JPS616917A

JPS616917A - Internal reflection type unidirectional surface acoustic wave converter using change in electrode width

Info

Publication number: JPS616917A
Application number: JP59128333A
Authority: JP
Inventors: Kazuhiko Yamanouchi; 和彦山之内
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-06-20
Filing date: 1984-06-20
Publication date: 1986-01-13

Abstract

PURPOSE:To obtain an internal reflection type unidirectional surface acoustic wave converter by splitting positive and negative electrodes of a reed screen electrode into several parts and utilizing the difference between the exciting center position and the reflecting center position. CONSTITUTION:The positive and negative reed screen electrodes 2 with an equal width are divided into two on the surface of a piezoelectric electrostatic substance 1. In the split method, the width of an electrode 3 at the left side of the positive electrode is wide, the width of an electrode 5 at the right side is narrow, the width of the electrode 5 at the left side of the negative electrode is wide and the width of an electrode 6 at the right side is narrow. Since the arrangement of the electrodes is unsymmetric within one wavelength in this way and the center position of a surface acoustic wave excitation and the center position of reflection are different, a surface acoustic wave where the exciting strength of a surface acoustic wave 7 in the right direction is large and the exciting strength of a surface acoustic wave 8 in the left direction is small is obtained.

Description

【発明の詳細な説明】この発明は、すだれ状電極を用いて弾性表面波を励振・
受信する変換器において、この変換器を一方向性化する
ことによって挿入損失と周波数特性の乱れを改良した弾
性表面波変換器に関するものである。[Detailed Description of the Invention] This invention uses interdigital electrodes to excite and generate surface acoustic waves.
The present invention relates to a surface acoustic wave transducer that improves insertion loss and frequency characteristic disturbance by making the transducer unidirectional.

第１図のように圧電・電歪物質１の表面に等しい幅の正
負のすだれ状電極２を２分割する。その分割の方法は、
１４−電極の左側の電極３の幅は広く、右側の電極５の
幅は狭く、また、負電極も左側の電極５の幅は広く、右
側の電極６の幅は狭くする。As shown in FIG. 1, the positive and negative interdigital electrodes 2 of equal width are divided into two parts on the surface of the piezoelectric/electrostrictive material 1. The method of division is
The width of the left electrode 3 of the 14-electrode is wide, and the width of the right electrode 5 is narrow, and the width of the left electrode 5 of the negative electrode is wide, and the width of the right electrode 6 is narrow.

このようにすることにより、１波長以内で電極の配置が
非対称となるため弾性表面波励振の中心位置と電極によ
る反射の中心位置が異なるため、右方向の弾性表面波７
の励振強度が大きく、左方向の弾性表面波８の励振強度
が小さい弾性表面波が得られる。方向性の大きさは電極
幅と電極位置を適当に選び、かっ、λ。を周期として、
数周期以Ｉ、にわたって、この電極を配置することによ
って第２図は、幅の等しくない正電極と負電極を２分割
した構造である。分割の方法は正電極の左側の電極９の
幅を広く、右側の電極１１の幅を小さくする。また、負
電極も同様に左側の電極ｌＯの幅を広く、右側の電極１
２の幅を狭くする。このようにすることにより、１波長
間での電極配置の非対称性により、励振中心と反射中心
の位置が異なるため右方向の弾性表面波７の振幅が大き
く左方向の弾性表面波８の振幅は小さくなる。これを１
周期とした電極を数波長以上にわたって周期的に配置し
、かつ、電極幅と空隙幅を変化さＵることにより、大き
な方向性をもつ弾性表面波変換器か得られる。By doing this, the arrangement of the electrodes becomes asymmetric within one wavelength, so the center position of surface acoustic wave excitation and the center position of reflection by the electrodes are different.
A surface acoustic wave is obtained in which the excitation intensity of the leftward surface acoustic wave 8 is large and the excitation intensity of the leftward surface acoustic wave 8 is small. The magnitude of the directionality can be determined by appropriately selecting the electrode width and electrode position. As the period,
By arranging this electrode over several cycles, the structure shown in FIG. 2 is a structure in which the positive electrode and the negative electrode are divided into two with unequal widths. The dividing method is to widen the width of the electrode 9 on the left side of the positive electrode, and reduce the width of the electrode 11 on the right side. Similarly, for the negative electrode, the width of the left electrode 10 is increased, and the width of the right electrode 1 is increased.
Narrow the width of 2. By doing this, due to the asymmetry of the electrode arrangement between one wavelength, the positions of the excitation center and the reflection center are different, so the amplitude of the surface acoustic wave 7 in the right direction is large, and the amplitude of the surface acoustic wave 8 in the left direction is becomes smaller. This is 1
By arranging periodic electrodes periodically over several wavelengths or more and changing the electrode width and gap width, a surface acoustic wave transducer with large directivity can be obtained.

