JPH0774588A - Vertical dual mode surface acoustic wave filter - Google Patents
Vertical dual mode surface acoustic wave filterInfo
- Publication number
- JPH0774588A JPH0774588A JP21858693A JP21858693A JPH0774588A JP H0774588 A JPH0774588 A JP H0774588A JP 21858693 A JP21858693 A JP 21858693A JP 21858693 A JP21858693 A JP 21858693A JP H0774588 A JPH0774588 A JP H0774588A
- Authority
- JP
- Japan
- Prior art keywords
- comb
- acoustic wave
- surface acoustic
- wave filter
- electrode
- 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
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/46—Filters
- H03H9/64—Filters using surface acoustic waves
- H03H9/6489—Compensation of undesirable effects
- H03H9/6496—Reducing ripple in transfer characteristic
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/25—Constructional features of resonators using surface acoustic waves
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/46—Filters
- H03H9/64—Filters using surface acoustic waves
- H03H9/6423—Means for obtaining a particular transfer characteristic
- H03H9/6433—Coupled resonator filters
Landscapes
- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- 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、縦型二重モード結合を
利用した低損失の弾性表面波フィルタに関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-loss surface acoustic wave filter utilizing vertical dual mode coupling.
【０００２】[0002]
【従来の技術】表面波の伝搬方向に発生する２つのエネ
ルギー閉じ込め型振動モードを利用した、いわゆる縦型
二重モード弾性表面波フィルタが公知であり、帯域幅の
設計余裕度が大きいため、コードレス電話のＲＦ部等に
おいて採用されている。この縦型二重モード弾性表面波
フィルタは、エネルギー閉じ込め型共振子を１枚の圧電
基板上に複数段形成し、多段縦続接続した構成を有す
る。2. Description of the Related Art A so-called vertical dual-mode surface acoustic wave filter utilizing two energy trapping vibration modes generated in the propagation direction of a surface wave is known, and has a large bandwidth design margin, and thus is cordless. It is used in the RF section of telephones. This vertical dual-mode surface acoustic wave filter has a configuration in which a plurality of energy trap type resonators are formed on one piezoelectric substrate and are cascade-connected.
【０００３】上記縦型二重モード弾性表面波フィルタで
は、使用する圧電基板材料の種類および基板のカット方
位によって、その特性が大きく変化する。従って、使用
する基板材料およびカット方位に適した設計が要求され
る。The characteristics of the above-mentioned vertical dual-mode surface acoustic wave filter vary greatly depending on the type of piezoelectric substrate material used and the cutting direction of the substrate. Therefore, a design suitable for the substrate material used and the cut orientation is required.
【０００４】また、充分な広帯域を有する弾性表面波フ
ィルタを得るには、３６°Ｙ回転カットＸ方向伝搬のＬ
ｉＴａＯ3 （以下、３６°Ｙ−ＸＬＴ）圧電基板のよう
に、電気機械結合係数の大きな圧電基板を用いることが
望ましい。Further, in order to obtain a surface acoustic wave filter having a sufficiently wide band, L of 36 ° Y rotation cut X direction propagation is obtained.
It is desirable to use a piezoelectric substrate having a large electromechanical coupling coefficient, such as an iTaO 3 (hereinafter, 36 ° Y-XLT) piezoelectric substrate.
【０００５】しかしながら、従来の縦型二重モード弾性
表面波フィルタでは、３６°Ｙ−ＸＬＴ圧電基板を用い
て構成した場合、通過帯域内に不要スプリアスが発生す
るという問題があった。However, in the conventional vertical dual-mode surface acoustic wave filter, when the 36 ° Y-XLT piezoelectric substrate is used, there is a problem that unnecessary spurious is generated in the pass band.
