JPH06260876A - Surface acoustic wave filter - Google Patents

Surface acoustic wave filter

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Publication number
JPH06260876A
JPH06260876A JP4805593A JP4805593A JPH06260876A JP H06260876 A JPH06260876 A JP H06260876A JP 4805593 A JP4805593 A JP 4805593A JP 4805593 A JP4805593 A JP 4805593A JP H06260876 A JPH06260876 A JP H06260876A
Authority
JP
Japan
Prior art keywords
surface acoustic
acoustic wave
terminal
wave resonator
resonator
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
Application number
JP4805593A
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Japanese (ja)
Other versions
JP3191473B2 (en
Inventor
Tsutomu Nagatsuka
勉 永塚
Shiyuuzou Wakou
修三 和高
Koichiro Misu
幸一郎 三須
Tomonori Kimura
友則 木村
Koji Murai
康治 村井
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mitsubishi Electric Corp
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Mitsubishi Electric Corp
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  • Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)

Abstract

PURPOSE:To realize a small loss and a large extent of out-band attenuation by constituting a surface acoustic wave filter of an one-post surface acoustic wave resonator and a surface two-ports acoustic wave resonator. CONSTITUTION:A surface acoustic wave resonator 4 to one terminal has such impedance characteristic that the impedance is 0 in the case of a resonance frequency fr and is infinite in the case of an antiresonance frequency fa. Consequently, the electric signal from an input terminal 6 passes an output terminal 7 in the case of the frequency fr but does not pass it at all in the case of the frequency fa to generate an attenuation pole when resonators 4 are connected in series to constitute a circuit to two terminals. Meanwhile, a surface acoustic wave resonator 5 to two terminals generates a spurious wave in a high band-side vicinity fs of the pass band. However, the spurious wave of the resonator 5 is cancelled by the attenuaLion pole of the resonator 4 to increase the extent of out-band attenuation because resonators 4 and 5 are cascade connected and are so constituted that frequencies fa and fs are equal to each other. Further, the pass band of the resonator 5 is equalized to the frequency fr of the resonator 4 to reduce the insertion loss in comparison with multistage connection of resonators 5.

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【産業上の利用分野】この発明は、移動体通信装置の高
周波回路などに用いられる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 surface acoustic wave filter used in a high frequency circuit of a mobile communication device.

【０００２】[0002]

【従来の技術】図１８は、例えば文献「電子情報通信学
会技術研究報告（超音波）」、ＵＳ９２−５２、ｐｐ．
９−１６に示された、従来のこの種の弾性表面波フィル
タの構成を示したものである。図１８において、４ａ、
４ｂは１端子対弾性表面波共振器、６は入力端子、７は
出力端子である。図において、直列腕に挿入した１端子
対弾性表面波共振器４ａと並列腕に挿入した１端子対弾
性表面波共振器４ｂを、入力端子６と出力端子７の間
に、複数個梯子型に接続している。図１８における１端
子対弾性表面波共振器４ａ、４ｂの一般的な構成を図１
９に示す。図１９において、１は圧電体基板、２はすだ
れ状電極、３は反射器である。圧電体基板１上にすだれ
状電極２と２つの反射器３を配置して１端子対弾性表面
波共振器４を構成している。2. Description of the Related Art FIG.
9-16 shows a configuration of a conventional surface acoustic wave filter of this type shown in 9-16. In FIG. 18, 4a,
4b is a one-terminal-pair surface acoustic wave resonator, 6 is an input terminal, and 7 is an output terminal. In the figure, a plurality of 1-terminal pair surface acoustic wave resonators 4a inserted in the series arm and 1-terminal pair surface acoustic wave resonators 4b inserted in the parallel arm are provided between the input terminal 6 and the output terminal 7 in a ladder type. Connected. A general structure of the one-terminal-pair surface acoustic wave resonators 4a and 4b in FIG. 18 is shown in FIG.
9 shows. In FIG. 19, 1 is a piezoelectric substrate, 2 is a comb-shaped electrode, and 3 is a reflector. The interdigital transducer 2 and the two reflectors 3 are arranged on the piezoelectric substrate 1 to form a one-terminal pair surface acoustic wave resonator 4.

【０００３】次に、動作について説明する。図１９の端
子間に電気信号を印加すると、すだれ状電極２から弾性
表面波が励振される。すだれ状電極２の両側に設けられ
た反射器３は、弾性表面波を反射する。このため、励振
された弾性表面波は、両側の反射器３の間で多重反射を
起こし、共振が生じる。Next, the operation will be described. When an electric signal is applied between the terminals in FIG. 19, surface acoustic waves are excited from the interdigital transducer 2. The reflectors 3 provided on both sides of the interdigital transducer 2 reflect surface acoustic waves. Therefore, the excited surface acoustic wave undergoes multiple reflection between the reflectors 3 on both sides, causing resonance.

【０００４】図２０は、図１９に示した１端子対弾性表
面波共振器４のインピーダンス特性を示したものであ
る。図中、縦軸はインピーダンスの虚数部を示してい
る。インピーダンスは共振周波数ｆｒで零となり、反共
振周波数ｆａで無限大となる。また、共振周波数ｆｒと
反共振周波数ｆａとの間ではインピーダンスは誘導性と
なり、それ以外の周波数ではインピーダンスは容量性と
なる。FIG. 20 shows impedance characteristics of the one-terminal pair surface acoustic wave resonator 4 shown in FIG. In the figure, the vertical axis represents the imaginary part of the impedance. The impedance becomes zero at the resonance frequency fr and becomes infinite at the anti-resonance frequency fa. Further, the impedance becomes inductive between the resonance frequency fr and the anti-resonance frequency fa, and the impedance becomes capacitive at other frequencies.

【０００５】図１８では、直列腕の１端子対弾性表面波
共振器４ａの共振周波数ｆｒと並列腕の１端子対弾性表
面波共振器４ｂの反共振周波数ｆａとを一致させてい
る。この周波数をｆ０とすれば、周波数ｆ０付近では、
直列腕の１端子対弾性表面波共振器４ａのインピーダン
スは小さく、並列腕の１端子対弾性表面波共振器４ｂの
インピーダンスは大きいため、入力端子６へ入力した電
気信号は、ほとんど減衰せずに出力端子７から出力し、
通過電力が大きくなる。逆に、ｆ０から離れた周波数で
は、直列腕の１端子対弾性表面波共振器４ａのインピー
ダンスが大きく、並列腕の１端子対弾性表面波共振器４
ｂのインピーダンスは小さくなっていくため、入力端子
６へ入力した電気信号は、ほとんど出力端子７から出力
されず、通過電力が小さくなる。したがって、ｆ０近傍
を通過帯域とし、それ以外の周波数を減衰帯域とするパ
ンドパスフィルタとして動作する。In FIG. 18, the resonance frequency fr of the one-terminal pair surface acoustic wave resonator 4a of the series arm and the anti-resonance frequency fa of the one-terminal pair surface acoustic wave resonator 4b of the parallel arm are matched. If this frequency is f0, near the frequency f0,
Since the impedance of the 1-terminal surface acoustic wave resonator 4a of the series arm is small and the impedance of the 1-terminal surface acoustic wave resonator 4b of the parallel arm is large, the electric signal input to the input terminal 6 is hardly attenuated. Output from output terminal 7,
The passing electric power becomes large. On the contrary, at a frequency away from f0, the impedance of the one-terminal pair surface acoustic wave resonator 4a of the series arm is large, and the one-terminal pair surface acoustic wave resonator 4 of the parallel arm is large.
Since the impedance of b decreases, the electric signal input to the input terminal 6 is hardly output from the output terminal 7, and the passing power decreases. Therefore, it operates as a bandpass filter having a pass band near f0 and an attenuation band at other frequencies.

【０００６】図２１に、図１８に示した弾性表面波フィ
ルタの通過特性を示す。直列腕の１端子対弾性表面波共
振器４ａの反共振周波数と並列腕の１端子対弾性表面波
共振器４ｂの共振周波数に対応して、それぞれ通過帯域
の高域側と低域側に減衰極が生じる。しかしながら、減
衰極より離れた周波数では、再び通過電力が大きくな
る。これは、直列腕の１端子対弾性表面波共振器４ａと
並列腕の１端子対弾性表面波共振器４ｂがともに容量性
のインピーダンスとなり、入力端子６へ入力した電気信
号の一部が、出力端子７に出力してしまうためである。
このため、通過帯域から離れた周波数において、十分な
帯域外減衰量を得にくい欠点がある。FIG. 21 shows the pass characteristic of the surface acoustic wave filter shown in FIG. Corresponding to the anti-resonance frequency of the one-terminal pair surface acoustic wave resonator 4a of the series arm and the resonance frequency of the one-terminal pair surface acoustic wave resonator 4b of the parallel arm, the damping is performed in the high band side and the low band side of the pass band, respectively. A pole arises. However, at frequencies away from the attenuation pole, the passing power becomes large again. This is because the one-terminal pair surface acoustic wave resonator 4a of the series arm and the one-terminal pair surface acoustic wave resonator 4b of the parallel arm both have capacitive impedance, and a part of the electric signal input to the input terminal 6 is output. This is because it is output to the terminal 7.
Therefore, there is a drawback that it is difficult to obtain a sufficient out-of-band attenuation amount at a frequency away from the pass band.

【０００７】また、実際には、反射器３はどんな周波数
の弾性表面波も反射するわけではなく、反射が生じる周
波数帯域は限られている。図２２は、反射器３の反射効
率の周波数特性を示したものである。ストップバンドと
呼ばれる帯域では、反射器３に入射した弾性表面波はほ
とんど完全に反射するが、それ以外の帯域では反射効率
が著しく低下する。反射器３のストップバンドの幅は、
反射器３を形成している金属膜の厚さなどによって変え
ることができ、一般には金属膜を厚くするほど大きくで
きる。しかし、金属膜を厚くするほどバルク変換損など
が増え、反射効率が全体に低下してしまう。このため、
反射器３のストップバンドの幅には限界がある。In reality, the reflector 3 does not reflect surface acoustic waves of any frequency, and the frequency band in which the reflection occurs is limited. FIG. 22 shows frequency characteristics of the reflection efficiency of the reflector 3. In the band called the stop band, the surface acoustic waves incident on the reflector 3 are almost completely reflected, but in the other bands, the reflection efficiency is significantly reduced. The width of the stop band of the reflector 3 is
It can be changed depending on the thickness of the metal film forming the reflector 3, and generally, the larger the metal film, the larger the thickness. However, the thicker the metal film is, the more bulk conversion loss or the like is increased, and the reflection efficiency is reduced as a whole. For this reason,
There is a limit to the width of the stop band of the reflector 3.

【０００８】反射器３の反射効率が小さいと弾性表面波
が反射されず、１端子対弾性表面波共振器４に入力した
電力に損失が生じる。したがって、弾性表面波フィルタ
を構成した際、通過帯域の損失が大きくなってしまう。
しかも、直列腕の１端子対弾性表面波共振器４ａの反射
器３のストップバンドと、並列腕の１端子対弾性表面波
共振器４ｂの反射器３のストップバンドとは、一般に帯
域がずれているので、両者が重なる周波数範囲以外では
電力の損失が生じ、フィルタの損失が大きくなる。この
ため、直列腕と並列腕の反射器３のストップバンドが重
なっている幅によって、弾性表面波フィルタの通過帯域
幅が制限されてしまう。If the reflection efficiency of the reflector 3 is low, the surface acoustic wave is not reflected and the power input to the one-terminal pair surface acoustic wave resonator 4 is lost. Therefore, when the surface acoustic wave filter is constructed, the loss in the pass band becomes large.
Moreover, the stop band of the reflector 3 of the one-terminal pair surface acoustic wave resonator 4a of the series arm and the stop band of the reflector 3 of the one-terminal pair surface acoustic wave resonator 4b of the parallel arm are generally displaced from each other. Therefore, power loss occurs outside the frequency range where the two overlap, and the filter loss increases. For this reason, the pass band width of the surface acoustic wave filter is limited by the overlapping width of the stop bands of the reflectors 3 of the series arm and the parallel arm.

【０００９】さらに、図１８において、１端子対弾性表
面波共振器４ａ、４ｂの間の接続は、実際には、金属の
ワイヤで結線されたり、圧電体基板１上に金属膜からな
る線路を形成して接続されたりする。このため、入力端
子６と出力端子７の間で、ワイヤや線路の長さが長くな
ると、これらの抵抗成分が増加し弾性表面波フィルタの
損失が全体的に大きくなってしまう。Further, in FIG. 18, the connection between the one-terminal surface acoustic wave resonators 4a and 4b is actually connected by a metal wire, or a line made of a metal film is formed on the piezoelectric substrate 1. Formed and connected. Therefore, when the length of the wire or the line between the input terminal 6 and the output terminal 7 becomes long, the resistance components of these wires increase and the loss of the surface acoustic wave filter becomes large as a whole.

【００１０】次に、従来の弾性表面波フィルタの他の構
成について述べる。図２３は、例えば文献「１９９０年
電子情報通信学会秋季全国大会」、ＳＡ−１０−３に示
された、従来のこの種の弾性表面波フィルタの他の構成
を示したものである。図２３において、１は圧電体基
板、２はすだれ状電極、３は反射器、５は２端子対弾性
表面波共振器、６は入力端子、７は出力端子である。図
２３において、圧電体基板１上に２つのすだれ状電極２
と、その両側に反射器３を配置することにより、２端子
対弾性表面波共振器５を構成している。また、２端子対
弾性表面波共振器５の２つのすだれ状電極２のうち一方
を入力端子６に、他方を出力端子７に接続している。Next, another structure of the conventional surface acoustic wave filter will be described. FIG. 23 shows another configuration of a conventional surface acoustic wave filter of this type, which is shown in SA-10-3 of the document “1990 Autumn National Convention of the Institute of Electronics, Information and Communication Engineers”, for example. In FIG. 23, 1 is a piezoelectric substrate, 2 is a comb-shaped electrode, 3 is a reflector, 5 is a two-terminal-pair surface acoustic wave resonator, 6 is an input terminal, and 7 is an output terminal. In FIG. 23, two interdigital electrodes 2 are provided on the piezoelectric substrate 1.
By arranging the reflectors 3 on both sides thereof, a two-terminal pair surface acoustic wave resonator 5 is constructed. Further, one of the two interdigital electrodes 2 of the two-terminal pair surface acoustic wave resonator 5 is connected to the input terminal 6 and the other is connected to the output terminal 7.

