JPH047125B2 - - Google Patents
Info
- Publication number
- JPH047125B2 JPH047125B2 JP6962082A JP6962082A JPH047125B2 JP H047125 B2 JPH047125 B2 JP H047125B2 JP 6962082 A JP6962082 A JP 6962082A JP 6962082 A JP6962082 A JP 6962082A JP H047125 B2 JPH047125 B2 JP H047125B2
- Authority
- JP
- Japan
- Prior art keywords
- electrode
- wavelength
- width
- surface acoustic
- acoustic wave
- 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.)
- Expired
Links
- 239000002184 metal Substances 0.000 claims description 37
- 238000010897 surface acoustic wave method Methods 0.000 claims description 27
- 239000000758 substrate Substances 0.000 claims description 8
- 230000005540 biological transmission Effects 0.000 claims 6
- 230000000694 effects Effects 0.000 description 6
- 238000000034 method Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 229910013641 LiNbO 3 Inorganic materials 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000001902 propagating effect Effects 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic elements; 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
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
- H03H9/02—Details
- H03H9/02535—Details of surface acoustic wave devices
- H03H9/02818—Means for compensation or elimination of undesirable effects
- H03H9/02842—Means for compensation or elimination of undesirable effects of reflections
Landscapes
- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
Description
【発明の詳細な説明】
〔発明の技術分野〕
この発明は圧電体上にインタデイジタル電極を
形成してなる弾性表面波装置に関する。DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a surface acoustic wave device in which interdigital electrodes are formed on a piezoelectric body.
弾性表面波装置として、圧電体基板表面にイン
タデイジタル電極を設けたものが実用化されてい
る。ところがこのような装置においては、インタ
デイジタル電極の電気的な再励起による電気的反
射波を生じるという問題がある。この反射波は出
力にスプリアスを発生し、弾性表面波フイルタ等
を構成した場合にその特性を劣化させる原因とな
つている。
As a surface acoustic wave device, one in which interdigital electrodes are provided on the surface of a piezoelectric substrate has been put into practical use. However, such a device has a problem in that electrically reflected waves are generated due to electrical re-excitation of the interdigital electrodes. This reflected wave generates spurious in the output, which causes deterioration of the characteristics of a surface acoustic wave filter or the like.
そこで従来このような電気的な反射波を、電極
構造による音響的反射波でキヤンセルする技術が
特開昭56−10724号により知られている。しかし
ながらこの特開昭56−10724号の発明においては
電気的反射波の時間軸レスポンスと音響的反射波
の時間軸レスポンスとは完全に相殺しない場合が
生じる。このような欠点を鑑みて第１図に示すよ
うにインタデイジタル電極部に音響的反射波を生
じさせる電極金属欠落部２１〜２６をアポダイズ
法によつて設け、時間軸レスポンスを完全に一致
させるものが提案されている。 Therefore, a technique is known from Japanese Patent Laid-Open No. 10724/1983 in which such electrical reflected waves are canceled by acoustic reflected waves caused by an electrode structure. However, in the invention of JP-A-56-10724, the time-domain response of the electrically reflected wave and the time-domain response of the acoustically reflected wave may not cancel each other out completely. In view of these drawbacks, as shown in Fig. 1, electrode metal missing parts 21 to 26 that produce acoustic reflected waves are provided in the interdigital electrode part by the apodization method to completely match the time axis responses. is proposed.
しかしながら、第１図に示すように音響反射波
発生部を有する電極部（金属欠落部）を通過する
弾性表面波Ａは、音響反射波発生部を有しない電
極部を通過する弾性表面波Ｂとは伝搬速度が異な
る為位相差が生じる。この速度差の生じる原因は
電極金属が弾性表面波による電界を短絡する為生
ずる速度低下と金属の質量が弾性表面波に与える
質量付加効果による速度低下とによるものであ
る。 However, as shown in Fig. 1, the surface acoustic wave A passing through the electrode part (metal missing part) having the acoustic reflected wave generating part is different from the surface acoustic wave B passing through the electrode part not having the acoustic reflected wave generating part. Since the propagation speed is different, a phase difference occurs. This speed difference is caused by a speed reduction caused by the electrode metal short-circuiting the electric field caused by the surface acoustic wave, and a speed reduction due to the mass addition effect that the mass of the metal has on the surface acoustic wave.
このような位相差が生じると、所望の周波数特
性が得られなくなる。 When such a phase difference occurs, desired frequency characteristics cannot be obtained.