【０００６】上記不要スプリアスを抑制し得るものとし
て、特開平４−４０７０５号には、複数のエネルギー閉
じ込め型共振子の接続部に、エネルギー閉じ込め型共振
子のインターデジタルトランスデューサ（以下、ＩＤＴ
と略す。）と電気的に並列にくし型電極等により構成さ
れる結合容量を接続した構造が開示されている。As a device capable of suppressing the above-mentioned unnecessary spurious, Japanese Patent Application Laid-Open No. 4-40705 discloses an interdigital transducer (hereinafter referred to as IDT) of an energy trapping resonator at a connecting portion of a plurality of energy trapping resonators.
Abbreviated. ) Is electrically connected in parallel with a coupling capacitor composed of a comb-shaped electrode or the like.
【０００７】[0007]
【発明が解決しようとする課題】しかしながら、特開平
４−４０７０５号に開示されている縦型二重モード弾性
表面波フィルタでは、上記通過帯域内の不要スプリアス
を抑制し得るものの、通過帯域内における挿入損失が比
較的大きく、挿入損失の低減が要望されている。However, in the vertical double-mode surface acoustic wave filter disclosed in Japanese Patent Application Laid-Open No. 4-40705, although unnecessary spurious in the pass band can be suppressed, it does not occur in the pass band. Since the insertion loss is relatively large, it is desired to reduce the insertion loss.
【０００８】本発明の目的は、３６°Ｙ−ＸＬＴ圧電基
板を用いて構成されており、通過帯域内における不要ス
プリアスを低減し得るだけでなく、挿入損失を著しく低
減することをも可能とする構造を備えた縦型二重モード
弾性表面波フィルタを提供することにある。An object of the present invention is to use a 36 ° Y-XLT piezoelectric substrate and to not only reduce unnecessary spurious in the pass band but also significantly reduce insertion loss. An object is to provide a vertical dual-mode surface acoustic wave filter having a structure.
【０００９】[0009]
【課題を解決するための手段】本発明の縦型二重モード
弾性表面波フィルタは、３６°Ｙ−ＸＬＴ圧電基板と、
前記圧電基板上に構成されており、かつ多段縦続接続さ
れた複数のエネルギー閉じ込め型共振子とを備え、前記
各エネルギー閉じ込め型共振子が、近接配置された少な
くとも２つのＩＤＴと、該少なくとも２つのＩＤＴの両
側に配置された反射器とを有し、前記複数のエネルギー
閉じ込め型共振子間の接続部に、前記ＩＤＴと電気的に
並列に接続されており、かつ表面波伝搬路上以外の圧電
基板上の領域に形成された結合容量構成用くし型電極を
さらに備える。A vertical dual mode surface acoustic wave filter of the present invention comprises a 36 ° Y-XLT piezoelectric substrate and
A plurality of energy trapping resonators configured on the piezoelectric substrate and connected in cascade, each energy trapping resonator having at least two IDTs arranged in close proximity to each other; A piezoelectric substrate having reflectors arranged on both sides of the IDT, electrically connected in parallel to the IDT at a connection portion between the plurality of energy trap resonators, and other than on the surface wave propagation path. It further comprises a comb-shaped electrode for forming a coupling capacitance formed in the upper region.
【００１０】さらに、前記ＩＤＴの電極指の周期を
λf 、くし型電極の電極指の周期をλcとしたときに、Further, when the period of the electrode fingers of the IDT is λ f and the period of the electrode fingers of the comb-shaped electrode is λ c ,
【００１１】[0011]
【数２】 [Equation 2]
【００１２】を満たすように、前記λf およびλc が決
定されている。なお、上記周期λf 及びλc とは、間挿
し合っている複数本の電極指の電極指間ピッチの２倍の
長さに相当し、すなわちＩＤＴにおいては励振される表
面波の周期に相当するものである。The λ f and λ c are determined so as to satisfy the above. The above-mentioned periods λ f and λ c correspond to twice the pitch between the electrode fingers of a plurality of electrode fingers that are interleaved, that is, the period of the surface wave excited in the IDT. To do.
