JP2002300004A - Surface acoustic wave filter - Google Patents
Surface acoustic wave filterInfo
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- JP2002300004A JP2002300004A JP2001096114A JP2001096114A JP2002300004A JP 2002300004 A JP2002300004 A JP 2002300004A JP 2001096114 A JP2001096114 A JP 2001096114A JP 2001096114 A JP2001096114 A JP 2001096114A JP 2002300004 A JP2002300004 A JP 2002300004A
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- Prior art keywords
- electrode
- surface acoustic
- acoustic wave
- wave filter
- signal
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- Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、圧電基板上に平衡
入力または平衡出力を行う平衡信号電極と、不平衡出力
または不平衡入力を行う不平衡信号電極とを備えて成る
共振器型の弾性表面波フィルタに関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resonator-type resilient type comprising a balanced signal electrode for performing balanced input or balanced output on a piezoelectric substrate, and an unbalanced signal electrode for performing unbalanced output or unbalanced input. The present invention relates to a surface acoustic wave filter.
【０００２】[0002]
【従来技術とその課題】近年、移動体通信機器等の小型
・軽量化および低コスト化のため、使用部品の削減が進
められ、弾性表面波フィルタに新たな機能の付加が要求
されてきている。その１つに不平衡入力−平衡出力型ま
たは平衡入力−不平衡出力型に構成できるようにすると
いった要求がある。ここで平衡入力または平衡出力と
は、信号が２つの信号線路間の電位差として入力または
出力するものをいい、各信号線路の信号は振幅が等し
く、位相が逆相になっている。これに対して、不平衡入
力または不平衡出力とは、信号がグランド電位に対する
１本の線路の電位として入力または出力するものをい
う。2. Description of the Related Art In recent years, in order to reduce the size, weight, and cost of mobile communication devices and the like, the number of components used has been reduced, and new functions have been required to be added to surface acoustic wave filters. . One of the demands is to be able to configure an unbalanced input-balanced output type or a balanced input-unbalanced output type. Here, the balanced input or balanced output means a signal that is input or output as a potential difference between two signal lines. The signals on each signal line have the same amplitude and opposite phases. On the other hand, an unbalanced input or an unbalanced output means that a signal is input or output as a potential of one line with respect to a ground potential.
【０００３】従来の弾性表面波フィルタは、一般的に不
平衡入力−不平衡出力型弾性表面波フィルタ（以下、不
平衡型弾性表面波フィルタという）であるため、弾性表
面波フィルタの後段に接続される回路や電子部品が平衡
入力型となっている場合は、弾性表面波フィルタと後段
との間に、不平衡−平衡変換器（以下、バランともい
う）を挿入した回路構成を採っていた。同様に弾性表面
波フィルタ前段の回路や電子部品が平衡出力型となって
いる場合は、前段と弾性表面波フィルタとの間にバラン
を挿入した回路構成となっていた。Since a conventional surface acoustic wave filter is generally an unbalanced input-unbalanced output type surface acoustic wave filter (hereinafter, referred to as an unbalanced surface acoustic wave filter), it is connected to a subsequent stage of the surface acoustic wave filter. When the circuit or electronic component to be used is of a balanced input type, a circuit configuration in which an unbalanced-balanced converter (hereinafter, also referred to as a balun) is inserted between the surface acoustic wave filter and a subsequent stage is employed. . Similarly, when a circuit or an electronic component at the front stage of the surface acoustic wave filter is of a balanced output type, the circuit configuration has a balun inserted between the front stage and the surface acoustic wave filter.
【０００４】現在、バランを削除するために、弾性表面
波フィルタに不平衡−平衡変換機能または平衡−不平衡
変換機能を持たせた、不平衡入力−平衡出力型弾性表面
波フィルタまたは平衡入力−不平衡出力型弾性表面波フ
ィルタ（以下、平衡型弾性表面波フィルタという）の実
用化が進められている。At present, in order to eliminate a balun, an unbalanced-balanced output type surface acoustic wave filter or a balanced input-balanced output type surface acoustic wave filter is provided with an unbalanced-balanced conversion function or a balanced-unbalanced conversion function. An unbalanced output type surface acoustic wave filter (hereinafter, referred to as a balanced type surface acoustic wave filter) has been put into practical use.
【０００５】例えば、複数個並設したＩＤＴ（Ｉｎｔｅ
ｒ Ｄｉｇｉｔａｌ Ｔｒａｎｓｄｕｃｅｒ）電極の弾
性表面波伝搬路の両端に、弾性表面波を効率よく共振さ
せるための反射器電極が設けられた共振器型電極パター
ンにおいて、通過帯域内での振幅と位相の平衡度の向上
が求められている。ここで、振幅と位相の平衡度とは、
信号が２つの信号線路間の電位差として入力または出力
するもので、各信号線路の信号の振幅の大きさが等しい
ほど振幅の平衡度が優れており、また、各信号の位相の
差が１８０°に等しいほど位相の平衡度が優れていると
いえる。For example, a plurality of IDTs (Inte
r Digital Transducer) In a resonator-type electrode pattern in which reflector electrodes for efficiently resonating surface acoustic waves are provided at both ends of a surface acoustic wave propagation path of an electrode, the amplitude and phase balance within a pass band. Improvement is required. Here, the degree of balance between amplitude and phase is
A signal is input or output as a potential difference between two signal lines. The greater the amplitude of the signal on each signal line, the better the amplitude balance, and the difference in phase between the signals is 180 °. It can be said that the degree of phase equilibrium is more excellent as
【０００６】図３、４に従来までの平衡入出力に対応し
た共振器型弾性表面波フィルタを示す。圧電基板１０１
上に配置させたＩＤＴ電極１０２は、一対の互いに対向
させた櫛歯状電極に電界を加え、弾性表面波を励振させ
るものである。その原理により、ＩＤＴ電極１０２に入
力信号を加えることで、励振された弾性表面波がＩＤＴ
電極１０２の両側に位置する、出力信号用のＩＤＴ電極
１０３，１０４に伝搬される。ＩＤＴ電極１０３、１０
４の一方の櫛状電極から出力信号端子１１３、他方から
出力信号端子１１５へ信号が伝わり平衡出力される。ま
た、図４は２段接続することによりフィルタ特性の帯域
外減衰量の向上ができる構成となっている。FIGS. 3 and 4 show a conventional resonator type surface acoustic wave filter corresponding to balanced input / output. Piezoelectric substrate 101
The IDT electrode 102 arranged above applies an electric field to a pair of mutually facing comb-teeth-shaped electrodes to excite a surface acoustic wave. According to the principle, by applying an input signal to the IDT electrode 102, the excited surface acoustic wave
The signal is propagated to output signal IDT electrodes 103 and 104 located on both sides of the electrode 102. IDT electrodes 103, 10
The signal is transmitted from one of the comb electrodes 4 to the output signal terminal 113 and the other to the output signal terminal 115 to be balanced and output. FIG. 4 shows a configuration in which the out-of-band attenuation of the filter characteristics can be improved by connecting two stages.