【００１１】次に、動作について説明する。入力端子６
に電気信号を入力すると、一方のすだれ状電極２から弾
性表面波が励振される。弾性表面波は反射器３で反射さ
れるため、２つの反射器３の間で多重反射し、特定の周
波数において共振する。共振した弾性表面波の一部は他
方のすだれ状電極２で再び電気信号に変換され出力端子
７から出力する。図２４は、図２３に示した２端子対弾
性表面波共振器５の共振周波数における振幅分布を示し
たものである。図中に実線で示す対称モードと、破線で
示す反対称モードとが生じ、これら２つモードの共振周
波数は若干異なっている。この共振周波数の差を所要の
値にすれば、バンドパス特性を有する２重モードフィル
タが得られる。Next, the operation will be described. Input terminal 6
When an electric signal is input to, the interdigital transducer 2 excites a surface acoustic wave. Since the surface acoustic wave is reflected by the reflector 3, it is multiply reflected between the two reflectors 3 and resonates at a specific frequency. A part of the resonated surface acoustic wave is converted into an electric signal again by the other interdigital transducer 2 and output from the output terminal 7. FIG. 24 shows an amplitude distribution at the resonance frequency of the two-terminal pair surface acoustic wave resonator 5 shown in FIG. In the figure, a symmetric mode indicated by a solid line and an antisymmetric mode indicated by a broken line occur, and the resonance frequencies of these two modes are slightly different. If the difference between the resonance frequencies is set to a required value, a dual mode filter having a bandpass characteristic can be obtained.

【００１２】図２５に、図２３に示した弾性表面波フィ
ルタの通過特性を示す。通過帯域から離れた周波数で
は、すだれ状電極２から弾性表面波があまり励振されな
いため、図２１に比べて大きい減衰量が得られる。しか
し、通過帯域の近傍で、通過帯域よりやや高域側に減衰
量が小さい部分が生じている。これは、通過帯域よりや
や高い周波数でも、すだれ状電極２中での弾性表面波の
多重反射が生じてしまい、この共振がスプリアスとなる
ためである。スプリアスのレベルを低減するため、２端
子対弾性表面波共振器５を多数縦続接続して段数を増や
す事が考えられるが、同時に通過帯域の挿入損失も増加
してしまう。FIG. 25 shows the pass characteristic of the surface acoustic wave filter shown in FIG. At frequencies apart from the pass band, the surface acoustic waves are not excited much from the interdigital transducer 2, so that a larger amount of attenuation can be obtained as compared with FIG. However, in the vicinity of the pass band, there is a portion where the amount of attenuation is slightly higher than the pass band. This is because multiple reflections of the surface acoustic wave occur in the interdigital transducer 2 even at a frequency slightly higher than the pass band, and this resonance becomes spurious. In order to reduce the spurious level, it is conceivable to connect a large number of two-terminal surface acoustic wave resonators 5 in cascade to increase the number of stages, but at the same time, the insertion loss in the pass band also increases.

【００１３】[0013]

【発明が解決しようとする課題】以上のように、従来の
弾性表面波フィルタでは、１端子対弾性表面波共振器４
のみを用いて構成していたり、２端子対弾性表面波共振
器５のみを用いて構成しているため、通過帯域から離れ
た周波数や通過帯域の近傍において、帯域外減衰量が小
さくなる問題がある。さらに、帯域外減衰量を大きくす
るために段数を増やすと、挿入損失が大きくなるなどの
欠点が生じる。さらに、１端子対弾性表面波共振器４を
梯子形に接続して構成した場合では、反射器３のストッ
プバンドの制限により、挿入損失が大きくなったり、通
過帯域幅が狭くなるなどの欠点が生じる。この発明は、
上述した問題点を解決するためになされたもので、損失
が小さく帯域外減衰量が大きい弾性表面波フィルタを得
ることを目的とする。また、損失が小さく通過帯域幅の
広い弾性表面波フィルタを得ることを目的とする。As described above, in the conventional surface acoustic wave filter, the one-terminal pair surface acoustic wave resonator 4 is used.
Since it is configured by using only the two-terminal paired surface acoustic wave resonators 5, there is a problem that the out-of-band attenuation amount becomes small in the frequency away from the pass band or in the vicinity of the pass band. is there. Furthermore, if the number of stages is increased in order to increase the out-of-band attenuation amount, there is a drawback that the insertion loss increases. Further, in the case where the one-terminal pair surface acoustic wave resonator 4 is connected in a ladder shape, there are drawbacks such as a large insertion loss and a narrow pass band width due to the restriction of the stop band of the reflector 3. Occurs. This invention
The present invention has been made in order to solve the above-mentioned problems, and an object thereof is to obtain a surface acoustic wave filter having a small loss and a large out-of-band attenuation. Another object is to obtain a surface acoustic wave filter having a small loss and a wide pass band width.

【００１４】[0014]

【課題を解決するための手段】請求項１の発明に係る弾
性表面波フィルタは、弾性表面波共振器を複数個電気的
に接続し、上記弾性表面波共振器に１端子対弾性表面波
共振器と２端子対弾性表面波共振器を共に用いたことを
特徴とするものである。A surface acoustic wave filter according to a first aspect of the present invention electrically connects a plurality of surface acoustic wave resonators, and the surface acoustic wave resonator has a one-terminal-pair surface acoustic wave resonance. It is characterized in that both the resonator and the two-terminal pair surface acoustic wave resonator are used.

【００１５】請求項２の発明に係る弾性表面波フィルタ
は、弾性表面波共振器を複数個電気的に接続し、上記弾
性表面波共振器に１端子対弾性表面波共振器と２端子対
弾性表面波共振器を共に用い、かつ、上記１端子対弾性
表面波共振器と上記２端子対弾性表面波共振器とを、入
力端子と出力端子に対して対称に接続したことを特徴と
するものである。A surface acoustic wave filter according to a second aspect of the present invention electrically connects a plurality of surface acoustic wave resonators, and the surface acoustic wave resonator includes a one-terminal-pair surface acoustic wave resonator and a two-terminal-pair elastic surface. A surface acoustic wave resonator is used together, and the one-terminal-pair surface acoustic wave resonator and the two-terminal-pair surface acoustic wave resonator are connected symmetrically with respect to an input terminal and an output terminal. Is.

【００１６】請求項３の発明に係る弾性表面波フィルタ
は、弾性表面波共振器を複数個電気的に接続し、上記弾
性表面波共振器に１端子対弾性表面波共振器と２端子対
弾性表面波共振器を共に用い、かつ上記２端子対弾性表
面波共振器は３個以上のすだれ状電極を有することを特
徴とするものである。In a surface acoustic wave filter according to a third aspect of the present invention, a plurality of surface acoustic wave resonators are electrically connected, and the surface acoustic wave resonator has a one-terminal-pair surface acoustic wave resonator and a two-terminal-pair elastic surface. The surface acoustic wave resonator is used together, and the two-terminal pair surface acoustic wave resonator has three or more interdigital electrodes.

【００１７】請求項４の発明に係る弾性表面波フィルタ
は、１端子対弾性表面波共振器と、弾性表面波を励振す
るすだれ状電極とを梯子形に接続したことを特徴とする
ものである。A surface acoustic wave filter according to a fourth aspect of the present invention is characterized in that a one-terminal-pair surface acoustic wave resonator and a interdigital transducer for exciting a surface acoustic wave are connected in a ladder shape. .

【００１８】請求項５の発明に係る弾性表面波フィルタ
は、１端子対弾性表面波共振器と、弾性表面波を励振す
るすだれ状電極とを梯子形に接続し、上記すだれ状電極
の一部をキャパシタに置き換えたことを特徴とするもの
である。A surface acoustic wave filter according to a fifth aspect of the present invention connects a one-terminal-pair surface acoustic wave resonator and a comb-shaped electrode that excites a surface acoustic wave in a ladder shape, and forms a part of the comb-shaped electrode. Is replaced with a capacitor.

【００１９】請求項６の発明に係る弾性表面波フィルタ
は、直列腕の構成要素および並列腕の構成要素として１
端子対弾性表面波共振器を用い、上記直列腕の１端子対
弾性表面波共振器と上記並列腕の１端子対弾性表面波共
振器とを梯子形に接続し、上記１端子対弾性表面波共振
器のうち少なくとも１つは、すだれ状電極と反射器とを
有し、かつ、上記すだれ状電極の電極指配列周期と上記
反射器の格子配列周期が異なることを特徴とするもので
ある。A surface acoustic wave filter according to a sixth aspect of the present invention comprises a series arm and a parallel arm as a constituent element and a parallel arm, respectively.
Using the terminal pair surface acoustic wave resonator, the one terminal pair surface acoustic wave resonator of the series arm and the one terminal pair surface acoustic wave resonator of the parallel arm are connected in a ladder shape, and the one terminal pair surface acoustic wave is connected. At least one of the resonators has a comb-shaped electrode and a reflector, and the electrode finger arrangement period of the comb-shaped electrode is different from the grating arrangement period of the reflector.

【００２０】請求項７の発明に係る弾性表面波フィルタ
は、直列腕の構成要素および並列腕の構成要素として、
すだれ状電極と反射器とを有する１端子対弾性表面波共
振器を用い、上記直列腕の１端子対弾性表面波共振器と
上記並列腕の１端子対弾性表面波共振器とを梯子形に接
続し、上記直列腕の１端子対弾性表面波共振器の、上記
直列腕のすだれ状電極の電極指配列周期および上記反射
器の格子配列周期をそれぞれＬｉｓ、Ｌｒｓとし、上記
並列腕の１端子対弾性表面波共振器の、上記すだれ状電
極の電極指配列周期および上記反射器の格子配列周期を
それぞれＬｉｐ、Ｌｒｐとしたとき、Ｌｉｓ／Ｌｒｓ
＜ Ｌｉｐ／Ｌｒｐとしたことを特徴とするものであ
る。A surface acoustic wave filter according to a seventh aspect of the present invention includes: a constituent element of a series arm and a constituent element of a parallel arm,
A one-terminal pair surface acoustic wave resonator having a comb-shaped electrode and a reflector is used, and the one-terminal pair surface acoustic wave resonator of the series arm and the one-terminal pair surface acoustic wave resonator of the parallel arm are formed in a ladder shape. 1 terminal of the series arm pair, and the electrode finger array period of the interdigital electrode of the series arm and the grating array period of the reflector of the surface acoustic wave resonator are set to Lis and Lrs, respectively, and 1 terminal of the parallel arm is connected. When the electrode finger arrangement period of the interdigital transducer and the grating arrangement period of the reflector of the surface acoustic wave resonator are Lip and Lrp, respectively, Lis / Lrs
<Lip / Lrp.

【００２１】請求項８の発明に係る弾性表面波フィルタ
は、直列腕の構成要素および並列腕の構成要素として１
端子対弾性表面波共振器を用い、上記直列腕の１端子対
弾性表面波共振器と上記並列腕の１端子対弾性表面波共
振器とを梯子形に接続し、上記直列腕の１端子対弾性表
面波共振器のうち少なくとも１つは、他の上記直列腕の
１端子対弾性表面波共振器と、共振周波数が異なること
を特徴とするものである。The surface acoustic wave filter according to the eighth aspect of the present invention is characterized in that the constituent elements of the series arm and the parallel arm are 1
Using the terminal pair surface acoustic wave resonator, the one-terminal pair surface acoustic wave resonator of the series arm and the one-terminal pair surface acoustic wave resonator of the parallel arm are connected in a ladder shape, and the one-terminal pair of the series arm is connected. At least one of the surface acoustic wave resonators has a resonance frequency different from that of the other one-terminal pair surface acoustic wave resonator of the series arm.

【００２２】請求項９の発明に係る弾性表面波フィルタ
は、直列腕の構成要素および並列腕の構成要素として１
端子対弾性表面波共振器を用い、上記直列腕の１端子対
弾性表面波共振器と上記並列腕の１端子対弾性表面波共
振器とを梯子形に接続し、上記並列腕の１端子対弾性表
面波共振器のうち少なくとも１つは、他の上記並列腕の
１端子対弾性表面波共振器と、反共振周波数が異なるこ
とを特徴とするものである。A surface acoustic wave filter according to a ninth aspect of the present invention is characterized in that the constituent elements of the series arm and the parallel arm are 1
A terminal pair surface acoustic wave resonator is used, and the one-terminal pair surface acoustic wave resonator of the series arm and the one-terminal pair surface acoustic wave resonator of the parallel arm are connected in a ladder shape to form one terminal pair of the parallel arm. At least one of the surface acoustic wave resonators is characterized by having an antiresonance frequency different from that of the other one-terminal pair surface acoustic wave resonator of the parallel arm.

【００２３】請求項１０の発明に係る弾性表面波フィル
タは、直列腕の構成要素および並列腕の構成要素として
１端子対弾性表面波共振器を用い、上記直列腕の１端子
対弾性表面波共振器と上記並列腕の１端子対弾性表面波
共振器とを梯子形に接続し、上記直列腕の１端子対弾性
表面波共振器を複数個有し、上記複数個の直列腕の１端
子対弾性表面波共振器のうち少なくとも２つを隣接して
配置したことを特徴とするものである。A surface acoustic wave filter according to a tenth aspect of the present invention uses a one-terminal-pair surface acoustic wave resonator as a constituent element of a series arm and a constituent element of a parallel arm, and the one-terminal pair surface acoustic wave resonance of the series arm. And a parallel arm one-terminal pair surface acoustic wave resonator are connected in a ladder shape, and a plurality of series-arm one-terminal pair surface acoustic wave resonators are provided, and the plurality of series-arm one-terminal pair. It is characterized in that at least two of the surface acoustic wave resonators are arranged adjacent to each other.