【００１３】[0013]
【作用】本発明では、３６°Ｙ−ＸＬＴ圧電基板を用い
て構成されており、かつ複数のエネルギー閉じ込め型共
振子間の接続部に上記結合容量が接続されているため、
特開平４−４０７０５号に開示されている縦型二重モー
ド弾性表面波フィルタの場合と同様に、通過帯域内のス
プリアスが効果的に抑制される。In the present invention, since the 36 ° Y-XLT piezoelectric substrate is used and the coupling capacitance is connected to the connection portion between the plurality of energy trap type resonators,
As in the case of the vertical dual mode surface acoustic wave filter disclosed in JP-A-4-40705, spurious in the pass band is effectively suppressed.
【００１４】しかも、本願発明者らの実験により確かめ
られ、かつ後述の実施例で示されるように、上記エネル
ギー閉じ込め型共振子におけるＩＤＴの電極指の周期を
λf、上記結合容量帯域用くし型電極の電極指の周期を
λc としたときに、比λf ／λc が上記特定の関係を満
たすように決定されているので、挿入損失が低減され
る。Moreover, as confirmed by the experiments conducted by the inventors of the present application and as shown in Examples described later, the period of the electrode fingers of the IDT in the energy trap type resonator is λ f , and the comb type for the coupling capacitance band is When the period of the electrode fingers of the electrodes is λ c , the ratio λ f / λ c is determined so as to satisfy the above specific relationship, so that the insertion loss is reduced.
【００１５】[0015]
【発明の効果】本発明によれば、広帯域化に適した電気
機械結合係数の大きい３６°Ｙ−ＸＬＴ圧電基板を用い
て構成された縦型二重モード弾性表面波フィルタにおい
て、上記結合容量構成用くし型電極の作用により通過帯
域内の不要スプリアスを抑制し得るだけでなく、上記Ｉ
ＤＴおよびくし型電極の周期が、上記特定の関係を満た
すように決定されているため、通過帯域内における挿入
損失を効果的に低減することができる。According to the present invention, in a vertical dual-mode surface acoustic wave filter constructed by using a 36 ° Y-XLT piezoelectric substrate having a large electromechanical coupling coefficient suitable for wide band, the coupling capacitance configuration described above is used. Not only can unwanted spurious in the pass band be suppressed by the action of the comb electrode, but
Since the periods of the DT and the comb-shaped electrode are determined so as to satisfy the above specific relationship, the insertion loss in the pass band can be effectively reduced.
【００１６】よって、高周波域において使用するのに適
しており、広帯域化を容易に計ることができ、フィルタ
としての周波数特性に優れており、さらに低損失の縦型
二重モード弾性表面波フィルタを提供することが可能と
なる。Therefore, it is suitable for use in a high frequency range, can easily achieve a wide band, has excellent frequency characteristics as a filter, and has a low loss vertical double mode surface acoustic wave filter. It becomes possible to provide.
【００１７】[0017]
【実施例の説明】以下、図面を参照しつつ本発明の非限
定的な実施例を説明することにより、本発明を明らかに
する。DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be clarified by describing non-limiting embodiments of the present invention with reference to the drawings.
【００１８】図１は、本発明の一実施例が適用される縦
型二重モード弾性表面波フィルタを説明するための模式
的平面図である。縦型二重モード弾性表面波フィルタ１
は、３６°Ｙ−ＸＬＴよりなる矩形の圧電基板２を用い
て構成されている。圧電基板２上には、以下の電極構造
を形成することにより、第１，第２のエネルギー閉じ込
め型共振子が構成されている。FIG. 1 is a schematic plan view for explaining a vertical dual mode surface acoustic wave filter to which an embodiment of the present invention is applied. Vertical dual-mode surface acoustic wave filter 1
Is formed by using a rectangular piezoelectric substrate 2 made of 36 ° Y-XLT. The first and second energy trap resonators are formed on the piezoelectric substrate 2 by forming the following electrode structure.