【０００７】上記のような共振器型弾性表面波フィルタ
では、ＩＤＴ電極１０３、１０４の対向する櫛状電極の
電極本数、配置された位置、または、寄生容量を発生さ
せる要因となる周辺の電極パターンなど構造が異なるた
めに、出力信号端子１１３、１１５に伝わる信号が互い
に振幅が異なり、また位相が逆相からずれてしまい、そ
の結果、平衡度の劣化した共振器型弾性表面波フィルタ
しか得られなかった。In the above-described resonator type surface acoustic wave filter, the number of comb electrodes facing the IDT electrodes 103 and 104, the positions where the comb electrodes are arranged, or the peripheral electrode pattern which causes a parasitic capacitance is generated. Due to the different structure, the signals transmitted to the output signal terminals 113 and 115 have different amplitudes and the phases are shifted from the opposite phases. As a result, only a resonator-type surface acoustic wave filter with a deteriorated balance is obtained. Did not.
【０００８】近年、弾性表面波フィルタは各種通信機器
の小形化、無調整化に一役を担っている。そして、通信
機器の高周波数化、高機能化の進展にともない、弾性表
面波フィルタの広帯域化の要求が益々増大してきてい
る。例えば、９００ＭＨｚ帯携帯電話用のフィルタとし
ては、実効通過帯域幅３５ＭＨｚ以上（比帯域幅約３．
７％以上）の高性能な広帯域フィルタが要求されてい
る。なお、比帯域幅ＢＲは、ＢＲ＝ＢＷ／ｆｃ（ＢＷは
帯域内挿入損失が３ｄＢにおける通過帯域幅、ｆｃは帯
域内挿入損失が３ｄＢにおける通過帯域の中心周波数）
であらわすことができる。In recent years, surface acoustic wave filters have played a role in downsizing and non-adjusting various communication devices. As the frequency and function of communication devices increase, the demand for a wider surface acoustic wave filter has been increasing. For example, as a filter for a 900-MHz band mobile phone, an effective pass bandwidth of 35 MHz or more (fractional bandwidth of about 3.
(7% or more) is required. Note that the fractional bandwidth BR is BR = BW / fc (BW is the pass band width when the in-band insertion loss is 3 dB, fc is the center frequency of the pass band when the in-band insertion loss is 3 dB)
Can be represented by
【０００９】このような広帯域化を実現するために、従
来、様々な方法が提案されている。例えば、３個のＩＤ
Ｔ（Ｉｎｔｅｒ Ｄｉｇｉｔａｌ Ｔｒａｎｓｄｕｃｅ
ｒ）電極（１対の櫛歯状電極を互いに対向させた電極）
を設け、縦１次モードと縦３次モードを利用した、いわ
ゆる２重モード弾性表面波共振子フィルタが知られてい
る。In order to realize such a wide band, conventionally, various methods have been proposed. For example, three IDs
T (Inter Digital Transduction)
r) Electrode (electrode in which a pair of comb-shaped electrodes are opposed to each other)
And a so-called dual mode surface acoustic wave resonator filter using a first-order longitudinal mode and a third-order longitudinal mode is known.
【００１０】図３に示すように、両端に位置する反射器
電極１０７により弾性表面波が反射され、反射器電極１
０７，１０７間で定在波となる。この定在波のモードに
は、３つのＩＤＴ電極により１次モードとその高次（３
次）モードが含まれる。これらのモードで発生する共振
周波数で通過特性が得られるため、共振周波数の間隔を
制御することにより、通過帯域を広くさせることができ
る。なお、図中、１０５，１０６はＩＤＴ電極間部位、
１０８はＩＤＴ電極と反射器電極間部位、１１１は入力
信号端子、１１２は接地端子、１１３，１１５は出力信
号端子である。As shown in FIG. 3, the surface acoustic waves are reflected by the reflector electrodes 107 located at both ends, and the reflector electrodes 1
It becomes a standing wave between 07 and 107. In this standing wave mode, the first mode and its higher order (3
Next) mode is included. Since the pass characteristics can be obtained at the resonance frequencies generated in these modes, the pass band can be widened by controlling the interval between the resonance frequencies. In the figures, 105 and 106 are portions between IDT electrodes,
108 is a portion between the IDT electrode and the reflector electrode, 111 is an input signal terminal, 112 is a ground terminal, and 113 and 115 are output signal terminals.
【００１１】従来、このモード間の周波数制御に、全て
のＩＤＴ電極を同じピッチＬにし、かつ、中央およびそ
の両側に位置するＩＤＴ電極の端部（ＩＤＴ電極間部
位）１０５，１０６における電極指中心間の間隔ｄの制
御により、前記のモード間の周波数を制御する方法がと
られていた。また、出力信号用のＩＤＴ電極に容量を付
加して周波数を制御していた。Conventionally, in order to control the frequency between the modes, all the IDT electrodes have the same pitch L, and the center of the electrode fingers at the end portions (portions between IDT electrodes) 105 and 106 located at the center and on both sides thereof. A method of controlling the frequency between the above modes by controlling the interval d between them has been adopted. Further, the frequency is controlled by adding a capacitor to the IDT electrode for the output signal.
【００１２】このため、従来の２重モード弾性表面波共
振器フィルタでは、例えば圧電基板としてＬｉＴａＯ３
単結晶の基板を用いた場合、比帯域幅（中心周波数に対
する通過帯域幅の値）は約０．４０％程度（特開平１−
２３１４１７号公報を参照）、または高々２％程度しか
得られていなかった（特開平４−４０７０５号公報を参
照）。また、最大の帯域幅で３．７％が実現されている
が（特開平７−５８５８１号公報を参照）、前記したよ
うに、システムの占有帯域幅の比率が３．７％であるた
め、フィルタとしては温度変動と作製時のばらつき変動
の周波数分が必要であることから、広い通過帯域幅が要
求されている携帯電話等の通信機器への適用には問題が
あった。For this reason, in a conventional dual mode surface acoustic wave resonator filter, for example, LiTaO3 is used as a piezoelectric substrate.
When a single crystal substrate is used, the relative bandwidth (the value of the pass band width with respect to the center frequency) is about 0.40% (Japanese Patent Laid-Open No.
