JPH03238909A - Surface acoustic wave filter - Google Patents
Surface acoustic wave filterInfo
- Publication number
- JPH03238909A JPH03238909A JP3372490A JP3372490A JPH03238909A JP H03238909 A JPH03238909 A JP H03238909A JP 3372490 A JP3372490 A JP 3372490A JP 3372490 A JP3372490 A JP 3372490A JP H03238909 A JPH03238909 A JP H03238909A
- Authority
- JP
- Japan
- Prior art keywords
- surface acoustic
- electrode
- acoustic wave
- electrode fingers
- wave filter
- 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.)
- Pending
Links
- 238000010897 surface acoustic wave method Methods 0.000 title claims abstract description 26
- 230000005284 excitation Effects 0.000 claims abstract description 9
- 239000000758 substrate Substances 0.000 claims description 2
- 230000000694 effects Effects 0.000 abstract description 11
- 230000000644 propagated effect Effects 0.000 abstract description 2
- 230000002035 prolonged effect Effects 0.000 abstract 1
- 238000007796 conventional method Methods 0.000 description 2
- 238000003780 insertion Methods 0.000 description 2
- 230000037431 insertion Effects 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
Landscapes
- Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
Abstract
Description
【発明の詳細な説明】
[産業上の利用分野]
本発明は、交差幅重み付けを施した場合に、交差幅が狭
い部分のために生じていた回折波の影響を抑圧した弾性
表面波フィルタに関する。Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a surface acoustic wave filter that suppresses the influence of diffracted waves caused by narrow crossing width portions when cross width weighting is applied. .
[従来の技術〕
弾性表面波フィルタでは、所望の周波数特性を得るため
に、対向する電極指対の交差幅に重み付けを行ったすだ
れ状電極を使用する例がある。第3図はこのような従来
のすだれ状電極の一例の平面図を示し1図中、4,5は
、対向電極をI威する電極指群それぞれを接硫する上下
の共通母線である。各対向電極の電極指の交差部分では
それぞれの交差幅に比例した強度の弾性表面波が励振さ
れる。交差幅が狭い電極指対の間で励振された弾性衣g
波は、対向電極の長さ方向に短い交差部分だけに電力強
度が集中しており1回折波の影響が生ずるという問題が
あった。[Prior Art] In order to obtain desired frequency characteristics, some surface acoustic wave filters use interdigital electrodes in which the width of intersection of pairs of opposing electrode fingers is weighted. FIG. 3 is a plan view of an example of such a conventional interdigital electrode, and in FIG. 1, numerals 4 and 5 are upper and lower common busbars that connect the respective groups of electrode fingers that connect the opposing electrodes. At the intersection of the electrode fingers of each counter electrode, surface acoustic waves with an intensity proportional to the width of each intersection are excited. Elastic garment g excited between a pair of electrode fingers with a narrow crossing width
There is a problem in that the power intensity of the waves is concentrated only at short intersections in the length direction of the opposing electrodes, resulting in the influence of single diffracted waves.
上記問題の対策として、特開昭50−24050号公報
に、対向IE[Iを長さ方向に2!iまたは3個以上に
分割して得られる浮遊中間電極を直列接硫して成る対向
電極部を複数対並列接硫して構成することが開示されて
いる。第4図はこの技術により、電極膜が励振部にほぼ
一様に配列された。As a countermeasure to the above problem, Japanese Patent Laid-Open No. 50-24050 discloses that the opposing IE [I is 2 in the length direction! It is disclosed that a counter electrode section is formed by connecting floating intermediate electrodes obtained by dividing i or three or more in series and connecting them in parallel. FIG. 4 shows that by this technique, the electrode films were arranged almost uniformly in the excitation part.
すだれ状tIiの平面図を示している。この技術は対向
電極の長さ方向について電力強度の分布がほぼ一様にな
るという利点がある。A plan view of the blind-shaped tIi is shown. This technique has the advantage that the power intensity distribution is approximately uniform in the length direction of the opposing electrode.
[発明が解決しようとする課題]
しかし、上記従来の技術は、電極構造がamになり1分
割数が多くなると広い電極面積から咳かな励振電力しか
得られず、大面積の圧電性基板が必要になるなどの問題
がある。[Problems to be Solved by the Invention] However, with the above conventional technology, when the electrode structure becomes am and the number of divisions increases, only a modest excitation power can be obtained from a wide electrode area, and a piezoelectric substrate with a large area is required. There are problems such as becoming
本発明は上記従来の技術の問題点を解決し、比較的簡単
な1極構造で、回折効果の影響を抑圧した弾性表面波フ
ィルタを提供することを目的とする。SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the above-mentioned conventional techniques and to provide a surface acoustic wave filter that has a relatively simple one-pole structure and suppresses the influence of diffraction effects.
[allを解決するための手段] 本発明においては上記目的を達成するために。[Means for solving all] In order to achieve the above object in the present invention.
