WO2005036743A1 - 弾性境界波装置 - Google Patents
弾性境界波装置 Download PDFInfo
- Publication number
- WO2005036743A1 WO2005036743A1 PCT/JP2004/012814 JP2004012814W WO2005036743A1 WO 2005036743 A1 WO2005036743 A1 WO 2005036743A1 JP 2004012814 W JP2004012814 W JP 2004012814W WO 2005036743 A1 WO2005036743 A1 WO 2005036743A1
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- WIPO (PCT)
- Prior art keywords
- acoustic wave
- wave device
- boundary acoustic
- boundary
- electrode
- Prior art date
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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
- H03H9/02—Details
- H03H9/0222—Details of interface-acoustic, boundary, pseudo-acoustic or Stonely wave devices
Definitions
- the present invention relates to a boundary acoustic wave device using a boundary acoustic wave propagating along a boundary between first and second medium layers having different sound speeds, and more particularly, to a boundary acoustic wave device having an improved electrode structure.
- a boundary acoustic wave device using a boundary acoustic wave propagating along a boundary between first and second medium layers having different sound speeds, and more particularly, to a boundary acoustic wave device having an improved electrode structure.
- a surface acoustic wave device using a surface acoustic wave such as a Rayleigh wave or a first leaky wave can be reduced in size and weight and does not require adjustment.
- surface acoustic wave devices are widely used for RF filters or IF filters for mobile phones, resonators for VCOs, VIF filters for televisions, and the like.
- a boundary acoustic wave device has been proposed as a device that does not require a package having a cavity as described above.
- FIG. 6 is a schematic partial cutaway front sectional view showing an example of a conventional boundary acoustic wave device.
- first and second medium layers 102 and 103 having different sound velocities are stacked.
- An IDT 104 as an electroacoustic transducer is arranged at a boundary A between the first and second medium layers 102 and 103. Further, reflectors (not shown) are arranged on both sides of the IDT 104 in the direction of propagation of the boundary acoustic wave.
- boundary acoustic wave device 101 a boundary acoustic wave is excited by applying an input signal to the IDT 104.
- the boundary acoustic wave is represented by a boundary acoustic wave device as schematically shown by arrow B in Fig. 6. Energy is concentrated and propagates near the boundary A of the location 101.
- Non-Patent Document 1 shows an example of such a boundary acoustic wave device.
- the IDT is formed on a 126 ° rotating Y-plate X-propagating LiTaO substrate,
- a Si ⁇ film is formed to a predetermined thickness on a LiTaO substrate so as to cover the substrate.
- Non-Patent Document 1 when the thickness of the SiO film is 1. 1. ⁇ (where ⁇ is the wavelength of the boundary acoustic wave),
- Patent Document 1 listed below discloses that A1 is formed on a 126 ° rotation plate X-propagation LiTaO substrate.
- a boundary acoustic wave device having a structure comprising an IDT is disclosed.
- the thickness of the electrode finger of the interdigital electrode is H
- the width of the electrode finger is L
- the interval between the electrode fingers is S
- the duty ratio L / (L + S) of the interdigital electrode is set to 0.5.
- Patent document 1 W098-52279
- Non-Noon Document 1 “Piezoelectric Acoustic Boundary Waves Propagating Long the Interface Between Si ⁇ 2 and LiTaO 3 J IEEE Trans. Sonics and ultrason., VOL. SU—25, No. 6, 1978 IEEE
- boundary acoustic wave device is strongly required to have low loss.
- conventional boundary acoustic wave devices have not been able to adequately satisfy this requirement.
- An object of the present invention is to provide good resonance characteristics and filter characteristics in view of the state of the art.
- Another object of the present invention is to provide a boundary acoustic wave device having low loss.
- the present invention provides an elastic boundary including a first medium layer, a second medium layer, and an interdigital electrode and / or a reflector disposed at a boundary between the first and second medium layers.
- a boundary acoustic wave device characterized in that when the duty ratio of the interdigital electrode and / or the reflector is d, 0.54 ⁇ d ⁇ 0.89.
- the first medium layer is formed of LiNb. It is configured using a substrate mainly composed of o.
