JP2001230657A - Surface acoustic wave filter - Google Patents
Surface acoustic wave filterInfo
- Publication number
- JP2001230657A JP2001230657A JP2000037815A JP2000037815A JP2001230657A JP 2001230657 A JP2001230657 A JP 2001230657A JP 2000037815 A JP2000037815 A JP 2000037815A JP 2000037815 A JP2000037815 A JP 2000037815A JP 2001230657 A JP2001230657 A JP 2001230657A
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- JP
- Japan
- Prior art keywords
- acoustic wave
- surface acoustic
- wave filter
- resonator
- wave 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.)
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- Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は特に移動体通信機器
の高周波領域において急峻なカットオフ特性が求められ
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 which is required to have a sharp cutoff characteristic particularly in a high frequency region of a mobile communication device.
【０００２】[0002]
【従来の技術】移動体通信用の高周波フィルタとして
は、従来から小型で低損失でカットオフ特性に優れた弾
性表面波フィルタが広く用いられている。2. Description of the Related Art As a high-frequency filter for mobile communication, a surface acoustic wave filter having a small size, low loss, and excellent cutoff characteristics has been widely used.
【０００３】近年、通過帯域へのスロープ上といった通
過帯域の極めて近傍に帯域外減衰量が求められる場合が
ある。[0003] In recent years, out-of-band attenuation may be required very close to the pass band, such as on the slope to the pass band.
【０００４】従来の弾性表面波フィルタは特開平７−８
６８７０号公報に記載されているように圧電性基板上に
おいて二端子対弾性表面波フィルタに一端子対弾性表面
波共振器を直列に接続したものであり、前記一端子対弾
性表面波共振器の***振周波数を前記二端子対弾性表面
波共振器フィルタの通過帯域よりも高周波数側に設定し
たものであった。そしてこのような構成にすることによ
り、通過帯域の近傍の高周波側でのサイドローブのレベ
ルを低減させた弾性表面波フィルタを提供することがで
きる。A conventional surface acoustic wave filter is disclosed in Japanese Unexamined Patent Publication No.
As described in Japanese Patent No. 6870, a two-terminal pair surface acoustic wave filter is connected in series with a two-terminal pair surface acoustic wave filter on a piezoelectric substrate. The anti-resonance frequency was set higher than the pass band of the two-port surface acoustic wave resonator filter. With such a configuration, it is possible to provide a surface acoustic wave filter having a reduced side lobe level on the high frequency side near the pass band.
【０００５】[0005]
【発明が解決しようとする課題】しかしながら従来の弾
性表面波フィルタでは、通過帯域の近傍の帯域外減衰量
を大きくすることができるものの、通過帯域外減衰域に
スプリアス状のサイドローブがあり、このサイドローブ
により所望の周波数特性が得られないという問題点を有
していた。However, in the conventional surface acoustic wave filter, although the amount of out-of-band attenuation near the pass band can be increased, spurious side lobes are present in the out-of-band attenuation band. There is a problem that a desired frequency characteristic cannot be obtained by the side lobe.
【０００６】そこで本発明は、通過帯域の極めて近傍だ
けでなく従来スプリアス状のサイドローブが発生してい
た周波数での帯域外減衰量が大きく、低損失で良好な周
波数特性を有する弾性表面波フィルタを提供することを
目的とするものである。Accordingly, the present invention provides a surface acoustic wave filter having a large amount of out-of-band attenuation not only in the vicinity of a pass band but also at a frequency at which spurious side lobes have conventionally occurred, low loss and good frequency characteristics. The purpose is to provide.
【０００７】[0007]
【課題を解決するための手段】この目的を達成するため
に本発明の弾性表面波フィルタは、圧電性基板と、この
圧電性基板上に設けた少なくとも一つの直列腕弾性表面
波共振器と少なくとも一つの並列腕弾性表面波共振器と
を有するラダー型弾性表面波フィルタと、前記圧電性基
板上でこのラダー型弾性表面波フィルタに縦続接続した
二端子対弾性表面波フィルタとを備え、前記直列腕弾性
表面波共振器の***振周波数は前記二端子対弾性表面波
フィルタの通過帯域近傍にあり、かつ前記並列腕弾性表
面波共振器の共振周波数は前記二端子対弾性表面波フィ
ルタの通過帯域外にあるものであり、上記目的を達成す
ることができる。In order to achieve this object, a surface acoustic wave filter according to the present invention comprises a piezoelectric substrate, at least one series-arm surface acoustic wave resonator provided on the piezoelectric substrate, and A ladder-type surface acoustic wave filter having one parallel arm surface acoustic wave resonator; and a two-terminal pair surface acoustic wave filter cascade-connected to the ladder-type surface acoustic wave filter on the piezoelectric substrate; The anti-resonance frequency of the arm surface acoustic wave resonator is near the pass band of the two-port surface acoustic wave filter, and the resonance frequency of the parallel arm surface acoustic wave filter is the pass band of the two-port surface acoustic wave filter. Outside and can achieve the above objectives.