弾性表面波フィルタの、従来の方式では対向電極指対の
交差幅が狭くなる部分に対応する儒所で、隣接する電極
と電気的に分離された浮遊電極指が。In the conventional method of surface acoustic wave filters, there is a floating electrode finger that is electrically separated from the adjacent electrode at the point where the crossing width of the pair of opposing electrode fingers becomes narrow.
対向電極を構成する電極指群それぞれを接硫する上下の
共通母線それぞれから伸びた上下1対の電極指夫々と、
互いに交差幅が異なる上下2交差部を形成するようにし
た。a pair of upper and lower electrode fingers extending from each of the upper and lower common busbars connecting each of the electrode finger groups constituting the counter electrode;
Two upper and lower intersections having different intersection widths are formed.
[作用] 浮遊電極は上下共通tWの中間の電位を持つ。[Effect] The floating electrode has an intermediate potential between the upper and lower electrodes tW.
それによって、上下2交差部に生ずる電界の方向は互い
に逆向きになるので、2交差部それぞれで励振される弾
性表面波は打ち消し合い、2交差部の交差幅の差に対応
した狭い交差幅の従来の対向電極指間の1交差部で励振
される弾性表面波と同様な強度になる。2交差部はそれ
ぞれ交差幅を従来の場合に比べて長くできるので1回折
波の影響を抑圧できる。As a result, the directions of the electric fields generated at the two upper and lower intersections are opposite to each other, so the surface acoustic waves excited at each of the two intersections cancel each other out, resulting in a narrow intersection width corresponding to the difference in the intersection width between the two intersections. The intensity is similar to that of a conventional surface acoustic wave excited at one intersection between opposing electrode fingers. Since the intersection width of each of the two intersections can be made longer than in the conventional case, the influence of the single diffracted wave can be suppressed.
[実施例]
第1JIは本発明−実施男のすだれ状電極の平面@を示
す、上下の共通母線4及び5から伸びる電極指1及び3
と浮遊電極と2は、2個所で交差幅がWl及びW、の交
差部を、lI接する対向電極とは電気的に独立して、構
成する。浮遊電li2の電位は、電極指lの電位と電極
指3の電位の中間の電位を持つので、交差幅W、及びw
2の2儒所の交差部で得られる弾性表面波の励振の位相
は逆相となり、それぞれ交差幅W、及びW□の交差幅に
比例した強度の励振を与える。従って、浮遊電極2と電
極指1,3によって励振される弾性表面波は、上記の2
Il所で励振された弾性表面波が打ち消し合わされて伝
搬するため、交差11wt及びw2を適当に選ぶことに
より、所望強度の弾性表面波の励振を得ることができる
。[Example] 1st JI shows the plane @ of the interdigital electrode of the present invention-implementation man, electrode fingers 1 and 3 extending from the upper and lower common bus lines 4 and 5
The floating electrode 2 and the floating electrode 2 form an intersection having intersection widths Wl and W at two locations, electrically independent of the counter electrode in contact with II. Since the potential of the floating electric current li2 has an intermediate potential between the potential of the electrode finger l and the potential of the electrode finger 3, the crossing width W and w
The phases of the excitation of the surface acoustic waves obtained at the intersections of the two locations in 2 are opposite in phase, giving excitations with intensities proportional to the intersection widths W and W□, respectively. Therefore, the surface acoustic waves excited by the floating electrode 2 and the electrode fingers 1 and 3 are
Since the surface acoustic waves excited at Il are canceled and propagated, by appropriately selecting the intersections 11wt and w2, it is possible to obtain surface acoustic wave excitation with a desired intensity.
第2@は、スプリット電極を用いた本発明の他の実施例
のすだれ状電極の平面図を示す、浮遊電極7は、共通電
極4及び5から伸びる電極指6及び8とのみ交差してい
る。このように、各浮遊電極は、上下の共通母1[4及
び5から伸びるIIILの電極指とのみ交差しており、
11接部の影響は殆ど受けることがないので、交差幅を
選択する自由度が一層増す。第5図は、この実施例フィ
ルタの挿入損失の周波数特性を実線で示し、従来のすだ
れ状Saを用いたフィルタの周波数特性を破線で示して
いる。このように本実施例によると、従来のものに比べ
て、高域帯域外における周波数特性の抑圧度が5dB改
善される。2nd @ shows a plan view of the interdigital electrode of another embodiment of the invention using split electrodes, the floating electrode 7 intersects only with the electrode fingers 6 and 8 extending from the common electrodes 4 and 5 . In this way, each floating electrode intersects only the electrode fingers of IIIL extending from the upper and lower common roots 1[4 and 5,
11, so the degree of freedom in selecting the crossing width is further increased. In FIG. 5, the frequency characteristic of the insertion loss of the filter of this embodiment is shown by a solid line, and the frequency characteristic of the conventional filter using interdigital Sa is shown by a broken line. As described above, according to this embodiment, the degree of suppression of frequency characteristics outside the high frequency band is improved by 5 dB compared to the conventional one.