第３図は、正電極１３．１４と負電極Ｉ５のうち正電極
のみを２分割し、正電極の左側の電極１３の幅を広く右
側の電極１４を狭くした電極と分割していない負電極１
５から成る。このような構成とすることにより右側の弾
性表面波７の振幅の大きい一方向性弾性表面波が得られ
る。Figure 3 shows an electrode in which only the positive electrode of the positive electrode 13, 14 and the negative electrode I5 is divided into two, and the electrode 13 on the left side of the positive electrode is widened and the electrode 14 on the right side is narrowed, and the negative electrode is not divided. 1
Consists of 5. With such a configuration, a unidirectional surface acoustic wave with a large amplitude of the surface acoustic wave 7 on the right side can be obtained.

以上は、正電極を２分割まで、負電極は２分割及び分割
しない場合について説明したが、正電極及び負電極の分
割数は、０，１．’２．３・・・にし、かつ、その幅及
び空隙を適当な値とすることによって、一方向性変換器
を得ることができる。In the above, the case where the positive electrode is divided into two parts and the negative electrode is divided into two parts or not is explained. '2.3... and by setting the width and gap to appropriate values, a unidirectional transducer can be obtained.

以上、すだれ状電極の正電極及び負電極を数分割し、励
振中心位置と反射中心位置との差を利用することにより
内部反射型の一方向性弾性表面波変換器を得ることかで
きる。As described above, an internal reflection type unidirectional surface acoustic wave transducer can be obtained by dividing the positive electrode and the negative electrode of the interdigital electrode into several parts and utilizing the difference between the excitation center position and the reflection center position.

【図面の簡単な説明】[Brief explanation of drawings]

第１図は、等しい幅の正電極と負電極を等しくない幅に
分割した構造の一方向性すだれ状電極変換器である。　
　１　・圧電・電歪物質の基板、２・　・すだれ状電極
、　３・・・幅の広い正電極、４・　幅の広い負電極、
　５・・・・幅の狭い正電極、　６・・幅の狭い負電極
、　７・・・右方向の弾性表面波、　８・・・左方向の
弾性表面波。第２図は、等しくない正電極と負電極を２分割しその分
割幅の関係を、正電極の左の幅を広く、また負電極も左
の幅を広くした一方向性変換器である。　９−・　正電
極側の幅の広い電極、　　１゜・・　負電極側の幅の広
い電極　ＩＩ・・・・正電極側の幅の狭い電極、１２・
・・・負電極側の幅の狭い電極。第３図は、等しくない正電極と負電極のうち、１［電極
のみを分割し、正電極の左方の幅を広く、右方の幅を狭
くした構造の一方向性変換器である。１３　・正電極の幅の広い電極、　　１４・・・・正電
極の幅の狭い電極、　　Ｉ５　・分割されていない負電
極。なお、図面の中の番号で、他の図面の中の番号と同一数
字は同一内容である。FIG. 1 shows a unidirectional interdigital transducer having a structure in which positive and negative electrodes of equal width are divided into unequal widths.
1. Substrate of piezoelectric/electrostrictive material, 2. - Interdigital electrode, 3. Wide positive electrode, 4. Wide negative electrode.
5...Narrow positive electrode, 6...Narrow negative electrode, 7...Rightward surface acoustic wave, 8...Leftward surface acoustic wave. FIG. 2 shows a unidirectional transducer in which the unequal positive and negative electrodes are divided into two parts, and the width of the division is such that the left side of the positive electrode is wider, and the negative electrode is also wider on the left. 9-. Wide electrode on the positive electrode side, 1°... Wide electrode on the negative electrode side II... Narrow electrode on the positive electrode side, 12.
...Narrow electrode on the negative electrode side. FIG. 3 shows a unidirectional transducer having a structure in which only one of the unequal positive and negative electrodes is divided, and the width on the left side of the positive electrode is wide and the width on the right side is narrow. 13 - Wide positive electrode, 14...Narrow positive electrode, I5 - Undivided negative electrode. Note that numbers in a drawing that are the same as numbers in other drawings have the same content.