【０００８】[0008]
【発明の実施の形態】本発明の請求項１に記載の発明
は、圧電性基板と、この圧電性基板上に設けた少なくと
も一つの直列腕弾性表面波共振器と少なくとも一つの並
列腕弾性表面波共振器とを有するラダー型弾性表面波フ
ィルタと、前記圧電性基板上でこのラダー型弾性表面波
フィルタに縦続接続した二端子対弾性表面波フィルタと
を備え、前記直列腕弾性表面波共振器の***振周波数は
前記二端子対弾性表面波フィルタの通過帯域近傍にあ
り、かつ前記並列腕弾性表面波共振器の共振周波数は前
記二端子対弾性表面波フィルタの通過帯域外にある弾性
表面波フィルタであり、通過帯域の極めて近傍の帯域外
減衰量が大きく、低損失で、かつ通過帯域外減衰量が優
れた良好な周波数特性を有するものである。DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention according to claim 1 of the present invention provides a piezoelectric substrate, at least one series arm surface acoustic wave resonator provided on the piezoelectric substrate, and at least one parallel arm surface acoustic wave. A ladder type surface acoustic wave filter having a wave resonator; and a two-terminal pair surface acoustic wave filter cascaded to the ladder type surface acoustic wave filter on the piezoelectric substrate, wherein the series arm surface acoustic wave resonator is provided. The anti-resonance frequency is near the pass band of the two-port surface acoustic wave filter, and the resonance frequency of the parallel arm surface acoustic wave resonator is outside the pass band of the two-port surface acoustic wave filter. The filter is a filter having a large out-of-band attenuation very close to the pass band, low loss, and excellent frequency characteristics with excellent out-of-pass-band attenuation.
【０００９】請求項２に記載の発明は、直列腕弾性表面
波共振器のすだれ状電極の対数と交差幅の積で決まる静
電容量をＣｓ［pF］とし、並列腕弾性表面波共振器のす
だれ状電極の対数と交差幅の積で決まる静電容量をＣｐ
［pF］とするとき、Ｃｓ＞Ｃｐである請求項１に記載の
弾性表面波フィルタであり、通過帯域の極めて近傍の帯
域外減衰量をさらに大きくすることができる。According to a second aspect of the present invention, the capacitance determined by the product of the logarithm of the interdigital transducer of the series arm surface acoustic wave resonator and the intersection width is Cs [pF], and the capacitance of the parallel arm surface acoustic wave resonator is The capacitance determined by the product of the logarithm of the IDT and the intersection width is Cp
The surface acoustic wave filter according to claim 1, wherein when [pF], Cs> Cp, and the out-of-band attenuation very close to the pass band can be further increased.
【００１０】請求項３に記載の発明は、弾性表面波フィ
ルタの中心周波数をｆｏ［MHz］とするとき、Ｃｓ・ｆ
ｏ≧１００００である請求項１に記載の弾性表面波フィ
ルタであり、通過帯域の極めて近傍の帯域外減衰量をさ
らに大きく、低損失な周波数特性が得られる。According to a third aspect of the present invention, when the center frequency of the surface acoustic wave filter is fo [MHz], Cs · f
2. The surface acoustic wave filter according to claim 1, wherein o ≧ 10000, wherein the out-of-band attenuation very close to the pass band is further increased, and a low-loss frequency characteristic is obtained.
【００１１】請求項４に記載の発明は、二端子対弾性表
面波フィルタはすだれ状電極を三個以上備えた縦結合二
重モード弾性表面波フィルタである請求項１に記載の弾
性表面波フィルタであり、通過帯域外減衰量に優れた周
波数特性が得られる。According to a fourth aspect of the present invention, there is provided the surface acoustic wave filter according to the first aspect, wherein the two-port surface acoustic wave filter is a longitudinally coupled double mode surface acoustic wave filter having three or more interdigital electrodes. Thus, a frequency characteristic excellent in the amount of attenuation outside the pass band can be obtained.
【００１２】請求項５に記載の発明は、二端子対弾性表
面波フィルタはラダー型弾性表面波フィルタである請求
項１に記載の弾性表面波フィルタであり、低損失な周波
数特性が得られる。According to a fifth aspect of the present invention, the two-terminal pair surface acoustic wave filter is a ladder type surface acoustic wave filter, and a low loss frequency characteristic is obtained.
【００１３】請求項６に記載の発明は、少なくとも一つ
の並列腕弾性表面波共振器のアース端子と二端子対弾性
表面波フィルタのアース端子とを圧電性基板上で電気的
に接続した請求項１に記載の弾性表面波フィルタであ
り、通過帯域外減衰量がさらに良好な周波数特性が得ら
れる。According to a sixth aspect of the present invention, the ground terminal of the at least one parallel arm surface acoustic wave resonator and the ground terminal of the two-terminal surface acoustic wave filter are electrically connected on the piezoelectric substrate. 1. The surface acoustic wave filter according to 1, wherein a further excellent frequency characteristic with an attenuation outside the pass band is obtained.
【００１４】以下、本発明の実施の形態について、図面
を用いて説明する。Hereinafter, embodiments of the present invention will be described with reference to the drawings.