- the second medium layer is formed of SiO 2
- the duty ratio d of the interdigital electrode and Z or the reflector is set to be larger than 0.54 and smaller than 0.89. Therefore, as will be clear from a specific experimental example described later, the insertion loss can be reduced.
- the present invention is characterized in that the loss in the boundary acoustic wave device is reduced by setting the duty ratio in the above specific range in the boundary acoustic wave device.
- FIG. 1 is a schematic plan view showing an electrode structure of a boundary acoustic wave device according to one embodiment of the present invention.
- FIG. 2 is a surface cross-sectional view showing a main part of the boundary acoustic wave device shown in FIG. 1.
- FIG. 3 is a diagram showing a change in impedance when the duty ratio of an interdigital electrode and a reflector of a boundary acoustic wave device is changed.
- FIG. 4 is a diagram showing a circuit configuration of a four-stage ⁇ -type ladder type filter configured using a plurality of boundary acoustic wave devices shown in FIG. 1.
- FIG. 4 is a diagram showing a circuit configuration of a four-stage ⁇ -type ladder type filter configured using a plurality of boundary acoustic wave devices shown in FIG. 1.
- FIG. 5 is a diagram showing a relationship between a duty ratio of an electrode finger of a boundary acoustic wave device and a minimum insertion loss in a four-stage ⁇ -type ladder filter.
- FIG. 6 is a schematic partially cutaway front sectional view for explaining a conventional boundary acoustic wave device.
- FIG. 1 is a schematic sectional view showing an electrode structure of a boundary acoustic wave device according to one embodiment of the present invention.
- a rectangular plate-shaped LiNbO substrate 2 is used as the first medium layer.
- the LiNbO substrate 2 uses a 15 ° rotating Y-plate X-propagation LiNbO substrate.
- a rotating Y-plate X-propagating LiNbO substrate having another rotation angle may be used.
- O film 3 is laminated.
- the illustration of the Si ⁇ film is omitted, and the SiO 3 film 3 is omitted.
- the electrode structure arranged at the boundary with the LiNbO substrate 2 is shown. That is, LiNbO
- an interdigital electrode 4 and reflectors 5 and 6 are formed on the substrate 2.
- the digital electrode 4 has a plurality of mutually interleaved electrode fingers 4a and 4b.
- the interdigital electrode 4 is weighted so that the crossing width changes in the surface acoustic wave propagation direction as shown in the figure.
- interdigital electrode 4 is weighted by the cross width as described above is to suppress the transverse mode spurious.
- grating reflectors 5 and 5 are provided on both sides of the interdigital electrode 4 in the surface wave propagation direction.
- the reflectors 5, 6 have a structure in which a plurality of electrode fingers 5a, 6a are short-circuited at both ends.
- the duty ratio of the interdigital electrode 4 and the reflectors 5 and 6 is set to be larger than 0.54 and smaller than 0.89, the input loss can be reduced and the frequency at the time of manufacturing can be reduced. Wave number variation can be reduced. This will be described based on specific experimental examples.
- the duty ratio in the present invention refers to a distance between electrode finger centers in a space between left and right adjacent electrode fingers.
- the duty ratio is a value determined by L / P.
- the interdigital electrode 4 and the reflectors 5 and 6 were formed by the following thin film forming method. You In other words, a NiCr film having a thickness of 0.001 ⁇ is deposited on the LiNbO substrate 2 as
- An Au film having a thickness of 0.4 ⁇ was formed on the NiCr film by the same vapor deposition method. Thereafter, patterning was performed by a lift-off method, and interdigital electrodes 4 and reflectors 5 and 6 were formed.
- the wavelength ⁇ of the interdigital electrode 4 was 3 ⁇ m.
- the number of electrode fingers in the interdigital electrode 4 was 50 pairs, the number of electrode fingers in the reflector was 50, and the aperture length A in the reflector was 30 ⁇ .
- the SiO film 3 is
- a film was formed by the Ron sputtering method.
- the temperature for film formation should be in the range of 200 ⁇ 50 ° C.
- the thickness of the film was 1.5 ⁇ .
- the SH type boundary acoustic wave is excited and confined between the reflectors 5 and 6, and the resonance characteristics of the SH type boundary acoustic wave are obtained. Can be.