No. 231417), or only about 2% at most (see Japanese Patent Application Laid-Open No. 4-40705). Although 3.7% is realized with the maximum bandwidth (see Japanese Patent Application Laid-Open No. 7-58581), as described above, the ratio of the occupied bandwidth of the system is 3.7%. Since the filter needs the frequency of the temperature variation and the variation variation at the time of fabrication, there is a problem in application to a communication device such as a mobile phone that requires a wide pass bandwidth.
【００１３】そこで本発明は、平衡型として動作可能で
振幅と位相の平衡度が良好で高品質な弾性表面波フィル
タ、さらには挿入損失が良好であり、通過帯域幅の広い
弾性表面波フィルタとして機能できる、優れた弾性表面
波フィルタを提供することを目的とする。Accordingly, the present invention provides a high-quality surface acoustic wave filter which can operate as a balanced type and has a good degree of balance between amplitude and phase, and further has a good insertion loss and a wide pass band width. It is an object to provide an excellent surface acoustic wave filter that can function.
【００１４】[0014]
【課題を解決するための手段】前記目的を達成するため
に、本発明の共振器型の弾性表面波フィルタは、圧電基
板上に、平衡入力または平衡出力を行う平衡信号電極
と、不平衡出力または不平衡入力を行う不平衡信号電極
とを配設して成り、前記平衡信号電極は、１つの櫛歯状
浮き電極または櫛歯状接地電極に対し、該電極の両端に
位置する電極指の間に、隣接させた複数の櫛歯状信号電
極を噛み合わせるように対向させて成るとともに、隣合
う櫛歯状信号電極が互いに逆位相であることを特徴とす
る。また、隣合う櫛歯状信号電極の端部に位置する電極
指どうしが隣接していることを特徴とする。また、平衡
信号電極の中央から隣合う不平衡信号電極の中央までの
平均電極指幅を共振器全体の平均電極指幅よりも小さく
したことを特徴とする。To achieve the above object, a resonator type surface acoustic wave filter according to the present invention comprises a balanced signal electrode for performing balanced input or balanced output on a piezoelectric substrate, and an unbalanced output. Or an unbalanced signal electrode for performing unbalanced input, wherein the balanced signal electrode is provided with respect to a single comb-like floating electrode or a comb-like ground electrode, of electrode fingers located at both ends of the electrode. A plurality of adjacent comb-shaped signal electrodes are opposed to each other so as to mesh with each other, and adjacent comb-shaped signal electrodes have opposite phases. Also, electrode fingers located at the ends of adjacent comb-tooth signal electrodes are adjacent to each other. Further, the average electrode finger width from the center of the balanced signal electrode to the center of the adjacent unbalanced signal electrode is smaller than the average electrode finger width of the entire resonator.
【００１５】[0015]
【発明の実施の形態】以下、本発明の実施形態を模式的
に図示した図面に基づいて詳細に説明する。DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings schematically showing the embodiments.
【００１６】図１に本発明に係る弾性表面波フィルタの
平面図を示す。不平衡信号電極であるＩＤＴ電極３，４
および平衡信号電極であるＩＤＴ電極２を複数配置さ
せ、その両端に反射器電極７を載置させることは、従来
構造と同様であるが、本発明の構造では、ＩＤＴ電極２
が、１つの櫛歯状浮き電極または櫛歯状接地電極２１に
対し、その電極の両端に位置する電極指の間に、隣接さ
せた複数の櫛歯状信号電極２２，２３を噛み合わせるよ
うに対向させて成るとともに、隣合う櫛歯状信号電極２
２、２３が互いに逆位相に成るように構成され、それぞ
れの電極部が平衡信号電極として形成されている。上記
構造により振幅および位相バランスを制御していること
を特徴としている。なお、ＩＤＴ電極２，３，４および
反射器電極７の電極指の本数は数本〜数１００本にもお
よぶため、その形状を簡略化して図示している。以下、
弾性表面波フィルタを示す図面においては、全て同様に
簡略化して図示するものとする。FIG. 1 is a plan view of a surface acoustic wave filter according to the present invention. IDT electrodes 3 and 4 which are unbalanced signal electrodes
The arrangement of a plurality of IDT electrodes 2 as balanced signal electrodes and the placement of reflector electrodes 7 at both ends thereof are the same as in the conventional structure, but in the structure of the present invention, the IDT electrodes 2
However, a plurality of adjacent comb-teeth signal electrodes 22 and 23 are engaged with one comb-teeth floating electrode or comb-teeth ground electrode 21 between electrode fingers located at both ends of the electrode. Opposed and adjacent comb-tooth signal electrodes 2
2 and 23 are configured to have phases opposite to each other, and each electrode portion is formed as a balanced signal electrode. The amplitude and phase balance are controlled by the above structure. Since the number of electrode fingers of the IDT electrodes 2, 3, 4 and the reflector electrode 7 ranges from several to several hundred, their shapes are simplified. Less than,
In the drawings showing the surface acoustic wave filter, all of them are similarly simplified and shown.
【００１７】ここで、３個のＩＤＴ電極２〜４のうち、
中央に配置されたＩＤＴ電極２は不平衡入力用または不
平衡出力用のＩＤＴ電極であり、その両端に配置された
ＩＤＴ電極３，４はそれぞれ平衡入力用または平衡出力
用のＩＤＴ電極である。出力用のＩＤＴ電極を形成して
いる１対の電極のうち、一方を出力１とすると、他方が
出力１に対して振幅が同じ大きさで位相が逆相になって
いる出力２となり、平衡型の動作を行う。Here, among the three IDT electrodes 2 to 4,
The IDT electrode 2 arranged at the center is an IDT electrode for unbalanced input or unbalanced output, and the IDT electrodes 3 and 4 arranged at both ends are IDT electrodes for balanced input or balanced output, respectively. If one of the pair of electrodes forming the output IDT electrode is output 1, the other is output 2 having the same amplitude and the opposite phase to output 1, and is balanced. Perform the type operation.
【００１８】不平衡入出力部の信号線Ｓ３と平衡出入力
部の信号線Ｓ２の間隔ｄ２とフィルタ特性の相関を調査
したところ、ｄ２が大きくなるほど互いの電磁界の干渉
が小さくなり、その結果平衡出入力部の振幅と位相の平
衡度が改善され、逆にｄ２が小さくなるほど弾性表面波
の伝搬損失が小さくなり、その結果フィルタ特性の挿入
損失が小さくなり、最適な構造はｄ２が弾性表面波の波
長をλとするとλ＋ｄに等しくなるところでもっとも挿
入損失が小さく、振幅と位相の平衡度もよくなることが
判明した。When the correlation between the filter characteristic and the distance d2 between the signal line S3 of the unbalanced input / output section and the signal line S2 of the balanced input / output section was examined, the interference between the electromagnetic fields became smaller as d2 became larger. The degree of balance between the amplitude and the phase of the balanced input / output section is improved. Conversely, as d2 decreases, the propagation loss of the surface acoustic wave decreases. As a result, the insertion loss of the filter characteristics decreases. Assuming that the wavelength of the wave is λ, it has been found that the insertion loss is the smallest where the wavelength becomes equal to λ + d, and the balance between the amplitude and the phase is also improved.