【００１９】すなわち、第１のエネルギー閉じ込め型共
振子は、ＩＤＴ３，４と、ＩＤＴ３，４の両側に配置さ
れた反射器５，６とを有する。ＩＤＴ３，４は、それぞ
れ、互いの電極指が間挿し合う一対のくし歯電極３ａ，
３ｂおよび４ａ，４ｂにより構成されており、図示のよ
うに近接配置されている。また、反射器５，６は、ＩＤ
Ｔ３，４の電極指と平行に延びる複数本の直線状の電極
の両端を表面波伝搬方向に平行に延びる電極により接続
した構造を有する。That is, the first energy trap type resonator has IDTs 3 and 4 and reflectors 5 and 6 arranged on both sides of the IDTs 3 and 4, respectively. Each of the IDTs 3 and 4 has a pair of comb-teeth electrodes 3a and 3a, in which the electrode fingers of the IDTs 3 and 4 are respectively inserted.
It is composed of 3b and 4a, 4b, and is arranged close to each other as shown in the drawing. In addition, the reflectors 5 and 6 are ID
It has a structure in which both ends of a plurality of linear electrodes extending parallel to the electrode fingers of T3 and T4 are connected by electrodes extending parallel to the surface wave propagation direction.
【００２０】第２のエネルギー閉じ込め型共振子は、第
１のエネルギー閉じ込め型共振子と同様に構成されてお
り、中央に近接配置されたＩＤＴ７，８を有し、ＩＤＴ
７，８の両側に反射器９，１０を有する。The second energy trapping resonator has the same structure as the first energy trapping resonator, and has IDTs 7 and 8 arranged close to each other in the center.
Reflectors 9 and 10 are provided on both sides of 7 and 8.
【００２１】第１のエネルギー閉じ込め型共振子におけ
るＩＤＴ３のくし歯電極３ａが入力端に接続され、くし
歯電極３ｂは基準電位に接続される。また、ＩＤＴ４の
一方のくし歯電極４ａが基準電位に接続され、他方のく
し歯電極４ｂが、第２エネルギー閉じ込め型共振子のＩ
ＤＴ７の一方のくし歯電極７ａに電気的に接続されてい
る。くし歯電極４ｂと、くし歯電極７ａとを電気的に接
続することにより、第１，第２のエネルギー閉じ込め型
共振子が縦続接続されている。The comb-teeth electrode 3a of the IDT 3 in the first energy trap resonator is connected to the input end, and the comb-teeth electrode 3b is connected to the reference potential. Further, one comb tooth electrode 4a of the IDT 4 is connected to the reference potential, and the other comb tooth electrode 4b of the IDT 4 is I of the second energy trap type resonator.
It is electrically connected to one comb tooth electrode 7a of DT7. By electrically connecting the comb-teeth electrode 4b and the comb-teeth electrode 7a, the first and second energy trap type resonators are cascade-connected.
【００２２】また、上記第１，第２のエネルギー閉じ込
め型共振子間の接続部には、くし型電極１１が電気的に
接続されている。くし型電極１１は、互いに間挿し合う
電極指を有する一対のくし歯電極１１ａ，１１ｂにより
構成されている。A comb electrode 11 is electrically connected to the connection between the first and second energy trap resonators. The comb-shaped electrode 11 is composed of a pair of comb-shaped electrodes 11a and 11b having electrode fingers which are inserted into each other.
【００２３】くし型電極１１の一方のくし歯電極１１ａ
は、上記接続部に電気的に接続されている。なお、他方
のくし歯電極１１ｂは基準電位に接続されている。くし
型電極１１は、第１，第２のエネルギー閉じ込め型共振
子間の接続部において、上記ＩＤＴ４，７に並列に結合
容量を構成するために設けられているものであり、それ
によって特開平４−４０７０５号に開示されている弾性
表面波フィルタの場合と同様に、通過帯域内におけるス
プリアスが抑制される。One of the comb-shaped electrodes 11a of the comb-shaped electrode 11
Are electrically connected to the connection part. The other comb-shaped electrode 11b is connected to the reference potential. The comb-shaped electrode 11 is provided to form a coupling capacitance in parallel with the IDTs 4 and 7 at the connection portion between the first and second energy confinement resonators. As in the case of the surface acoustic wave filter disclosed in No. -40705, spurious in the pass band is suppressed.