【００２４】請求項１１の発明に係る弾性表面波フィル
タは、直列腕の構成要素および並列腕の構成要素として
１端子対弾性表面波共振器を用い、上記直列腕の１端子
対弾性表面波共振器と上記並列腕の１端子対弾性表面波
共振器とを梯子形に接続し、かつ、インダクタを接続し
たことを特徴とするものである。A surface acoustic wave filter according to an eleventh aspect of the present invention uses a one-terminal-pair surface acoustic wave resonator as a constituent element of a series arm and a constituent element of a parallel arm, and the one-terminal pair surface acoustic wave resonance of the series arm. And a one-terminal pair surface acoustic wave resonator of the parallel arm are connected in a ladder shape, and an inductor is connected.

【００２５】[0025]

【作用】請求項１の発明によれば、１端子対弾性表面波
共振器と２端子対弾性表面波共振器を共に用いて弾性表
面波フィルタを構成したので、２端子対弾性表面波共振
器のスプリアスを１端子対弾性表面波共振器の減衰極で
打ち消すことができ、低損失で帯域外減衰量の大きい弾
性表面波フィルタが得られる。According to the first aspect of the present invention, since the surface acoustic wave filter is constructed by using the one-terminal-pair surface acoustic wave resonator and the two-terminal-pair surface acoustic wave resonator together, the two-terminal-pair surface acoustic wave resonator. Can be canceled by the attenuation pole of the one-terminal-pair surface acoustic wave resonator, and a surface acoustic wave filter with low loss and large out-of-band attenuation can be obtained.

【００２６】請求項２の発明によれば、１端子対弾性表
面波共振器と上記２端子対弾性表面波共振器とを、入力
端子と出力端子に対して対称に接続したので、入力端子
と出力端子のインピーダンスを等しくすることができ、
外部回路との整合がとりやすく、低損失な弾性表面波フ
ィルタが得られる。According to the second aspect of the invention, the one-terminal-pair surface acoustic wave resonator and the two-terminal-pair surface acoustic wave resonator are connected symmetrically with respect to the input terminal and the output terminal. The impedance of the output terminals can be made equal,
A low-loss surface acoustic wave filter can be obtained which is easily matched with an external circuit.

【００２７】請求項３の発明によれば、３個以上のすだ
れ状電極を有する２端子対弾性表面波共振器を用いたの
で、通過帯域の広い弾性表面波フィルタが得られる。According to the third aspect of the invention, since the two-terminal pair surface acoustic wave resonator having three or more interdigital electrodes is used, a surface acoustic wave filter having a wide pass band can be obtained.

【００２８】請求項４および請求項５の発明によれば、
１端子対弾性表面波共振器と、弾性表面波を励振するす
だれ状電極とを梯子形に接続したので、帯域外の特定の
周波数で入力信号を弾性表面波に変換でき、この周波数
で帯域外減衰量の大きい弾性表面波フィルタが得られ
る。According to the inventions of claims 4 and 5,
Since the one-terminal pair surface acoustic wave resonator and the interdigital transducer that excites the surface acoustic wave are connected in a ladder shape, the input signal can be converted into a surface acoustic wave at a specific frequency outside the band, and at this frequency the band outside the band can be converted. A surface acoustic wave filter having a large amount of attenuation can be obtained.

【００２９】請求項６の発明によれば、１端子対弾性表
面波共振器を梯子形に接続した弾性表面波フィルタの、
上記１端子対弾性表面波共振器のすだれ状電極の電極指
配列周期と反射器の格子配列周期を異ならせたので、反
射器のストップバンドを有効に利用でき、挿入損失が小
さく通過帯域の広い弾性表面波フィルタが得られる。According to a sixth aspect of the present invention, there is provided a surface acoustic wave filter having a one-terminal-pair surface acoustic wave resonator connected in a ladder shape.
Since the electrode finger arrangement period of the interdigital transducer and the grating lattice period of the reflector of the 1-terminal pair surface acoustic wave resonator are made different, the stop band of the reflector can be effectively used, the insertion loss is small, and the pass band is wide. A surface acoustic wave filter is obtained.

【００３０】請求項７の発明によれば、直列腕と並列腕
の１端子対弾性表面波共振器にそれぞれの、すだれ状電
極の電極指配列周期と反射器の格子配列周期を所定の関
係が満たされるようにしたので、反射器のストップバン
ドをさらに有効に利用でき、通過帯域のさらに広い弾性
表面波フィルタが得られる。According to the seventh aspect of the present invention, the electrode finger arrangement period of the interdigital electrode and the grating arrangement period of the reflector of the one-terminal pair surface acoustic wave resonator of the series arm and the parallel arm have a predetermined relationship. Since it is satisfied, the stop band of the reflector can be used more effectively, and a surface acoustic wave filter having a wider pass band can be obtained.

【００３１】請求項８の発明によれば、直列腕の１端子
対弾性表面波共振器のうち少なくとも１の共振周波数を
他と異ならせたので、所要の帯域内通過特性を有する弾
性表面波フィルタが得られる。According to the invention of claim 8, the resonance frequency of at least one of the one-terminal-pair surface acoustic wave resonators of the series arm is made different from the others, so that the surface acoustic wave filter having a required in-band pass characteristic. Is obtained.

【００３２】請求項９の発明によれば、並列腕の１端子
対弾性表面波共振器のうち少なくとも１つの反共振周波
数を他と異ならせたので、所要の帯域内通過特性を有す
る弾性表面波フィルタが得られる。According to the ninth aspect of the present invention, since the antiresonance frequency of at least one of the one-terminal pair surface acoustic wave resonators of the parallel arm is made different from the others, the surface acoustic wave having a required in-band pass characteristic. A filter is obtained.

【００３３】請求項１０の発明によれば、複数個の直列
腕の１端子対弾性表面波共振器を隣接して配置したの
で、入出力端子間の線路等を短くでき、挿入損失の小さ
い弾性表面波フィルタが得られる。According to the tenth aspect of the present invention, the surface-acoustic-wave resonator having a pair of one-armed series arms is arranged adjacent to each other, so that the line between the input and output terminals can be shortened and the insertion loss is small. A surface wave filter is obtained.

【００３４】請求項１１の発明によれば、１端子対弾性
表面波共振器を梯子形に接続し、さらに、インダクタを
接続したので、通過帯域幅が広く、帯域外減衰量の大き
い弾性表面波フィルタが得られる。According to the eleventh aspect of the present invention, since the one-terminal pair surface acoustic wave resonators are connected in a ladder shape and further the inductor is connected, the surface acoustic waves having a wide pass band width and a large out-of-band attenuation amount. A filter is obtained.

【００３５】[0035]

【実施例】実施例１ この発明の一実施例の構成を図１を参照しながら説明す
る。図１は、この発明の実施例１を示す構成図である。
図１において、１は圧電体基板、２はすだれ状電極、３
は反射器、４は１端子対弾性表面波共振器、５は２端子
対弾性表面波共振器、６は入力端子、７は出力端子であ
る。図において、圧電体基板１上に、１つのすだれ状電
極２からなる１端子対弾性表面共振器４と、２つのすだ
れ状電極２からなる２端子対弾性表面波共振器５とを配
置し、上記１端子対弾性表面波共振器４と、上記２端子
対弾性表面波共振器５とを電気的に接続している。Embodiment 1 The construction of an embodiment of the present invention will be described with reference to FIG. First Embodiment FIG. 1 is a configuration diagram showing a first embodiment of the present invention.
In FIG. 1, 1 is a piezoelectric substrate, 2 is a comb-shaped electrode, and 3
Is a reflector, 4 is a one-terminal-pair surface acoustic wave resonator, 5 is a two-terminal-pair surface acoustic wave resonator, 6 is an input terminal, and 7 is an output terminal. In the figure, on a piezoelectric substrate 1, a one-terminal pair surface acoustic resonator 4 composed of one interdigital electrode 2 and a two terminal pair surface acoustic wave resonator 5 composed of two interdigital electrodes 2 are arranged. The 1-terminal pair surface acoustic wave resonator 4 and the 2-terminal pair surface acoustic wave resonator 5 are electrically connected.

【００３６】次に、動作について説明する。図１におけ
る１端子対弾性表面波共振器４は、図１８に用いている
ものと同様に、図２０に示したようなインピーダンス特
性を有している。すなわち、共振周波数ｆｒでインピー
ダンスは零となり、反共振周波数ｆａでインピーダンス
は無限大となる。したがって１端子対弾性表面波共振器
４を図２のように直列に接続して２端子対回路とすれ
ば、入力端子６に入力した電気信号は、共振周波数ｆｒ
ではすべて出力端子７に通過し、反共振周波数ｆａでは
全く通過せず減衰極が生じる。したがって、図３（ａ）
のような通過特性を示す。Next, the operation will be described. The one-terminal pair surface acoustic wave resonator 4 in FIG. 1 has the impedance characteristic as shown in FIG. 20, like the one used in FIG. That is, the impedance becomes zero at the resonance frequency fr and becomes infinite at the anti-resonance frequency fa. Therefore, if the one-terminal pair surface acoustic wave resonator 4 is connected in series as shown in FIG. 2 to form a two-terminal pair circuit, the electric signal input to the input terminal 6 will have a resonance frequency fr.
All pass through to the output terminal 7, and do not pass at all at the anti-resonance frequency fa, resulting in an attenuation pole. Therefore, FIG.
Shows a passage characteristic like.

【００３７】一方、図１における２端子対弾性表面波共
振器５は、図２３と同様に、図３（ｂ）に示すような通
過特性となり、通過帯域の高域側近傍ｆｓにスプリアス
が生じる。On the other hand, the two-terminal pair surface acoustic wave resonator 5 shown in FIG. 1 has a pass characteristic as shown in FIG. 3 (b) as in FIG. 23, and spurious is generated near the high frequency side fs of the pass band. .

【００３８】しかし、図１においては、上記１端子対弾
性表面波共振器４と、上記２端子対弾性表面波共振器５
とを縦続接続した構成となっている。さらに、図１で
は、図３（ａ）の減衰極ｆａと、図３（ｂ）のスプリア
スが生じる周波数ｆｓが、ほぼ等しくなるように、上記
１端子対弾性表面波共振器４と、上記２端子対弾性表面
波共振器５を構成している。したがって、全体の通過特
性は、図３（ｃ）に示すようになり、上記２端子対弾性
表面波共振器５のスプリアスが、上記１端子対弾性表面
波共振器４の減衰極によって打ち消され、帯域外減衰量
を大きくできる。However, in FIG. 1, the one-terminal pair surface acoustic wave resonator 4 and the two-terminal pair surface acoustic wave resonator 5 are shown.
It has a configuration in which and are connected in cascade. Further, in FIG. 1, the 1-terminal-pair surface acoustic wave resonator 4 and the 2 above-mentioned 2 are arranged so that the attenuation pole fa of FIG. 3A and the frequency fs of FIG. The terminal pair surface acoustic wave resonator 5 is configured. Therefore, the overall pass characteristic is as shown in FIG. 3C, and the spurious of the two-terminal pair surface acoustic wave resonator 5 is canceled by the attenuation pole of the one-terminal pair surface acoustic wave resonator 4. Out-of-band attenuation can be increased.

【００３９】さらにこのとき、２端子対弾性表面波共振
器５の通過帯域と、１端子対弾性表面波共振器４の共振
周波数ｆｒとはほぼ等しくできるので、２端子対弾性表
面波共振器５単体の挿入損失に対して、１端子対弾性表
面波共振器４を接続したことによる挿入損失の増加は小
さい。したがって、２端子対弾性表面波共振器５を多段
に接続した場合に比べ、挿入損失を小さくできる。以上
のように、この発明の実施例１によれば、低損失で帯域
外減衰量の大きい弾性表面波フィルタが得られる。Further, at this time, since the pass band of the two-terminal pair surface acoustic wave resonator 5 and the resonance frequency fr of the one-terminal pair surface acoustic wave resonator 4 can be made substantially equal, the two-terminal pair surface acoustic wave resonator 5 is formed. The increase in insertion loss due to the connection of the one-terminal surface acoustic wave resonator 4 is small with respect to the insertion loss of a single unit. Therefore, the insertion loss can be reduced as compared with the case where the two-terminal pair surface acoustic wave resonators 5 are connected in multiple stages. As described above, according to the first embodiment of the present invention, a surface acoustic wave filter having a low loss and a large out-of-band attenuation can be obtained.

【００４０】実施例２ 図４は、この発明の実施例２を示す構成図である。図４
において、１から７は図１と同様のものである。図にお
いて、圧電体基板１上に、２端子対弾性表面波共振器５
を配置し、その両側に１端子対弾性表面波共振器４を１
つずつ配置し、上記２つの１端子対弾性表面波共振器４
と上記２端子対弾性表面波共振器５とを、入力端子６と
出力端子７に対して対称となるように電気的に接続して
いる。Second Embodiment FIG. 4 is a block diagram showing a second embodiment of the present invention. Figure 4
In, 1 to 7 are the same as those in FIG. In the figure, on the piezoelectric substrate 1, a two-terminal pair surface acoustic wave resonator 5 is provided.
And a 1-terminal pair surface acoustic wave resonator 4 on each side of the
They are arranged one by one, and the above two 1-terminal pair surface acoustic wave resonators 4 are arranged.
And the two-terminal SAW resonator 5 are electrically connected so as to be symmetrical with respect to the input terminal 6 and the output terminal 7.

【００４１】次に、動作について説明する。図４におけ
る１端子対弾性表面波共振器４と２端子対弾性表面波共
振器５の動作は、それぞれ、実施例１の場合と同様であ
る。しかし、図４では、図１と異なり、１端子対弾性表
面波共振器４を２つ用いているため、図３（ａ）におけ
る減衰極の効果が大きくなり、帯域外減衰量をより大き
くできる。Next, the operation will be described. The operations of the one-terminal pair surface acoustic wave resonator 4 and the two-terminal pair surface acoustic wave resonator 5 in FIG. 4 are the same as in the case of the first embodiment. However, unlike FIG. 1, in FIG. 4, since two one-terminal-pair surface acoustic wave resonators 4 are used, the effect of the attenuation pole in FIG. 3A becomes large, and the out-of-band attenuation amount can be made larger. .

