JPH07336187A - Surface acoustic wave device - Google Patents
Surface acoustic wave deviceInfo
- Publication number
- JPH07336187A JPH07336187A JP12245994A JP12245994A JPH07336187A JP H07336187 A JPH07336187 A JP H07336187A JP 12245994 A JP12245994 A JP 12245994A JP 12245994 A JP12245994 A JP 12245994A JP H07336187 A JPH07336187 A JP H07336187A
- Authority
- JP
- Japan
- Prior art keywords
- acoustic wave
- surface acoustic
- reflectance
- wave device
- reflector
- Prior art date
- Legal status (The legal status 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 status listed.)
- Granted
Links
Landscapes
- Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は通信機器などに用いられ
る弾性表面波デバイスに関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave device used for communication equipment.
【０００２】[0002]
【従来の技術】図３（ａ）は従来の共振子型弾性表面波
デバイスを示すものである。図３（ａ）において、１は
圧電基板、２は櫛形電極、３は反射器である。つまり櫛
形電極２で励振された弾性表面波が両側に伝播し、反射
器３の間に閉じ込められることにより共振子あるいはフ
ィルタとして機能するものである。2. Description of the Related Art FIG. 3 (a) shows a conventional resonator type surface acoustic wave device. In FIG. 3A, 1 is a piezoelectric substrate, 2 is a comb-shaped electrode, and 3 is a reflector. That is, the surface acoustic wave excited by the comb-shaped electrode 2 propagates to both sides and is confined between the reflectors 3 to function as a resonator or a filter.
【０００３】[0003]
【発明が解決しようとする課題】従来の共振子型弾性表
面波デバイスでは、反射器３は共振周波数に対応した波
長のおよそ４分の１の一定の線幅のストリップ電極を、
波長のおよそ２分の１の一定のピッチで並べたものであ
り、反射器３自体の周波数特性は図３（ｂ）のように通
過帯域の両側にスプリアスが大きく出ているため、デバ
イスの周波数特性にもスプリアスが現れ、帯域外特性が
劣化していた。In the conventional resonator type surface acoustic wave device, the reflector 3 is a strip electrode having a constant line width of about a quarter of the wavelength corresponding to the resonance frequency.
The frequency characteristics of the reflector 3 itself are such that they are arranged at a fixed pitch of about ½ of the wavelength, and as shown in FIG. Spurious also appeared in the characteristics, and the out-of-band characteristics were deteriorated.
【０００４】そこでこの帯域外特性の劣化を防止するこ
とを目的とするものである。Therefore, an object is to prevent the deterioration of the out-of-band characteristic.
【０００５】[0005]
【課題を解決するための手段】本発明は、スプリアスが
発生する原因を追求検討することにより、上記スプリア
スが発生する原因は反射器のそれぞれのストリップ電極
の反射率が一様であることにより、帯域外のレスポンス
が大きくなることを見出したものであり、上記目的を達
成するために、本発明の弾性表面波デバイスでは、反射
器を構成するストリップ電極のそれぞれの反射率を場所
によって異ならせるものである。According to the present invention, by pursuing and examining the cause of spurious emission, the cause of the spurious emission is that the strip electrodes of the reflector have a uniform reflectance. It has been found that the response outside the band becomes large, and in order to achieve the above object, in the surface acoustic wave device of the present invention, the reflectance of each of the strip electrodes constituting the reflector is made to differ depending on the location. Is.
【０００６】[0006]
【作用】このように構成することにより、櫛形電極にア
ポダイズをかけるように、重み付けがされたようにな
り、反射器自体の周波数特性で帯域外スプリアスが抑圧
され、帯域外特性の優れた弾性表面波デバイスが得られ
る。With this configuration, the comb-shaped electrodes are weighted so as to be apodized, the out-of-band spurious is suppressed by the frequency characteristics of the reflector itself, and the elastic surface having excellent out-of-band characteristics is obtained. Wave device is obtained.