本発明は前述の電気反射を音響反射でキヤンセ
ルする方法において、音響反射発生部の有無によ
つて電極部での弾性表面波の伝搬速度が変化しな
い電極形状を提供し、周波数特性の良好な弾性表
面波装置、とりわけフイルタを提供することを目
的とする。
The present invention provides an electrode shape in which the propagation speed of a surface acoustic wave in an electrode part does not change depending on the presence or absence of an acoustic reflection generating part in the method of canceling the above-mentioned electrical reflection by acoustic reflection, and provides elasticity with good frequency characteristics. The object is to provide a surface wave device, in particular a filter.
本発明は音響反射発生部以外の電極部にも1/8
波長幅の金属のない部分を設けることにより、電
極のどの部分でも弾性表面波の伝搬速度を等しく
したもので、さらにこのダミーの電極金属欠落部
が音響反射波を生じては、本来の反射波キヤンセ
ルの目的を達成できなくなることから本発明では
新たに設けたダミーの電極金属欠落部からの音響
反射波をキヤンセルするような構造にして上記目
的を達成している。
The present invention also applies to electrode parts other than the acoustic reflection generating part.
By providing a portion with no metal in the wavelength width, the propagation speed of the surface acoustic wave is equalized in all parts of the electrode.Furthermore, if this dummy electrode metal missing portion generates an acoustic reflected wave, the original reflected wave Since the purpose of canceling cannot be achieved, the present invention achieves the above purpose by using a structure that cancels the acoustic reflected waves from the newly provided dummy electrode metal missing portion.
以下本発明を図面を参照して詳細に説明する。
第２図は本発明の一実施例の弾性表面波装置のイ
ンタデイジタル電極構成を示すものである。図示
するように、このインタデイジタル電極１１，１
２はそれぞれ1/8波長幅電極指および5/8波長幅電
極指を有し、これら電極指が1/8波長幅の間隔を
おいて互いに噛み合うよう形成されている。なお
このインタデイジタル電極１１，１２は図示しな
いがLiTaO3やLiNbO3等の圧電性基板上に形成
されている。インタデイジタル電極12の5/8波長
幅の電極指には第１図と同様に音響的反射波を生
じさせる電極金属欠落部２１〜２６がアポダイズ
法によつて設けられている。すなわち電極金属欠
落部２１〜２６の長さが電極指間で徐々に変化し
ている。従つて第１図の装置と同様に反射波のキ
ヤンセル効果が維持されている。
The present invention will be described in detail below with reference to the drawings.
FIG. 2 shows an interdigital electrode configuration of a surface acoustic wave device according to an embodiment of the present invention. As shown in the figure, these interdigital electrodes 11,1
2 each have a 1/8 wavelength width electrode finger and a 5/8 wavelength width electrode finger, and these electrode fingers are formed to mesh with each other at intervals of 1/8 wavelength width. Although not shown, the interdigital electrodes 11 and 12 are formed on a piezoelectric substrate such as LiTaO 3 or LiNbO 3 . The 5/8 wavelength width electrode fingers of the interdigital electrodes 12 are provided with electrode metal missing portions 21 to 26 by the apodization method, which produce acoustic reflected waves, as in FIG. 1. That is, the lengths of the electrode metal missing parts 21 to 26 gradually change between the electrode fingers. Therefore, like the device shown in FIG. 1, the effect of canceling reflected waves is maintained.
本実施例の弾性表面波装置が第１図の装置と異
なる点はインタデイジタル電極１２の5/8波長幅
の電極指に上記電極金属欠落部２１〜２６の他に
ダミーの電極金属欠落部３１〜３５及び４１〜４
５が設けられている点である。このダミーの電極
金属欠落部３１〜３６，４１〜４６は金属電極欠
落部２１〜２６と同じ1/8波長幅で、金属電極欠
落部２１〜２６の外側部分に形成されている。ま
た同一電極指内のダミーの電極金属欠落部３１と
４１，３２と４２，３３と４３…はその長さが等
しく、かつ両者は各々1/4波長ずつ表面波伝搬方
向にずれている。 The surface acoustic wave device of this embodiment is different from the device shown in FIG. ~35 and 41~4
5 is provided. The dummy electrode metal missing parts 31-36, 41-46 have the same 1/8 wavelength width as the metal electrode missing parts 21-26, and are formed outside the metal electrode missing parts 21-26. Further, the lengths of the dummy electrode metal missing portions 31 and 41, 32 and 42, 33 and 43, . . . within the same electrode finger are equal, and they are each shifted by 1/4 wavelength in the surface wave propagation direction.