【００１９】また２つの平衡出入力部の信号線Ｓ２２，
Ｓ２３の間隔ｄ３についても調査したところ、隣合う櫛
歯状信号電極の端部に位置する電極指どうしが隣接し、
ｄ３がλ／２に近づくほどフィルタ特性の挿入損失が小
さくなることが判明した。すなわち、本発明の構造にす
ることにより、フィルタ特性の挿入損失、振幅と位相の
平衡度ともに優れた弾性表面波フィルタを提供すること
ができることが判明した。The signal lines S22,
When the distance d3 in S23 was also investigated, the electrode fingers located at the ends of the adjacent comb-shaped signal electrodes were adjacent to each other,
It has been found that the insertion loss of the filter characteristics decreases as d3 approaches λ / 2. That is, it was found that the structure of the present invention can provide a surface acoustic wave filter excellent in both the insertion loss of filter characteristics and the degree of balance between amplitude and phase.
【００２０】次に、本発明の電極構成の変形例を図２、
９、１０、１１に示す。Next, a modification of the electrode configuration of the present invention is shown in FIG.
9, 10, and 11.
【００２１】図２は共振器型フィルタを２段接続した弾
性表面波フィルタである。不平衡信号電極であるＩＤＴ
電極９１へ不平衡信号が入力され、ＩＤＴ電極９２から
不平衡信号が出力される。そして、ＩＤＴ電極９２と隣
の共振器型フィルタの不平衡信号電極３，４が接続され
る。上記構造によりフィルタ特性の帯域外減衰量を大き
く向上させることができる。FIG. 2 shows a surface acoustic wave filter in which two resonator-type filters are connected. IDT which is an unbalanced signal electrode
An unbalanced signal is input to the electrode 91, and an unbalanced signal is output from the IDT electrode 92. Then, the IDT electrode 92 is connected to the unbalanced signal electrodes 3 and 4 of the adjacent resonator type filter. With the above structure, the amount of out-of-band attenuation of the filter characteristics can be greatly improved.
【００２２】図９は、平衡信号電極２の中央から隣合う
不平衡信号電極３，４の中央までのＩＤＴ電極間部位
５，６の平均電極指幅を共振器全体の平均電極指幅より
も小さくしたことを特徴とする。上記構造によりフィル
タ特性の通過帯域幅を制御することができる。FIG. 9 shows that the average electrode finger width of the portions 5 and 6 between the IDT electrodes from the center of the balanced signal electrode 2 to the center of the adjacent unbalanced signal electrodes 3 and 4 is larger than the average electrode finger width of the entire resonator. It is characterized by being made smaller. With the above structure, the pass band width of the filter characteristic can be controlled.
【００２３】図１０は共振器型フィルタを２段接続し、
平衡信号電極であるＩＤＴ電極２の中央から隣合う不平
衡信号電極であるＩＤＴ電極３，４の中央までのＩＤＴ
電極間部位５，６の平均電極指幅を共振器全体の平均電
極指幅よりも小さくしたことを特徴とする。上記構造に
よりフィルタ特性の帯域外減衰量を大きく向上させるこ
とができ、さらに、フィルタ特性の通過帯域幅を制御す
ることができる。FIG. 10 shows two resonator-type filters connected in series.
IDT from the center of the IDT electrode 2 which is a balanced signal electrode to the center of the IDT electrodes 3 and 4 which are adjacent unbalanced signal electrodes
The average electrode finger width of the inter-electrode portions 5 and 6 is smaller than the average electrode finger width of the entire resonator. With the above structure, the attenuation of the filter characteristic out of the band can be greatly improved, and the pass band width of the filter characteristic can be controlled.
【００２４】かくして、前記のような条件を満足するＩ
ＤＴ電極構造の弾性表面波フィルタによれば、ＩＤＴ電
極対数が最適化された組み合わせとなり、その結果、比
帯域幅、振幅および位相の平衡度の特性が良好な品質的
に優れたフィルタを作製することができるのである。Thus, I which satisfies the above condition is satisfied.
According to the surface acoustic wave filter having the DT electrode structure, a combination in which the number of IDT electrode pairs is optimized is obtained, and as a result, a filter having excellent characteristics of relative bandwidth, amplitude and phase balance, and excellent quality is produced. You can do it.
【００２５】図１１は平衡信号電極の櫛歯状電極を４つ
噛み合わせたことを特徴とする。これにより、電極を４
つ使用することにより設計パラメータを増やすことがで
き、より要求仕様に適した設計を行えることができる。FIG. 11 is characterized in that four comb-shaped electrodes of the balanced signal electrode are engaged. As a result, four electrodes
By using one, the design parameters can be increased, and a design more suitable for the required specification can be performed.
【００２６】なお、図１においては弾性表面波フィルタ
を１セクションの共振器で構成したが、これに限定され
るものではなく、共振器を２個以上縦続接続した弾性表
面波フィルタやＩＤＴ電極を５個以上並べた弾性表面波
フィルタにおいても本発明を適用することができる。In FIG. 1, the surface acoustic wave filter is composed of one section of resonator. However, the present invention is not limited to this. For example, a surface acoustic wave filter or an IDT electrode in which two or more resonators are connected in cascade is used. The present invention can be applied to five or more surface acoustic wave filters.
【００２７】また、図２、９、１０、１１の弾性表面波
フィルタの電極構造においてもこれに限定されるもので
はなく、２つの反射器電極の間に少なくとも３つのＩＤ
Ｔ電極を配するとともに、これら３つのＩＤＴ電極のう
ち中央に位置するＩＤＴ電極を不平衡入力部または不平
衡出力部とし、かつ両端に位置するＩＤＴ電極を平衡出
力部または平衡入力部としたものであれば、多数段に構
成したりすることもできる。The electrode structure of the surface acoustic wave filter shown in FIGS. 2, 9, 10 and 11 is not limited to this, and at least three IDs are provided between two reflector electrodes.