【００１５】（実施の形態１）図１は本発明の実施の形
態１における弾性表面波フィルタの上面図であり、１は
圧電性基板、２は入力電気端子、３は出力電気端子、４
ａ，４ｂ，４ｃ，４ｄはアース端子であり、入力電気端
子２および出力電気端子３の間に直列腕弾性表面波共振
器１０、並列腕弾性表面波共振器１１および２端子対弾
性表面波フィルタである三電極型縦結合二重モード弾性
表面波フィルタ１２が縦続接続されている。また１０
ａ，１１ａ，１２ａはすだれ状電極、１０ｂ，１１ｂ，
１２ｂは反射器電極である。(Embodiment 1) FIG. 1 is a top view of a surface acoustic wave filter according to Embodiment 1 of the present invention, wherein 1 is a piezoelectric substrate, 2 is an input electric terminal, 3 is an output electric terminal,
Reference numerals a, 4b, 4c, and 4d denote ground terminals, and a series arm surface acoustic wave resonator 10, a parallel arm surface acoustic wave resonator 11, and a two-terminal pair surface acoustic wave filter between an input electric terminal 2 and an output electric terminal 3. The three-electrode type vertically coupled double mode surface acoustic wave filter 12 is connected in cascade. Also 10
a, 11a, 12a are interdigital electrodes, 10b, 11b,
12b is a reflector electrode.
【００１６】次にこの弾性表面波フィルタの動作につい
て説明する。Next, the operation of the surface acoustic wave filter will be described.
【００１７】図２（ａ）は、三電極型縦結合二重モード
弾性表面波フィルタ１２の周波数特性図である。中心周
波数をｆｏとし、通過帯域は周波数ｆ１から周波数ｆ２
の間である。この三電極型縦結合二重モード弾性表面波
フィルタ１２は、３つのすだれ状電極１２ａを弾性表面
波が伝播する方向に並べて配置し、このすだれ状電極１
２ａ内で弾性表面波が伝播する方向に沿って両側に反射
器電極１２ｂを備えたものである。FIG. 2A is a frequency characteristic diagram of the three-electrode type longitudinally coupled double mode surface acoustic wave filter 12. The center frequency is fo, and the pass band is from frequency f1 to frequency f2.
Between. In the three-electrode type vertically coupled double mode surface acoustic wave filter 12, three IDTs 12a are arranged side by side in the direction in which the SAW propagates.
A reflector electrode 12b is provided on both sides along the direction in which the surface acoustic wave propagates in 2a.
【００１８】近年、通過帯域の極めて近傍［（通過帯域
の低周波数側限界周波数ｆ１−通過帯域幅）近傍の周波
数］において帯域外減衰量が求められ、例えば、図２
（ａ）においては通過帯域近傍の通過帯域へのスロープ
上に大きな帯域外減衰量が求められる。In recent years, the amount of out-of-band attenuation has been determined very close to the pass band [frequency near the (low-frequency limit frequency f1-pass band width) of the pass band].
In (a), a large out-of-band attenuation is required on the slope to the pass band near the pass band.
【００１９】一方図３は、直列腕弾性表面波共振器１０
の構造を示しており、中央にすだれ状電極１０ａがあ
り、すだれ状電極１０ａ内で弾性表面波が伝播する方向
に沿って両側に反射器電極１０ｂが備えられている。た
だし、これら反射器電極１０ｂは必ずしも必要ではない
が、直列腕弾性表面波共振器１０のＱ値をより高めるた
めには備えている方がよい。この直列腕弾性表面波共振
器１０は、図４（ａ）に示すようなインピーダンス特性
を有しており、この周波数特性Ｓ２１は図４（ｂ）に示
すように***振周波数付近でノッチを形成するものであ
る。従って、三電極型縦結合二重モード弾性表面波フィ
ルタ１２において周波数ｆｎ付近の帯域外減衰量を確保
するためには、周波数ｆｎ付近に***振周波数をもつ図
２（ｂ）に示すような周波数特性を有する図３のような
直列腕弾性表面波共振器１０を三電極型縦結合二重モー
ド弾性表面波フィルタ１２に縦続接続すればよい。FIG. 3 shows a series arm surface acoustic wave resonator 10.
The interdigital electrode 10a is provided at the center, and the reflector electrodes 10b are provided on both sides along the direction in which the surface acoustic wave propagates in the interdigital electrode 10a. However, these reflector electrodes 10b are not always necessary, but are preferably provided to further increase the Q value of the serial arm surface acoustic wave resonator 10. This series arm surface acoustic wave resonator 10 has impedance characteristics as shown in FIG. 4A, and this frequency characteristic S21 forms a notch near the anti-resonance frequency as shown in FIG. 4B. Is what you do. Therefore, in order to secure an out-of-band attenuation near the frequency fn in the three-electrode longitudinally coupled double-mode surface acoustic wave filter 12, a frequency having an anti-resonance frequency near the frequency fn as shown in FIG. A series arm surface acoustic wave resonator 10 having characteristics as shown in FIG. 3 may be connected in cascade to a three-electrode type vertically coupled double mode surface acoustic wave filter 12.