上記構成によると、図中左方から伝搬して来た
弾性表面波Ｃはダミーの電極金属欠落部３１，３
２，…，３６で音響反射を生じる。一方、同様に
弾性表面波Ｄもダミーの電極金属欠落部４１，４
２，…，４６で音響反射を生ずる。この場合電極
金属欠落部３１と４１，３２と４２……３６と４
６の長さは互いに等しいので、各電極金属欠落部
３１と４１，３２と４２……、３６と４６からの
反射量は等しい。しかしながら弾性波ＣとＤの音
響反射波は、ダミーの電極金属欠落部３１と４
１，３２と４２，……３６と４６がそれぞれ1/4
波長ずれているので往復1/2波長分すなわち180°
位相差が異なつている。この為、反射波が入力電
極側に達した時、電極金属欠落部３１からの反射
波と４１からの反射波とはキヤンセルする。同様
に各電極金属欠落部３２と４２，３３と４３，…
…３６と４６の反射波もキヤンセルする。従つて
ダミーの電極金属欠落部３１〜３６，４１〜４６
からの音響反射波についても全く問題とならず、
しかも同一電極指の長さ方向のどの位置でも電極
金属欠落部の幅が一定とすることができる。 According to the above configuration, the surface acoustic wave C propagating from the left side in the figure is transmitted to the dummy electrode metal missing portions 31 and 3.
2, . . . , 36 cause acoustic reflection. On the other hand, similarly, the surface acoustic wave D also has dummy electrode metal missing parts 41, 4.
2, . . . , 46 causes acoustic reflection. In this case, electrode metal missing parts 31 and 41, 32 and 42...36 and 4
Since the lengths of the electrodes 6 are equal, the amount of reflection from each electrode metal missing portion 31 and 41, 32 and 42, . . . , 36 and 46 is equal. However, the acoustic reflected waves of the elastic waves C and D are the dummy electrode metal missing parts 31 and 4.
1, 32 and 42, ...36 and 46 are each 1/4
Since the wavelength is shifted, the round trip is 1/2 wavelength, or 180°.
The phase difference is different. Therefore, when the reflected wave reaches the input electrode side, the reflected wave from the electrode metal missing portion 31 and the reflected wave from 41 are canceled. Similarly, each electrode metal missing portion 32 and 42, 33 and 43,...
...It also cancels the reflected waves of 36 and 46. Therefore, dummy electrode metal missing parts 31 to 36, 41 to 46
There is no problem with acoustic reflected waves from
Moreover, the width of the electrode metal missing portion can be made constant at any position in the length direction of the same electrode finger.
本発明によれば、電気的反射と音響的反射が完
全にキヤンセルされしかも電極のどの部分でも弾
性表面波の伝搬速度は等しい為、位相差が生じず
周波数特性を設計どうりのものにすることができ
る。しかもこの効果は電極形状を変えるだけであ
りしかもこの電極は最も細い部分でもせいぜい1/
８波長幅であることにより製造時の困難性もほと
んどない。
According to the present invention, electrical reflection and acoustic reflection are completely canceled, and the propagation speed of surface acoustic waves is the same in any part of the electrode, so no phase difference occurs and the frequency characteristics can be made as designed. I can do it. Moreover, this effect only changes the shape of the electrode, and even at its thinnest part, the electrode is only 1/2
Since it has a width of 8 wavelengths, there is almost no difficulty in manufacturing.
前記実施例では、同一電極指内に1/4波長の間
隔をおいて一対のダミー電極金属欠落部３１，４
１を設けるようにしたが、第３図に示すようにこ
のダミーの電極金属欠落部３１，４１を複数個に
分割して３１ａ，３１ｂ，３１ｃ，３１ｄと４１
ａ，４１ｂ，４１ｃ，４１ｄとして形成すること
もできる。この場合電極金属欠落部３１ａ〜３１
ｄからの音響反射波の量と４１ａ〜４１ｄからの
音響反射波の量が互いに等しくなり、完全にキヤ
ンセルするよう電極金属欠落部３１ａ〜３１ｄの
長さの合計と４１ａ〜４１ｄの長さの合計とが等
しいことが望ましい。このような実施例において
も第２図の実施例と同様の効果を奏することは明
らかである。
In the above embodiment, a pair of dummy electrode metal missing portions 31, 4 are provided within the same electrode finger with an interval of 1/4 wavelength.
As shown in FIG.
They can also be formed as a, 41b, 41c, and 41d. In this case, electrode metal missing parts 31a to 31
The sum of the lengths of the electrode metal missing portions 31a to 31d and the sum of the lengths of 41a to 41d is set so that the amount of acoustic reflected waves from d and the amount of acoustic reflected waves from 41a to 41d are equal to each other and are completely canceled. It is desirable that they are equal. It is clear that such an embodiment also provides the same effects as the embodiment of FIG. 2.
