとも1つが有するIDT電極は、前記第2間引き電極を含む、
弾性波フィルタ。 - 前記1以上の直列腕共振子のそれぞれが有するIDT電極は、前記第1間引き電極を含む、
請求項1に記載の弾性波フィルタ。 - 前記1以上の並列腕共振子のそれぞれが有するIDT電極は、前記第2間引き電極を含む、
請求項1または2に記載の弾性波フィルタ。 - 前記1以上の直列腕共振子のそれぞれが有するIDT電極において、前記複数の電極指の総数に対する前記第1間引き電極の本数の割合を、当該IDT電極の第1間引き率と定義した場合、
前記第1間引き電極を含む前記IDT電極の前記第1間引き率は、30%以下である、
請求項1~3のいずれか1項に記載の弾性波フィルタ。 - 前記1以上の並列腕共振子のそれぞれが有するIDT電極において、前記複数の電極指の総数に対する前記第2間引き電極の本数の割合を、当該IDT電極の第2間引き率と定義した場合、
前記第2間引き電極を含む前記IDT電極の前記第2間引き率は、30%以下である、
請求項1~4のいずれか1項に記載の弾性波フィルタ。 - 前記基板は、
前記IDT電極が一方の面上に形成された圧電膜と、
前記圧電膜を伝搬する弾性波音速よりも、伝搬するバルク波音速が高速である高音速支持基板と、
前記高音速支持基板と前記圧電膜との間に配置され、前記圧電膜を伝搬するバルク波音速よりも、伝搬するバルク波音速が低速である低音速膜と、を備える、
請求項1~5のいずれか1項に記載の弾性波フィルタ。
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JP2019561661A JP6801797B2 (ja) | 2017-12-27 | 2018-12-21 | 弾性波フィルタ |
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US (1) | US10958246B2 (ja) |
JP (1) | JP6801797B2 (ja) |
KR (1) | KR102205186B1 (ja) |
CN (1) | CN111527699B (ja) |
WO (1) | WO2019131530A1 (ja) |
Cited By (5)
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WO2021002321A1 (ja) * | 2019-07-01 | 2021-01-07 | 株式会社村田製作所 | 弾性波フィルタおよびマルチプレクサ |
WO2021045031A1 (ja) * | 2019-09-02 | 2021-03-11 | 株式会社村田製作所 | 弾性波フィルタ |
KR20220020975A (ko) * | 2019-07-25 | 2022-02-21 | 가부시키가이샤 무라타 세이사쿠쇼 | 탄성파 필터 |
WO2022158470A1 (ja) * | 2021-01-25 | 2022-07-28 | 株式会社村田製作所 | 弾性波フィルタおよびマルチプレクサ |
JP2022186631A (ja) * | 2021-06-03 | 2022-12-15 | レゾナント インコーポレイテッド | 低損失横方向励起フィルムバルク音響共振器及びフィルタ |
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JP6801797B2 (ja) | 2020-12-16 |
US20200280302A1 (en) | 2020-09-03 |
KR20200061409A (ko) | 2020-06-02 |
CN111527699A (zh) | 2020-08-11 |
KR102205186B1 (ko) | 2021-01-20 |
US10958246B2 (en) | 2021-03-23 |
JPWO2019131530A1 (ja) | 2020-08-27 |
CN111527699B (zh) | 2021-02-05 |
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