- the impedance ratio is the ratio of the impedance Za at the anti-resonance frequency to the impedance Zr at the resonance frequency in the resonance characteristics, and is 20 -1 og I Za / Zr I [dB]. The higher the impedance ratio, the better the characteristics.
- a four-stage ⁇ -type ladder-type filter was configured. . That is, as shown in the circuit diagram of FIG. 4, the series arm resonators Sl, S2, S3, and S4 were connected to the series arm between the input port 11 and the output port 12. Then, the parallel arm resonator P1 was connected between the connection point of the series arm resonator S1 not connected to the series arm resonator S2 and the ground potential. Parallel arm resonators P2 and P3 were connected between the two connection points between series arm resonators S2 and S3 and the ground potential, respectively. Further, a parallel arm resonator P4 was connected between the connection point on the side of the series arm resonator S4 not connected to the series arm resonator S3 and the ground potential.
- the force S constituting the four-stage ⁇ -type ladder filter, the series arm resonators SI-S4 and the parallel arm resonators P1 and P4 were configured using the boundary acoustic wave device 1.
- the electrode fingers in the boundary acoustic wave device 1 constituting the series arm resonators S1 and S4 are so set that the resonance frequency of the series arm resonators S1 and S4 is approximately equal to the antiresonance frequency of the parallel arm resonators P1 and P4. Is slightly different from the period of the electrode fingers of the boundary acoustic wave device that constitutes the parallel arm resonators P1 to P4.
- the four-stage ⁇ -type ladder-type filter was configured.
- the duty ratio of the boundary acoustic wave device used was varied, and the minimum insertion loss of the ladder-type filter was measured.
- Fig. 5 shows the results.
- the minimum insertion loss is 1.22dB, but when the duty ratio is in the range of 0.53-0.89, It can be seen that the minimum insertion loss is as low as 1.08 dB or less. In other words, by setting the duty ratio to be larger than 0.53 and smaller than 0.89, it is possible to effectively reduce the insertion loss and obtain good resonance characteristics and filter characteristics as described above.
- the receiving block of the mobile phone is provided with these components in the order of, for example, an antenna, an RF top fin- olator, a noise amplifier, an RF interstage filter, a mixer, an IF filter and an IF-IC from the antenna side.
- I have.
- the insertion loss of components closer to the antenna has a greater effect on the overall characteristics.
- the force due to the design conditions S, the degradation of 0.1 dB minimum insertion loss in the RF top filter and the degradation of the minimum insertion loss at 5 dB in the IF filter have the same effect, CZN ratio (carrier noise ratio) Give to.
- the minimum input loss is reduced from 1.22 dB to 1.08 dB.
- the performance of the reception block can be significantly improved. Therefore, by using the ladder-type filter as an RF top filter or an RF interstage filter, and by setting the duty ratio to a value greater than 0.53 and less than 0.89, the portability of the ladder-type filter is reduced. It can be seen that the reception characteristics of the mobile phone can be improved dramatically.
- the electrode material forming the interdigital electrodes and the reflectors 5 and 6 is configured by laminating an Au film on a base layer made of NiCr.
- the electrode material is not limited to those mainly composed of Au, and metals and alloys such as Ag, Cu, Al, Fe, Ni, W, Ta, Pt, Mo, Cr, Ti, Zn ⁇ and ITO.
- an oxide conductor may be used.
- the material constituting the first medium layer is not limited to the LiNbO substrate 2 but may be LiTaO
- the first medium layer may be made of glass or the like.
- the second medium layer is not limited to the Si film, but may be an A1 film, a SiN film, or a polycrystalline Si film.
- the second medium layer may be made of another material, such as a thin film.
- boundary portion composed of the first and second medium layers is not particularly limited as long as the medium is filled in the space between the interdigital electrodes 4 and the electrode fingers of the reflectors 5 and 6. It is not done.
- the interdigital electrode 4 and the reflectors 5 and 6 are provided in the boundary acoustic wave device 1, but the number of the interdigital electrodes and the number of the reflectors are particularly large. Not limited. That is, a longitudinally-coupled boundary acoustic wave filter in which a plurality of interdigital electrodes are arranged between a pair of reflectors may be configured. , May be arranged in parallel or in cascade.