【００２４】第２のエネルギー閉じ込め型共振子におい
ては、上記ＩＤＴ７の他方のくし歯電極７ｂは基準電位
に接続されている。また、ＩＤＴ８の一方のくし歯電極
８ａが基準電位に接続されており、他方のくし歯電極８
ｂが出力端とされる。In the second energy trap resonator, the other comb-teeth electrode 7b of the IDT 7 is connected to the reference potential. Further, one comb tooth electrode 8a of the IDT 8 is connected to the reference potential, and the other comb tooth electrode 8a is connected.
b is the output end.
【００２５】以上のように、図１に示した縦型二重モー
ド弾性表面波フィルタ１は、特開平４−４０７０５号に
開示されている縦型二重モード弾性表面波フィルタと構
造的にはほぼ同様である。もっとも、本実施例では、上
記ＩＤＴ３，４，７，８における電極指の周期をλf と
し、くし型電極１１の電極指の周期をλc としたとき
に、比λf ／λc が１．０とされている。As described above, the vertical double-mode surface acoustic wave filter 1 shown in FIG. 1 is structurally similar to the vertical double-mode surface acoustic wave filter disclosed in Japanese Patent Laid-Open No. 4-40705. It is almost the same. However, in this embodiment, when the period of the electrode fingers in the IDTs 3, 4, 7 and 8 is λ f and the period of the electrode fingers of the comb-shaped electrode 11 is λ c , the ratio λ f / λ c is 1. It is set to 0.
【００２６】本実施例の縦型二重モード弾性表面波フィ
ルタの第１の挿入損失−周波数特性を、図２に実線Ａ
で、及びその要部を拡大して一点鎖線Ｂで示す。なお、
一点鎖線Ｂで示す挿入損失−周波数特性は、実線Ａで示
す挿入損失−周波数特性曲線を拡大したものであり、図
２の挿入損失についての１目盛りを２ｄＢとして図示し
たものである。The first insertion loss-frequency characteristic of the vertical dual mode surface acoustic wave filter of this embodiment is shown in FIG.
And the main part thereof are enlarged and shown by a one-dot chain line B. In addition,
The insertion loss-frequency characteristic indicated by the alternate long and short dashed line B is an enlargement of the insertion loss-frequency characteristic curve indicated by the solid line A, and one scale for the insertion loss in FIG. 2 is shown as 2 dB.
【００２７】比較のために、上記比λf ／λc ＝３．０
としたことを除いては上記実施例と全く同様に構成され
た縦型二重モード弾性表面波フィルタの挿入損失−周波
数特性を、図２に実線Ｃで、及びその要部を拡大して一
点鎖線Ｄで示す。For comparison, the ratio λ f / λ c = 3.0.
The insertion loss-frequency characteristics of the vertical dual-mode surface acoustic wave filter having the same structure as that of the above-mentioned embodiment except that the above is shown by a solid line C in FIG. 2 and an enlarged main part thereof. It is indicated by a chain line D.
【００２８】上記実線Ａおよび一点鎖線Ｂで示す特性
と、実線Ｃおよび一点鎖線Ｄで示す特性とを比較すれば
明らかなように、本実施例の縦型二重モード弾性表面波
フィルタでは、λf ／λc ＝３．０の縦型二重モード弾
性表面波フィルタに比べて挿入損失が効果的に低減され
得ることがわかる。As can be seen by comparing the characteristics indicated by the solid line A and the alternate long and short dash line B with the characteristics indicated by the solid line C and the alternate long and short dash line, the longitudinal double mode surface acoustic wave filter of this embodiment has a λ It can be seen that the insertion loss can be effectively reduced as compared with the vertical dual-mode surface acoustic wave filter with f / λ c = 3.0.