A T electrode is arranged, and the IDT electrode located at the center of these three IDT electrodes is used as an unbalanced input or unbalanced output, and the IDT electrodes located at both ends are used as a balanced output or a balanced input. If so, it may be configured in multiple stages.
【００２８】また、弾性表面波フィルタ用の圧電基板１
として、３６°±３°ＹカットＸ伝搬タンタル酸リチウ
ム単結晶、４２°±３°ＹカットＸ伝搬タンタル酸リチ
ウム単結晶、６４°±３°ＹカットＸ伝搬ニオブ酸リチ
ウム単結晶、４１°±３°ＹカットＸ伝搬リチウム単結
晶、４５°±３°ＸカットＺ伝搬四ホウ酸リチウム単結
晶は電気機械結合係数が大きく、かつ、周波数温度係数
が小さいため圧電基板として好ましい。圧電基板の厚み
は０．１ｍｍ〜０．５ｍｍ程度がよく、０．１ｍｍ未満
では圧電基板がもろくなり、０．５ｍｍ超では材料コス
トと部品寸法が大きくなり、使用できない。A piezoelectric substrate 1 for a surface acoustic wave filter
36 ° ± 3 ° Y-cut X-propagating lithium tantalate single crystal, 42 ° ± 3 ° Y-cut X-propagating lithium tantalate single crystal, 64 ° ± 3 ° Y-cut X-propagating lithium niobate single crystal, 41 ° ± A 3 ° Y-cut X-propagating lithium single crystal and a 45 ° ± 3 ° X-cut Z-propagating lithium tetraborate single crystal have a large electromechanical coupling coefficient and a small frequency temperature coefficient, and thus are preferable as a piezoelectric substrate. The thickness of the piezoelectric substrate is preferably about 0.1 mm to 0.5 mm. If the thickness is less than 0.1 mm, the piezoelectric substrate becomes brittle. If the thickness exceeds 0.5 mm, the material cost and component dimensions increase, and the piezoelectric substrate cannot be used.
【００２９】また、ＩＤＴ電極２，３，４は、Ａｌもし
くはＡｌ合金（Ａｌ−Ｃｕ系、Ａｌ−Ｔｉ系）からな
り、蒸着法、スパッタ法、またはＣＶＤ法などの薄膜形
成法により形成する。電極厚みは０．１μｍ〜０．５μ
ｍ程度とすることが弾性表面波フィルタとしての特性を
得るうえで好適である。The IDT electrodes 2, 3, and 4 are made of Al or an Al alloy (Al-Cu system, Al-Ti system), and are formed by a thin film forming method such as an evaporation method, a sputtering method, or a CVD method. Electrode thickness is 0.1μm ~ 0.5μ
It is preferable to set it to about m in order to obtain characteristics as a surface acoustic wave filter.
【００３０】さらに、本発明に係る弾性表面波フィルタ
の電極および圧電基板上の弾性表面波伝搬部にＳｉ、Ｓ
ｉＯ２、ＳｉＮｘ、Ａｌ２Ｏ３を保護膜として形成し
て、導電性異物による通電防止や耐電力向上を行っても
かまわない。Further, the electrodes of the surface acoustic wave filter according to the present invention and the surface acoustic wave propagating portions on the piezoelectric substrate have Si, S
iO2, SiNx, or Al2O3 may be formed as a protective film to prevent conduction by a conductive foreign substance and improve power resistance.
【００３１】[0031]
【実施例】本発明に係る弾性表面波フィルタを具体的に
試作した実施例について説明する。An embodiment in which a surface acoustic wave filter according to the present invention is specifically manufactured will be described.
【００３２】３８．７°ＹカットのＬｉＴａＯ３単結晶
の圧電基板上に、図１に示すようなＡｌ（９９ｗｔ％）
−Ｃｕ（１ｗｔ％）による微細電極パターンを形成し
た。ＩＤＴ電極２の対数は１６対、ＩＤＴ電極３，４の
対数は１１対、電極の周期はＩＤＴ電極２，３，４とも
に２．１μｍ、ＩＤＴ電極２−３間または２−４間のＩ
ＤＴ電極の端部における電極指中心間の間隔ｄは３．３
μｍとした。パターン作製には、スパッタリング装置、
縮小投影露光機（ステッパー）、およびＲＩＥ（Ｒｅａ
ｃｔｉｖｅ Ｉｏｎ Ｅｔｃｈｉｎｇ）装置によりフォ
トリソグラフィを行った。Al (99 wt%) as shown in FIG. 1 was placed on a 38.7 ° Y-cut LiTaO 3 single crystal piezoelectric substrate.
-A fine electrode pattern of Cu (1 wt%) was formed. The IDT electrode 2 has a logarithm of 16 pairs, the IDT electrodes 3 and 4 have a logarithm of 11 pairs, and the electrode period is 2.1 μm for both the IDT electrodes 2, 3, and 4.
The distance d between the centers of the electrode fingers at the end of the DT electrode is 3.3.
μm. For pattern production, sputtering equipment,
Reduction projection exposure machine (stepper) and RIE (Rea)
Photolithography was performed using an active ion etching apparatus.
【００３３】まず、基板材料をアセトン・ＩＰＡ等によ
って超音波洗浄し、有機成分を落とした。次に、クリー
ンオーブンによって充分に基板乾燥を行った後、電極の
成膜を行った。電極の成膜にはスパッタリング装置を使
用し、Ａｌ−Ｃｕ１ｗｔ％合金から成る材料を用いた。
このときの電極膜厚は約０．２μｍとした。First, the substrate material was ultrasonically cleaned with acetone, IPA or the like to remove organic components. Next, after sufficiently drying the substrate with a clean oven, an electrode was formed. A sputtering apparatus was used to form the electrodes, and a material made of an Al-Cu 1 wt% alloy was used.
At this time, the electrode film thickness was about 0.2 μm.
【００３４】次に、フォトレジストを約０．５μｍの厚
みにスピンコートし、縮小投影露光装置（ステッパー）
により、所望形状にパターニングを行ない、現像装置に
て不要部分のフォトレジストをアルカリ現像液で溶解さ
せ、所望パターンを表出した後、ＲＩＥ（Ｒｅａｃｔｉ
ｖｅ Ｉｏｎ Ｅｔｃｈｉｎｇ）装置により電極膜のエ
ッチングを行ないパターンニングを終了し、梯子型弾性
表面波フィルタを構成する弾性表面波共振器の電極パタ
ーンを得た。Next, a photoresist is spin-coated to a thickness of about 0.5 μm, and a reduction projection exposure apparatus (stepper) is used.