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- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
Abstract
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JP2005514536A JPWO2005036743A1 (ja) | 2003-10-10 | 2004-09-03 | 弾性境界波装置 |
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Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2006319887A (ja) * | 2005-05-16 | 2006-11-24 | Murata Mfg Co Ltd | 弾性境界波装置 |
US7471171B2 (en) * | 2006-02-28 | 2008-12-30 | Fujitsu Media Devices Limited | Elastic boundary wave device, resonator, and filter |
US7804221B2 (en) | 2006-06-16 | 2010-09-28 | Murata Manufacturing Co., Ltd. | Surface acoustic wave device |
US7898145B2 (en) | 2006-09-25 | 2011-03-01 | Murata Manufacturing Co., Ltd. | Boundary acoustic wave device |
WO2012026207A1 (ja) * | 2010-08-27 | 2012-03-01 | 株式会社村田製作所 | 弾性波フィルタ |
JP2013077880A (ja) * | 2011-09-29 | 2013-04-25 | Murata Mfg Co Ltd | ラダー型フィルタ |
DE112007001405B4 (de) * | 2006-06-16 | 2013-12-24 | Murata Manufacturing Co., Ltd. | Oberflächenschallwellenvorrichtung |
US9394163B2 (en) | 2010-04-14 | 2016-07-19 | Epcos Ag | Method for producing a dielectric layer on a component |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5830217A (ja) * | 1981-08-17 | 1983-02-22 | Hitachi Ltd | 弾性波装置 |
JPS5830216A (ja) * | 1981-08-17 | 1983-02-22 | Hitachi Ltd | 弾性波装置 |
JPS5883420A (ja) * | 1981-11-13 | 1983-05-19 | Hitachi Ltd | 弾性境界波装置 |
JP2002232255A (ja) * | 2001-01-30 | 2002-08-16 | Toshiba Corp | 弾性表面波装置 |
-
2004
- 2004-09-03 WO PCT/JP2004/012814 patent/WO2005036743A1/ja active Application Filing
- 2004-09-03 JP JP2005514536A patent/JPWO2005036743A1/ja active Pending
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5830217A (ja) * | 1981-08-17 | 1983-02-22 | Hitachi Ltd | 弾性波装置 |
JPS5830216A (ja) * | 1981-08-17 | 1983-02-22 | Hitachi Ltd | 弾性波装置 |
JPS5883420A (ja) * | 1981-11-13 | 1983-05-19 | Hitachi Ltd | 弾性境界波装置 |
JP2002232255A (ja) * | 2001-01-30 | 2002-08-16 | Toshiba Corp | 弾性表面波装置 |
Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2006319887A (ja) * | 2005-05-16 | 2006-11-24 | Murata Mfg Co Ltd | 弾性境界波装置 |
US7471171B2 (en) * | 2006-02-28 | 2008-12-30 | Fujitsu Media Devices Limited | Elastic boundary wave device, resonator, and filter |
US7804221B2 (en) | 2006-06-16 | 2010-09-28 | Murata Manufacturing Co., Ltd. | Surface acoustic wave device |
DE112007001405B4 (de) * | 2006-06-16 | 2013-12-24 | Murata Manufacturing Co., Ltd. | Oberflächenschallwellenvorrichtung |
DE112007001426B4 (de) * | 2006-06-16 | 2014-02-13 | Murata Mfg. Co., Ltd. | Oberflächenschallwellenvorrichtung |
US7898145B2 (en) | 2006-09-25 | 2011-03-01 | Murata Manufacturing Co., Ltd. | Boundary acoustic wave device |
US9394163B2 (en) | 2010-04-14 | 2016-07-19 | Epcos Ag | Method for producing a dielectric layer on a component |
WO2012026207A1 (ja) * | 2010-08-27 | 2012-03-01 | 株式会社村田製作所 | 弾性波フィルタ |
JP2013077880A (ja) * | 2011-09-29 | 2013-04-25 | Murata Mfg Co Ltd | ラダー型フィルタ |
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JPWO2005036743A1 (ja) | 2007-11-22 |
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