JPH07283688A - Surface acoustic wave filter - Google Patents
Surface acoustic wave filterInfo
- Publication number
- JPH07283688A JPH07283688A JP6931394A JP6931394A JPH07283688A JP H07283688 A JPH07283688 A JP H07283688A JP 6931394 A JP6931394 A JP 6931394A JP 6931394 A JP6931394 A JP 6931394A JP H07283688 A JPH07283688 A JP H07283688A
- Authority
- JP
- Japan
- Prior art keywords
- acoustic wave
- surface acoustic
- resonator
- wave filter
- substrate
- 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
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
- H03H9/02—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
- H03H9/14547—Fan shaped; Tilted; Shifted; Slanted; Tapered; Arched; Stepped finger transducers
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—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
- H03H9/14594—Plan-rotated or plan-tilted transducers
-
- 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
- H03H9/6483—Ladder SAW filters
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H2009/0019—Surface acoustic wave multichip
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、弾性表面波フィルター
に関し、特に高周波領域において使用される弾性表面波
フィルターに関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave filter, and more particularly to a surface acoustic wave filter used in a high frequency range.
【０００２】[0002]
【従来の技術】近年、フィルターに使用するために、弾
性表面波素子の研究が盛んに行われてきた。特に、最近
における移動体通信の発達、及び高周波化により、弾性
表面波素子、特に弾性表面波フィルターの開発が盛んに
行われている。従来から高周波帯、特に数１００ＭＨｚ
において弾性表面波素子によってフィルターを構成する
方法として、種々の方法が提案されている。その代表的
なものとして、特開昭５２−１９０４４号公報に示され
るような弾性表面波共振子を複数個使用してフィルター
を構成するもの、特開昭５８−１５４９１７号公報に示
されるような多電極型といわれるもの、特開平３−２２
２５１２号公報に示されるような弾性表面波共振器を隣
接して設置し、共振子間の結合を利用したものなどがあ
る。2. Description of the Related Art In recent years, surface acoustic wave devices have been actively researched for use in filters. In particular, due to recent developments in mobile communication and higher frequencies, surface acoustic wave devices, particularly surface acoustic wave filters, have been actively developed. Conventionally, high frequency band, especially several hundred MHz
Various methods have been proposed as a method of forming a filter by a surface acoustic wave element. As a typical example thereof, a filter is constructed by using a plurality of surface acoustic wave resonators as disclosed in JP-A-52-19044, as disclosed in JP-A-58-154917. What is called a multi-electrode type, JP-A-3-22
For example, a surface acoustic wave resonator as shown in Japanese Patent No. 2512 is installed adjacently and the coupling between the resonators is used.
【０００３】[0003]
【発明が解決しようとする課題】ところで、移動体通信
機器の小型化を図るためには、弾性表面波フィルターに
も小型で特性の良いフィルターが要求される。そして、
この弾性表面波フィルターは、送信部の段間フィルター
や受信部の段間、局部発振器の出力フィルターなどとし
て使用される場合が多い。弾性表面波フィルターに限ら
ずフィルター一般に要求される特性として、（１）帯域
内における低挿入損失、（２）帯域外における高減衰、
（３）帯域外から帯域内への急峻な立ち上がりが挙げら
れる。これら全てを理想的に満足させることは不可能で
あるため、通常はいずれかの特性に重点をおいて設計さ
れ、フィルターの特徴によって使い分けられている。特
に弾性表面波フィルターに要求される特性は、帯域外か
ら帯域内への急峻な立ち上がりである場合が多い。By the way, in order to miniaturize the mobile communication equipment, a small surface acoustic wave filter with good characteristics is also required. And
This surface acoustic wave filter is often used as an interstage filter of a transmitter, an interstage of a receiver, an output filter of a local oscillator, or the like. Not only surface acoustic wave filters, but generally required characteristics include (1) low insertion loss in the band, (2) high attenuation outside the band,
(3) A steep rise from the outside of the band to the inside of the band can be mentioned. Since it is impossible to satisfy all of these ideally, it is usually designed with emphasis on one of the characteristics and used properly according to the characteristics of the filter. Particularly, the characteristic required for the surface acoustic wave filter is often a sharp rise from the outside of the band to the inside of the band.