【００２０】また、図５は並列腕弾性表面波共振器１１
の構造を示しており、直列腕弾性表面波共振器１０と同
様にすだれ状電極１１ａとこの両側に設けた反射器電極
１１ｂで構成されている。並列腕弾性表面波共振器１１
は、図６（ａ）に示すようなインピーダンス特性を有
し、この周波数特性Ｓ２１は図６（ｂ）に示すように共
振周波数付近でノッチを形成するフィルタ特性となる。
従って三電極型縦結合二重モード弾性表面波フィルタ１
２の通過帯域外の減衰量を確保したい周波数、例えば周
波数ｆｓにあるスプリアスを抑圧するために、ｆｓにほ
ぼ一致する共振周波数を有する並列腕弾性表面波共振器
１１を入、出力電気端子２，３間に並列に接続する。FIG. 5 shows a parallel arm surface acoustic wave resonator 11.
In the same manner as the serial arm surface acoustic wave resonator 10, the structure includes an interdigital electrode 11a and reflector electrodes 11b provided on both sides thereof. Parallel arm surface acoustic wave resonator 11
Has an impedance characteristic as shown in FIG. 6A, and the frequency characteristic S21 is a filter characteristic that forms a notch near the resonance frequency as shown in FIG. 6B.
Therefore, the three-electrode type longitudinally coupled double mode surface acoustic wave filter 1
2, a parallel arm surface acoustic wave resonator 11 having a resonance frequency substantially equal to fs is input to suppress a spurious component at a frequency at which the amount of attenuation outside the pass band is desired, for example, frequency fs. 3 is connected in parallel.
【００２１】ここで、通過帯域の挿入損失の低下を極力
抑制するためには、周波数ｆｎ付近に***振周波数をも
つ直列腕弾性表面波共振器１０のインピーダンスを小さ
くし、並列腕弾性表面波共振器１１のインピーダンスを
大きくする必要がある。Here, in order to minimize the decrease in the insertion loss in the pass band, the impedance of the series arm surface acoustic wave resonator 10 having an anti-resonance frequency near the frequency fn is reduced, and the parallel arm surface acoustic wave resonance is reduced. It is necessary to increase the impedance of the vessel 11.
【００２２】弾性表面波共振器のインピーダンスは、す
だれ状電極１０ａ，１０ｂの対数と交差幅の積で決まる
静電容量に反比例する。従って、通過帯域の挿入損失の
低下を極力抑制するためには、直列腕弾性表面波共振器
１０の静電容量Ｃｓ［ｐＦ］を並列腕弾性表面波共振器
１１の静電容量Ｃｐ［ｐＦ］よりも大きくすることが望
ましい。The impedance of the surface acoustic wave resonator is inversely proportional to the capacitance determined by the product of the logarithm of the IDTs 10a and 10b and the intersection width. Therefore, in order to minimize the decrease in the insertion loss in the pass band, the capacitance Cs [pF] of the serial arm surface acoustic wave resonator 10 is changed to the capacitance Cp [pF] of the parallel arm surface acoustic wave resonator 11. It is desirable to make it larger.
【００２３】図７に直列腕弾性表面波共振器１０の静電
容量Ｃｓ［ｐＦ］と本発明の弾性表面波フィルタの挿入
損失の関係をさらに詳しく調べた結果を示す。ここで、
通過帯域の極めて近傍の基準周波数をｆｎ＝０．９９・
ｆ１とし、この周波数ｆｎを***振周波数とする直列腕
弾性表面波共振器１０について調べた。図７において、
横軸は直列腕弾性表面波共振器１０の静電容量Ｃｓ［ｐ
Ｆ］と三電極型縦結合二重モード弾性表面波フィルタ１
２の中心周波数ｆｏ［MHz］の積であり、縦軸は三電極
型縦結合二重モード弾性表面波フィルタ１２に直列腕弾
性表面波共振器１０を縦続接続したときの挿入損失の低
下量を表している。図７より、Ｃｓ・ｆｏが大きくなる
と挿入損失の低下量が小さくなり、挿入損失の低下量の
許容値を３［dB］とすると、Ｃｓ・ｆｏは１００００以
上であればよいことがわかる。FIG. 7 shows the results of a more detailed examination of the relationship between the capacitance Cs [pF] of the series arm surface acoustic wave resonator 10 and the insertion loss of the surface acoustic wave filter of the present invention. here,
The reference frequency very close to the pass band is fn = 0.99 ·
f1 and the series arm surface acoustic wave resonator 10 having this frequency fn as an anti-resonance frequency was examined. In FIG.
The horizontal axis represents the capacitance Cs [p of the series arm surface acoustic wave resonator 10.
F] and a three-electrode type vertically coupled double mode surface acoustic wave filter 1
2 is the product of the center frequency fo [MHz], and the vertical axis represents the amount of decrease in the insertion loss when the series arm surface acoustic wave resonator 10 is cascaded to the three-electrode longitudinally coupled double mode surface acoustic wave filter 12. Represents. From FIG. 7, it can be seen that as Cs · fo increases, the amount of decrease in insertion loss decreases, and when the allowable value of the amount of decrease in insertion loss is 3 [dB], Cs · fo only needs to be 10,000 or more.
