JPH10173467A - Transversal saw filter - Google Patents
Transversal saw filterInfo
- Publication number
- JPH10173467A JPH10173467A JP35287896A JP35287896A JPH10173467A JP H10173467 A JPH10173467 A JP H10173467A JP 35287896 A JP35287896 A JP 35287896A JP 35287896 A JP35287896 A JP 35287896A JP H10173467 A JPH10173467 A JP H10173467A
- Authority
- JP
- Japan
- Prior art keywords
- electrode
- saw filter
- dummy
- idt
- electrodes
- 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.)
- Withdrawn
Links
Landscapes
- Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は弾性表面波フィルタ
に関し、特に位相特性と減衰傾度を改善したトランスバ
ーサル型ＳＡＷフィルタに関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave filter, and more particularly to a transversal SAW filter having improved phase characteristics and attenuation gradient.
【０００２】[0002]
【従来の技術】近年、弾性表面波フィルタは小型化、高
周波化、量産性等に優れているため、携帯電話をはじめ
とする無線機に多く利用されている。特に最近のＴＤＭ
Ａ、ＣＤＭＡ等のデジタル通信方式の無線機の第一ＩＦ
フィルタにおいては小型化に加え広帯域、且つ高減衰量
であって平坦位相特性の優れたものが要求されている。
特にトランスバーサル型ＳＡＷフィルタは他のデバイス
に比べ周波数−位相特性が直線的である点で優れてお
り、これらの要求の実現に最も近いデバイスとして注目
されている。図５は従来のトランスバーサル型ＳＡＷフ
ィルタの模式的電極パターンの平面図であって、水晶基
板１１の主面上に表面波の伝搬方向に沿って、２個のＩ
ＤＴ１２、１３を所定の間隙をおいて配置したトランス
バーサル型ＳＡＷフィルタである。前記２個のＩＤＴ１
２、１３はそれぞれ互いに間挿し合う複数本の電極指を
有する一対のくし形電極により構成されている。ＩＤＴ
１２、１３を構成するくし型電極の一方はアース電位端
子に接続され、他方のくし形電極は入力端子または出力
端子に電気的に接続されている。2. Description of the Related Art In recent years, surface acoustic wave filters have been widely used in wireless devices such as mobile phones because of their excellent miniaturization, high frequency, and mass productivity. Especially recent TDM
A, the first IF of a digital communication radio such as CDMA
In addition to miniaturization, filters are required to have a wide band, high attenuation, and excellent flat phase characteristics.
In particular, a transversal type SAW filter is superior to other devices in that the frequency-phase characteristics are linear, and is attracting attention as a device closest to fulfilling these requirements. FIG. 5 is a plan view of a schematic electrode pattern of a conventional transversal type SAW filter.
This is a transversal type SAW filter in which DTs 12 and 13 are arranged with a predetermined gap. The two IDTs 1
Reference numerals 2 and 13 each include a pair of comb-shaped electrodes having a plurality of electrode fingers interposed therebetween. IDT
One of the interdigital electrodes constituting the electrodes 12 and 13 is connected to a ground potential terminal, and the other interdigital electrode is electrically connected to an input terminal or an output terminal.
【０００３】図６、７は、ＣＤＭＡ等のディジタル通信
方式に用いる中心周波数Ｆ０＝２００ＭＨｚ、５ｄＢ通
過帯域幅Ｂ5 ＝１．２６ＭＨＺ以上、阻止域の減衰量と
して３３ｄＢ帯域幅Ｂ3 3 ＝２．５ＭＨＺ以下、平坦位
相特性等の要求に基づいて試作したトランスバーサル型
ＳＡＷフィルタの特性図である。いずれも圧電基板とし
て水晶基板を用い、電極パターンは図５に示したいわゆ
る正規型配置を採用し、ＩＤＴ１２は３４０対、ＩＤＴ
１３は６０４対とした。[0003] FIGS. 6 and 7, a center frequency F0 = 200 MHz for use in digital communication systems such as CDMA, 5 dB passband width B 5 = 1.26MHZ more, 33 dB bandwidth as attenuation of the stop band B 3 3 = 2. FIG. 7 is a characteristic diagram of a transversal SAW filter prototyped based on a requirement of flat phase characteristics and the like at 5 MHZ or less. In each case, a quartz substrate is used as the piezoelectric substrate, and the electrode pattern adopts a so-called regular arrangement shown in FIG.