【０００４】しかし、現状のような構成のフィルターで
は、帯域外における減衰量を大きくとろうとすると、こ
の弾性表面波フィルターの特徴である帯域外から帯域内
への急峻な立ち上がりという特徴が失われてしまう。However, in the filter having the current configuration, when an attempt is made to increase the amount of attenuation outside the band, the characteristic of the surface acoustic wave filter that is a sharp rise from the outside of the band to the inside of the band is lost. I will end up.
【０００５】そこで、本発明者等は、複数個の弾性表面
波共振子を使用してフィルターを構成する、いわゆる共
振子型フィルターについて検討した。この共振子型フィ
ルターにおいて、帯域幅、及び帯域外から帯域内への立
ち上がり特性は共振子の特性によって決定されるが、そ
の中でも特に基板の電気機械結合係数と共振子に接続さ
れている接続部のインピーダンスによって決定される。
共振子型フィルターには、（ａ）並列腕の共振周波数、
（ｂ）並列腕の反共振周波数、（ｃ）直列腕の共振周波
数、（ｄ）直列腕の反共振周波数という４つの特徴点が
存在する。低域側の立ち上がりは、並列腕の共振周波数
と反共振周波数との差によって決定され、高域側の立ち
上がりは、直列腕の共振周波数と反共振周波数との差に
よって決定される。実際に作製したところ、高域側にお
いては十分急峻な立ち上がりを得ることができたが、低
域側においては、並列腕を接続するためのパターン、及
び接地するためのワイヤーの影響により、等価的にイン
ダクタが共振子と直列に挿入されることとなるため、共
振周波数が低下し、共振周波数と反共振周波数との周波
数差が大きくなり、急峻な立ち上がりを得ることはでき
なかった。Therefore, the present inventors have studied a so-called resonator type filter, which is a filter constructed by using a plurality of surface acoustic wave resonators. In this resonator type filter, the bandwidth and the rising characteristic from the outside of the band to the inside of the band are determined by the characteristics of the resonator. Among them, especially the electromechanical coupling coefficient of the substrate and the connecting portion connected to the resonator. Determined by the impedance of.
The resonator type filter includes (a) the resonance frequency of the parallel arm,
There are four characteristic points: (b) anti-resonance frequency of parallel arm, (c) resonance frequency of series arm, and (d) anti-resonance frequency of series arm. The rising on the low frequency side is determined by the difference between the resonance frequency and the anti-resonance frequency of the parallel arm, and the rising on the high frequency side is determined by the difference between the resonance frequency and the anti-resonance frequency of the series arm. As a result of actual fabrication, a sufficiently steep rise could be obtained on the high frequency side, but on the low frequency side, an equivalent pattern was created due to the pattern for connecting the parallel arms and the wire for grounding. Since the inductor is inserted in series with the resonator, the resonance frequency is lowered, the frequency difference between the resonance frequency and the anti-resonance frequency is increased, and a steep rise cannot be obtained.
【０００６】上記課題を解決するためには、並列腕の共
振子に直列に入るインダクタ分を減少させればよいが、
並列腕を接続したり接地したりするためには必要であ
り、その絶対的な値には限界がある。また、帯域外にお
ける減衰量を大きくとるためには、この並列腕の共振子
を大きくすること、すなわち対数と交差幅との積を大き
くすることが必要であるが、これによりインダクタによ
る共振周波数の低下が一層大きくなってしまう。In order to solve the above-mentioned problems, it is sufficient to reduce the number of inductors in series with the resonator of the parallel arm.