また本発明の主旨は電気的反射と音響的反射を
キヤンセルし、かつ電極の長さ方向のどの部分で
も弾性表面波の伝搬速度が等しくなるようにする
ことであるから第４図に示すように電極金属欠落
部５１〜５３を5/8波長幅電極指の長さ方向すべ
てにわたり形成するようなものも考えられる。 Furthermore, the gist of the present invention is to cancel electrical reflection and acoustic reflection, and to make the propagation speed of surface acoustic waves equal at any part in the length direction of the electrode, so as shown in FIG. It is also conceivable that the electrode metal missing portions 51 to 53 are formed over the entire length of the 5/8 wavelength width electrode fingers.
第１図の従来例では音響反射用電極金属欠落部
２１〜２６が左方より徐々に長さ変わつている
が、これは反射率を変える主旨によるものであ
る。 In the conventional example shown in FIG. 1, the lengths of the acoustic reflecting electrode metal missing portions 21 to 26 gradually change from the left side, but this is for the purpose of changing the reflectance.
第４図の実施例では反射率を変えるのに電極金
属欠落部５１〜５３の幅を電極指間で徐々に変え
て行つている。但し、同一電極指内では電極金属
欠落部の幅は同一である。この時、電極金属欠落
部の幅の中心位置は5/8波長幅電極の左端より3/1
６波長で一定でなければならない。また電極の対
数が多くなつてくると電極の再励起効果などの影
響で電気的反射波の周波数特性の位相が直線でな
くなつてくる場合がある。この時、音響波発生用
電極欠落部２１〜２６あるいは５１〜５３の幅の
中心位置を、5/8波長幅電極の左端より3/16波長
の距離からわずかに変化させて、電気的反射波と
音響反射波を完全にキヤンセルすることも可能で
ある。 In the embodiment shown in FIG. 4, the width of the electrode metal missing parts 51 to 53 is gradually changed between the electrode fingers in order to change the reflectance. However, within the same electrode finger, the width of the electrode metal missing portion is the same. At this time, the center position of the width of the electrode metal missing part is 3/1 from the left end of the 5/8 wavelength width electrode.
Must be constant at 6 wavelengths. Furthermore, as the number of pairs of electrodes increases, the phase of the frequency characteristics of electrically reflected waves may become non-linear due to the re-excitation effect of the electrodes. At this time, the center position of the width of the acoustic wave generation electrode missing parts 21 to 26 or 51 to 53 is slightly changed from a distance of 3/16 wavelength from the left end of the 5/8 wavelength width electrode to generate the electrical reflected wave. It is also possible to completely cancel acoustic reflected waves.
第１図は電気的反射を音響的反射でキヤスセル
する従来の弾性表面波装置の電極形状を示す図、
第２図は本発明の弾性表面波装置の電極形状の一
実施例を示す図、第３図および第４図はそれぞれ
本発明の他の実施例を示す図である。
１１，１２……インタデイジタル電極、２１〜
２６……音響波発生用電極金属欠落部、３１〜３
６，４１〜４６……ダミーの電極金属欠落部、５
１〜５３……音響波発生用電極金属欠落部。
Figure 1 is a diagram showing the electrode shape of a conventional surface acoustic wave device that cancels electrical reflection with acoustic reflection.
FIG. 2 is a diagram showing one embodiment of the electrode shape of the surface acoustic wave device of the present invention, and FIGS. 3 and 4 are diagrams each showing other embodiments of the present invention. 11, 12...interdigital electrode, 21~
26... Electrode metal missing part for acoustic wave generation, 31-3
6, 41-46... Dummy electrode metal missing part, 5
1 to 53... Electrode metal missing portion for acoustic wave generation.