13 was 604 pairs.
【０００４】図６は交差長Ｗが６０λの場合の特性例で
あり、図６（ａ）はその通過域特性、（ｂ）は減衰特性
であり、周波数に対する振幅の減衰量を示している。同
（ｃ）は位相特性であり、周波数に対する通過帯域内の
位相の直線性を示している。横軸は１目盛り２００ｋＨ
ｚ、縦軸は１目盛り５度であり両矢印はほぼ通過帯域を
示している。また、図７は交差長Ｗが７５λの場合のト
ランスバーサル型ＳＡＷフィルタの特性例であり、図７
（ａ）はその通過域特性、（ｂ）は減衰特性、（ｃ）は
位相特性である。尚、ここでλとはＳＡＷフィルタの中
心周波数における波長である。また、ここではＣＤＭＡ
方式等の高速ディジタル通信に影響の大きい位相特性の
直線性に注目すべく、当該分野ではその影響が無視でき
るＴＴＥ（トリプル・トランジット・エコー）を除いた
特性を示した。FIG. 6 shows an example of characteristics when the intersection length W is 60λ. FIG. 6 (a) shows the pass band characteristics, and FIG. 6 (b) shows the attenuation characteristics, showing the amount of amplitude attenuation with respect to frequency. (C) is a phase characteristic, which shows the linearity of the phase in the pass band with respect to the frequency. The horizontal axis is 200kH per scale
z, the vertical axis is 5 degrees on one scale, and both arrows substantially indicate the pass band. FIG. 7 shows a characteristic example of the transversal type SAW filter when the intersection length W is 75λ.
(A) shows the passband characteristic, (b) shows the attenuation characteristic, and (c) shows the phase characteristic. Here, λ is the wavelength at the center frequency of the SAW filter. Also, here, CDMA
In order to pay attention to the linearity of the phase characteristic which has a large effect on high-speed digital communication such as a system, characteristics in the relevant field excluding TTE (triple transit echo), whose influence is negligible, are shown.
【０００５】図８はトランスバーサル型ＳＡＷフィルタ
の交差長Ｗに着目し図６、７の諸特性を一覧表に纏めた
図である。ここで図８における位相直線性とは、１つの
簡易表示法であって、一般的にトランスバーサル型ＳＡ
Ｗフィルタの周波数−位相特性は図９（ａ）に示すよう
に所定の通過帯域（本例ではＦ０±０．６３ＭＨｚ）に
おいて、周波数の増加に対し直線的に増加すると考えら
れているが、微視的にみると直線Ａから僅かに蛇行する
偏差を有することが知られており、図９（ｂ）に示すよ
うに周波数に対する基準直線Ａからの位相偏差を求め通
過帯域周波数における位相偏差の最大値を位相直線性と
して定義したものである。図６〜８より明らかなよう
に、交差長Ｗを６０λから７５λへと長くすると、電極
指のオーミックロスが大きくなるため損入損失が１ｄＢ
強劣化するが、位相直線性は二十数％改善されている。
他の測定値はほぼ近い値を示している。FIG. 8 is a table in which various characteristics shown in FIGS. 6 and 7 are summarized in a table, focusing on the intersection length W of the transversal type SAW filter. Here, the phase linearity in FIG. 8 is one simple display method, and is generally a transversal type SA.
The frequency-phase characteristic of the W filter is considered to increase linearly with an increase in frequency in a predetermined pass band (F0 ± 0.63 MHz in this example) as shown in FIG. It is known that there is a slight meandering deviation from the straight line A when viewed visually. As shown in FIG. 9B, the phase deviation from the reference straight line A with respect to the frequency is obtained, and the maximum phase deviation at the passband frequency is obtained. The value is defined as phase linearity. As is clear from FIGS. 6 to 8, when the intersection length W is increased from 60λ to 75λ, the ohmic cross of the electrode finger becomes large, so that the loss loss is 1 dB.