Claims

【特許請求の範囲】[Claims]

（１）圧電・電歪物質の表面に正負交互となるすだれ状
電極を配置して弾性表面波を励振・受信する構造の変換
器において、第１図のように、幅の等しい正電極と負電
極を等しくない幅で２分割し、正電極側の幅の広い電極
３と負電極側の幅の広い電極４の間の中心間隔をλ＿０
／２（λ＿０は電極の周期で弾性表面波が最も強く励振
される中心周波数での波長）、正電極側の幅の狭い電極
５と負電極側の幅の狭い電極６の間の中心間隔をλ＿０
／２とし、更にこれらの電極をλ＿０を周期として配置
した一方向性弾性表面波変換器。この場合は、電極幅は
必ずしもλ＿０／４幅及びλ＿０／８幅の必要はなく、
広い方の電極幅はλ＿０／８以上λ＿０／２迄、狭い方
の電極幅は０以上λ＿０／４迄の幅で変化させてもよい
。(1) In a transducer that excites and receives surface acoustic waves by arranging alternating positive and negative interdigital electrodes on the surface of a piezoelectric/electrostrictive material, as shown in Figure 1, a positive electrode of equal width and a negative Divide the electrode into two with unequal widths, and set the center distance between the wide electrode 3 on the positive electrode side and the wide electrode 4 on the negative electrode side as λ_0.
/2 (λ_0 is the wavelength at the center frequency where the surface acoustic wave is most strongly excited in the period of the electrode), the center distance between the narrow electrode 5 on the positive electrode side and the narrow electrode 6 on the negative electrode side. λ_0
/2, and these electrodes are arranged with a period of λ_0. In this case, the electrode width does not necessarily have to be λ_0/4 width and λ_0/8 width,
The width of the wider electrode may vary from λ_0/8 to λ_0/2, and the width of the narrower electrode may vary from 0 to λ_0/4.

（２）特許請求の範囲の（１）の項目では、等しい幅の
正電極と負電極の分割比は同一であるとしているが、第
２図のように、この項目では、等しい或いは、等しくな
い幅の正電極と負電極の分割比を１：１でない比に分割
し、かつこの電極をλ＿０を周期として配置した構造の
一方向性変換器。(2) Item (1) of the claims states that the division ratio of the positive electrode and negative electrode of equal width is the same, but as shown in FIG. A unidirectional converter with a structure in which the width of the positive electrode and the negative electrode are divided at a ratio other than 1:1, and the electrodes are arranged with a period of λ_0.

（３）等しくない正電極と負電極のすだれ状電極の幅の
広い電極を等しくない電極幅１３、１４に分割、一方、
幅の狭い電極１５は分割しない構造の第３図のような一
方向性変換器。(3) Dividing the wide electrodes of the unequal positive and negative interdigital electrodes into unequal electrode widths 13 and 14, while
A unidirectional transducer as shown in FIG. 3 has a structure in which the narrow electrode 15 is not divided.

（４）正電極と負電極を等しくない電極幅に数分割した
構造の一方向性変換器(4) Unidirectional converter with a structure in which the positive and negative electrodes are divided into several unequal electrode widths