【００２９】このように、比λf ／λc を選択すること
により、挿入損失が低減されるのは、スプリアス抑制用
結合容量が、容量成分だけを有することが理想であるに
も関わらず、実際にはコンダクタンス成分をも有し、該
コンダクタンス成分が大きい場合に挿入損失が増加する
ことに起因するものと考えられる。Thus, by selecting the ratio λ f / λ c , the insertion loss is reduced even though it is ideal that the spurious suppressing coupling capacitance has only a capacitance component. Actually, it also has a conductance component, and it is considered that this is because the insertion loss increases when the conductance component is large.
【００３０】そこで、くし型電極１１における容量とコ
ンダクタンスが、比λf ／λc を変化させた時に、どの
ように変化するかを測定した（電極指の対数は１０対、
交差幅は６００μｍとした。）。結果を図３に示す。図
３から明らかなように、比λ f ／λc が、Therefore, the capacitance and
The inductance is the ratio λf/ ΛcWhich when you change
Was measured (the number of pairs of electrode fingers is 10 pairs,
The intersection width was 600 μm. ). The results are shown in Fig. 3. Figure
As is clear from 3, the ratio λ f/ ΛcBut,
【００３１】[0031]
【数３】 [Equation 3]
【００３２】を満たす範囲において、コンダクタンス部
分が小さくなることがわかった。そこで、このような範
囲の結合容量をくし型電極１１により構成し、種々の縦
型二重モード弾性表面波フィルタを作成し、その挿入損
失と、λf ／λc との関係を調べた。結果を図４に示
す。It has been found that the conductance portion becomes smaller in the range satisfying the condition. Therefore, various longitudinal double-mode surface acoustic wave filters were constructed by forming the coupling capacitance in such a range by the comb-shaped electrode 11, and the relationship between the insertion loss and λ f / λ c was investigated. The results are shown in Fig. 4.
【００３３】図４から明らかなように、比λf ／λc が
上記特定の関係を満たすようにくし型電極１１を構成す
ることにより、挿入損失を上記実施例と同様に低減し得
ることがわかる。従って、本発明では、比λf ／λ
c を、上記特定の関係を満たすように決定することが必
要である。As is apparent from FIG. 4, by forming the comb-shaped electrode 11 so that the ratio λ f / λ c satisfies the above-mentioned specific relationship, it is possible to reduce the insertion loss as in the above-mentioned embodiment. Recognize. Therefore, in the present invention, the ratio λ f / λ
It is necessary to determine c so as to satisfy the above specific relationship.
【００３４】なお、上述した実施例では、第１，第２の
エネルギー閉じ込め型共振子が圧電基板２上に構成され
ていたが、本発明は、３段以上のエネルギー閉じ込め型
共振子が縦続接続されている縦型二重モード弾性表面波
フィルタにも適用することができる。In the above-mentioned embodiment, the first and second energy trapping resonators are formed on the piezoelectric substrate 2, but in the present invention, three or more stages of energy trapping resonators are connected in cascade. The present invention can also be applied to the existing vertical dual-mode surface acoustic wave filter.
【００３５】さらに、上記実施例では、各エネルギー閉
じ込め型共振子が２個のＩＤＴを有するように構成され
ていたが、例えば図５に示す縦型二重モード弾性表面波
フィルタ２１のように圧電基板２２上において、各エネ
ルギー閉じ込め型共振子が３個のＩＤＴ２３〜２５，２
８〜３０を有するものであってもよい。なお、図５にお
いて２６，２７，３１，３２は反射器を示す。Further, in the above-mentioned embodiment, each energy trapping type resonator is constructed to have two IDTs. For example, as in the vertical double mode surface acoustic wave filter 21 shown in FIG. On the substrate 22, each energy trap type resonator has three IDTs 23 to 25,2.
It may have 8 to 30. In FIG. 5, reference numerals 26, 27, 31, 32 denote reflectors.