Although it deteriorates strongly, the phase linearity is improved by more than 20%.
Other measured values are almost similar.
【０００６】このことは弾性素子技術ハンドブックP.18
1図3.56〜57 の「導波路の原理とその特性」の薄膜導波
路についての説明からも明らかなように、圧電基板の表
面に薄膜を付着するとその薄膜のスチフネス負荷効果、
質量負荷効果、電界短絡効果等により、弾性表面波の速
度が変化する。この速度変化を利用し、速度の速い領域
でサンドイッチ状に挟み込まれた速度の遅い領域に弾性
波エネルギーが閉じ込められたものが薄膜導波路であ
り、図３．５７には波長λに対する導波路幅ａの比ａ／
λにより、複数の低次のモードが近接する様子が示され
ており、導波路幅ａを広くしたとき複数の低次モードが
近接して位相変化が小さくなるため、周波数−位相特性
の直線性が向上すると考えられる。This is described in Elastic Element Technology Handbook P.18
1 As is clear from the explanation of the thin film waveguide in “Principles and characteristics of waveguides” in Figs. 3.56 to 57, when a thin film is attached to the surface of a piezoelectric substrate, the stiffness loading effect of the thin film,
The speed of the surface acoustic wave changes due to a mass load effect, an electric field short-circuit effect, and the like. A thin film waveguide in which elastic wave energy is confined in a low-speed region sandwiched in a sandwich between high-speed regions using this speed change is shown in FIG. 3.57. a ratio a /
λ indicates that a plurality of low-order modes are close to each other. When the waveguide width a is widened, the plurality of low-order modes are close to each other and the phase change is small, so that the linearity of the frequency-phase characteristic is small. Is thought to improve.
【０００７】[0007]
【発明が解決しようとする課題】しかしながら、従来の
トランスバーサル型ＳＡＷフィルタの位相特性は２つの
ＩＤＴの間隙を一定とすれば表面波の位相速度、即ち周
波数に比例し、周波数−位相特性は直線となるはずであ
るが、実際の位相特性は上述したように位相偏差が生じ
る。図８に示すトランスバーサル型ＳＡＷフィルタをＣ
ＤＭＡ等の高速デジタル通信の第１ＩＦとして用いるに
は、位相直線性が不十分であり、また減衰特性も要求を
満たすことができないという欠点がある。特に、周波数
−位相特性の直線性が不十分の場合には、ＣＤＭＡ等の
高速ディジタル信号を処理する場合に位相ズレによるビ
ットエラーが発生するという問題があった。また、上記
文献の理論に従ってさらに導波路の幅を広げるべく、図
１０のようにＩＤＴの電極指を長くし、交差長Ｗを広げ
ると、トランスバーサル型ＳＡＷフィルタを構成する低
次のモードを近接させることはできる。その結果、フィ
ルタの濾波特性、位相特性が改善される可能性がある
が、前記電極指のオーミックロス、即ち電極パターンの
抵抗分の増大による電気的損失が大きくなり、フィルタ
の挿入損失が増大するため、むやみに電極指を長くする
こともできないという問題があった。本発明は上記課題
を解決するためになされたものであって位相特性と減衰
傾度を改善したトランスバーサル型ＳＡＷフィルタを提
供することを目的とする。However, if the gap between the two IDTs is fixed, the phase characteristic of the conventional transversal type SAW filter is proportional to the phase velocity of the surface wave, that is, the frequency, and the frequency-phase characteristic is linear. However, the actual phase characteristic has a phase deviation as described above. The transversal type SAW filter shown in FIG.