【００２４】図８は本発明の弾性表面波フィルタの周波
数特性図である。これを見るとわかるように本発明の弾
性表面波フィルタは、通過帯域の極めて近傍にノッチを
形成する直列腕弾性表面波共振器１０があるため通過帯
域の極めて近傍の減衰量に優れ、また通過帯域外のスプ
リアス位置にノッチを形成する並列腕弾性表面波共振器
１１があるため帯域外減衰量に優れた低損失な周波数特
性を有することが分かる。FIG. 8 is a frequency characteristic diagram of the surface acoustic wave filter of the present invention. As can be seen from the figure, the surface acoustic wave filter of the present invention has a series arm surface acoustic wave resonator 10 that forms a notch in the vicinity of the pass band, and therefore has excellent attenuation in the vicinity of the pass band. It can be seen that the presence of the parallel arm surface acoustic wave resonator 11 that forms a notch at a spurious position outside the band has a low-loss frequency characteristic with excellent out-of-band attenuation.
【００２５】以上のように本実施の形態１の弾性表面波
フィルタは、通過帯域の極近傍の帯域外減衰量が大き
く、低損失で、かつ通過帯域外減衰量が優れた良好な周
波数特性を有するものである。As described above, the surface acoustic wave filter according to the first embodiment has good frequency characteristics with a large out-of-band attenuation near the pass band, low loss, and excellent out-of-pass-band attenuation. Have
【００２６】（実施の形態２）図９は本発明の実施の形
態２における弾性表面波フィルタの上面図であり、１は
圧電性基板、２は入力電気端子、３は出力電気端子、４
ａ，４ｂ，４ｃはアース端子であり、入力電気端子２お
よび出力電気端子３の間に直列腕弾性表面波共振器１
０、並列腕弾性表面波共振器１１および２端子対弾性表
面波フィルタである三電極型縦結合二重モード弾性表面
波フィルタ１２が縦続接続されている。図１に示す実施
の形態１の弾性表面波フィルタとの相違は、並列腕弾性
表面波共振器１１のアース端子４ａと二端子対弾性表面
波フィルタ１２のアース端子４ｂ，４ｃが圧電性基板１
上で電気的に接続されていることである。(Embodiment 2) FIG. 9 is a top view of a surface acoustic wave filter according to Embodiment 2 of the present invention, wherein 1 is a piezoelectric substrate, 2 is an input electric terminal, 3 is an output electric terminal,
Reference characters a, 4b, and 4c denote ground terminals, and a series arm surface acoustic wave resonator 1 is connected between the input electric terminal 2 and the output electric terminal 3.
0, a parallel arm surface acoustic wave resonator 11 and a three-electrode longitudinally coupled double mode surface acoustic wave filter 12 which is a two-terminal pair surface acoustic wave filter are cascaded. The difference from the surface acoustic wave filter of the first embodiment shown in FIG. 1 is that the ground terminal 4a of the parallel arm surface acoustic wave resonator 11 and the ground terminals 4b and 4c of the two-terminal pair surface acoustic wave filter 12 are
Above is electrically connected.
【００２７】本実施の形態２における弾性表面波フィル
タの周波数特性を図１０に示す。図１０より、アース端
子４ａ，４ｂを圧電性基板１上で電気的に接続すると、
通過帯域外減衰量をより大きくすることができる。これ
は、圧電性基板１上で入、出力電気端子２、３間に、並
列腕弾性表面波共振器１１を経て出力電気端子３への別
経路が形成されることによると考えられる。FIG. 10 shows the frequency characteristics of the surface acoustic wave filter according to the second embodiment. From FIG. 10, when the ground terminals 4a and 4b are electrically connected on the piezoelectric substrate 1,
The attenuation outside the pass band can be further increased. This is considered to be because another path to the output electric terminal 3 is formed between the incoming and outgoing electric terminals 2 and 3 on the piezoelectric substrate 1 via the parallel arm surface acoustic wave resonator 11.
【００２８】なお、本実施の形態においても実施の形態
１と同様に三電極型縦結合二重モード弾性表面波フィル
タ１２に代えてラダー型フィルタを用いても同様の効果
が得られる。In this embodiment, similar to the first embodiment, the same effect can be obtained by using a ladder type filter instead of the three-electrode type longitudinally coupled double mode surface acoustic wave filter 12.
【００２９】以上のように本実施の形態２の弾性表面波
フィルタは、実施の形態１の弾性表面波フィルタと比較
するとさらに通過帯域の極めて近傍の減衰量を大きくす
ることができる。As described above, the surface acoustic wave filter according to the second embodiment can further increase the amount of attenuation very near the pass band as compared with the surface acoustic wave filter according to the first embodiment.
【００３０】なお、上記各実施の形態では通過帯域の低
周波数側の極めて近傍及びスプリアス位置の減衰量の確
保を例に説明したが、通過帯域の高周波数側の極めて近
傍及びスプリアス位置の減衰量を確保する場合も同様
に、通過帯域の高周波数側の極めて近傍の周波数を***
振周波数とする直列腕弾性表面波共振器１０を、通過帯
域の高周波数側のスプリアスに対応する周波数を共振周
波数とする並列腕弾性表面波共振器１１を入、出力電気
端子２、３間にそれぞれ電気的に接続すれば良い。In each of the above embodiments, an example has been described in which the attenuation near the low frequency side of the pass band and the spurious position is ensured. However, the attenuation near the high frequency side of the pass band and the spurious position are ensured. In the same manner, the series arm surface acoustic wave resonator 10 having an anti-resonance frequency at a frequency very close to the high frequency side of the pass band is changed to a frequency corresponding to the spurious at the high frequency side of the pass band. The parallel arm surface acoustic wave resonator 11 may be inserted and electrically connected between the output electric terminals 2 and 3 respectively.