Is performed to form a desired pattern, the unnecessary portion of the photoresist is dissolved with an alkali developing solution using a developing device, and the desired pattern is exposed. Then, RIE (Reacti
The patterning was completed by etching the electrode film with a Ve Ion Etching (Ve Ion Etching) apparatus to obtain an electrode pattern of a surface acoustic wave resonator constituting a ladder type surface acoustic wave filter.
【００３５】この後、前記電極の所定領域上に保護膜を
作製した。すなわち、ＣＶＤ（Ｃｈｅｍｉｃａｌ Ｖａ
ｐｏｒ Ｄｅｐｏｓｉｔｉｏｎ）装置により、電極パタ
ーンおよび圧電基板上にＳｉＯ２を約０．０２μｍの厚
みに形成した。その後、フォトリソグラフィによってフ
ォトレジストのパターニングを行ない、ＲＩＥ装置等で
ワイヤボンディング用窓開け部のエッチングを行ない、
保護膜パターンを完成した。Thereafter, a protective film was formed on a predetermined region of the electrode. That is, CVD (Chemical Va)
Using a por deposition apparatus, SiO 2 was formed to a thickness of about 0.02 μm on the electrode patterns and the piezoelectric substrate. Thereafter, the photoresist is patterned by photolithography, and the window opening for wire bonding is etched by an RIE apparatus or the like.
A protective film pattern was completed.
【００３６】次に、基板をダイシング線に沿ってダイシ
ング加工を施し、チップごとに分割した。そして、各チ
ップをダイボンド装置にてピックアップし、シリコーン
を主成分とする樹脂を用いパッケージ内に接着した。こ
の後、約１６０℃の温度において乾燥・硬化させた。パ
ッケージは３ｍｍ角の積層構造のものを用いた。Next, the substrate was diced along the dicing line, and divided into chips. Then, each chip was picked up by a die bonding apparatus and bonded in a package using a resin containing silicone as a main component. Thereafter, drying and curing were performed at a temperature of about 160 ° C. The package used was a 3 mm square laminated structure.
【００３７】次に、３０μｍφＡｕワイヤをパッケージ
の電極部とチップ上のＡｌ電極パッド上にボールボンデ
ィングした後、リッドをパッケージに被せ、封止機にて
溶接封止して弾性表面波フィルタを完成した。なお、チ
ップ上のグランド電極は各々分離して配線し、Ａｕボー
ルボンディングにてパッケージ上のグランド電極にボン
ディングを行った。Next, a 30 μm φ Au wire was ball-bonded to the electrode portion of the package and the Al electrode pad on the chip, and then the lid was put on the package, and the package was welded and sealed with a sealing machine to complete a surface acoustic wave filter. . The ground electrodes on the chip were separately wired and bonded to the ground electrodes on the package by Au ball bonding.
【００３８】比較用サンプルとして図３に示すような微
細電極パターンも上記と同様な工程で作製を行った。Ｉ
ＤＴ電極１０２の対数は１６対、ＩＤＴ電極１０３，１
０４の対数は１１対、電極の周期はＩＤＴ電極１０２，
１０３，１０４ともに２．１μｍ、ＩＤＴ電極１０２−
１０３間または１０２−１０４間のＩＤＴ電極の端部に
おける電極指中心間の間隔ｄは３．３μｍとした。As a comparative sample, a fine electrode pattern as shown in FIG. 3 was produced in the same process as described above. I
The number of pairs of the DT electrode 102 is 16, and the IDT electrodes 103 and 1 are paired.
04 is 11 pairs, and the period of the electrode is IDT electrode 102,
The IDT electrode 102-
The distance d between the centers of the electrode fingers at the end of the IDT electrode between 103 or 102-104 was 3.3 μm.
【００３９】次に、本実施例における弾性表面波フィル
タの特性測定を行った。０ｄＢｍの信号を入力し、周波
数８４２．５ＭＨｚ〜１０４２．５ＭＨｚ、測定ポイン
ト数８０１ポイントの条件および周波数１０ＭＨｚ〜６
ＧＨｚ、測定ポイント４０１ポイントの条件にて測定し
た。サンプル数は３０個、測定機器はアジレント・テク
ノロジー社製ネットワークアナライザ８７５３Ｄであ
る。Next, the characteristics of the surface acoustic wave filter according to the present embodiment were measured. A signal of 0 dBm is input, and the conditions of a frequency of 842.5 MHz to 1042.5 MHz, a number of measurement points of 801 points, and a frequency of 10 MHz to 6
The measurement was performed under the conditions of GHz and 401 measurement points. The number of samples is 30, and the measuring instrument is a network analyzer 8753D manufactured by Agilent Technologies.
【００４０】通過帯域近傍の周波数特性グラフを図５、
６に示す。ここで、図５はフィルタの伝送特性を表す挿
入損失の周波数依存性（図中５１）および反射信号の大
きさを評価する比率ＶＳＷＲ（Ｖｏｌｔａｇｅ Ｓｔａ
ｎｄｉｎｇ Ｗａｖｅ Ｒａｔｉｏ）の周波数依存性
（図中５２）を示すグラフである。また、図６はフィル
タ特性の平衡度を示すグラフであり、出力信号端子１３
から出力された挿入損失の周波数特性と出力信号端子１
５から出力された挿入損失の周波数特性の差を振幅の平
衡度とする。また、出力信号端子１３から出力された位
相の周波数特性と出力信号端子１５から出力された位相
の周波数特性の差から１８０°を差し引いた値を位相の
平衡度とする。振幅の平衡度が０ｄＢであり位相の平衡
度が０°であるほど弾性表面波フィルタの平衡度が優れ
ていると評価できる。FIG. 5 shows a frequency characteristic graph near the pass band.
6 is shown. Here, FIG. 5 shows a frequency VSWR (Voltage Stage) for evaluating the frequency dependence of the insertion loss (51 in the figure) representing the transmission characteristics of the filter and the magnitude of the reflected signal.
35 is a graph illustrating frequency dependence (52 in the figure) of an Nending Wave Ratio. FIG. 6 is a graph showing the degree of balance of the filter characteristics.
Characteristics of the Insertion Loss Output from the Output Signal Terminal 1
The difference between the frequency characteristics of the insertion loss output from 5 is defined as the amplitude balance. The value obtained by subtracting 180 ° from the difference between the frequency characteristic of the phase output from the output signal terminal 13 and the frequency characteristic of the phase output from the output signal terminal 15 is defined as the phase balance. It can be evaluated that the degree of balance of the surface acoustic wave filter is superior as the amplitude balance is 0 dB and the phase balance is 0 °.