It is necessary to connect or ground the parallel arms, and their absolute value is limited. In addition, in order to increase the attenuation outside the band, it is necessary to increase the resonator of this parallel arm, that is, to increase the product of the logarithm and the cross width. The drop will be even greater.
【０００７】本発明は、従来技術における前記課題を解
決するため、帯域外から帯域内にかけて急峻な立ち上が
りを有する弾性表面波フィルターを提供することを目的
とする。In order to solve the above problems in the prior art, it is an object of the present invention to provide a surface acoustic wave filter having a steep rise from outside the band to within the band.
【０００８】[0008]
【課題を解決するための手段】前記目的を達成するた
め、本発明に係る弾性表面波フィルターの第１の構成
は、複数個の弾性表面波共振子を直列及び並列に接続し
て構成される弾性表面波フィルターであって、直列腕に
接続された共振子の弾性表面波の伝搬方向と並列腕に接
続された共振子の弾性表面波の伝搬方向とが異なること
を特徴とする。In order to achieve the above object, a first structure of a surface acoustic wave filter according to the present invention is configured by connecting a plurality of surface acoustic wave resonators in series and in parallel. The surface acoustic wave filter is characterized in that the propagation direction of the surface acoustic wave of the resonator connected to the series arm is different from the propagation direction of the surface acoustic wave of the resonator connected to the parallel arm.
【０００９】また、本発明に係る弾性表面波フィルター
の第２の構成は、複数個の弾性表面波共振子を直列及び
並列に接続して構成される弾性表面波フィルターであっ
て、並列腕に接続された共振子を作製する基板の等価的
な電気機械結合係数が直列腕に接続された共振子を作製
する基板の等価的な電気機械結合係数よりも小さいこと
を特徴とする。A second structure of the surface acoustic wave filter according to the present invention is a surface acoustic wave filter constituted by connecting a plurality of surface acoustic wave resonators in series and in parallel, wherein It is characterized in that the equivalent electromechanical coupling coefficient of the substrate for producing the connected resonator is smaller than the equivalent electromechanical coupling coefficient of the substrate for producing the resonator connected to the series arm.
【００１０】また、前記第１又は第２の構成において
は、弾性表面波共振子を構成する基板として、タンタル
酸リチウム及びニオブ酸リチウムから選ばれる少なくと
も１つを使用するのが好ましい。In the first or second structure, it is preferable that at least one selected from lithium tantalate and lithium niobate is used as the substrate forming the surface acoustic wave resonator.
【００１１】[0011]
【作用】前記本発明の第１の構成によれば、直列腕に接
続された共振子の弾性表面波の伝搬方向と並列腕に接続
された共振子の弾性表面波の伝搬方向とを異ならせるよ
うにしたことにより、それに応じて等価的な電気機械結
合係数をも異ならせることができる。従って、並列腕に
接続された共振子の方が直列腕に接続された共振子より
も等価的な電気機械結合係数が小さくなるように弾性表
面波の伝搬方向を選択すれば、両方を同じ方向に選んだ
場合よりも並列腕に接続された共振子の共振周波数と反
共振周波数との差が小さくなり、帯域外から帯域内にか
けて従来よりも急峻な立ち上がりを有する弾性表面波フ
ィルターを実現することができる。According to the first configuration of the present invention, the propagation direction of the surface acoustic wave of the resonator connected to the series arm is made different from the propagation direction of the surface acoustic wave of the resonator connected to the parallel arm. By doing so, the equivalent electromechanical coupling coefficient can be changed accordingly. Therefore, if the propagation direction of the surface acoustic wave is selected so that the equivalent electromechanical coupling coefficient of the resonator connected to the parallel arm is smaller than that of the resonator connected to the series arm, both of them are in the same direction. The difference between the resonance frequency and the anti-resonance frequency of the resonator connected to the parallel arm is smaller than in the case of selecting, and it is possible to realize a surface acoustic wave filter that has a steeper rise from outside the band to within the band than before. You can