【００３１】また、直列腕弾性表面波共振器１０及び並
列腕弾性表面波共振器１１をそれぞれ複数個設けてもか
まわない。この場合、二つの直列腕弾性表面波共振器１
０の***振周波数が弾性表面波フィルタの通過帯域の低
周波数側及び高周波数側の極めて近傍の周波数となるよ
うなものを用い、また二つの並列腕弾性表面波共振器１
１の共振周波数が弾性表面波フィルタの通過帯域外のス
プリアスに対応する周波数となるようなものを用いるこ
とにより、通過帯域の低周波数側及び高周波数側の両方
の極めて近傍及び通過帯域外の減衰量を確保することが
できる。A plurality of series arm surface acoustic wave resonators 10 and a plurality of parallel arm surface acoustic wave resonators 11 may be provided. In this case, two series arm surface acoustic wave resonators 1
The anti-resonance frequency of 0 is very close to the low frequency side and the high frequency side of the pass band of the surface acoustic wave filter, and two parallel arm surface acoustic wave resonators 1
1 is used so that the resonance frequency is a frequency corresponding to spurious components outside the pass band of the surface acoustic wave filter, so that the attenuation is extremely close to both the low frequency side and the high frequency side of the pass band and outside the pass band. Quantity can be secured.
【００３２】さらに、本実施の形態１では、二端子対弾
性表面波フィルタを三電極型縦結合二重モード弾性表面
波フィルタ１２としているが、これに代えて図１１に示
すようにラダー型弾性表面波フィルタ１３の場合におい
ても同様の効果が得られる（実施の形態１においてラダ
ー型弾性表面波フィルタ１３に代えた場合を示す）。こ
のラダー型弾性表面波フィルタ１３は、それぞれ中央に
すだれ状電極１３ａがあり、すだれ状電極１３ａ内で弾
性表面波が伝搬する方向に沿って両側に反射器電極１３
ｂを有する直列腕弾性表面波共振器１３ｃ、並列腕弾性
表面波共振器１３ｄで構成されている。Further, in the first embodiment, the two-terminal pair surface acoustic wave filter is a three-electrode type vertically coupled double mode surface acoustic wave filter 12, but instead of a ladder type surface acoustic wave filter as shown in FIG. The same effect can be obtained in the case of the surface acoustic wave filter 13 (the case where the ladder type surface acoustic wave filter 13 is replaced in the first embodiment). The ladder type surface acoustic wave filter 13 has an interdigital electrode 13a at the center, and a reflector electrode 13a on both sides along the direction in which the surface acoustic wave propagates in the interdigital electrode 13a.
It is composed of a series arm surface acoustic wave resonator 13c having b and a parallel arm surface acoustic wave resonator 13d.
【００３３】[0033]
【発明の効果】以上本発明によれば、通過帯域の極めて
近傍だけでなく、従来スプリアス状のサイドローブが発
生していた周波数での帯域外減衰量が大きく、低損失で
良好な周波数特性を有する弾性表面波フィルタを提供す
ることができる。As described above, according to the present invention, the out-of-band attenuation is large not only in the vicinity of the pass band but also at the frequency at which spurious side lobes are conventionally generated, and a good frequency characteristic with low loss is obtained. The surface acoustic wave filter having the above can be provided.
【図１】本発明の実施の形態１における弾性表面波フィ
ルタの上面図FIG. 1 is a top view of a surface acoustic wave filter according to Embodiment 1 of the present invention.
【図２】（ａ）本発明の実施の形態１、２における二端
子対弾性表面波フィルタの周波数特性曲線図 （ｂ）本発明の実施の形態１における直列腕弾性表面波
共振器の周波数特性曲線図FIG. 2 (a) is a frequency characteristic curve diagram of a two-port surface acoustic wave filter according to the first and second embodiments of the present invention; and (b) is a frequency characteristic curve of a series arm surface acoustic wave resonator according to the first embodiment of the present invention. Curve diagram
【図３】本発明の実施の形態１、２における直列腕弾性
表面波共振器の構成図FIG. 3 is a configuration diagram of a serial arm surface acoustic wave resonator according to the first and second embodiments of the present invention.
【図４】（ａ）本発明の実施の形態１、２における直列
腕弾性表面波共振器のインピーダンス特性曲線図 （ｂ）本発明の実施の形態１、２における直列腕弾性表
面波共振器の周波数特性曲線図FIG. 4 (a) is an impedance characteristic curve diagram of the serial arm surface acoustic wave resonator according to the first and second embodiments of the present invention; and (b) the serial arm surface acoustic wave resonator according to the first and second embodiments of the present invention. Frequency characteristic curve diagram
【図５】本発明の実施の形態１、２における並列腕弾性
表面波共振器の構成図FIG. 5 is a configuration diagram of a parallel arm surface acoustic wave resonator according to the first and second embodiments of the present invention.