【００４２】さらに、図４においては、弾性表面波フィ
ルタの構成が、入力端子６と出力端子７に対して対称な
構成となっている。したがって、入力端子６からみた入
力インピーダンスと出力端子７からみた入力インピーダ
ンスが、互いに等しくなっている。弾性表面波フィルタ
の入力端子６と出力端子７のそれぞれに接続される外部
回路のインピーダンスは、通常同一であるから、図４の
構成では外部回路とのインピーダンス整合が容易にな
る。したがって、フィルタの不整合損失や、外部整合回
路による損失が少なくなり、低損失な弾性表面波フィル
タが得られる。Further, in FIG. 4, the structure of the surface acoustic wave filter is symmetrical with respect to the input terminal 6 and the output terminal 7. Therefore, the input impedance seen from the input terminal 6 and the input impedance seen from the output terminal 7 are equal to each other. Since the impedance of the external circuit connected to each of the input terminal 6 and the output terminal 7 of the surface acoustic wave filter is usually the same, impedance matching with the external circuit becomes easy in the configuration of FIG. Therefore, the mismatch loss of the filter and the loss due to the external matching circuit are reduced, and a low-loss surface acoustic wave filter can be obtained.

【００４３】実施例３ 図５は、この発明の実施例３を示す構成図である。図５
において、１から７は図１と同様のものである。図にお
いて、圧電体基板１上に、２端子対弾性表面波共振器５
を配置し、その両側に１端子対弾性表面波共振器４を２
つ配置し、上記２つの１端子対弾性表面波共振器４と上
記２端子対弾性表面波共振器５とを電気的に接続してい
る。さらに、２端子対弾性表面波共振器５として、すだ
れ状電極２を３個用いた、いわゆる３電極形を用いてい
る。Third Embodiment FIG. 5 is a block diagram showing a third embodiment of the present invention. Figure 5
In, 1 to 7 are the same as those in FIG. In the figure, on the piezoelectric substrate 1, a two-terminal pair surface acoustic wave resonator 5
Are arranged, and two 1-terminal surface acoustic wave resonators 4 are arranged on both sides of
The two one-terminal-pair surface acoustic wave resonators 4 and the two-terminal-pair surface acoustic wave resonators 5 are electrically connected. Further, as the two-terminal surface acoustic wave resonator 5, a so-called three-electrode type using three interdigital electrodes 2 is used.

【００４４】次に、動作について説明する。図５におけ
る１端子対弾性表面波共振器４と２端子対弾性表面波共
振器５の動作は、それぞれ、実施例１、実施例２の場合
と同様である。しかし、図５では、２端子対弾性表面波
共振器５のすだれ状電極２が３個あり、中央のすだれ状
電極２を入力側とし、両端のすだれ状電極２を接続して
出力側としている。図６は、図５における２端子対弾性
表面波共振器５の共振周波数における振幅分布を示した
ものである。図中に実線で示す０次対称モードと、破線
で示す２次対称モードとが生じ、図２４に示した反対称
モードは励振されない。このときも図２３の場合と同
様、０次対称モードと２次対称モードの共振周波数の差
を所要の値にすれば、バンドパス特性を有する２重モー
ドフィルタが得られる。Next, the operation will be described. The operations of the one-terminal-pair surface acoustic wave resonator 4 and the two-terminal-pair surface acoustic wave resonator 5 in FIG. 5 are the same as those in the first and second embodiments, respectively. However, in FIG. 5, there are three interdigital electrodes 2 of the two-terminal surface acoustic wave resonator 5, the central interdigital electrode 2 is the input side, and the interdigital electrodes 2 at both ends are connected to be the output side. . FIG. 6 shows an amplitude distribution at the resonance frequency of the two-terminal pair surface acoustic wave resonator 5 in FIG. A 0th-order symmetric mode shown by a solid line and a 2nd-order symmetric mode shown by a broken line occur in the figure, and the antisymmetric mode shown in FIG. 24 is not excited. Also at this time, as in the case of FIG. 23, if the difference between the resonance frequencies of the 0th-order symmetric mode and the 2nd-order symmetric mode is set to a required value, a dual-mode filter having bandpass characteristics can be obtained.

【００４５】しかも、図６の０次対称モードと２次対称
モードの共振周波数の差は、図２４の対称モードと反対
称モードの共振周波数の差よりも大きくできるので、図
５における３電極形の２端子対弾性表面波共振器５の方
が、図２３における２電極形の２端子対弾性表面波共振
器５よりも通過帯域を広くできる。したがって、実施例
３では、実施例１よりもさらに通過帯域の広い弾性表面
波フィルタが得られる効果がある。Moreover, the difference between the resonance frequencies of the 0th-order symmetric mode and the 2nd-order symmetric mode in FIG. 6 can be made larger than the difference between the resonance frequencies of the symmetric mode and the antisymmetric mode in FIG. 24. The two-terminal pair surface acoustic wave resonator 5 can have a wider pass band than the two-electrode type two-terminal pair surface acoustic wave resonator 5 in FIG. Therefore, the third embodiment has the effect of obtaining a surface acoustic wave filter having a wider pass band than the first embodiment.

【００４６】以上の実施例１から３においては、１端子
対弾性表面波共振器４と２端子対弾性表面波共振器５と
を同一の圧電体基板１上に配置した場合を示したが、本
発明はこれに限らず、１端子対弾性表面波共振器４と２
端子対弾性表面波共振器５とを別々の圧電体基板１上に
配置してもよく、このとき異なる種類の圧電体基板１を
用いてもよい。また、１端子対弾性表面波共振器４の数
や２端子対弾性表面波共振器５の数は、以上の実施例に
示したものとは限らない。一般に、１端子対弾性表面波
共振器４や２端子対弾性表面波共振器５を多数縦続接続
すれば、接続する数を増やすと帯域外減衰量は大きくな
り、挿入損失は増加する。したがって、帯域外減衰量や
挿入損失の所要値に応じて、接続数を任意に選択してよ
い。In the above Examples 1 to 3, the case where the one-terminal-pair surface acoustic wave resonator 4 and the two-terminal-pair surface acoustic wave resonator 5 are arranged on the same piezoelectric substrate 1 is shown. The present invention is not limited to this, and the one-terminal pair surface acoustic wave resonators 4 and 2 are connected.
The terminal-paired surface acoustic wave resonator 5 may be arranged on different piezoelectric substrate 1, and at this time, different types of piezoelectric substrate 1 may be used. Further, the number of 1-terminal pair surface acoustic wave resonators 4 and the number of 2-terminal pair surface acoustic wave resonators 5 are not limited to those shown in the above embodiments. Generally, if a large number of one-terminal-pair surface acoustic wave resonators 4 and two-terminal-pair surface acoustic wave resonators 5 are connected in cascade, the out-of-band attenuation increases and the insertion loss increases as the number of connections increases. Therefore, the number of connections may be arbitrarily selected according to the required values of the out-of-band attenuation and the insertion loss.

【００４７】さらに、以上の実施例１から３において
は、１端子対弾性表面波共振器４や２端子対弾性表面波
共振器５として反射器３を有するものを用いているが、
これに限らず、反射器３を有さずすだれ状電極２自体の
共振のみを利用した弾性表面波共振器を用いてもよい。Furthermore, in the above-mentioned Examples 1 to 3, the one-terminal pair surface acoustic wave resonator 4 and the two-terminal pair surface acoustic wave resonator 5 having the reflector 3 are used.
The present invention is not limited to this, and a surface acoustic wave resonator that does not have the reflector 3 but uses only the resonance of the interdigital transducer 2 itself may be used.

【００４８】実施例４ 図７は、この発明の実施例４を示す構成図である。図７
において、１は圧電体基板、２はすだれ状電極、３は反
射器、４は１端子対弾性表面波共振器、６は入力端子、
７は出力端子である。図において、圧電体基板１上に、
１端子対弾性表面波共振器４と、すだれ状電極２を配置
し、これらを電気的に接続し、逆Ｌ形回路を構成してい
る。Fourth Embodiment FIG. 7 is a configuration diagram showing a fourth embodiment of the present invention. Figure 7
In FIG. 1, 1 is a piezoelectric substrate, 2 is a comb-shaped electrode, 3 is a reflector, 4 is a one-terminal-pair surface acoustic wave resonator, 6 is an input terminal,
Reference numeral 7 is an output terminal. In the figure, on the piezoelectric substrate 1,
The 1-terminal pair surface acoustic wave resonator 4 and the interdigital transducer 2 are arranged and electrically connected to each other to form an inverted L-shaped circuit.

【００４９】次に、動作について説明する。図８は、こ
の発明の実施例４の動作を説明するための図であり、８
はキャパシタである。図８において、入力端子６と出力
端子７との間に、１端子対弾性表面波共振器４を直列
に、キャパシタ８を並列に、それぞれ挿入している。１
端子対弾性表面波共振器４は、前述したように、図２０
のようなインピーダンス特性を有しているので、共振周
波数ｆｒと反共振周波数ｆａとの間で誘導性インピーダ
ンスとなる。このとき、キャパシタ８は容量性のインピ
ーダンスであるので、図８の回路は、伝送回路理論で良
く知られている定Ｋ形フィルタと同様の低損失なバンド
パスフィルタが得られる。ただし、１端子対弾性表面波
共振器４の反共振周波数ｆａでは、減衰極が生じるの
で、通過特性は図９の実線に示すように通過帯域の高域
側に減衰極を有する特性となる。Next, the operation will be described. FIG. 8 is a diagram for explaining the operation of the fourth embodiment of the present invention.
Is a capacitor. In FIG. 8, the one-terminal pair surface acoustic wave resonator 4 is inserted in series and the capacitor 8 is inserted in parallel between the input terminal 6 and the output terminal 7. 1
As described above, the terminal-paired surface acoustic wave resonator 4 has the structure shown in FIG.
Since it has such impedance characteristics, it becomes an inductive impedance between the resonance frequency fr and the anti-resonance frequency fa. At this time, since the capacitor 8 has a capacitive impedance, the circuit of FIG. 8 can provide a low-loss bandpass filter similar to the constant K filter well known in the transmission circuit theory. However, at the anti-resonance frequency fa of the one-terminal-pair surface acoustic wave resonator 4, since an attenuation pole occurs, the pass characteristic becomes a characteristic having an attenuation pole on the high frequency side of the pass band as shown by the solid line in FIG.

【００５０】図７では、図８のキャパシタ８を、すだれ
状電極２で置き換えた構成となっている。すだれ状電極
２のインピーダンスは、弾性表面波を励振する周波数以
外の周波数では、キャパシタ８と同様の容量性の特性を
示す。したがって、図７に示す弾性表面波フィルタは、
すだれ状電極２が弾性表面波を励振する周波数以外の周
波数では、図８に示したフィルタと同様の特性を示す。
したがって、通過帯域特性も図８と同様に低損失にでき
る。しかし、すだれ状電極２が弾性表面波を励振する周
波数では、すだれ状電極２に入力した電気信号は弾性表
面波に変換され、電力の損失が生じる。したがって、図
９の破線に示すように、すだれ状電極２が弾性表面波を
励振する周波数ｆｉで、入力信号の電力が損失を受け、
出力信号の電力が小さくなる。したがって、周波数ｆｉ
で通過特性の減衰量が大きくすることができる。このと
き、弾性表面波が励振される周波数ｆｉは、すだれ状電
極２の電極指配列周期を変えることにより自由に変える
ことができるから、帯域外の任意の周波数で減衰量を大
きくすることができる。In FIG. 7, the capacitor 8 of FIG. 8 is replaced by the interdigital electrode 2. The impedance of the interdigital transducer 2 exhibits the same capacitive characteristic as the capacitor 8 at frequencies other than the frequency at which the surface acoustic wave is excited. Therefore, the surface acoustic wave filter shown in FIG.
At frequencies other than the frequency at which the interdigital transducer 2 excites the surface acoustic wave, the characteristics similar to those of the filter shown in FIG. 8 are exhibited.
Therefore, the pass band characteristic can be reduced as in the case of FIG. However, at the frequency at which the interdigital transducer 2 excites the surface acoustic wave, the electric signal input to the interdigital electrode 2 is converted into the surface acoustic wave, and power loss occurs. Therefore, as shown by the broken line in FIG. 9, the power of the input signal is lost at the frequency fi at which the interdigital transducer 2 excites the surface acoustic wave,
The power of the output signal is reduced. Therefore, the frequency fi
Thus, the attenuation amount of the pass characteristic can be increased. At this time, the frequency fi at which the surface acoustic wave is excited can be freely changed by changing the electrode finger arrangement period of the interdigital electrode 2, so that the attenuation amount can be increased at any frequency outside the band. .

【００５１】実施例５ 図１０は、この発明の実施例５を示す構成図である。図
１０において、１から７は図７と同様のものである。図
において、圧電体基板１上に、２つの１端子対弾性表面
波共振器４と、すだれ状電極２を配置し、これらを電気
的に接続し、Ｔ形回路を構成している。Fifth Embodiment FIG. 10 is a configuration diagram showing a fifth embodiment of the present invention. In FIG. 10, 1 to 7 are the same as those in FIG. In the figure, two 1-terminal-pair surface acoustic wave resonators 4 and interdigital transducers 2 are arranged on a piezoelectric substrate 1 and are electrically connected to form a T-shaped circuit.

【００５２】次に、動作について説明する。図１０の構
成は、図７に示した弾性表面波フィルタを２個、出力端
子７どうしで接続し、中央にできる２個並列に並んだす
だれ状電極２を１つにまとめたものである。したがっ
て、図７と同様のバンドパスフィルタとして動作する。
しかも、図７よりもフィルタの段数が増える分、帯域外
減衰量を大きくでき、急峻なフィルタ特性が得られる。
この場合も、すだれ状電極２から弾性表面波が励振され
る周波数を変えることにより帯域外の任意の周波数で減
衰量をさらに大きくすることができる。Next, the operation will be described. The configuration of FIG. 10 is one in which two surface acoustic wave filters shown in FIG. 7 are connected by the output terminals 7, and two interdigital electrodes 2 arranged in parallel at the center are combined into one. Therefore, it operates as a bandpass filter similar to that in FIG.
Moreover, since the number of filter stages is larger than that in FIG. 7, the amount of out-of-band attenuation can be increased and a steep filter characteristic can be obtained.
Also in this case, the attenuation amount can be further increased at an arbitrary frequency outside the band by changing the frequency at which the surface acoustic wave is excited from the interdigital transducer 2.