【００１２】また、前記本発明の第２の構成によれば、
並列腕に接続された共振子を作製する基板の等価的な電
気機械結合係数が直列腕に接続された共振子を作製する
基板の等価的な電気機械結合係数よりも小さくすること
によって、並列腕に接続された共振子の共振周波数と反
共振周波数との差を小さくするようにしたものであるた
め、並列腕に接続された共振子を作製する基板と直列腕
に接続された共振子を作製する基板を適切に選択するこ
とにより、帯域外から帯域内にかけて従来よりも急峻な
立ち上がりを有する弾性表面波フィルターを実現するこ
とができる。According to the second aspect of the present invention,
By making the equivalent electromechanical coupling coefficient of the substrate for making the resonator connected to the parallel arm smaller than the equivalent electromechanical coupling coefficient of the substrate for making the resonator connected to the series arm, the parallel arm Since the difference between the resonance frequency and the anti-resonance frequency of the resonator connected to is made small, the substrate connected to the parallel arm is made and the resonator connected to the series arm is made. By appropriately selecting the substrate to be used, it is possible to realize a surface acoustic wave filter having a steeper rise from the outside to the inside of the band than in the conventional case.
【００１３】[0013]
【実施例】以下、実施例を用いて本発明をさらに具体的
に説明する。 （実施例１）まず、本発明の第１の実施例について説明
する。図１は本発明に係る弾性表面波フィルターの一実
施例を示す構成図である。EXAMPLES The present invention will be described in more detail below with reference to examples. (Embodiment 1) First, a first embodiment of the present invention will be described. FIG. 1 is a block diagram showing an embodiment of a surface acoustic wave filter according to the present invention.
【００１４】基板として３６°回転ＹカットＸ伝搬のタ
ンタル酸リチウム基板１０１を使用し、電極としてアル
ミニウムを使用して弾性表面波共振子（以下「共振子」
という）１０２、１０３を作製した。そして、図１に示
すように、直列腕の共振子１０２と並列腕の共振子１０
３をそれぞれ１個ずつ用いてＬ型に接続し、弾性表面波
フィルター（以下「フィルター」という）を作製した。
尚、図１中、１０４は入力端子、１０５は出力端子、１
０６はアースへの接続端子である。但し、図面記載の都
合上、共振子の電極対数、反射器対数は減らしてある。A 36 ° rotated Y-cut X-propagation lithium tantalate substrate 101 is used as a substrate, and aluminum is used as an electrode.
102) and 103 were produced. Then, as shown in FIG. 1, the series arm resonator 102 and the parallel arm resonator 10 are arranged.
Three of them were used one by one and connected in an L-shape to produce a surface acoustic wave filter (hereinafter referred to as “filter”).
In FIG. 1, 104 is an input terminal, 105 is an output terminal, 1
Reference numeral 06 is a connection terminal to the ground. However, the number of electrode pairs and the number of reflectors of the resonator are reduced for convenience of illustration in the drawings.
【００１５】この構成において、直列腕の共振子（以下
「直列共振子」という）１０２は弾性表面波の伝搬方向
がＸ方向であり、この３６°回転ＹカットＸ伝搬のタン
タル酸リチウム基板１０１において最大の電気機械結合
係数が得られる方向である。一方、並列腕の共振子（以
下「並列共振子」という）１０３は、弾性表面波の伝搬
方向を最大の電気機械結合係数が得られる方向からずら
してあり、その結果、直列共振子１０２に比べて電気機
械結合係数が小さくなるので、直列共振子１０２に比べ
て共振周波数と反共振周波数との差が小さくなる。In this structure, the resonator of the series arm (hereinafter referred to as “series resonator”) 102 has the propagation direction of the surface acoustic wave in the X direction, and in this 36 ° rotation Y cut X propagation lithium tantalate substrate 101. This is the direction in which the maximum electromechanical coupling coefficient is obtained. On the other hand, in the parallel arm resonator (hereinafter referred to as “parallel resonator”) 103, the propagation direction of the surface acoustic wave is shifted from the direction in which the maximum electromechanical coupling coefficient is obtained, and as a result, compared with the series resonator 102. Since the electromechanical coupling coefficient becomes small, the difference between the resonance frequency and the antiresonance frequency becomes smaller than that of the series resonator 102.