【図６】（ａ）本発明の実施の形態１、２における並列
腕弾性表面波共振器のインピーダンス特性曲線図 （ｂ）本発明の実施の形態１、２における並列腕弾性表
面波共振器の周波数特性曲線図FIG. 6 (a) is an impedance characteristic curve diagram of the parallel arm surface acoustic wave resonator according to the first and second embodiments of the present invention; and (b) the parallel arm surface acoustic wave resonator according to the first and second embodiments of the present invention. Frequency characteristic curve diagram
【図７】本発明の実施の形態１における直列腕弾性表面
波共振器の静電容量と弾性表面波フィルタの挿入損失と
の関係曲線図FIG. 7 is a graph showing the relationship between the capacitance of the serial arm surface acoustic wave resonator and the insertion loss of the surface acoustic wave filter according to the first embodiment of the present invention.
【図８】本発明の実施の形態１における弾性表面波フィ
ルタの周波数特性曲線図FIG. 8 is a frequency characteristic curve diagram of the surface acoustic wave filter according to Embodiment 1 of the present invention.
【図９】本発明の実施の形態２における弾性表面波フィ
ルタの上面図FIG. 9 is a top view of the surface acoustic wave filter according to Embodiment 2 of the present invention.
【図１０】本発明の実施の形態２における弾性表面波フ
ィルタの周波数特性曲線図FIG. 10 is a frequency characteristic curve diagram of the surface acoustic wave filter according to Embodiment 2 of the present invention.
【図１１】本発明の他の実施の形態における弾性表面波
フィルタの上面図FIG. 11 is a top view of a surface acoustic wave filter according to another embodiment of the present invention.
１ 圧電性基板 ２ 入力電気端子 ３ 出力電気端子 ４ａ アース端子 ４ｂ アース端子 ４ｃ アース端子 ４ｄ アース端子 １０ 直列腕弾性表面波共振器 １０ａ すだれ状電極 １０ｂ 反射器電極 １１ 並列腕弾性表面波共振器 １１ａ すだれ状電極 １１ｂ 反射器電極 １２ 三電極型縦結合二重モード弾性表面波フィルタ １２ａ すだれ状電極 １２ｂ 反射器電極 １３ ラダー型弾性表面波フィルタ １３ａ すだれ状電極 １３ｂ 反射器電極 １３ｃ 直列腕弾性表面波共振器 １３ｄ 並列腕弾性表面波共振器 DESCRIPTION OF SYMBOLS 1 Piezoelectric substrate 2 Input electric terminal 3 Output electric terminal 4a Earth terminal 4b Earth terminal 4c Earth terminal 4d Earth terminal 10 Series arm surface acoustic wave resonator 10a Interdigital electrode 10b Reflector electrode 11 Parallel arm surface acoustic wave resonator 11a Shaped electrode 11b Reflector electrode 12 Three electrode type longitudinally coupled double mode surface acoustic wave filter 12a IDT 12b Reflector electrode 13 Ladder type SAW filter 13a IDT 13b Reflector electrode 13c Series arm surface acoustic wave resonator 13d parallel arm surface acoustic wave resonator
───────────────────────────────────────────────────── フロントページの続き (72)発明者 常川 昭雄 大阪府門真市大字門真1006番地 松下電器 産業株式会社内 (72)発明者 三田 成大 大阪府門真市大字門真1006番地 松下電器 産業株式会社内 Ｆターム(参考） 5J097 AA14 AA16 BB02 BB11 CC05 JJ08 KK04 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akio Tsunekawa 1006 Kazuma Kadoma, Osaka Pref.Matsushita Electric Industrial Co., Ltd. F term (reference) 5J097 AA14 AA16 BB02 BB11 CC05 JJ08 KK04
Claims (6)
た少なくとも一つの直列腕弾性表面波共振器と少なくと
も一つの並列腕弾性表面波共振器とを有するラダー型弾
性表面波フィルタと、前記圧電性基板上でこのラダー型
弾性表面波フィルタに縦続接続した二端子対弾性表面波
フィルタとを備え、前記直列腕弾性表面波共振器の***
振周波数は前記二端子対弾性表面波フィルタの通過帯域
近傍にあり、かつ前記並列腕弾性表面波共振器の共振周
波数は前記二端子対弾性表面波フィルタの通過帯域外に
ある弾性表面波フィルタ。A ladder type surface acoustic wave filter having a piezoelectric substrate, at least one series arm surface acoustic wave resonator provided on the piezoelectric substrate, and at least one parallel arm surface acoustic wave resonator; A two-terminal pair surface acoustic wave filter cascaded to the ladder type surface acoustic wave filter on the piezoelectric substrate, and the anti-resonance frequency of the series arm surface acoustic wave resonator is the same as that of the two-terminal pair surface acoustic wave filter. A surface acoustic wave filter which is in the vicinity of a pass band and whose resonance frequency of the parallel arm surface acoustic wave resonator is outside the pass band of the two-port surface acoustic wave filter.