【００５３】実施例６ 図１１は、この発明の実施例６を示す構成図である。図
１１において、１から７は図７と同様のものである。図
において、圧電体基板１上に、１端子対弾性表面波共振
器４と、すだれ状電極２を配置し、これらを電気的に接
続し、逆Ｌ形回路を構成している。しかし、図１１で
は、図７と異なり、入力端子６と出力端子７との間に、
すだれ状電極２を直列に、１端子対弾性表面波共振器４
を並列に、それぞれ挿入している。Sixth Embodiment FIG. 11 is a block diagram showing a sixth embodiment of the present invention. 11, 1 to 7 are the same as those in FIG. In the figure, a one-terminal pair surface acoustic wave resonator 4 and a comb-shaped electrode 2 are arranged on a piezoelectric substrate 1 and are electrically connected to each other to form an inverted L-shaped circuit. However, unlike FIG. 7, in FIG. 11, between the input terminal 6 and the output terminal 7,
The interdigital transducer 2 is connected in series to the one-terminal surface acoustic wave resonator 4
Are inserted in parallel.

【００５４】図１１も、図７と同様にバンドパスフィル
タとして動作する。この場合は、１端子対弾性表面波共
振器４の共振周波数ｆｒで減衰極が生じるので、通過特
性は通過帯域の低域側に減衰極を有する特性となる。し
かし、図１１も図７と同様にすだれ状電極２から弾性表
面波が励振される周波数を変えることにより、帯域外の
任意の周波数で減衰量をさらに大きくすることができる
ことはいうまでもない。Similarly to FIG. 7, FIG. 11 also operates as a bandpass filter. In this case, since an attenuation pole is generated at the resonance frequency fr of the one-terminal pair surface acoustic wave resonator 4, the pass characteristic is a characteristic having an attenuation pole on the low frequency side of the pass band. However, in FIG. 11 as well, it is needless to say that the attenuation amount can be further increased at an arbitrary frequency outside the band by changing the frequency at which the surface acoustic wave is excited from the interdigital transducer 2 as in FIG. 7.

【００５５】実施例７ 図１２は、この発明の実施例７を示す構成図である。図
１２において、１から７は図７と同様のものである。図
において、圧電体基板１上に、２つのすだれ状電極２
と、１端子対弾性表面波共振器４を配置し、これらを電
気的に接続し、Ｔ形回路を構成している。Seventh Embodiment FIG. 12 is a configuration diagram showing a seventh embodiment of the present invention. 12, 1 to 7 are the same as those in FIG. In the figure, two interdigital electrodes 2 are provided on a piezoelectric substrate 1.
A 1-terminal pair surface acoustic wave resonator 4 is arranged and electrically connected to form a T-type circuit.

【００５６】図１２の構成は、図１１に示した弾性表面
波フィルタを２個、出力端子どうしで接続し、中央にで
きる２個並列に並んだ１端子対弾性表面波共振器を１つ
にまとめたものである。したがって、図１１と同様のバ
ンドパスフィルタとして動作し、図１１よりも急峻なフ
ィルタ特性が得られる。この場合も、すだれ状電極２か
ら弾性表面波が励振される周波数を変えることにより帯
域外の任意の周波数で減衰量をさらに大きくすることが
できる。さらに、上下２つのすだれ状電極２について、
弾性表面波が励振される周波数を、それぞれ異ならせる
ことにより、異なる２つの帯域で減衰量を大きくするこ
とができる効果がある。In the configuration of FIG. 12, two surface acoustic wave filters shown in FIG. 11 are connected to each other at their output terminals to form two centrally arranged one-terminal pair surface acoustic wave resonators. It is a summary. Therefore, it operates as a bandpass filter similar to that of FIG. 11, and a sharper filter characteristic than that of FIG. 11 is obtained. Also in this case, the attenuation amount can be further increased at an arbitrary frequency outside the band by changing the frequency at which the surface acoustic wave is excited from the interdigital transducer 2. Furthermore, regarding the upper and lower two interdigital electrodes 2,
By differentiating the frequencies at which the surface acoustic waves are excited, it is possible to increase the amount of attenuation in two different bands.

【００５７】以上の実施例４から７においては、弾性表
面波フィルタの回路構成を、逆Ｌ形やＴ形としたものに
ついて示したが、本発明はこれに限らず、π形の回路構
成としてもよく、より段数を増やしてもよい。さらに、
すだれ状電極２の変わりに、キャパシタ８を一部残して
いても構わない。また、多数のすだれ状電極２がある場
合、これらから弾性表面波が励振される周波数は、個別
に変えてもよいし、同一のものがあってもよい。In the above fourth to seventh embodiments, the circuit configuration of the surface acoustic wave filter is shown as an inverted L type or a T type, but the present invention is not limited to this, and a π type circuit configuration is possible. Also, the number of stages may be increased. further,
Instead of the interdigital electrode 2, a part of the capacitor 8 may be left. In addition, when there are a large number of interdigital electrodes 2, the frequencies at which surface acoustic waves are excited from these electrodes may be individually changed or may be the same.

【００５８】また、以上の実施例４から７においては、
１端子対弾性表面波共振器４とすだれ状電極２とを同一
の圧電体基板１上に配置した場合を示したが、本発明は
これに限らず、１端子対弾性表面波共振器４とすだれ状
電極２とを別々の圧電体基板１上に配置してもよく、こ
のとき異なる種類の圧電体基板１を用いてもよい。Further, in the above fourth to seventh embodiments,
Although the case where the one-terminal pair surface acoustic wave resonator 4 and the interdigital transducer 2 are arranged on the same piezoelectric substrate 1 is shown, the present invention is not limited to this, and the one-terminal pair surface acoustic wave resonator 4 and The interdigital transducer 2 and the interdigital electrodes 2 may be arranged on different piezoelectric substrates 1, and different types of piezoelectric substrates 1 may be used at this time.

【００５９】実施例８ 図１３は、この発明の実施例８を示す構成図である。図
１３において、１は圧電体基板、２はすだれ状電極、３
は反射器、４ａ、４ｂは１端子対弾性表面波共振器、６
は入力端子、７は出力端子である。図において、圧電体
基板１上に、１端子対弾性表面波共振器４を複数個配置
し、これらを電気的に接続して梯子形回路を構成してい
る。また、直列腕の１端子対弾性表面波共振器４ａにお
いて、すだれ状電極２の電極指配列周期（以下、すだれ
状電極２のピッチという）Ｌｉｓと、反射器３の格子配
列周期（以下、反射器３のピッチという）Ｌｒｓとを異
ならせ、Ｌｉｓ＜Ｌｒｓとしている。Eighth Embodiment FIG. 13 is a block diagram showing the eighth embodiment of the present invention. In FIG. 13, 1 is a piezoelectric substrate, 2 is a comb-like electrode, and 3 is
Is a reflector, 4a and 4b are 1-terminal-pair surface acoustic wave resonators, 6
Is an input terminal, and 7 is an output terminal. In the figure, a plurality of one-terminal-pair surface acoustic wave resonators 4 are arranged on a piezoelectric substrate 1 and are electrically connected to form a ladder circuit. Further, in the one-terminal pair surface acoustic wave resonator 4a of the series arm, the electrode finger arrangement period Lis of the interdigital electrode 2 (hereinafter referred to as the pitch of the interdigital electrode 2) Lis and the lattice arrangement period of the reflector 3 (hereinafter referred to as reflection) Lrs (which is referred to as the pitch of the container 3) is made different, and Lis <Lrs.

【００６０】次に、動作について説明する。図１３にお
いて、直列腕の１端子対弾性表面波共振器４ａの共振周
波数ｆｒと並列腕の１端子対弾性表面波共振器４ｂの反
共振周波数ｆａとをほぼ一致させ、バンドパスフィルタ
として動作させている。これは、図１８に示した従来の
弾性表面波フィルタと同様である。したがって、直列腕
の１端子対弾性表面波共振器４ａの共振周波数ｆｒは、
フィルタの中心周波数となる。Next, the operation will be described. In FIG. 13, the resonance frequency fr of the one-terminal pair surface acoustic wave resonator 4a of the series arm and the anti-resonance frequency fa of the one-terminal pair surface acoustic wave resonator 4b of the parallel arm are made to substantially coincide with each other to operate as a bandpass filter. ing. This is similar to the conventional surface acoustic wave filter shown in FIG. Therefore, the resonance frequency fr of the one-terminal surface acoustic wave resonator 4a of the series arm is
It becomes the center frequency of the filter.

【００６１】図１４は、図１９に示したものと同様の１
端子対弾性表面波共振器４において、反射器３のピッチ
Ｌｒを一定としたまま、すだれ状電極２のピッチＬｉの
みを変化させたときの、共振周波数ｆｒと反共振周波数
ｆａの変化を等価回路モデルを用いて計算したものであ
る。横軸はＬｉ／Ｌｒとしているので、Ｌｉ／Ｌｒが１
のとき、すだれ状電極２と反射器３のピッチが等しくな
る。すだれ状電極２のピッチＬｉを変えても、すだれ状
電極２と反射器３の間の距離は一定としている。図か
ら、すだれ状電極２のピッチＬｉを変えたとき、共振周
波数ｆｒと反共振周波数ｆａがともに変化し、共振周波
数ｆｒと反共振周波数ｆａとの周波数差は余り変化しな
いことが分かった。FIG. 14 shows a circuit similar to that shown in FIG.
In the terminal-paired surface acoustic wave resonator 4, an equivalent circuit is used for changing the resonance frequency fr and the anti-resonance frequency fa when only the pitch Li of the interdigital electrode 2 is changed while keeping the pitch Lr of the reflector 3 constant. It is calculated using a model. Since the horizontal axis is Li / Lr, Li / Lr is 1
At this time, the pitch between the interdigital transducer 2 and the reflector 3 becomes equal. Even if the pitch Li of the interdigital electrode 2 is changed, the distance between the interdigital electrode 2 and the reflector 3 is constant. From the figure, it was found that when the pitch Li of the interdigital electrode 2 was changed, both the resonance frequency fr and the anti-resonance frequency fa changed, and the frequency difference between the resonance frequency fr and the anti-resonance frequency fa did not change so much.

【００６２】図１４中点線で示しているのは、反射器３
のストップバンドの下限周波数および上限周波数であ
る。すだれ状電極２と反射器３のピッチが等しいとき、
共振周波数ｆｒは、反射器３のストップバンドの下限周
波数にほぼ等しくなっている。したがって、共振周波数
ｆｒより少しでも低い周波数では、反射器３のストップ
バンドから外れてしまうため、反射器３の反射効率が小
さくなる。The dotted line in FIG. 14 indicates the reflector 3
Is the lower limit frequency and the upper limit frequency of the stop band. When the pitches of the interdigital transducer 2 and the reflector 3 are equal,
The resonance frequency fr is substantially equal to the lower limit frequency of the stop band of the reflector 3. Therefore, at a frequency even lower than the resonance frequency fr, the frequency is out of the stop band of the reflector 3, so that the reflection efficiency of the reflector 3 becomes small.

【００６３】図１３では、直列腕の１端子対弾性表面波
共振器４ａにおいて、すだれ状電極２のピッチＬｉｓ
と、反射器３のピッチＬｒｓとを異ならせ、Ｌｉｓ＜Ｌ
ｒｓとしている。このため、図１４から分かるように、
共振周波数ｆｒは反射器３のストップバンドの下限周波
数よりも高くなる。このとき、共振周波数ｆｒより少し
低い周波数でもストップバンドに含まれるので、大きい
反射効率が得られる。In FIG. 13, the pitch Lis of the interdigital electrodes 2 in the one-terminal-pair surface acoustic wave resonator 4a of the series arm.
And the pitch Lrs of the reflector 3 are made different, and Lis <L
rs. Therefore, as can be seen from FIG.
The resonance frequency fr becomes higher than the lower limit frequency of the stop band of the reflector 3. At this time, even a frequency slightly lower than the resonance frequency fr is included in the stop band, so that a high reflection efficiency can be obtained.

【００６４】前にも述べたように、直列腕の１端子対弾
性表面波共振器４ａの共振周波数ｆｒは、フィルタの中
心周波数となっている。よって、すだれ状電極２と反射
器３のピッチを図１３のように変えることにより、フィ
ルタの中心周波数より低い周波数での反射器３の反射効
率低下による損失を小さくでき、通過帯域でのフィルタ
の挿入損失を小さくできる。また直列腕と並列腕の反射
器３のストップバンドが重なり合う周波数幅を広くでき
るので、フィルタの通過帯域をより広帯域にできる。As described above, the resonance frequency fr of the one-terminal pair surface acoustic wave resonator 4a of the series arm is the center frequency of the filter. Therefore, by changing the pitch between the interdigital electrode 2 and the reflector 3 as shown in FIG. 13, it is possible to reduce the loss due to the reduction of the reflection efficiency of the reflector 3 at a frequency lower than the center frequency of the filter, and to reduce the loss of the filter in the pass band. Insertion loss can be reduced. In addition, since the frequency width in which the stop bands of the reflectors 3 of the series arm and the parallel arm overlap can be widened, the pass band of the filter can be made wider.