【００１６】上記のようにして作製したフィルターの特
性を図２に示す。比較のために直列共振子、並列共振子
ともに３６°回転ＹカットＸ伝搬のタンタル酸リチウム
基板において最大の電気機械結合係数が得られる配置と
した場合のフィルターの特性を図５に示す。図２、図５
から明らかなように、本実施例１の場合には通過周波数
帯域よりも低い周波数の立ち上がりが鋭くなっているこ
とが分かる。また、同時に通過帯域が若干狭くなってい
るが、通過帯域は使用するシステム、要求される特性に
よって変化するものであり、また、直列共振子１０２と
並列共振子１０３との周波数差を調整することによって
変えることができる。The characteristics of the filter manufactured as described above are shown in FIG. For comparison, FIG. 5 shows the characteristics of the filter in the case where both the series resonator and the parallel resonator are arranged so that the maximum electromechanical coupling coefficient is obtained on the lithium tantalate substrate of 36 ° rotation Y cut X propagation. 2 and 5
As is clear from the above, in the case of the first embodiment, the rising of the frequency lower than the pass frequency band is sharp. At the same time, although the pass band is slightly narrowed, the pass band changes depending on the system used and the required characteristics. Further, the frequency difference between the series resonator 102 and the parallel resonator 103 should be adjusted. Can be changed by
【００１７】（実施例２）次に、本発明の第２の実施例
について説明する。図３は本発明に係る弾性表面波フィ
ルターの他の実施例を示す構成図である。(Second Embodiment) Next, a second embodiment of the present invention will be described. FIG. 3 is a configuration diagram showing another embodiment of the surface acoustic wave filter according to the present invention.
【００１８】基板として４１°回転ＹカットＸ伝搬のニ
オブ酸リチウム基板２０１と３６°回転ＹカットＸ伝搬
のタンタル酸リチウム基板２０２を使用し、電極として
アルミニウムを使用して共振子を作製した。そして、図
３に示すように、４１°回転ＹカットＸ伝搬のニオブ酸
リチウム基板２０１の上に作製した直列共振子２０３と
３６°回転ＹカットＸ伝搬のタンタル酸リチウム基板２
０２の上に作製した並列共振子２０４を、基板間を接続
するワイヤー２０８を介してＬ型に接続し、フィルター
を作製した。尚、図３中、２０５は入力端子、２０６は
出力端子、２０７はアースへの接続端子である。但し、
図面記載の都合上、共振子の電極対数、反射器対数は減
らしてある。A 41 ° rotated Y-cut X-propagation lithium niobate substrate 201 and a 36 ° rotated Y-cut X-propagation lithium tantalate substrate 202 were used as substrates, and aluminum was used as electrodes to fabricate a resonator. Then, as shown in FIG. 3, the series resonator 203 formed on the 41 ° rotation Y-cut X-propagation lithium niobate substrate 201 and the 36 ° rotation Y-cut X-propagation lithium tantalate substrate 2
The parallel resonator 204 produced on 02 was connected in an L-shape via a wire 208 connecting the substrates to produce a filter. In FIG. 3, 205 is an input terminal, 206 is an output terminal, and 207 is a connection terminal to ground. However,
For convenience of illustration in the drawings, the number of electrode pairs and the number of reflector pairs of the resonator are reduced.