【００３６】また、第２の実施例の縦型二重モード弾性
表面波フィルタ２１では第１，第２のエネルギー閉じ込
め型共振子の接続は、第１のエネルギー閉じ込め型共振
子のＩＤＴ２３，２５の一方のくし歯電極２３ａ，２５
ａと、第２のエネルギー閉じ込め型共振子のＩＤＴ２
８，３０の一方のくし歯電極２８ａ，３０ａとを接続す
ることにより行われ、該接続部にくし型電極３３が電気
的に接続されている。なお、ＩＤＴ２３，２５，２８，
３０の他方のくし歯電極２３ｂ，２５ｂ，２８ｂ，３０
ｂは図示のように基準電位に接続されており、さらにＩ
ＤＴ２４，２９の一方のくし歯電極２４ａ，２９ａも基
準電位に接続されている。そして、ＩＤＴ２４の他方の
くし歯電極２４ｂが入力端に、ＩＤＴ２９の他方のくし
歯電極２９ｂが出力端に接続される。Further, in the vertical double mode surface acoustic wave filter 21 of the second embodiment, the connection of the first and second energy trap resonators is made by connecting the IDTs 23 and 25 of the first energy trap resonators. One of the comb tooth electrodes 23a, 25
a and the IDT2 of the second energy trap type resonator
This is performed by connecting one of the comb-shaped electrodes 28a and 30a of the electrodes 8 and 30, and the comb-shaped electrode 33 is electrically connected to the connection portion. The IDTs 23, 25, 28,
The other comb tooth electrode 23b, 25b, 28b, 30
b is connected to the reference potential as shown, and further I
One of the comb-teeth electrodes 24a and 29a of the DTs 24 and 29 is also connected to the reference potential. The other comb-teeth electrode 24b of the IDT 24 is connected to the input end, and the other comb-teeth electrode 29b of the IDT 29 is connected to the output end.
【００３７】第２の実施例の縦型二重モード弾性表面波
フィルタ２１においても、くし型電極３３より付加され
る結合容量に加えて、上記比λf ／λc を上記特定の範
囲となるように選択することにより第１の実施例と同様
に挿入損失の低減を計ることができる。Also in the vertical dual-mode surface acoustic wave filter 21 of the second embodiment, in addition to the coupling capacitance added by the comb electrode 33, the ratio λ f / λ c falls within the specific range. By making such selection, the insertion loss can be reduced as in the first embodiment.
【図１】第１の実施例の縦型二重モード弾性表面波フィ
ルタを示す模式的平面図。FIG. 1 is a schematic plan view showing a vertical dual-mode surface acoustic wave filter according to a first embodiment.
【図２】実施例および比較のために用意した縦型二重モ
ード弾性表面波フィルタの挿入損失−周波数特性を示す
図。FIG. 2 is a diagram showing insertion loss-frequency characteristics of vertical dual-mode surface acoustic wave filters prepared for the examples and the comparison.
【図３】縦型二重モード弾性表面波フィルタにおけるコ
ンダクタンスおよび容量の比λ f ／λc に対する依存性
を示す図。[Fig. 3] Fig. 3 is a schematic view of a vertical double mode surface acoustic wave filter.
Conductance and capacity ratio λ f/ ΛcDependence on
FIG.
【図４】挿入損失と比λf ／λc との関係を示す図。FIG. 4 is a diagram showing a relationship between an insertion loss and a ratio λ f / λ c .
【図５】第２の実施例の縦型二重モード弾性表面波フィ
ルタを示す模式的平面図。FIG. 5 is a schematic plan view showing a vertical dual mode surface acoustic wave filter according to a second embodiment.