【００６５】実施例９ 図１５は、この発明の実施例９を示す構成図である。図
１５において、１から４および６、７は、図１３と同様
のものである。図において、圧電体基板１上に、１端子
対弾性表面波共振器４を複数個配置し、これらを電気的
に接続して梯子形回路を構成している。また、図に示す
ように、直列腕の１端子対弾性表面波共振器４ａのすだ
れ状電極２および反射器３のピッチを、それぞれＬｉ
ｓ、Ｌｒｓとし、並列腕の１端子対弾性表面波共振器４
ｂのすだれ状電極２および反射器３のピッチを、それぞ
れＬｉｐ、Ｌｒｐとしたとき、Ｌｉｓ／Ｌｒｓ＜１と
し、かつ、Ｌｉｐ／Ｌｒｐ＞１となるようにしている。
このとき、Ｌｉｓ／Ｌｒｓ ＜Ｌｉｐ／Ｌｒｐが成り立
っている。Embodiment 9 FIG. 15 is a block diagram showing Embodiment 9 of the present invention. In FIG. 15, 1 to 4 and 6, 7 are the same as those in FIG. In the figure, a plurality of one-terminal-pair surface acoustic wave resonators 4 are arranged on a piezoelectric substrate 1 and are electrically connected to form a ladder circuit. In addition, as shown in the figure, the pitch of the interdigital transducer 2 and the reflector 3 of the one-terminal surface acoustic wave resonator 4a of the series arm is set to Li.
s, Lrs, 1 terminal pair surface acoustic wave resonator 4 in parallel arm
When the pitches of the interdigital transducer 2 and the reflector 3 of b are Lip and Lrp, respectively, Lis / Lrs <1 and Lip / Lrp> 1.
At this time, Lis / Lrs <Lip / Lrp holds.

【００６６】実施例９の動作は、実施例８と同様であ
る。しかし、実施例９では、並列腕の１端子対弾性表面
波共振器４ｂにおいても、すだれ状電極２のピッチＬｉ
ｐと反射器３のピッチＬｒｐとを異ならせ、Ｌｉｐ／Ｌ
ｒｐ＞１としている。このとき、図１４から分かるよう
に、ピッチが等しい場合に比べ、反共振周波数ｆａを反
射器３のストップバンドの中心周波数に、より近付ける
ことができる。したがって、反共振周波数ｆａより高い
周波数で、反射器３のストップバンドに含まれる周波数
幅がより広くなる。The operation of the ninth embodiment is similar to that of the eighth embodiment. However, in the ninth embodiment, the pitch Li of the interdigital electrodes 2 is also in the one-terminal surface acoustic wave resonator 4b of the parallel arm.
p and the pitch Lrp of the reflector 3 are made different, and Lip / L
rp> 1. At this time, as can be seen from FIG. 14, the anti-resonance frequency fa can be brought closer to the center frequency of the stop band of the reflector 3 as compared with the case where the pitches are equal. Therefore, the frequency width included in the stop band of the reflector 3 becomes wider at a frequency higher than the anti-resonance frequency fa.

【００６７】並列腕の１端子対弾性表面波共振器４ｂの
反共振周波数ｆａも、フィルタの中心周波数となってい
るので、図１５では、フィルタの中心周波数より高い周
波数で反射器３の反射効率が低下しない周波数幅を広げ
ることができ、直列腕と並列腕の反射器３のストップバ
ンドが重なり合う周波数幅をより広くできるので、フィ
ルタの通過帯域を図１３以上に広帯域にできる。Since the anti-resonance frequency fa of the one-terminal surface acoustic wave resonator 4b of the parallel arm is also the center frequency of the filter, the reflection efficiency of the reflector 3 is higher than the center frequency of the filter in FIG. Can be widened, and the frequency band in which the stop bands of the reflectors 3 in the series arm and the parallel arm overlap can be further widened, so that the pass band of the filter can be made wider than that in FIG.

【００６８】なお、図１５では、直列腕の１端子対弾性
表面波共振器４ａが２個あり、これらの交差幅を互いに
異ならせている。このように１端子対弾性表面波共振器
４の交差幅は、それぞれ変化してもよい。同様に、直列
腕の１端子対弾性表面波共振器４ａが３個以上ある場合
にも、それぞれの交差幅を変化してよく、変化のしかた
は種々考えられる。これは、並列腕の１端子対弾性表面
波共振器４ｂに関しても同様である。Note that, in FIG. 15, there are two one-terminal surface acoustic wave resonators 4a of the series arm, and the cross widths thereof are different from each other. In this way, the cross width of the one-terminal pair surface acoustic wave resonator 4 may be changed. Similarly, even when there are three or more one-terminal surface acoustic wave resonators 4a in the series arm, the cross widths of the three terminals may be changed, and various changes can be considered. This also applies to the one-terminal pair surface acoustic wave resonator 4b of the parallel arm.

【００６９】このとき、直列腕の１端子対弾性表面波共
振器４ａや並列腕の１端子対弾性表面波共振器４ｂの交
差幅を変化させ、交差幅を所要の値にすることにより、
フィルタの帯域通過特性を、伝送回路理論で知られてい
る振幅平坦特性、振幅波状特性（チェビシェフ特性）、
遅延平坦特性などの種々の特性に近似することができ、
任意の特性を得ることができる。At this time, the cross width of the one-terminal pair surface acoustic wave resonator 4a of the series arm and the one-terminal pair surface acoustic wave resonator 4b of the parallel arm is changed so that the cross width becomes a required value.
The band pass characteristic of the filter is the amplitude flat characteristic, the amplitude wavy characteristic (Chebyshev characteristic), which is known in the transmission circuit theory,
Can be approximated to various characteristics such as delay flatness characteristics,
Arbitrary characteristics can be obtained.

【００７０】さらに、図１５では明示していないが、複
数の直列腕の１端子対弾性表面波共振器４ａの共振周波
数ｆｒを全く等しくする必要はなく、それぞれ変えても
よい。これは、前述したように、すだれ状電極２のピッ
チＬｉや、反射器３のピッチＬｒ、さらにこれらの比Ｌ
ｉ／Ｌｒなどを変化することにより容易に実現できる。
また、並列腕の１端子対弾性表面波共振器４ｂの反共振
周波数ｆａに関しても、それらをそれぞれ変えてもよ
い。この場合にも、共振周波数ｆｒや反共振周波数ｆａ
を所要の値にすることにより、フィルタの帯域通過特性
を種々の特性に近似することができる。Further, although not explicitly shown in FIG. 15, it is not necessary to make the resonance frequencies fr of the one-terminal-pair surface acoustic wave resonators 4a of the plurality of series arms equal, and they may be changed. As described above, this is because the pitch Li of the interdigital electrode 2, the pitch Lr of the reflector 3, and the ratio L of these.
It can be easily realized by changing i / Lr and the like.
Further, the anti-resonance frequency fa of the one-terminal pair surface acoustic wave resonator 4b of the parallel arm may be changed. Also in this case, the resonance frequency fr and the anti-resonance frequency fa
The band pass characteristic of the filter can be approximated to various characteristics by setting to a required value.

【００７１】実施例１０ 図１６は、この発明の実施例１０を示す構成図である。
図１６において、１から４および６、７は、図１３と同
様のものである。図１３と同様に、圧電体基板１上に、
１端子対弾性表面波共振器４を複数個配置し、これらを
電気的に接続して梯子形回路を構成している。また、図
１３では、５個の１端子対弾性表面波共振器４のうち、
直列腕の１端子対弾性表面波共振器４ａが３個あり、こ
れら直列腕の１端子対弾性表面波共振器４ａ３つを隣接
して配置している。Embodiment 10 FIG. 16 is a block diagram showing Embodiment 10 of the present invention.
In FIG. 16, 1 to 4 and 6, 7 are the same as those in FIG. Similar to FIG. 13, on the piezoelectric substrate 1,
A plurality of one-terminal surface acoustic wave resonators 4 are arranged and electrically connected to each other to form a ladder circuit. In addition, in FIG. 13, among the five 1-terminal-pair surface acoustic wave resonators 4,
There are three one-terminal-pair surface acoustic wave resonators 4a of the series arm, and these three one-terminal-pair surface acoustic wave resonators 4a of the series arm are arranged adjacent to each other.

【００７２】実施例１０の動作も、実施例８および実施
例９と同様である。しかし、実施例１０では、直列腕の
１端子対弾性表面波共振器４ａを３つ隣接して配置する
ことにより、同数の直列腕の１端子対弾性表面波共振器
４ａおよび並列腕の１端子対弾性表面波共振器４ｂを互
い違いに配置した場合に比べ、入力端子６と出力端子７
の間の距離を短くできる。したがって、直列腕の１端子
対弾性表面波共振器４ａどうしを接続するワイヤあるい
は線路の長さを短くでき、これらの抵抗成分の影響を少
なくできるため、挿入損失の小さい弾性表面波フィルタ
が得られる。The operation of the tenth embodiment is similar to that of the eighth and ninth embodiments. However, in the tenth embodiment, by arranging three one-terminal-pair surface acoustic wave resonators 4a of the series arm adjacent to each other, the same number of one-terminal-pair surface acoustic wave resonators 4a and one terminal of the parallel arm are arranged. Compared to the case where the surface acoustic wave resonators 4b are arranged alternately, the input terminal 6 and the output terminal 7 are
The distance between can be shortened. Therefore, the length of the wire or line connecting the one-terminal surface acoustic wave resonators 4a of the series arm can be shortened, and the influence of these resistance components can be reduced, so that a surface acoustic wave filter with a small insertion loss can be obtained. .

【００７３】このとき、逆に、並列腕の１端子対弾性表
面波共振器４ｂを接続するワイヤあるいは線路の長さは
長くなり、抵抗成分が増えてしまう。しかし、フィルタ
の通過域ではもともと並列腕のインピーダンスがほぼ無
限大と大きくなっているので、抵抗成分が増えても、フ
ィルタの挿入損失はほとんど変わらず、低損失の特性が
得られる。At this time, conversely, the length of the wire or line connecting the one-terminal pair surface acoustic wave resonator 4b of the parallel arm becomes long, and the resistance component increases. However, since the impedance of the parallel arm is essentially infinite in the pass band of the filter, even if the resistance component increases, the insertion loss of the filter remains almost unchanged and low loss characteristics are obtained.

【００７４】以上の実施例８から１０においては、１端
子対弾性表面波共振器４を同一の圧電体基板１上に配置
した場合を示したが、本発明はこれに限らず、１端子対
弾性表面波共振器４とすだれ状電極２とを別々の圧電体
基板１上に配置してもよく、このとき異なる種類の圧電
体基板１を用いてもよい。また、１端子対弾性表面波共
振器４ａ、４ｂの数は、以上の実施例に示したものとは
限らず、帯域外減衰量や挿入損失の所要値に応じて任意
に選択してよい。In the above-mentioned Embodiments 8 to 10, the case where the one-terminal-pair surface acoustic wave resonator 4 is arranged on the same piezoelectric substrate 1 is shown. However, the present invention is not limited to this, and one-terminal-pair. The surface acoustic wave resonator 4 and the interdigital transducer 2 may be arranged on different piezoelectric substrates 1, and at this time, different types of piezoelectric substrates 1 may be used. Further, the number of the one-terminal pair surface acoustic wave resonators 4a and 4b is not limited to that shown in the above embodiment, and may be arbitrarily selected according to the required values of the out-of-band attenuation amount and the insertion loss.

【００７５】実施例１１ 図１７は、この発明の実施例１１を示す構成図である。
図１７において、４ａ、４ｂ、６、７は、図１８や図１
３などと同様のものであり、９はインダクタである。図
１３と同様に、直列腕の１端子対弾性表面波共振器４ａ
と並列腕の１端子対弾性表面波共振器４ｂを、入力端子
６と出力端子７の間に、複数個梯子形に接続している。
しかし、図１７では図１３と異なり、インダクタ９を１
端子対弾性表面波共振器４に対して直列あるいは並列に
接続している。さらにインダクタ９を、複数個の１端子
対弾性表面波共振器４にまたがって接続している。Eleventh Embodiment FIG. 17 is a block diagram showing the eleventh embodiment of the present invention.
In FIG. 17, 4a, 4b, 6, and 7 are the same as those in FIG.
The same as 3 and the like, and 9 is an inductor. Similar to FIG. 13, one terminal of the serial arm paired with the surface acoustic wave resonator 4a.
A plurality of one-terminal surface acoustic wave resonators 4b of the parallel arm are connected between the input terminal 6 and the output terminal 7 in a ladder shape.
However, unlike FIG. 13, in FIG.
The terminals are connected in series or in parallel with the surface acoustic wave resonator 4. Further, the inductor 9 is connected across the plurality of one-terminal-pair surface acoustic wave resonators 4.

【００７６】実施例１１の動作も、実施例８から実施例
１０と同様であり、低損失なバンドパスフィルタとして
動作する。しかし、実施例１１では、インダクタ９を１
端子対弾性表面波共振器４に対して、例えば、直列に接
続している。このとき、１端子対弾性表面波共振器４と
インダクタ９とを合わせたインピーダンス特性を考える
と、図２０に示した１端子対弾性表面波共振器４単独の
インピーダンスに対して、インダクタ９を接続した分イ
ンピーダンスの虚部が全体に大きくなる。よって、反共
振周波数ｆａは変わらないが共振周波数ｆｒが低くな
り、ｆｒとｆａとの周波数差が大きくなる。また、イン
ダクタ９を並列に接続した場合には、インダクタ９を接
続した分インピーダンスの逆数の虚部が全体に小さくな
る。このときは、共振周波数ｆｒは変わらないが反共振
周波数ｆａが高くなり、やはり、ｆｒとｆａとの周波数
差が大きくなる。The operation of the eleventh embodiment is similar to that of the eighth to tenth embodiments and operates as a low-loss bandpass filter. However, in the eleventh embodiment, the inductor 9 is set to 1
The terminals are connected in series to the surface acoustic wave resonator 4, for example. At this time, considering the impedance characteristics of the 1-terminal-pair surface acoustic wave resonator 4 and the inductor 9, the inductor 9 is connected to the impedance of the 1-terminal-pair surface acoustic wave resonator 4 alone shown in FIG. As a result, the imaginary part of the impedance becomes large as a whole. Therefore, the anti-resonance frequency fa does not change, but the resonance frequency fr decreases, and the frequency difference between fr and fa increases. Further, when the inductors 9 are connected in parallel, the imaginary part of the reciprocal of the impedance is reduced as a whole because the inductors 9 are connected. At this time, the resonance frequency fr does not change, but the anti-resonance frequency fa increases, and the frequency difference between fr and fa also increases.