Claims (1)
と5/8波長幅電極指との組み合わせからなる弾性
表面波送信あるいは受信用インターデイジタル電
極と、 この弾性表面波送信あるいは受信用インターデ
イジタル電極の5/8波長幅電極指に形成され、そ
の長さが電極指間で徐々に変化する音響反射用電
極金属欠落部と、同一電極指内の長さ方向のどの
位置でも欠落部幅が1/8波長一定となるように、
同一電極指内で少なくとも２カ所以上に分散して
配置された1/8波長幅のダミーの電極金属欠落部
とからなる電極金属欠落部と、 前記ダミーの電極金属欠落部の幅の中心位置は
お互いに1/4波長弾性表面波伝搬方向にずれてお
り1/4波長左の欠落部の長さの合計と、1/4波長右
の欠落部の長さの合計とが等しく形成されている
ことを特徴とする弾性表面波装置。 ２ 圧電基板と、 この圧電基板上に設けられた1/8波長幅電極指
と5/8波長電極指との組み合わせからなる弾性表
面波送信あるいは受信用インターデイジタル電極
と、 この弾性表面波送信あるいは受信用インターデ
イジタル電極の5/8波長幅電極指の長さ方向全て
にわたつて形成される音響反射用電極欠落部は、
欠落部の幅が同一電極指内では同一であるが電極
指間では徐々に変化しており、さらに前記欠落部
の幅の中心が5/8波長幅電極指の端部から3/16波
長の位置にあることを特徴とする弾性表面波装
置。 ３ 圧電基板と、 この圧電基板上に設けられた1/8波長幅電極指
と5/8波長電極指との組み合わせからなる弾性表
面波送信あるいは受信用インターデイジタル電極
と、 この弾性表面波送信あるいは受信用インターデ
イジタル電極の5/8波長幅電極指の長さ方向全て
にわたつて形成される音響反射用電極欠落部は、
欠落部の幅が同一電極指内では同一であるが電極
指間では徐々に変化しており、さらに前記欠落部
の幅の中心位置が5/8波長幅電極指の端部から3/1
６波長よりわずかにずらして5/8波長幅電極指内に
形成されてなることを特徴とする弾性表面波装
置。[Claims] 1. A piezoelectric substrate, and an interdigital electrode for surface acoustic wave transmission or reception consisting of a combination of 1/8 wavelength width electrode fingers and 5/8 wavelength width electrode fingers provided on the piezoelectric substrate. , This interdigital electrode for surface acoustic wave transmission or reception is formed on the 5/8 wavelength width electrode finger, and the length of the electrode metal missing part for acoustic reflection gradually changes between the electrode fingers, and The width of the missing part is kept constant at 1/8 wavelength at any position in the length direction.
The electrode metal missing portion is composed of 1/8 wavelength width dummy electrode metal missing portions distributed in at least two locations within the same electrode finger, and the center position of the width of the dummy electrode metal missing portion is They are shifted from each other in the 1/4 wavelength surface acoustic wave propagation direction, and the total length of the missing part on the left side of 1/4 wavelength is equal to the sum of the length of the missing part on the right side of 1/4 wavelength. A surface acoustic wave device characterized by: 2. A piezoelectric substrate, an interdigital electrode for surface acoustic wave transmission or reception consisting of a combination of 1/8 wavelength width electrode fingers and 5/8 wavelength electrode fingers provided on this piezoelectric substrate, and this surface acoustic wave transmission or reception interdigital electrode. The missing part of the acoustic reflecting electrode, which is formed along the entire length of the 5/8 wavelength width electrode finger of the receiving interdigital electrode, is
The width of the missing part is the same within the same electrode finger, but it gradually changes between electrode fingers, and the center of the width of the missing part is 3/16 wavelength from the end of the 5/8 wavelength electrode finger. A surface acoustic wave device characterized in that: 3 A piezoelectric substrate, an interdigital electrode for surface acoustic wave transmission or reception consisting of a combination of 1/8 wavelength width electrode fingers and 5/8 wavelength electrode fingers provided on this piezoelectric substrate, and this surface acoustic wave transmission or reception interdigital electrode. The missing part of the acoustic reflecting electrode, which is formed along the entire length of the 5/8 wavelength width electrode finger of the receiving interdigital electrode, is
Although the width of the missing part is the same within the same electrode finger, it gradually changes between electrode fingers, and furthermore, the center position of the width of the missing part is 3/1 from the end of the 5/8 wavelength electrode finger.
A surface acoustic wave device characterized by being formed within a 5/8 wavelength width electrode finger slightly shifted from 6 wavelengths.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6962082A JPS58187013A (en) | 1982-04-27 | 1982-04-27 | Surface acoustic wave device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6962082A JPS58187013A (en) | 1982-04-27 | 1982-04-27 | Surface acoustic wave device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS58187013A JPS58187013A (en) | 1983-11-01 |
| JPH047125B2 true JPH047125B2 (en) | 1992-02-10 |
Family
ID=13408093
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP6962082A Granted JPS58187013A (en) | 1982-04-27 | 1982-04-27 | Surface acoustic wave device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS58187013A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60241313A (en) * | 1984-05-16 | 1985-11-30 | Toshiba Corp | Elastic surface wave device |
-
1982
- 1982-04-27 JP JP6962082A patent/JPS58187013A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS58187013A (en) | 1983-11-01 |
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