１…縦型二重モード弾性表面波フィルタ ２…圧電基板 ３，４，７，８，…ＩＤＴ ５，６，９，１０…反射器 １１…結合容量構成用くし型電極 DESCRIPTION OF SYMBOLS 1 ... Vertical dual mode surface acoustic wave filter 2 ... Piezoelectric substrate 3, 4, 7, 8, ... IDT 5, 6, 9, 10 ... Reflector 11 ... Comb-shaped electrode for coupling capacitance structure
Claims (1)
ａＯ3 圧電基板と、 前記圧電基板上に構成されており、かつ多段縦続接続さ
れた複数のエネルギー閉じ込め型共振子とを備え、 前記各エネルギー閉じ込め型共振子が、近接配置された
少なくとも２つのインターデジタルトランスデューサ
と、該少なくとも２つのインターデジタルトランスデュ
ーサの両側に配置された反射器とを有し、 前記複数のエネルギー閉じ込め型共振子間の接続部に、
前記インターデジタルトランスデューサと電気的に並列
に接続されており、かつ表面波伝搬路上以外の圧電基板
上の領域に形成された結合容量構成用くし型電極をさら
に備え、 前記インターデジタルトランスデューサの電極指の周期
をλf 、くし型電極の電極指の周期をλc としたとき
に、 【数１】 を満たすように、前記λf およびλc が決定されている
縦型二重モード弾性表面波フィルタ。1. LiT of 36 ° Y rotation cut X direction propagation
An aO 3 piezoelectric substrate and a plurality of energy trap resonators that are formed on the piezoelectric substrate and are cascade-connected to each other are provided. At least two interleaved resonators are provided. A digital transducer and reflectors arranged on both sides of the at least two interdigital transducers, the connection between the plurality of energy trap resonators,
The interdigital transducer is further electrically connected in parallel, and further includes a comb-shaped electrode for forming a coupling capacitance, which is formed in a region on the piezoelectric substrate other than on the surface wave propagation path. When the period is λ f and the period of the electrode fingers of the comb-shaped electrode is λ c , A vertical dual-mode surface acoustic wave filter in which λ f and λ c are determined so as to satisfy
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP21858693A JP3291860B2 (en) | 1993-09-02 | 1993-09-02 | Vertical double mode surface acoustic wave filter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP21858693A JP3291860B2 (en) | 1993-09-02 | 1993-09-02 | Vertical double mode surface acoustic wave filter |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0774588A true JPH0774588A (en) | 1995-03-17 |
| JP3291860B2 JP3291860B2 (en) | 2002-06-17 |
Family
ID=16722279
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP21858693A Expired - Lifetime JP3291860B2 (en) | 1993-09-02 | 1993-09-02 | Vertical double mode surface acoustic wave filter |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3291860B2 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2008068951A1 (en) | 2006-12-07 | 2008-06-12 | Murata Manufacturing Co., Ltd. | Surface acoustic wave filter device |
| US7394336B2 (en) | 2005-05-16 | 2008-07-01 | Murata Manufacturing Co. Ltd. | Elastic boundary wave apparatus |
| US7518471B2 (en) | 2005-04-08 | 2009-04-14 | Epson Toyocom Corporation | Surface acoustic wave filter utilizing a floating electrode |
| US8138858B1 (en) * | 2007-10-29 | 2012-03-20 | Rf Micro Devices, Inc. | Architectures using multiple dual-mode surface acoustic wave devices |
-
1993
- 1993-09-02 JP JP21858693A patent/JP3291860B2/en not_active Expired - Lifetime
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7518471B2 (en) | 2005-04-08 | 2009-04-14 | Epson Toyocom Corporation | Surface acoustic wave filter utilizing a floating electrode |
| US7394336B2 (en) | 2005-05-16 | 2008-07-01 | Murata Manufacturing Co. Ltd. | Elastic boundary wave apparatus |
| WO2008068951A1 (en) | 2006-12-07 | 2008-06-12 | Murata Manufacturing Co., Ltd. | Surface acoustic wave filter device |
| US8138858B1 (en) * | 2007-10-29 | 2012-03-20 | Rf Micro Devices, Inc. | Architectures using multiple dual-mode surface acoustic wave devices |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3291860B2 (en) | 2002-06-17 |
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