【００１９】この構成において、直列共振子２０３は４
１°回転ＹカットＸ伝搬のニオブ酸リチウム基板２０１
の上に作製されているために、３６°回転ＹカットＸ伝
搬のタンタル酸リチウム基板２０２の上に作製されてい
る並列共振子２０４に比べて電気機械結合係数が大き
く、並列共振子２０４に比べて共振周波数と反共振周波
数との差が大きくなる。すなわち、実施例１の場合と同
様に、並列共振子２０４における共振周波数と反共振周
波数との差は、直列共振子２０３に比べて小さくなる。In this configuration, the series resonator 203 has four
1 ° rotation Y-cut X-propagation lithium niobate substrate 201
Since it is manufactured above, the electromechanical coupling coefficient is larger than that of the parallel resonator 204 manufactured on the 36 ° rotation Y-cut X-propagation lithium tantalate substrate 202. As a result, the difference between the resonance frequency and the anti-resonance frequency becomes large. That is, as in the case of the first embodiment, the difference between the resonance frequency and the anti-resonance frequency in the parallel resonator 204 is smaller than that in the series resonator 203.
【００２０】上記のようにして作製したフィルターの特
性を図４に示す。比較のために３６°回転ＹカットＸ伝
搬のタンタル酸リチウム基板を用い、同様にして作製し
た場合のフィルターの特性を図５に示す。図４、図５か
ら明らかなように、本実施例２の場合には通過周波数帯
域よりも低い周波数の立ち上がりが鋭くなっていること
が分かる。また、同時に通過帯域が若干広くなっている
が、これは直列共振子２０３の基板として３６°回転Ｙ
カットＸ伝搬のタンタル酸リチウム基板よりも電気機械
結合係数の大きい４１°回転ＹカットＸ伝搬のニオブ酸
リチウム基板を使用しているためである。The characteristics of the filter produced as described above are shown in FIG. For comparison, FIG. 5 shows the characteristics of the filter when a 36 ° rotated Y-cut X-propagation lithium tantalate substrate was used and manufactured in the same manner. As is clear from FIGS. 4 and 5, in the case of the second embodiment, it can be seen that the rising of the frequency lower than the pass frequency band is sharp. At the same time, although the pass band is slightly wider, this is a 36 ° rotation Y as the substrate of the series resonator 203.
This is because a 41 ° rotated Y-cut X-propagation lithium niobate substrate having a larger electromechanical coupling coefficient than the cut X-propagation lithium tantalate substrate is used.
【００２１】以上のように、本実施例２によれば、並列
共振子２０４を作製する基板と直列共振子２０３を作製
する基板を適切に選択することにより、帯域外から帯域
内にかけて従来よりも急峻な立ち上がりを有する弾性表
面波フィルターを実現することができる。As described above, according to the second embodiment, by appropriately selecting the substrate on which the parallel resonator 204 is formed and the substrate on which the series resonator 203 is formed, the range from the out-of-band to the in-band is higher than in the conventional case. It is possible to realize a surface acoustic wave filter having a steep rise.
【００２２】尚、上記実施例１、２においては、圧電基
板として３６°回転ＹカットＸ伝搬のタンタル酸リチウ
ム基板、４１°回転ＹカットＸ伝搬のニオブ酸リチウム
基板を使用しているが、必ずしもこれらに限定されるも
のではなく、同様の圧電基板であれば差し支えない。In Examples 1 and 2, the 36 ° -rotation Y-cut X-propagation lithium tantalate substrate and the 41 ° -rotation Y-cut X-propagation lithium niobate substrate are used as the piezoelectric substrate. The present invention is not limited to these, and any similar piezoelectric substrate may be used.
【００２３】また、上記実施例１、２においては、説明
の便宜上、直列共振子及び並列共振子１個ずつを接続し
た場合について説明しているが、必ずしもこれに限定さ
れるものではなく、それぞれの共振子を複数個使用した
場合にも同様の効果を得ることができる。Further, in the first and second embodiments, for convenience of description, the case where one series resonator and one parallel resonator are connected is described, but the present invention is not necessarily limited to this, and each is not limited thereto. The same effect can be obtained when a plurality of the resonators are used.