【０００７】[0007]
【実施例】以下本発明の一実施例について、図面を参照
しながら説明する。図１（ａ）は本発明の第一の実施例
における共振子型弾性表面波フィルタを示す概略図であ
る。図１（ａ）において、圧電基板１には水晶を用い、
その表面上の入、出力用の櫛形電極２はそれぞれ１００
対で構成され、横モードによるスプリアスを抑圧するた
めにアポダイズがかけられている。櫛形電極２の両側の
圧電基板１上には反射器３がそれぞれ２００本のショー
トストリップ電極３ａで構成されている。反射器３は図
１（ｂ）のように横軸に位置、縦軸にストリップ電極一
本当たりの反射率に取ると、中心に対称にほぼハミング
の窓関数になるように構成されている。このように反射
率に重み付けをすることにより、反射器３自体の周波数
特性は図１（ｃ）のようになり、従来の等線幅、等ピッ
チの反射器に比べて帯域外を抑圧した特性が得られる。
反射率を変える方法としては、まずストリップ電極の線
幅を変える方法がとられる。通常反射器３ではストリッ
プ電極の線幅が、共振周波数に対応する波長の４分の１
のとき反射率はほぼ最大となり、線幅を細くしていけ
ば、しだいに反射率は小さくなっていき、８分の１のと
きほぼ０になる。従って必要な反射率に応じて線幅を設
定していけば所定の周波数特性が得られる。また、図１
（ｄ）のようにストリップ電極３ａの位置を、隣合う二
本をペアにして、その平均の位置を従来のストリップ電
極３Ａと変えずに、両者の間隔を広げるか、狭めるよう
に位置をずらすと、共振周波数を変えずに反射率を小さ
くすることができる。さらに、水晶のように電気機械結
合係数の小さい圧電基板１を使用する場合は、オープン
ストリップ電極であっても、ショートストリップ電極で
あっても反射率はほとんど変わらないが、タンタル酸リ
チウムあるいはニオブ酸リチウムのような電気機械結合
係数の大きい圧電基板を使用する場合はショートストリ
ップ電極とオープンストリップ電極で反射率が異なって
くるので、これを利用することができる。以上のような
方法を単独に、あるいは組み合わせて用いることによ
り、帯域外特性の優れた共振子型弾性表面波デバイスを
得ることができる。DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1A is a schematic view showing a resonator type surface acoustic wave filter according to the first embodiment of the present invention. In FIG. 1A, quartz is used for the piezoelectric substrate 1,
The input and output comb electrodes 2 on the surface are 100
It is composed of pairs and is apodized to suppress spurious due to transverse modes. On the piezoelectric substrate 1 on both sides of the comb-shaped electrode 2, the reflectors 3 are each composed of 200 short strip electrodes 3a. As shown in FIG. 1 (b), the reflector 3 is constructed so as to have a hamming window function symmetrically with respect to the center when the horizontal axis represents the position and the vertical axis represents the reflectance per strip electrode. By weighting the reflectance in this manner, the frequency characteristic of the reflector 3 itself becomes as shown in FIG. 1C, which is a characteristic that suppresses out-of-band compared to the conventional reflector having an equal line width and an equal pitch. Is obtained.
As a method of changing the reflectance, a method of changing the line width of the strip electrode is first used. In the normal reflector 3, the line width of the strip electrode is 1/4 of the wavelength corresponding to the resonance frequency.
In this case, the reflectance becomes almost maximum, and as the line width is made thinner, the reflectance gradually becomes smaller, and when it is 1/8, it becomes almost zero. Therefore, if the line width is set according to the required reflectance, a predetermined frequency characteristic can be obtained. Also, FIG.
As shown in (d), the position of the strip electrode 3a is set such that two adjacent electrodes are paired, and the average position thereof is not changed from that of the conventional strip electrode 3A, and the position is widened or narrowed. Thus, the reflectance can be reduced without changing the resonance frequency. Further, when the piezoelectric substrate 1 having a small electromechanical coupling coefficient such as quartz is used, the reflectance is almost the same regardless of whether it is an open strip electrode or a short strip electrode, but lithium tantalate or niobate is used. When a piezoelectric substrate having a large electromechanical coupling coefficient such as lithium is used, the short strip electrode and the open strip electrode have different reflectivities, which can be used. A resonator type surface acoustic wave device having excellent out-of-band characteristics can be obtained by using the above methods alone or in combination.