For use as the first IF in high-speed digital communication such as DMA, there are disadvantages that the phase linearity is insufficient and the attenuation characteristics cannot meet the requirements. In particular, when the linearity of the frequency-phase characteristic is insufficient, there is a problem that a bit error due to a phase shift occurs when processing a high-speed digital signal such as CDMA. Further, in order to further increase the width of the waveguide according to the theory of the above-mentioned document, if the electrode fingers of the IDT are lengthened and the cross length W is widened as shown in FIG. It can be done. As a result, the filtering characteristics and phase characteristics of the filter may be improved. Therefore, there is a problem that the electrode finger cannot be lengthened unnecessarily. The present invention has been made to solve the above problems, and has as its object to provide a transversal SAW filter having improved phase characteristics and attenuation gradient.
【０００８】[0008]
【課題を解決するための手段】上記目的を達成するため
に本発明に係るの請求項１記載の発明は、圧電基板の主
面上に表面波の伝搬方向に沿って少なくとも２個以上の
ＩＤＴを配置したトランスバーサル型ＳＡＷフィルタに
おいて、前記ＩＤＴにダミー電極を形成すると共に該ダ
ミー電極と電極指とを互いに連結する連結電極を設けた
ことを特徴とするトランスバーサル型ＳＡＷフィルタで
ある。請求項２記載の発明は、請求項１のトランスバー
サル型ＳＡＷフィルタであって、ダミー電極間のスペー
スに電極を付着し、該電極を挟むダミー電極と一体化し
た電極指を少なくとも一カ所もうけて電極指のオーミッ
クロスを軽減したことを特徴とするトランスバーサル型
ＳＡＷフィルタである。According to a first aspect of the present invention, there is provided a piezoelectric substrate having at least two IDTs on a main surface of a piezoelectric substrate along a propagation direction of a surface wave. In the transversal SAW filter, a dummy electrode is formed on the IDT and a connection electrode for connecting the dummy electrode and the electrode finger is provided. According to a second aspect of the present invention, there is provided the transversal SAW filter according to the first aspect, wherein an electrode is attached to a space between the dummy electrodes, and at least one electrode finger integrated with the dummy electrode sandwiching the electrode is provided. A transversal SAW filter characterized by reducing ohmic loss of electrode fingers.
【０００９】[0009]
【発明の実施の形態】以下本発明を図面に示した実施の
形態に基づいて詳細に説明する。図１は本発明に係るト
ランスバーサル型ＳＡＷフィルタの実施の一例を示す模
式的電極パターンの平面図であって、水晶圧電基板１の
主面上に表面波の伝搬方向に沿って、２個のＩＤＴ２、
３を所定の間隙をおいて配置する。前記２個のＩＤＴ
２、３はそれぞれ互いに間挿し合う複数本の電極指を有
する一対のくし形電極と、ＩＤＴ２、３には対向するく
し形電極の電極指とほぼ同じ周期であって、バスバーか
ら対向する電極指の先端近傍まで延びるダミー電極４、
４・・と該ダミー電極４、４・・と相隣接した電極指と
を電気的に結ぶ複数本の微細線状の連結電極５、５・・
とから構成されている。DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the drawings. FIG. 1 is a plan view of a schematic electrode pattern showing an embodiment of a transversal type SAW filter according to the present invention. IDT2,
3 are arranged at a predetermined gap. The two IDTs
Reference numerals 2 and 3 denote a pair of comb-shaped electrodes each having a plurality of electrode fingers interposed therebetween, and IDTs 2 and 3 have substantially the same period as the electrode fingers of the opposing comb-shaped electrodes and oppose the electrode fingers from the bus bar. Dummy electrode 4 extending to near the tip of
A plurality of fine linear connection electrodes 5, 5,... Electrically connecting the dummy electrodes 4, 4,.