【００２４】また、上記実施例１、２においては、直列
共振子と並列共振子をＬ型に接続しているが、必ずしも
この接続方法に限定されるものではなく、例えば、Ｔ型
やπ型に接続してもよい。In the first and second embodiments, the series resonator and the parallel resonator are connected to each other in an L-type, but the connection method is not limited to this. For example, a T-type or a π-type is used. You may connect to.
【００２５】また、上記実施例１、２においては、説明
の便宜上、入力、出力端子として説明しているが、回路
の特性上一方が入力で一方が出力であると規定されるも
のではなく、上記説明とは反対に接続してもよい。In the first and second embodiments, the input and output terminals are described for convenience of description, but it is not specified that one is an input and the other is an output due to the characteristics of the circuit. Connection may be made in the opposite manner to the above description.
【００２６】[0026]
【発明の効果】以上説明したように、本発明に係る弾性
表面波フィルターの第１の構成によれば、直列腕に接続
された共振子の弾性表面波の伝搬方向と並列腕に接続さ
れた共振子の弾性表面波の伝搬方向とを異ならせるよう
にしたことにより、それに応じて等価的な電気機械結合
係数をも異ならせることができる。そして、並列腕に接
続された共振子の方が直列腕に接続された共振子よりも
等価的な電気機械結合係数が小さくなるように弾性表面
波の伝搬方向を選択すれば、両方を同じ方向に選んだ場
合よりも並列腕に接続された共振子の共振周波数と反共
振周波数との差が小さくなり、帯域外から帯域内にかけ
て従来よりも急峻な立ち上がりを有する弾性表面波フィ
ルターを実現することができる。As described above, according to the first structure of the surface acoustic wave filter of the present invention, the propagation direction of the surface acoustic wave of the resonator connected to the series arm is connected to the parallel arm. By making the propagation direction of the surface acoustic wave of the resonator different, the equivalent electromechanical coupling coefficient can be changed accordingly. Then, if the propagation direction of the surface acoustic wave is selected so that the equivalent electromechanical coupling coefficient of the resonator connected to the parallel arm is smaller than that of the resonator connected to the series arm, both of them are in the same direction. The difference between the resonance frequency and the anti-resonance frequency of the resonator connected to the parallel arm will be smaller than in the case selected above, and a surface acoustic wave filter that has a steeper rise from the outside of the band to the inside of the band will be realized. You can
【００２７】また、本発明に係る弾性表面波フィルター
の第２の構成によれば、並列腕に接続された共振子を作
製する基板の等価的な電気機械結合係数が直列腕に接続
された共振子を作製する基板の等価的な電気機械結合係
数よりも小さくすることによって、並列腕に接続された
共振子の共振周波数と反共振周波数との差を小さくする
ようにしたものであるため、並列腕に接続された共振子
を作製する基板と直列腕に接続された共振子を作製する
基板を適切に選択することにより、帯域外から帯域内に
かけて従来よりも急峻な立ち上がりを有する弾性表面波
フィルターを実現することができる。Further, according to the second structure of the surface acoustic wave filter of the present invention, the equivalent electromechanical coupling coefficient of the substrate for producing the resonator connected to the parallel arm has the resonance connected to the series arm. Since the difference between the resonant frequency and the anti-resonant frequency of the resonator connected to the parallel arm is made smaller by making it smaller than the equivalent electromechanical coupling coefficient of the substrate on which the child is made, A surface acoustic wave filter having a steeper rise from the outside of the band to the inside of the band by appropriately selecting a substrate for manufacturing a resonator connected to an arm and a substrate for manufacturing a resonator connected to a series arm. Can be realized.
【図１】本発明に係る弾性表面波フィルターの一実施例
を示す構成図である。FIG. 1 is a configuration diagram showing an embodiment of a surface acoustic wave filter according to the present invention.