の対数と交差幅の積で決まる静電容量をＣｓ［pF］と
し、並列腕弾性表面波共振器のすだれ状電極の対数と交
差幅の積で決まる静電容量をＣｐ［pF］とするとき、Ｃ
ｓ＞Ｃｐである請求項１に記載の弾性表面波フィルタ。2. The capacitance determined by the product of the logarithm of the interdigital transducer of the series arm surface acoustic wave resonator and the cross width is Cs [pF], and the capacitance intersects the logarithm of the interdigital transducer of the parallel arm surface acoustic wave resonator. When the capacitance determined by the product of the width is Cp [pF], C
The surface acoustic wave filter according to claim 1, wherein s> Cp.
［MHz］とするとき、Ｃｓ・ｆｏ≧１００００である請
求項１に記載の弾性表面波フィルタ。3. The center frequency of the surface acoustic wave filter is fo.
2. The surface acoustic wave filter according to claim 1, wherein Cs · fo ≧ 10000 when [MHz] is set.
電極を三個以上備えた縦結合二重モード弾性表面波フィ
ルタである請求項１に記載の弾性表面波フィルタ。4. The surface acoustic wave filter according to claim 1, wherein the two-terminal pair surface acoustic wave filter is a longitudinally coupled double-mode surface acoustic wave filter having three or more interdigital electrodes.
弾性表面波フィルタである請求項１に記載の弾性表面波
フィルタ。5. The surface acoustic wave filter according to claim 1, wherein the two-terminal pair surface acoustic wave filter is a ladder type surface acoustic wave filter.
器のアース端子と二端子対弾性表面波フィルタのアース
端子とを圧電性基板上で電気的に接続した請求項１に記
載の弾性表面波フィルタ。6. The surface acoustic wave according to claim 1, wherein a ground terminal of at least one parallel arm surface acoustic wave resonator and a ground terminal of the two-terminal pair surface acoustic wave filter are electrically connected on a piezoelectric substrate. filter.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2000037815A JP2001230657A (en) | 2000-02-16 | 2000-02-16 | Surface acoustic wave filter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2000037815A JP2001230657A (en) | 2000-02-16 | 2000-02-16 | Surface acoustic wave filter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2001230657A true JP2001230657A (en) | 2001-08-24 |
Family
ID=18561648
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2000037815A Pending JP2001230657A (en) | 2000-02-16 | 2000-02-16 | Surface acoustic wave filter |
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| Country | Link |
|---|---|
| JP (1) | JP2001230657A (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100437495B1 (en) * | 2002-07-04 | 2004-06-25 | 주식회사 케이이씨 | Surface Acoustic Wave Filter |
| KR100847737B1 (en) | 2007-02-07 | 2008-07-23 | 주식회사 아이.티.에프 | Low shape filter in a mobile communication repeater |
| JP2010519813A (en) * | 2007-02-19 | 2010-06-03 | エプコス アクチエンゲゼルシャフト | Surface acoustic wave filter |
| US7733197B2 (en) * | 2006-12-25 | 2010-06-08 | Kyocera Corporation | Duplexer and communications equipment |
| US8988162B2 (en) | 2011-12-05 | 2015-03-24 | Taiyo Yuden Co., Ltd. | Filter and duplexer |
| US20150222247A1 (en) * | 2012-10-19 | 2015-08-06 | Murata Manufacturing Co., Ltd. | Antenna branching filter |
| US9148119B2 (en) | 2011-11-21 | 2015-09-29 | Taiyo Yuden Co., Ltd. | Filter and duplexer |
| JP2020182119A (en) * | 2019-04-25 | 2020-11-05 | 京セラ株式会社 | Acoustic wave filter, branching splitter, and communication device |
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2000
- 2000-02-16 JP JP2000037815A patent/JP2001230657A/en active Pending
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100437495B1 (en) * | 2002-07-04 | 2004-06-25 | 주식회사 케이이씨 | Surface Acoustic Wave Filter |
| US7733197B2 (en) * | 2006-12-25 | 2010-06-08 | Kyocera Corporation | Duplexer and communications equipment |
| KR100847737B1 (en) | 2007-02-07 | 2008-07-23 | 주식회사 아이.티.에프 | Low shape filter in a mobile communication repeater |
| JP2010519813A (en) * | 2007-02-19 | 2010-06-03 | エプコス アクチエンゲゼルシャフト | Surface acoustic wave filter |
| US8125300B2 (en) * | 2007-02-19 | 2012-02-28 | Epcos Ag | Surface acoustic wave filter comprising a band-pass filter and a band-stop filter |
| DE112008000116B4 (en) | 2007-02-19 | 2021-08-19 | Snaptrack, Inc. | FILTER WORKING WITH ACOUSTIC WAVES |
| US9148119B2 (en) | 2011-11-21 | 2015-09-29 | Taiyo Yuden Co., Ltd. | Filter and duplexer |
| US8988162B2 (en) | 2011-12-05 | 2015-03-24 | Taiyo Yuden Co., Ltd. | Filter and duplexer |
| US20150222247A1 (en) * | 2012-10-19 | 2015-08-06 | Murata Manufacturing Co., Ltd. | Antenna branching filter |
| JP2020182119A (en) * | 2019-04-25 | 2020-11-05 | 京セラ株式会社 | Acoustic wave filter, branching splitter, and communication device |
| JP7213747B2 (en) | 2019-04-25 | 2023-01-27 | 京セラ株式会社 | Acoustic wave filters, demultiplexers and communication devices |
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