It is composed of
【００１０】以下、本発明の原理について説明する。周
波数−位相特性が直線となるのは単一共振モードのみで
トランスバーサル型ＳＡＷフィルタを構成する場合であ
り、実際のトランスバーサル型ＳＡＷフィルタでは上述
したように前記ＩＤＴ２、３の上に複数のモードが存在
し、これらモードの合成で構成されるトランスバーサル
型ＳＡＷフィルタの周波数−位相関係は直線とは成らず
位相偏差が生ずる。そこで本発明者は先に述べたように
トランスバーサル型ＳＡＷフィルタの導波路を広くする
ことにより位相偏差が改善されるとの知見に基づき、広
い導波路を確保すべくバスバーをその間隔が広くなるよ
うに配置すると共にＩＤＴの交差長はほぼ従来の値と
し、比較的長さの長いダミー電極を配置することによ
り、ＩＤＴの交差部分より外側のＤの領域においても音
響的連続性が保たれることとなり実質的には交差幅を広
くした場合と同様に、複数の低次モードの位相速度を互
いに近接し、位相特性が改善できると推論し試作を重ね
た。本発明に係る図１に示す実施例では、種々の実験結
果より最適な条件として、ダミー電極同士を横に連結す
る連結電極（概略幅λ／５）をほぼ２λ毎に設けること
により、ダミー電極を長くしたことによるオーミックロ
スの軽減を図る電極パターンを構成している。Hereinafter, the principle of the present invention will be described. The frequency-phase characteristic is linear when a transversal type SAW filter is constituted only by a single resonance mode. In an actual transversal type SAW filter, a plurality of modes are provided on the IDTs 2 and 3 as described above. And the frequency-phase relationship of the transversal SAW filter configured by combining these modes does not form a straight line, and a phase deviation occurs. The present inventor has found that the phase deviation is improved by widening the waveguide of the transversal type SAW filter as described above, and based on the finding that the width of the bus bar is widened to secure a wide waveguide. And the IDT intersection length is set to a substantially conventional value, and a relatively long dummy electrode is arranged, so that acoustic continuity is maintained even in the region D outside the IDT intersection. In other words, as in the case where the width of the crossing is substantially widened, the phase velocities of a plurality of lower-order modes are brought close to each other, and it is inferred that the phase characteristics can be improved, and trial production is repeated. In the embodiment shown in FIG. 1 according to the present invention, as an optimum condition based on various experimental results, a dummy electrode is provided by providing a connection electrode (approximately λ / 5) for connecting the dummy electrodes horizontally approximately every 2λ. The electrode pattern is designed to reduce the ohmic loss due to the lengthening of the electrode pattern.
【００１１】上記のように、ダミー電極の長さを長くし
これらが形成する導波路の幅が広くなると、前記したよ
うに表面波の伝搬方向と直交する方向に対称なモードが
複数個前記導波路下に存在できるようになる。従来はト
ランスバーサル型ＳＡＷフィルタの設計は、モードが複
数存在するという考え方をとらず、交差長方向に一様な
変位分布が伝搬方向に進行すると考えて設計していた。
本発明では、日本音響学会講演論文集、平成８年３月、
2-9-8「重み付けＩＤＴの道波モードを考慮したＣＯＭ
等価回路」の基づき、モードを考慮に入れる新しい考え
方で試作した。即ち、トランスバーサル型ＳＡＷフィル
タ諸特性は主モード単一で構成されるのではなく、図２
に振幅特性を示すようＳ１、Ｓ２、Ｓ３等の複数の低次
対称モードの合成によって構成されるものであって、モ
ードの次数が大きくなるにつれてそのフィルタの中心周
波数は高くなり、その挿入損失は大きくなる。これらの
低次モードの濾波特性の合成がトランスバーサル型ＳＡ
Ｗフィルタの振幅特性、即ち濾波特性となる。従って、
電極指の交差長とダミー電極の長とで形成する導波路幅
を広くすることにより、ＩＤＴ２、３上に存在する低次
のモード、即ちＳ１、Ｓ２、Ｓ３・・等の低次モードが
互いに近接し、各モードの和で構成されるトランスバー
サル型ＳＡＷフィルタの減衰特性は減衰傾度が改善され
ることになる。As described above, when the length of the dummy electrode is increased and the width of the waveguide formed by the dummy electrode is increased, as described above, a plurality of modes symmetric with respect to the direction orthogonal to the propagation direction of the surface wave are generated. Be able to exist under the wave path. Conventionally, the design of a transversal SAW filter has not been based on the concept that a plurality of modes exist, but has been designed on the assumption that a uniform displacement distribution in the direction of the intersection length proceeds in the propagation direction.