[発明の効果コ
以上説明したように本発明によれば、所望の弾性表面波
励振強度を変えることなく、従来の交差幅重み付は電極
では交差幅が狭くなる部分で、対向する電極指の交差幅
を拡大できるので9回折効果を抑圧する効果が得られる
。[Effects of the Invention] As explained above, according to the present invention, without changing the desired surface acoustic wave excitation intensity, the conventional cross-width weighting is applied at the portion where the cross-width becomes narrow in the electrode, and the weighting of the opposing electrode fingers is Since the intersection width can be expanded, the effect of suppressing the 9-diffraction effect can be obtained.
また、外部から印加される電圧を高くしても、対向電極
指の交差幅を拡大できるので1回折効果が抑圧され、チ
ップサイズを小さくする効果も得られる。Furthermore, even if the externally applied voltage is increased, the crossing width of the opposing electrode fingers can be increased, thereby suppressing the single diffraction effect and achieving the effect of reducing the chip size.
第1図は本発明一実施例弾性表面波フィルタのすだれ状
を擺のの平面図、第2茗はスプリット型にした本発明実
施例弾性表面波フィルタのすだれ状電極の平面図、第3
図と第4翼は夫々異なる従来の弾性表面波フィルタのす
だれ状電極の平面図。
第5図は第2図に示した実施例フィルタと従来のフィル
タの挿入損失周波数特性を比較して示す図である。
工、3.6.8・・・共通母線から伸びる電極指、2.
7・・・浮遊側1 4.5・・・共通母線。Fig. 1 is a plan view of a transducer-shaped surface acoustic wave filter according to an embodiment of the present invention; Fig. 2 is a plan view of a transducer-shaped electrode of a surface acoustic wave filter according to an embodiment of the present invention;
The figure and the fourth wing are plan views of interdigital electrodes of a conventional surface acoustic wave filter, respectively different from each other. FIG. 5 is a diagram showing a comparison of the insertion loss frequency characteristics of the example filter shown in FIG. 2 and the conventional filter. 3.6.8... Electrode fingers extending from the common bus bar, 2.
7...Floating side 1 4.5...Common bus bar.
Claims (4)
電極を配設し、これらすだれ状電極の少なくとも1電極
の対向する電極指の交差幅に重み付けをした弾性表面波
フィルタにおいて、対向する電極指対の間の弾性表面波
励振強度を変えずに、対向する電極指対の交差幅を拡大
することによって、回折波の影響を抑圧するようにした
ことを特徴とする弾性表面波フィルタ。1. In a surface acoustic wave filter in which a plurality of interdigital electrodes are disposed on a piezoelectric substrate for input and output, and the intersecting width of the opposing electrode fingers of at least one of these interdigital electrodes is weighted, the intersecting width of the opposing electrode fingers is weighted. A surface acoustic wave filter characterized in that the influence of diffracted waves is suppressed by expanding the crossing width of a pair of opposing electrode fingers without changing the surface acoustic wave excitation intensity between the pairs.
電極指間の交差部が、電極指長さ方向に2交差部に分割
されていることを特徴とする請求項1記載の弾性表面波
フィルタ。2. 2. The surface acoustic wave according to claim 1, wherein the intersection between a pair of opposing electrode fingers that are electrically independent from adjacent opposing electrodes is divided into two intersections in the length direction of the electrode fingers. filter.
対向電極を構成する電極指群それぞれを接硫する上下の
共通母線からそれぞれ伸びた上下1対の電極指と、互い
に交差幅が異なる上下2交差部を形成することを特徴と
する請求項1記載の弾性表面波フィルタ。3. Floating electrode fingers electrically isolated from adjacent electrodes
2. A pair of upper and lower electrode fingers each extending from an upper and lower common generatrix that connects each of the electrode finger groups constituting the counter electrode, forming two upper and lower intersection portions having different intersection widths. surface acoustic wave filter.
る請求項2記載の弾性表面波フィルタ。4. 3. The surface acoustic wave filter according to claim 2, wherein the interdigital electrodes are of a split type.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP3372490A JPH03238909A (en) | 1990-02-16 | 1990-02-16 | Surface acoustic wave filter |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP3372490A JPH03238909A (en) | 1990-02-16 | 1990-02-16 | Surface acoustic wave filter |
Publications (1)
Publication Number | Publication Date |
---|---|
JPH03238909A true JPH03238909A (en) | 1991-10-24 |
Family
ID=12394349
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP3372490A Pending JPH03238909A (en) | 1990-02-16 | 1990-02-16 | Surface acoustic wave filter |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPH03238909A (en) |
-
1990
- 1990-02-16 JP JP3372490A patent/JPH03238909A/en active Pending
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