【０００８】図２（ａ）は本発明の第二の実施例におけ
る弾性表面波共振子を示す概略図である。基本的な構成
は第一の実施例と同じであるが、ここでは反射率の分布
が異なる。すなわち、図２（ｂ）のように櫛形電極２か
ら遠ざかるほど反射率が高くなるように構成されてい
る。一般的に、共振子では特別な場合を除いてＱ値が高
いほど望ましい。従来の弾性表面波共振子ではＱ値を高
くするためには電極の膜厚を薄くしてストリップ電極一
本当たりの反射率を小さくする。そうすることにより共
振長を長くすることができ、Ｑ値が高くなる。しかしな
がらこの場合、共振抵抗を充分に小さくするためにはさ
らに多くの反射電極が必要になり、結果的にデバイスの
サイズが大きくなり、またコストアップにもなる。それ
に対して本実施例では、櫛形電極２の近くでは反射率は
小さく、離れるほど大きくなっていくため、反射器３の
反射中心は従来の弾性表面波共振子より外側にシフト
し、共振長が長くなるためＱ値が高くなる。また、第一
の実施例と同じようにスプリアスも抑圧されるので発振
周波数の飛びが起こりにくくなる。FIG. 2A is a schematic view showing a surface acoustic wave resonator according to the second embodiment of the present invention. The basic configuration is the same as that of the first embodiment, but the reflectance distribution is different here. That is, as shown in FIG. 2B, the reflectance increases as the distance from the comb-shaped electrode 2 increases. Generally, in a resonator, a higher Q value is preferable except in special cases. In the conventional surface acoustic wave resonator, in order to increase the Q value, the film thickness of the electrode is thinned to reduce the reflectance per strip electrode. By doing so, the resonance length can be lengthened and the Q value becomes high. However, in this case, more reflective electrodes are required to sufficiently reduce the resonance resistance, resulting in an increase in device size and an increase in cost. On the other hand, in the present embodiment, the reflectance is small near the comb-shaped electrode 2 and increases as the distance increases, so the reflection center of the reflector 3 shifts to the outside of the conventional surface acoustic wave resonator, and the resonance length becomes longer. Since it becomes longer, the Q value becomes higher. Further, as in the first embodiment, spurious is also suppressed, so that oscillation frequency jumps are less likely to occur.
【０００９】[0009]
【発明の効果】以上のように本発明は、反射器を構成す
るストリップ電極の反射率を場所によって変えることに
より、帯域外特性の優れた弾性表面波デバイス、あるい
はＱ値の高い弾性表面波共振子を得ることができる。INDUSTRIAL APPLICABILITY As described above, according to the present invention, a surface acoustic wave device having an excellent out-of-band characteristic or a surface acoustic wave resonance having a high Q value is obtained by changing the reflectance of the strip electrode constituting the reflector depending on the location. You can get a child.
【図１】本発明の第一の実施例における共振子型弾性表
面波フィルタの説明図FIG. 1 is an explanatory diagram of a resonator type surface acoustic wave filter according to a first embodiment of the present invention.
【図２】本発明の第二の実施例における弾性表面波共振
子の説明図FIG. 2 is an explanatory diagram of a surface acoustic wave resonator according to a second embodiment of the present invention.
【図３】（ａ）は従来の共振子型弾性表面波フィルタの
平面図 （ｂ）はその特性図3A is a plan view of a conventional resonator type surface acoustic wave filter, and FIG. 3B is a characteristic diagram thereof.
１ 圧電基板 ２ 櫛形電極 ３ 反射器 1 piezoelectric substrate 2 comb-shaped electrode 3 reflector
Claims (6)
形電極と、この櫛形電極の両側の圧電基板上に設けた多
数のストリップ電極からなる反射器とを備え、上記反射
器のストリップ電極のそれぞれの一本当たりの反射率を
場所によって異ならせたことを特徴とする弾性表面波デ
バイス。1. A strip electrode for a reflector, comprising: a piezoelectric substrate; a comb-shaped electrode provided on the piezoelectric substrate; and a reflector composed of a large number of strip electrodes provided on the piezoelectric substrate on both sides of the comb-shaped electrode. The surface acoustic wave device characterized in that the reflectance of each of the two is varied depending on the location.