【００４１】本発明品のフィルタ特性は非常に良好であ
った。図６に示すように、通過帯域内９２５ＭＨｚ〜９
６０ＭＨｚの振幅の平衡度６１は約±０．７ｄＢ以下で
あり、および位相の平衡度６２は約±７°以下であっ
た。これに対して、比較サンプルとして作製した従来構
造の弾性表面波フィルタは、図７、８に示すとおり、通
過帯域内９２５ＭＨｚ〜９６０ＭＨｚの振幅の平衡度８
１は約±１．４ｄＢ以下であり、位相の平衡度８２は約
±１５°以下であった。それぞれ約０．７ｄＢ、約８°
の改善が見られた。また、本発明品の通過帯域の挿入損
失５１は約２．４ｄＢ以下、ＶＳＷＲ５２は２．７以下
であるのに対し、従来品は挿入損失７１が約３．１ｄＢ
以下、ＶＳＷＲ７２は３．６以下であり、それぞれ約
０．７ｄＢ、０．９の改善が見られた。The filter characteristics of the product of the present invention were very good. As shown in FIG.
The 60 MHz amplitude balance 61 was less than about ± 0.7 dB, and the phase balance 62 was less than about ± 7 °. On the other hand, as shown in FIGS. 7 and 8, the surface acoustic wave filter having the conventional structure manufactured as a comparative sample has a balance δ of an amplitude of 925 MHz to 960 MHz in the pass band.
1 was about ± 1.4 dB or less, and the phase balance 82 was about ± 15 ° or less. About 0.7dB and about 8 ° respectively
Improvement was seen. The insertion loss 51 of the pass band of the present invention is about 2.4 dB or less and the VSWR 52 is 2.7 or less, whereas the insertion loss 71 of the conventional product is about 3.1 dB.
Hereinafter, the VSWR 72 is 3.6 or less, and an improvement of about 0.7 dB and 0.9 is observed, respectively.
【００４２】また、弾性表面波フィルタの小型化が要求
されているため上記実施例の弾性表面波フィルタをフリ
ップチップ実装により作製し、評価を行った。すなわ
ち、保護膜パターンを形成した後、バンプ形成装置によ
りバンプ形成用電極パターンにＡｕのバンプを形成し
た。次に、ダイシングにより、弾性表面波素子を個々に
切り出した。次に、２．５×２．０ｍｍ角のセラミック
パッケージにフリップチップボンディング装置により、
個々に切り出した弾性表面波素子を１つ、セラミックパ
ッケージ内に接着し、Ｎ２雰囲気中でベークを行った。
次に、封止装置によりパッケージに金属製のキャップを
被せてパッケージ内を密封し、弾性表面波フィルタを作
製した。上記構造のフィルタの特性を測定した結果、上
記と同様な結果が得られることを確認できた。Since the size of the surface acoustic wave filter is required to be reduced, the surface acoustic wave filter of the above embodiment was fabricated by flip-chip mounting and evaluated. That is, after the protective film pattern was formed, Au bumps were formed on the bump forming electrode patterns by the bump forming apparatus. Next, the surface acoustic wave devices were individually cut out by dicing. Next, a 2.5 × 2.0 mm square ceramic package was flip-chip bonded to the package.
One cutout surface acoustic wave element was adhered in a ceramic package and baked in an N2 atmosphere.
Next, the package was covered with a metal cap by a sealing device to seal the inside of the package, thereby producing a surface acoustic wave filter. As a result of measuring the characteristics of the filter having the above structure, it was confirmed that the same result as described above was obtained.
【００４３】[0043]
【発明の効果】以上説明したように、本発明の弾性表面
波フィルタは、共振器型の弾性表面波フィルタであっ
て、平衡信号電極は、１つの櫛歯状浮き電極または櫛歯
状接地電極に対し、該電極の両端に位置する電極指の間
に、隣接させた複数の櫛歯状信号電極を噛み合わせるよ
うに対向させて成るとともに、隣合う櫛歯状信号電極が
互いに逆位相であることを特徴とする。上記構造の特に
櫛歯状浮き電極または櫛歯状接地電極が平衡信号電極の
両端に位置するような構成により、不平衡電極と平衡電
極の電磁界の干渉を小さくすることができ、その結果、
平衡信号を制御することができ、振幅および位相の平衡
度が良好な品質的に優れた弾性表面波フィルタを実現す
ることができる。As described above, the surface acoustic wave filter of the present invention is a resonator type surface acoustic wave filter, and the balanced signal electrode is a single comb-like floating electrode or a comb-like ground electrode. In contrast, a plurality of adjacent comb-tooth signal electrodes are opposed to each other between the electrode fingers located at both ends of the electrode so as to mesh with each other, and the adjacent comb-tooth signal electrodes have opposite phases to each other. It is characterized by the following. With the above structure, in particular, the comb-like floating electrode or the comb-like ground electrode is located at both ends of the balanced signal electrode, it is possible to reduce the interference of the electromagnetic field between the unbalanced electrode and the balanced electrode, and as a result,
A balanced signal can be controlled, and a surface acoustic wave filter excellent in quality with good amplitude and phase balance can be realized.
【００４４】また、本発明の弾性表面波フィルタは、隣
合う櫛歯状信号電極の端部に位置する電極指どうしが隣
接していることを特徴とする。上記構造の電極指の間隔
を制御することにより平衡信号電極２２，２３の位相の
差を１８０°に近づけることができ、その結果、位相の
平衡度が良好な品質的に優れた弾性表面波フィルタを実
現することができるまた、本発明の弾性表面波フィルタ
は、平衡信号電極の中央から隣合う不平衡信号電極の中
央までの平均電極指幅を共振器全体の平均電極指幅より
も小さくしたことを特徴とする。上記構造の平均電極指
幅をそれぞれ変化させることにより弾性表面波の縦１次
モードと縦３次モードを制御することができる。Further, the surface acoustic wave filter according to the present invention is characterized in that electrode fingers located at the ends of adjacent comb-like signal electrodes are adjacent to each other. By controlling the distance between the electrode fingers having the above structure, the phase difference between the balanced signal electrodes 22 and 23 can be made close to 180 °, and as a result, a surface acoustic wave filter having a good phase balance and excellent quality can be obtained. In addition, the surface acoustic wave filter of the present invention has an average electrode finger width from the center of a balanced signal electrode to the center of an adjacent unbalanced signal electrode smaller than the average electrode finger width of the entire resonator. It is characterized by the following. The longitudinal primary mode and longitudinal tertiary mode of the surface acoustic wave can be controlled by changing the average electrode finger width of the above structure.
【００４５】以上により、フィルタ特性の通過帯域幅を
広帯域化した品質的に優れた弾性表面波フィルタを実現
することができる。As described above, it is possible to realize a surface acoustic wave filter excellent in quality in which the pass band width of the filter characteristics is widened.