【００７７】このように、インダクタ９を接続すること
により、１端子対弾性表面波共振器４の共振周波数ｆｒ
と反共振周波数ｆａとの周波数差を、見掛上大きくでき
る。したがって、図２１に示したフィルタの通過特性に
おいて、２つの減衰極の周波数間隔を広くすることがで
き、通過帯域幅の広い弾性表面波フィルタが得られる。By connecting the inductor 9 in this way, the resonance frequency fr of the one-terminal-pair surface acoustic wave resonator 4 is set.
The frequency difference between the antiresonance frequency fa and the anti-resonance frequency fa can be apparently increased. Therefore, in the pass characteristic of the filter shown in FIG. 21, the frequency interval between the two attenuation poles can be widened, and a surface acoustic wave filter having a wide pass bandwidth can be obtained.

【００７８】さらに、実施例１１では、インダクタ９を
複数個の１端子対弾性表面波共振器４にまたがって接続
している。すでに述べたように、フィルタの通過帯域か
ら離れた周波数では、１端子対弾性表面波共振器４は容
量性のインピーダンス特性を示す。よって、誘導性のイ
ンピーダンスを有するインダクタ９を接続することによ
り、帯域外での通過信号を互いに打ち消すことができ、
通過特性に減衰極を作ることができる。したがって、帯
域外減衰量の大きい弾性表面波フィルタが得られる。Further, in the eleventh embodiment, the inductor 9 is connected across the plurality of one-terminal pair surface acoustic wave resonators 4. As described above, at frequencies away from the pass band of the filter, the one-terminal pair surface acoustic wave resonator 4 exhibits a capacitive impedance characteristic. Therefore, by connecting the inductor 9 having an inductive impedance, it is possible to cancel out the pass signals outside the band,
An attenuation pole can be created in the pass characteristic. Therefore, a surface acoustic wave filter with large out-of-band attenuation can be obtained.

【００７９】実施例１１において、インダクタ９は図１
７に示した全てのものを用いる必要はなく、少なくとも
１つのインダクタ９を接続することによって、本発明の
効果が得られる。インダクタ９の構造はどのようなもの
でもよく、例えば、１端子対弾性表面波共振器４と同一
の圧電体基板１上に形成してもよいし、金属ワイヤなど
で構成してもよい。１端子対弾性表面波共振器４をパッ
ケージに封入する場合には、インダクタ９を同一パッケ
ージに収めてもよいし、インダクタ９を外部に設けて接
続してもよい。さらに、インダクタ９の接続方法は図１
７に示したものに限らず、種々の方法を用いることがで
きる。In Example 11, the inductor 9 is shown in FIG.
It is not necessary to use all the elements shown in FIG. 7, and the effect of the present invention can be obtained by connecting at least one inductor 9. The inductor 9 may have any structure, for example, it may be formed on the same piezoelectric substrate 1 as the one-terminal-pair surface acoustic wave resonator 4 or may be composed of a metal wire or the like. When the 1-terminal pair surface acoustic wave resonator 4 is enclosed in a package, the inductor 9 may be housed in the same package, or the inductor 9 may be provided outside and connected. Furthermore, the method for connecting the inductor 9 is shown in FIG.
Not limited to the one shown in FIG. 7, various methods can be used.

【００８０】以上の実施例１から１１において、圧電体
基板１の材料は単結晶でも他の基板に圧電薄膜を形成し
たものでもよく、弾性表面波を励振するものであれば何
を用いても構わない。また、弾性表面波はレイリー波と
は限らず、いわゆる擬似弾性表面波などの表面波を利用
しても差し支えない。さらに、以上の実施例において、
回路素子として用いている１端子対弾性表面波共振器４
やすだれ状電極２の代わりに、同一または異なる２つ以
上の１端子対弾性表面波共振器４やすだれ状電極２を直
列あるいは並列に接続したものを用いてもよく、この場
合にも本発明の効果が得られる。In Examples 1 to 11 above, the material of the piezoelectric substrate 1 may be a single crystal or another substrate on which a piezoelectric thin film is formed, and any material can be used as long as it can excite surface acoustic waves. I do not care. The surface acoustic waves are not limited to Rayleigh waves, and surface waves such as so-called pseudo surface acoustic waves may be used. Furthermore, in the above embodiment,
1-terminal pair surface acoustic wave resonator 4 used as a circuit element
Instead of the serpentine electrode 2, two or more one-terminal-pair surface acoustic wave resonators 4 which are the same or different from each other may be connected in series or in parallel, and in this case also, the present invention The effect of is obtained.

【００８１】[0081]

【発明の効果】請求項１の発明によれば、１端子対弾性
表面波共振器と２端子対弾性表面波共振器を共に用いて
弾性表面波フィルタを構成したので、２端子対弾性表面
波共振器のスプリアスを１端子対弾性表面波共振器の減
衰極で打ち消すことができ、低損失で帯域外減衰量の大
きい弾性表面波フィルタが得られる効果がある。According to the invention of claim 1, since the surface acoustic wave filter is constructed by using both the one-terminal-pair surface acoustic wave resonator and the two-terminal-pair surface acoustic wave resonator, the two-terminal-pair surface acoustic wave is formed. The spurious of the resonator can be canceled by the attenuation pole of the one-terminal-pair surface acoustic wave resonator, and there is an effect that a surface acoustic wave filter with low loss and large out-of-band attenuation can be obtained.

【００８２】請求項２の発明によれば、１端子対弾性表
面波共振器と上記２端子対弾性表面波共振器とを、入力
端子と出力端子に対して対称に接続したので、入力端子
と出力端子のインピーダンスを等しくすることができ、
外部回路との整合がとりやすく、低損失な弾性表面波フ
ィルタが得られる効果がある。According to the second aspect of the present invention, the one-terminal pair surface acoustic wave resonator and the two-terminal pair surface acoustic wave resonator are connected symmetrically with respect to the input terminal and the output terminal. The impedance of the output terminals can be made equal,
There is an effect that it is easy to obtain matching with an external circuit and a low-loss surface acoustic wave filter can be obtained.

【００８３】請求項３の発明によれば、３個以上のすだ
れ状電極を有する２端子対弾性表面波共振器を用いたの
で、通過帯域の広い弾性表面波フィルタが得られる効果
がある。According to the third aspect of the invention, since the two-terminal pair surface acoustic wave resonator having three or more interdigital electrodes is used, there is an effect that a surface acoustic wave filter having a wide pass band can be obtained.

【００８４】請求項４および請求項５の発明によれば、
１端子対弾性表面波共振器と、弾性表面波を励振するす
だれ状電極とを梯子形に接続したので、帯域外の特定の
周波数で入力信号を弾性表面波に変換でき、この周波数
で帯域外減衰量の大きい弾性表面波フィルタが得られる
効果がある。According to the inventions of claims 4 and 5,
Since the one-terminal pair surface acoustic wave resonator and the interdigital transducer that excites the surface acoustic wave are connected in a ladder shape, the input signal can be converted into a surface acoustic wave at a specific frequency outside the band, and at this frequency the band outside the band can be converted. There is an effect that a surface acoustic wave filter having a large amount of attenuation can be obtained.

【００８５】請求項６の発明によれば、１端子対弾性表
面波共振器を梯子形に接続した弾性表面波フィルタの、
上記１端子対弾性表面波共振器のすだれ状電極の電極指
配列周期と反射器の格子配列周期を異ならせたので、反
射器のストップバンドを有効に利用でき、挿入損失が小
さく通過帯域の広い弾性表面波フィルタが得られる効果
がある。According to the sixth aspect of the present invention, there is provided a surface acoustic wave filter comprising a one-terminal-pair surface acoustic wave resonator connected in a ladder shape.
Since the electrode finger arrangement period of the interdigital transducer and the grating lattice period of the reflector of the 1-terminal pair surface acoustic wave resonator are made different, the stop band of the reflector can be effectively used, the insertion loss is small, and the pass band is wide. There is an effect that a surface acoustic wave filter can be obtained.

【００８６】請求項７の発明によれば、直列腕と並列腕
の１端子対弾性表面波共振器にそれぞれの、すだれ状電
極の電極指配列周期と反射器の格子配列周期を所定の関
係が満たされるようにしたので、反射器のストップバン
ドをさらに有効に利用でき、通過帯域のさらに広い弾性
表面波フィルタが得られる効果がある。According to the seventh aspect of the present invention, the electrode finger arrangement period of the interdigital electrodes and the grating arrangement period of the reflector of the one-terminal pair surface acoustic wave resonator of the series arm and the parallel arm have a predetermined relationship. Since this is satisfied, the stop band of the reflector can be used more effectively, and a surface acoustic wave filter having a wider pass band can be obtained.

【００８７】請求項８の発明によれば、直列腕の１端子
対弾性表面波共振器のうち少なくとも１つの共振周波数
を他と異ならせたので、所要の帯域内通過特性を有する
弾性表面波フィルタが得られる。According to the invention of claim 8, the resonance frequency of at least one of the one-terminal pair surface acoustic wave resonators of the series arm is made different from the others, so that the surface acoustic wave filter having a required in-band pass characteristic. Is obtained.

【００８８】請求項９の発明によれば、並列腕の１端子
対弾性表面波共振器のうち少なくとも１つの反共振周波
数を他と異ならせたので、所要の帯域内通過特性を有す
る弾性表面波フィルタが得られる。According to the invention of claim 9, the antiresonance frequency of at least one of the one-terminal surface acoustic wave resonators of the parallel arm is made different from the other, so that the surface acoustic wave having a required in-band pass characteristic is obtained. A filter is obtained.

【００８９】請求項１０の発明によれば、複数個の直列
腕の１端子対弾性表面波共振器を隣接して配置したの
で、入出力端子間の線路等を短くでき、挿入損失の小さ
い弾性表面波フィルタが得られる効果がある。According to the tenth aspect of the invention, since the surface-acoustic-wave resonators having a pair of terminals of one series arm are arranged adjacent to each other, the line between the input and output terminals can be shortened and the insertion loss is small. The surface wave filter is effective.

【００９０】請求項１１の発明によれば、１端子対弾性
表面波共振器を梯子形に接続し、さらに、インダクタを
接続したので、通過帯域幅が広く、帯域外減衰量の大き
い弾性表面波フィルタが得られる。According to the eleventh aspect of the present invention, since the one-terminal paired surface acoustic wave resonators are connected in a ladder shape and further the inductor is connected, the surface acoustic waves having a wide pass band width and a large out-of-band attenuation amount. A filter is obtained.

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

【図１】この発明の実施例１を示す構成図である。FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

【図２】この発明の実施例１の動作を説明するための図
である。FIG. 2 is a diagram for explaining the operation of the first embodiment of the present invention.

【図３】この発明の実施例１の動作を説明するための図
である。FIG. 3 is a diagram for explaining the operation of the first embodiment of the present invention.

【図４】この発明の実施例２を示す構成図である。FIG. 4 is a configuration diagram showing a second embodiment of the present invention.

【図５】この発明の実施例３を示す構成図である。FIG. 5 is a configuration diagram showing a third embodiment of the present invention.

【図６】この発明の実施例３の動作を説明するための図
である。FIG. 6 is a diagram for explaining the operation of the third embodiment of the present invention.

【図７】この発明の実施例４を示す構成図である。FIG. 7 is a configuration diagram showing a fourth embodiment of the present invention.

【図８】この発明の実施例４の動作を説明するための図
である。FIG. 8 is a diagram for explaining the operation of the fourth embodiment of the present invention.

【図９】この発明の実施例４の動作を説明するための図
である。FIG. 9 is a diagram for explaining the operation of the fourth embodiment of the present invention.

【図１０】この発明の実施例５を示す構成図である。FIG. 10 is a configuration diagram showing a fifth embodiment of the present invention.

【図１１】この発明の実施例６を示す構成図である。FIG. 11 is a configuration diagram showing a sixth embodiment of the present invention.

【図１２】この発明の実施例７を示す構成図である。FIG. 12 is a configuration diagram showing a seventh embodiment of the present invention.

【図１３】この発明の実施例８を示す構成図である。FIG. 13 is a configuration diagram showing an eighth embodiment of the present invention.

【図１４】この発明の実施例８の動作を説明するための
図である。FIG. 14 is a diagram for explaining the operation of the eighth embodiment of the present invention.

【図１５】この発明の実施例９を示す構成図である。FIG. 15 is a configuration diagram showing a ninth embodiment of the present invention.

【図１６】この発明の実施例１０を示す構成図である。FIG. 16 is a configuration diagram showing an embodiment 10 of the present invention.

【図１７】この発明の実施例１１を示す構成図である。FIG. 17 is a configuration diagram showing an eleventh embodiment of the present invention.

【図１８】従来の弾性表面波フィルタを示す構成図であ
る。FIG. 18 is a configuration diagram showing a conventional surface acoustic wave filter.

【図１９】従来の弾性表面波フィルタの動作を説明する
ための図である。FIG. 19 is a diagram for explaining the operation of the conventional surface acoustic wave filter.

【図２０】従来の弾性表面波フィルタの動作を説明する
ための図である。FIG. 20 is a diagram for explaining the operation of the conventional surface acoustic wave filter.

【図２１】従来の弾性表面波フィルタの動作を説明する
ための図である。FIG. 21 is a diagram for explaining the operation of the conventional surface acoustic wave filter.

【図２２】従来の弾性表面波フィルタの動作を説明する
ための図である。FIG. 22 is a diagram for explaining the operation of the conventional surface acoustic wave filter.

【図２３】従来の弾性表面波フィルタを示す構成図であ
る。FIG. 23 is a configuration diagram showing a conventional surface acoustic wave filter.

【図２４】従来の弾性表面波フィルタの動作を説明する
ための図である。FIG. 24 is a diagram for explaining the operation of the conventional surface acoustic wave filter.

【図２５】従来の弾性表面波フィルタの動作を説明する
ための図である。FIG. 25 is a diagram for explaining the operation of the conventional surface acoustic wave filter.