【図２】本発明に係る弾性表面波フィルターの一実施例
におけるフィルターの特性図である。FIG. 2 is a characteristic diagram of a filter in an example of the surface acoustic wave filter according to the present invention.
【図３】本発明に係る弾性表面波フィルターの他の実施
例を示す構成図である。FIG. 3 is a configuration diagram showing another embodiment of the surface acoustic wave filter according to the present invention.
【図４】本発明に係る弾性表面波フィルターの他の実施
例におけるフィルターの特性図である。FIG. 4 is a characteristic diagram of a filter in another embodiment of the surface acoustic wave filter according to the present invention.
【図５】本発明との比較のためのフィルターの特性図で
ある。FIG. 5 is a characteristic diagram of a filter for comparison with the present invention.
１０１、２０１ ３６°回転ＹカットＸ伝搬のタンタル
酸リチウム基板 １０２、２０３ 直列腕の共振子（直列共振子） １０３、２０４ 並列腕の共振子（並列共振子） １０４、２０５ 入力端子 １０５、２０６ 出力端子 １０６、２０７ アースへの接続端子 ２０２ ４１°回転ＹカットＸ伝搬のニオブ酸リチウム
基板 ２０８ 基板間を接続するワイヤー101, 201 36 ° rotation Y-cut X-propagation lithium tantalate substrate 102, 203 Series arm resonator (series resonator) 103, 204 Parallel arm resonator (parallel resonator) 104, 205 Input terminal 105, 206 Output Terminals 106, 207 Ground connection terminal 202 41 ° rotation Y-cut X-propagation lithium niobate substrate 208 Wire for connecting the substrates
───────────────────────────────────────────────────── フロントページの続き (72)発明者 大西 慶治 大阪府門真市大字門真1006番地 松下電器 産業株式会社内 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Keiji Onishi Keiji Onishi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.
Claims (3)
列に接続して構成される弾性表面波フィルターであっ
て、直列腕に接続された共振子の弾性表面波の伝搬方向
と並列腕に接続された共振子の弾性表面波の伝搬方向と
が異なることを特徴とする弾性表面波フィルター。1. A surface acoustic wave filter configured by connecting a plurality of surface acoustic wave resonators in series and in parallel, wherein the surface acoustic wave propagation direction of the resonators connected to a series arm and a parallel arm. A surface acoustic wave filter, characterized in that a resonator connected to the resonator has a different propagation direction of the surface acoustic wave.
列に接続して構成される弾性表面波フィルターであっ
て、並列腕に接続された共振子を作製する基板の等価的
な電気機械結合係数が直列腕に接続された共振子を作製
する基板の等価的な電気機械結合係数よりも小さいこと
を特徴とする弾性表面波フィルター。2. A surface acoustic wave filter constituted by connecting a plurality of surface acoustic wave resonators in series and in parallel, which is an equivalent electric machine of a substrate for producing resonators connected to parallel arms. A surface acoustic wave filter having a coupling coefficient smaller than an equivalent electromechanical coupling coefficient of a substrate for forming a resonator connected to a series arm.
て、タンタル酸リチウム及びニオブ酸リチウムから選ば
れる少なくとも１つを使用する請求項１又は２に記載の
弾性表面波フィルター。3. The surface acoustic wave filter according to claim 1, wherein at least one selected from lithium tantalate and lithium niobate is used as a substrate forming the surface acoustic wave resonator.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6931394A JPH07283688A (en) | 1994-04-07 | 1994-04-07 | Surface acoustic wave filter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6931394A JPH07283688A (en) | 1994-04-07 | 1994-04-07 | Surface acoustic wave filter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH07283688A true JPH07283688A (en) | 1995-10-27 |
Family
ID=13398953
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP6931394A Pending JPH07283688A (en) | 1994-04-07 | 1994-04-07 | Surface acoustic wave filter |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH07283688A (en) |
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- 1994-04-07 JP JP6931394A patent/JPH07283688A/en active Pending
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