【図１】本発明の弾性表面波フィルタの構成例を模式的
に示す平面図である。FIG. 1 is a plan view schematically showing a configuration example of a surface acoustic wave filter according to the present invention.
【図２】本発明の弾性表面波フィルタの２段接続の構成
例を模式的に示す平面図である。FIG. 2 is a plan view schematically showing a configuration example of a two-stage connection of the surface acoustic wave filter of the present invention.
【図３】従来の弾性表面波フィルタの構成例を示す平面
図である。FIG. 3 is a plan view showing a configuration example of a conventional surface acoustic wave filter.
【図４】従来の弾性表面波フィルタの２段接続の構成例
を示す平面図である。FIG. 4 is a plan view showing a configuration example of a two-stage connection of a conventional surface acoustic wave filter.
【図５】本発明の弾性表面波フィルタにおける通過帯域
近傍の周波数特性を示すグラフである。FIG. 5 is a graph showing frequency characteristics near a pass band in the surface acoustic wave filter of the present invention.
【図６】本発明の弾性表面波フィルタにおける通過帯域
近傍の振幅および位相の平衡度を示すグラフである。FIG. 6 is a graph showing the degree of balance of amplitude and phase near the pass band in the surface acoustic wave filter of the present invention.
【図７】従来の弾性表面波フィルタにおける通過帯域近
傍の周波数特性を示すグラフである。FIG. 7 is a graph showing frequency characteristics near a pass band in a conventional surface acoustic wave filter.
【図８】従来の弾性表面波フィルタにおける通過帯域近
傍の振幅および位相の平衡度を示すグラフである。FIG. 8 is a graph showing the amplitude and phase balance in the vicinity of a pass band in a conventional surface acoustic wave filter.
【図９】本発明に係る１段構成の弾性表面波フィルタを
模式的に示す電極構成図である。FIG. 9 is an electrode configuration diagram schematically showing a one-stage surface acoustic wave filter according to the present invention.
【図１０】本発明に係る２段接続の弾性表面波フィルタ
を模式的に示す電極構成図である。FIG. 10 is an electrode configuration diagram schematically showing a two-stage connected surface acoustic wave filter according to the present invention.
【図１１】本発明に係る弾性表面波フィルタの変形例を
模式的に示す電極構成図である。FIG. 11 is an electrode configuration diagram schematically showing a modified example of the surface acoustic wave filter according to the present invention.
１，１０１ ：圧電基板 ２，３，４，９１，９２，１０２，１０３，１０４ ：
ＩＤＴ電極 ５，６，１０５，１０６ ：ＩＤＴ電極間部位 ７，１０７ ：反射器電極 ８，１０８ ：ＩＤＴ電極と反射器電極間部位 １１，１１１ ：入力信号端子 １２，１１２ ：接地端子 １３，１５，１１３，１１５ ：出力信号端子 ２１ ：接地端子または電気的浮き電極 ２２，２３ ：櫛歯状信号電極 ５１，７１ ：挿入損失の周波数特性 ５２，７２ ：ＶＳＷＲの周波数特性 ６１，８１ ：振幅の平衡度の周波数特性 ６２，８２ ：位相の平衡度の周波数特性 Ｓ２，Ｓ２２，Ｓ２３ ：平衡出入力部の信号線 Ｓ３ ：不平衡入出力部の信号線 ｄ ：電極指中心間の間隔 ｄ２ ：Ｓ２，Ｓ３の間隔 ｄ３ ：Ｓ２２，Ｓ３３の間隔1,101: piezoelectric substrate 2,3,4,91,92,102,103,104:
IDT electrodes 5, 6, 105, 106: part between IDT electrodes 7, 107: reflector electrode 8, 108: part between IDT electrode and reflector electrode 11, 111: input signal terminal 12, 112: ground terminal 13, 15, 113, 115: Output signal terminal 21: Ground terminal or electrically floating electrode 22, 23: Comb-like signal electrode 51, 71: Frequency characteristic of insertion loss 52, 72: Frequency characteristic of VSWR 61, 81: Balance of amplitude 62, 82: Frequency characteristics of phase balance S2, S22, S23: Signal line of balanced input / output unit S3: Signal line of unbalanced input / output unit d: Distance between electrode finger centers d2: S2, S3 Interval d3: interval between S22 and S33
Claims (3)
を行う平衡信号電極と、不平衡出力または不平衡入力を
行う不平衡信号電極とを配設して成る共振器型の弾性表
面波フィルタであって、前記平衡信号電極は、１つの櫛
歯状浮き電極または櫛歯状接地電極に対し、該電極の両
端に位置する電極指の間に、隣接させた複数の櫛歯状信
号電極を噛み合わせるように対向させて成るとともに、
隣合う櫛歯状信号電極が互いに逆位相であることを特徴
とする弾性表面波フィルタ。1. A resonator type surface acoustic wave filter having a balanced signal electrode for performing balanced input or balanced output and an unbalanced signal electrode for performing unbalanced output or unbalanced input on a piezoelectric substrate. The balanced signal electrode comprises a plurality of comb-like signal electrodes adjacent to one comb-like floating electrode or a comb-like ground electrode between electrode fingers located at both ends of the electrode. While facing each other so as to mesh with each other,
A surface acoustic wave filter characterized in that adjacent comb-toothed signal electrodes have opposite phases.
する電極指どうしが隣接していることを特徴とする請求
項１に記載の弾性表面波フィルタ。2. The surface acoustic wave filter according to claim 1, wherein electrode fingers located at ends of the adjacent comb-shaped signal electrodes are adjacent to each other.
衡信号電極の中央までの平均電極指幅を、共振器全体の
平均電極指幅よりも小さくしたことを特徴とする請求項
１に記載の弾性表面波フィルタ。3. The average electrode finger width from the center of the balanced signal electrode to the center of an adjacent unbalanced signal electrode is smaller than the average electrode finger width of the entire resonator. Surface acoustic wave filter.
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|---|---|---|---|
| JP2001096114A JP2002300004A (en) | 2001-03-29 | 2001-03-29 | Surface acoustic wave filter |
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| US7358832B2 (en) | 2004-11-04 | 2008-04-15 | Murata Manufacturing Co., Ltd. | Balanced saw filter |
| US7369016B2 (en) | 2004-11-04 | 2008-05-06 | Murata Manufacturing Co., Ltd. | Balanced saw filter |
| US7486159B2 (en) | 2004-07-23 | 2009-02-03 | Murata Manufacturing Co., Ltd. | Surface acoustic wave device |
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