【符号の説明】[Explanation of symbols]

１ 圧電体基板 ２ すだれ状電極 ３ 反射器 ４ １端子対弾性表面波共振器 ５ ２端子対弾性表面波共振器 ６ 入力端子 ７ 出力端子 ８ キャパシタ ９ インダクタ 1 Piezoelectric Substrate 2 Interdigital Electrode 3 Reflector 4 1 Terminal Pair Surface Acoustic Wave Resonator 5 2 Terminal Pair Surface Acoustic Wave Resonator 6 Input Terminal 7 Output Terminal 8 Capacitor 9 Inductor

─────────────────────────────────────────────────────
─────────────────────────────────────────────────── ───

【手続補正書】[Procedure amendment]

【提出日】平成５年７月１日[Submission date] July 1, 1993

【手続補正１】[Procedure Amendment 1]

【補正対象書類名】明細書[Document name to be amended] Statement

【補正対象項目名】請求項５[Name of item to be corrected] Claim 5

【補正方法】変更[Correction method] Change

【補正内容】[Correction content]

【手続補正２】[Procedure Amendment 2]

【補正対象書類名】明細書[Document name to be amended] Statement

【補正対象項目名】０００２[Name of item to be corrected] 0002

【補正方法】変更[Correction method] Change

【補正内容】[Correction content]

【０００２】[0002]

【従来の技術】図１８は、例えば文献「電子情報通信学
会技術研究報告（超音波）」、ＵＳ９２−５２、ｐｐ．
９−１６に示された、従来のこの種の弾性表面波フィル
タの構成を示したものである。図１８において、４ａ、
４ｂは１端子対弾性表面波共振器、６は入力端子、７は
出力端子である。図において、直列腕に挿入した１端子
対弾性表面波共振器４ａと並列腕に挿入した１端子対弾
性表面波共振器４ｂを、入力端子６と出力端子７の間
に、複数個梯子形に接続している。図１８における１端
子対弾性表面波共振器４ａ、４ｂの一般的な構成を図１
９に示す。図１９において、１は圧電体基板、２はすだ
れ状電極、３は反射器である。圧電体基板１上にすだれ
状電極２と２つの反射器３を配置して１端子対弾性表面
波共振器４を構成している。2. Description of the Related Art FIG.
9-16 shows a configuration of a conventional surface acoustic wave filter of this type shown in 9-16. In FIG. 18, 4a,
4b is a one-terminal-pair surface acoustic wave resonator, 6 is an input terminal, and 7 is an output terminal. In the figure, a plurality of 1-terminal pair surface acoustic wave resonators 4a inserted in the series arm and 1-terminal pair surface acoustic wave resonators 4b inserted in the parallel arm are arranged in a ladder shape between the input terminal 6 and the output terminal 7. Connected. A general structure of the one-terminal-pair surface acoustic wave resonators 4a and 4b in FIG. 18 is shown in FIG.
9 shows. In FIG. 19, 1 is a piezoelectric substrate, 2 is a comb-shaped electrode, and 3 is a reflector. The interdigital transducer 2 and the two reflectors 3 are arranged on the piezoelectric substrate 1 to form a one-terminal pair surface acoustic wave resonator 4.

【手続補正３】[Procedure 3]

【補正対象書類名】明細書[Document name to be amended] Statement

【補正対象項目名】００１８[Correction target item name] 0018

【補正方法】変更[Correction method] Change

【補正内容】[Correction content]

【００１８】請求項５の発明に係る弾性表面波フィルタ
は、１端子対弾性表面波共振器と、弾性表面波を励振す
るすだれ状電極とを梯子形に接続した弾性表面波フィル
タの、上記すだれ状電極の一部をキャパシタに置き換え
たことを特徴とするものである。A surface acoustic wave filter according to a fifth aspect of the present invention is a surface acoustic wave filter in which a one-terminal-pair surface acoustic wave resonator and a comb-shaped electrode for exciting a surface acoustic wave are connected in a ladder shape.
This is characterized in that a part of the above-mentioned interdigital electrode is replaced with a capacitor.

───────────────────────────────────────────────────── フロントページの続き (72)発明者 木村 友則 鎌倉市大船五丁目１番１号 三菱電機株式 会社電子システム研究所内 (72)発明者 村井 康治 尼崎市塚口本町８丁目１番１号 三菱電機 株式会社通信機製作所内 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomonori Kimura 5-1-1 Ofuna, Kamakura-shi Electronic Systems Research Laboratories, Mitsubishi Electric Corporation (72) Inventor Koji Murai 8-1-1 Tsukaguchihonmachi, Amagasaki Mitsubishi Electric Communication Equipment Co., Ltd.

Claims (11)

【特許請求の範囲】[Claims] 【請求項１】 弾性表面波共振器を複数個電気的に接続
してなる弾性表面波フィルタにおいて、上記弾性表面波
共振器に１端子対弾性表面波共振器と２端子対弾性表面
波共振器を共に用いたことを特徴とする弾性表面波フィ
ルタ。1. A surface acoustic wave filter comprising a plurality of surface acoustic wave resonators electrically connected to each other, wherein the surface acoustic wave resonator includes a one-terminal-pair surface acoustic wave resonator and a two-terminal-pair surface acoustic wave resonator. A surface acoustic wave filter characterized by using together. 【請求項２】 弾性表面波共振器を複数個電気的に接続
してなる弾性表面波フィルタにおいて、上記弾性表面波
共振器に１端子対弾性表面波共振器と２端子対弾性表面
波共振器を共に用い、かつ、上記１端子対弾性表面波共
振器と上記２端子対弾性表面波共振器とを、入力端子と
出力端子に対して対称に接続したことを特徴とする弾性
表面波フィルタ。2. A surface acoustic wave filter comprising a plurality of surface acoustic wave resonators electrically connected to each other, wherein the surface acoustic wave resonator includes a one-terminal-pair surface acoustic wave resonator and a two-terminal-pair surface acoustic wave resonator. And a two-terminal pair surface acoustic wave resonator and the two-terminal pair surface acoustic wave resonator are connected symmetrically with respect to an input terminal and an output terminal. 【請求項３】 弾性表面波共振器を複数個電気的に接続
してなる弾性表面波フィルタにおいて、上記弾性表面波
共振器に１端子対弾性表面波共振器と２端子対弾性表面
波共振器を共に用い、かつ上記２端子対弾性表面波共振
器は３個以上のすだれ状電極を有することを特徴とする
弾性表面波フィルタ。3. A surface acoustic wave filter comprising a plurality of surface acoustic wave resonators electrically connected to each other, wherein the surface acoustic wave resonator includes a one-terminal-pair surface acoustic wave resonator and a two-terminal-pair surface acoustic wave resonator. And the two-terminal pair surface acoustic wave resonator has three or more interdigital electrodes. 【請求項４】 １端子対弾性表面波共振器と、弾性表面
波を励振するすだれ状電極とを梯子形に接続したことを
特徴とする弾性表面波フィルタ。4. A surface acoustic wave filter comprising a one-terminal surface acoustic wave resonator and a comb-shaped electrode for exciting surface acoustic waves connected in a ladder shape. 【請求項５】 １端子対弾性表面波共振器と、弾性表面
波を励振するすだれ状電極とを梯子形に接続し、上記す
だれ状電極の一部をキャパシタに置き換えたことを特徴
とする弾性表面波フィルタ。5. A one-terminal-pair surface acoustic wave resonator and a comb-shaped electrode for exciting a surface acoustic wave are connected in a ladder shape, and a part of the comb-shaped electrode is replaced with a capacitor. Surface wave filter. 【請求項６】 直列腕の構成要素および並列腕の構成要
素として１端子対弾性表面波共振器を用い、上記直列腕
の１端子対弾性表面波共振器と上記並列腕の１端子対弾
性表面波共振器とを梯子形に接続してなる弾性表面波フ
ィルタにおいて、上記１端子対弾性表面波共振器のうち
少なくとも１つは、すだれ状電極と反射器とを有し、か
つ、上記すだれ状電極の電極指配列周期と上記反射器の
格子配列周期が異なることを特徴とする弾性表面波フィ
ルタ。6. A one-terminal-pair surface acoustic wave resonator is used as a constituent element of the series arm and a constituent element of the parallel arm, and the one-terminal pair surface acoustic wave resonator of the series arm and the one-terminal pair elastic surface of the parallel arm. In a surface acoustic wave filter having a wave resonator connected in a ladder shape, at least one of the one-terminal pair surface acoustic wave resonator has a comb-shaped electrode and a reflector, and the comb-shaped resonator. A surface acoustic wave filter characterized in that an electrode finger arrangement period of electrodes and a grating arrangement period of the reflector are different. 【請求項７】 直列腕の構成要素および並列腕の構成要
素として、すだれ状電極と反射器とを有する１端子対弾
性表面波共振器を用い、上記直列腕の１端子対弾性表面
波共振器と上記並列腕の１端子対弾性表面波共振器とを
梯子形に接続してなる弾性表面波フィルタにおいて、上
記直列腕の１端子対弾性表面波共振器の、上記すだれ状
電極の電極指配列周期および上記反射器の格子配列周期
をそれぞれＬｉｓ、Ｌｒｓとし、上記並列腕の１端子対
弾性表面波共振器の、上記すだれ状電極の電極指配列周
期および上記反射器の格子配列周期をそれぞれＬｉｐ、
Ｌｒｐとしたとき、Ｌｉｓ／Ｌｒｓ ＜ Ｌｉｐ／Ｌｒ
ｐとしたことを特徴とする弾性表面波フィルタ。7. A one-terminal-pair surface acoustic wave resonator having a comb-shaped electrode and a reflector is used as a constituent element of the series arm and a constituent element of the parallel arm, and the one-terminal pair surface acoustic wave resonator of the series arm is used. A surface acoustic wave filter in which the above-mentioned parallel arm and the one-terminal pair surface acoustic wave resonator are connected in a ladder shape, wherein the interdigital electrode finger array of the one-terminal pair surface acoustic wave resonator of the series arm is arranged. The period and the lattice arrangement period of the reflector are respectively set to Lis and Lrs, and the electrode finger arrangement period of the interdigital electrode and the lattice arrangement period of the reflector of the one-terminal pair surface acoustic wave resonator of the parallel arm are respectively Lip. ,
When Lrp is set, Lis / Lrs <Lip / Lr
A surface acoustic wave filter having p. 【請求項８】 直列腕の構成要素および並列腕の構成要
素として１端子対弾性表面波共振器を用い、上記直列腕
の１端子対弾性表面波共振器と上記並列腕の１端子対弾
性表面波共振器とを梯子形に接続してなる弾性表面波フ
ィルタにおいて、上記直列腕の１端子対弾性表面波共振
器のうち少なくとも１つは、他の上記直列腕の１端子対
弾性表面波共振器と、共振周波数が異なることを特徴と
する弾性表面波フィルタ。8. A one-terminal pair surface acoustic wave resonator is used as a constituent element of the series arm and a constituent element of the parallel arm, and the one-terminal pair surface acoustic wave resonator of the series arm and the one-terminal pair elastic surface of the parallel arm are used. In a surface acoustic wave filter in which a wave resonator is connected in a ladder shape, at least one of the one-terminal pair surface acoustic wave resonators of the series arm is a one-terminal pair surface acoustic wave resonance of the other series arm. The surface acoustic wave filter is characterized by having a different resonance frequency from the container. 【請求項９】 直列腕の構成要素および並列腕の構成要
素として１端子対弾性表面波共振器を用い、上記直列腕
の１端子対弾性表面波共振器と上記並列腕の１端子対弾
性表面波共振器とを梯子形に接続してなる弾性表面波フ
ィルタにおいて、上記並列腕の１端子対弾性表面波共振
器のうち少なくとも１つは、他の上記並列腕の１端子対
弾性表面波共振器と、反共振周波数が異なることを特徴
とする弾性表面波フィルタ。9. A one-terminal-pair surface acoustic wave resonator is used as a constituent element of the series arm and a constituent element of the parallel arm, and the one-terminal pair surface acoustic wave resonator of the series arm and the one-terminal pair elastic surface of the parallel arm. In a surface acoustic wave filter in which a wave resonator is connected in a ladder shape, at least one of the one-terminal pair surface acoustic wave resonators of the parallel arms is a one-terminal pair surface acoustic wave resonance of the other parallel arm. And a surface acoustic wave filter having a different anti-resonance frequency. 【請求項１０】 直列腕の構成要素および並列腕の構成
要素として１端子対弾性表面波共振器を用い、上記直列
腕の１端子対弾性表面波共振器と上記並列腕の１端子対
弾性表面波共振器とを梯子形に接続してなる弾性表面波
フィルタにおいて、上記直列腕の１端子対弾性表面波共
振器を複数個有し、上記複数個の直列腕の１端子対弾性
表面波共振器のうち少なくとも２つを隣接して配置した
ことを特徴とする弾性表面波フィルタ。10. A one-terminal pair surface acoustic wave resonator is used as a constituent element of the series arm and a constituent element of the parallel arm, and the one-terminal pair surface acoustic wave resonator of the series arm and the one-terminal pair elastic surface of the parallel arm. A surface acoustic wave filter including a wave resonator connected in a ladder shape, comprising a plurality of one-terminal-pair surface acoustic wave resonators of the series arm, and one-terminal-pair surface acoustic wave resonance of the plurality of series arms. A surface acoustic wave filter, wherein at least two of the vessels are arranged adjacent to each other. 【請求項１１】 直列腕の構成要素および並列腕の構成
要素として１端子対弾性表面波共振器を用い、上記直列
腕の１端子対弾性表面波共振器と上記並列腕の１端子対
弾性表面波共振器とを梯子形に接続し、かつ、インダク
タを接続したことを特徴とする弾性表面波フィルタ。11. A one-terminal pair surface acoustic wave resonator is used as a constituent element of the series arm and a constituent element of the parallel arm, and the one-terminal pair surface acoustic wave resonator of the series arm and the one-terminal pair elastic surface of the parallel arm. A surface acoustic wave filter characterized in that a wave resonator is connected in a ladder shape and an inductor is connected.
JP04805593A 1993-03-09 1993-03-09 Surface acoustic wave filter Expired - Lifetime JP3191473B2 (en)

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