射率が最大となり、両側にいくに従って反射率が小さく
なるようにしたことを特徴とする請求項１記載の弾性表
面波デバイス。2. The surface acoustic wave device according to claim 1, wherein the strip electrode near the center of the reflector has a maximum reflectance, and the reflectance decreases toward both sides.
プ電極の反射率が大きくなり、反射器の端部で反射率が
最大となるようにしたことを特徴とする請求項１記載の
弾性表面波デバイス。3. The surface acoustic wave device according to claim 1, wherein the reflectance of the strip electrode increases as the distance from the comb-shaped electrode increases, and the reflectance becomes maximum at the end of the reflector.
とにより、一本当たりの反射率を小さくすることを特徴
とする請求項１記載の弾性表面波デバイス。4. The surface acoustic wave device according to claim 1, wherein the strip electrode has a narrower line width to reduce the reflectance of each strip electrode.
の二本の平均の位置を変えずに、お互いの位置を変える
ことにより、上記ストリップ電極の一本当たりの反射率
を変えることを特徴とする請求項１記載の弾性表面波デ
バイス。5. The reflectance of each strip electrode is changed by changing the positions of two strip electrodes as a pair without changing the average position of the two strip electrodes. The surface acoustic wave device according to claim 1.
せ、残りをオープンストリップ電極としたことを特徴と
する請求項１記載の弾性表面波デバイス。6. The surface acoustic wave device according to claim 1, wherein some of the strip electrodes are short-circuited to each other and the rest are open strip electrodes.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12245994A JP3291912B2 (en) | 1994-06-03 | 1994-06-03 | Surface acoustic wave device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12245994A JP3291912B2 (en) | 1994-06-03 | 1994-06-03 | Surface acoustic wave device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH07336187A true JPH07336187A (en) | 1995-12-22 |
| JP3291912B2 JP3291912B2 (en) | 2002-06-17 |
Family
ID=14836385
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP12245994A Expired - Fee Related JP3291912B2 (en) | 1994-06-03 | 1994-06-03 | Surface acoustic wave device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3291912B2 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6278219B1 (en) | 1998-11-20 | 2001-08-21 | Fujitsu Limited | Surface acoustic wave reflecting device having reflectance similar to the hamming function |
| EP1480336A1 (en) * | 2002-02-27 | 2004-11-24 | Fujitsu Media Devices Limited | Elastic surface wave apparatus |
| JP2007053890A (en) * | 2005-07-19 | 2007-03-01 | Matsushita Electric Works Ltd | Surface acoustic wave actuator |
| JP2010187057A (en) * | 2009-02-10 | 2010-08-26 | Denso Corp | Surface acoustic wave element, method of producing same, and method of changing resonation frequency of same |
-
1994
- 1994-06-03 JP JP12245994A patent/JP3291912B2/en not_active Expired - Fee Related
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6278219B1 (en) | 1998-11-20 | 2001-08-21 | Fujitsu Limited | Surface acoustic wave reflecting device having reflectance similar to the hamming function |
| EP1480336A1 (en) * | 2002-02-27 | 2004-11-24 | Fujitsu Media Devices Limited | Elastic surface wave apparatus |
| EP1480336B1 (en) * | 2002-02-27 | 2011-08-24 | Taiyo Yuden Co., Ltd. | Elastic surface wave apparatus |
| JP2007053890A (en) * | 2005-07-19 | 2007-03-01 | Matsushita Electric Works Ltd | Surface acoustic wave actuator |
| JP2010187057A (en) * | 2009-02-10 | 2010-08-26 | Denso Corp | Surface acoustic wave element, method of producing same, and method of changing resonation frequency of same |
| US8253302B2 (en) | 2009-02-10 | 2012-08-28 | Denso Corporation | Surface acoustic wave element, method of producing the same, and method of changing resonation frequency of the same |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3291912B2 (en) | 2002-06-17 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| LAPS | Cancellation because of no payment of annual fees |