In the present invention, a collection of papers presented by the Acoustical Society of Japan, March 1996,
2-9-8 "COM with consideration for road mode of weighted IDT"
Based on the "equivalent circuit", a prototype was created with a new concept that takes modes into account. That is, the characteristics of the transversal type SAW filter are not composed of a single main mode, but are shown in FIG.
Is formed by synthesizing a plurality of low-order symmetric modes such as S1, S2, and S3 so as to exhibit an amplitude characteristic. As the mode order increases, the center frequency of the filter increases, and the insertion loss increases. growing. The synthesis of these low-order mode filtering characteristics is a transversal SA
It becomes the amplitude characteristic of the W filter, that is, the filtering characteristic. Therefore,
By increasing the width of the waveguide formed by the intersection length of the electrode fingers and the length of the dummy electrode, low-order modes existing on the IDTs 2 and 3, ie, low-order modes such as S1, S2, S3,. The attenuation characteristic of the transversal type SAW filter which is close to and composed of the sum of the modes has an improved attenuation gradient.
【００１２】同様に、トランスバーサル型ＳＡＷフィル
タの位相特性は低次モードのそれぞれの位相特性に影響
されるため、トランスバーサル型ＳＡＷフィルタの導波
路幅を狭くすると存在する低次モードの数が少なくな
り、且つこれらのモードのそれぞれの位相速度差が大き
くなり、その結果、それぞれのモードの周波数−位相特
性の差も大きくなり、これらのモードの合成で構成され
るトランスバーサル型ＳＡＷフィルタの位相特性は直線
性を欠くことになると推測される。逆に、ダミー電極を
長くし導波路を広くすると、低次のモードは互いに近接
し、低次モードそれぞれの位相速度が小さくなり、これ
ら低次モードの合成で構成されるトランスバーサル型Ｓ
ＡＷフィルタの位相特性も周波数に対し直線線性を増
し、偏差は小さくなると考えられる。更に、図１に示す
ようにＩＤＴ２、３にダミー電極と電極指との間に電極
パターンを充填した根元が幅広の電極６を間欠的に構成
し、電極指とダミー電極による音響的連続性を保ちつ
つ、オーミックロスの低減を実現することもできる。
尚、種々の実験結果より、ダミー電極をほぼ５λ／２毎
に電極指、スペース及び電極指を纏めて１つのダミー電
極６を形成することが望ましい。Similarly, the phase characteristics of the transversal type SAW filter are affected by the respective phase characteristics of the low-order modes. Therefore, when the waveguide width of the transversal type SAW filter is reduced, the number of existing low-order modes decreases. And the phase velocity difference between these modes becomes large. As a result, the difference between the frequency and phase characteristics of each mode also becomes large, and the phase characteristic of the transversal type SAW filter constituted by combining these modes becomes large. Is assumed to lack linearity. Conversely, when the length of the dummy electrode is increased and the waveguide is widened, the lower-order modes are closer to each other, and the phase velocities of the respective lower-order modes are reduced.
It is considered that the phase characteristic of the AW filter also increases linearity with respect to the frequency, and the deviation decreases. Further, as shown in FIG. 1, the IDTs 2 and 3 are formed with an electrode 6 having a wide base intermittently filled with an electrode pattern between the dummy electrode and the electrode finger, so that the acoustic continuity between the electrode finger and the dummy electrode is improved. It is also possible to reduce ohmic loss while maintaining the same.
From various experimental results, it is desirable to form one dummy electrode 6 by grouping the electrode fingers, the space, and the electrode fingers approximately every 5λ / 2.
【００１３】図３は本発明に係るトランスバーサル型Ｓ
ＡＷフィルタの特性例を示す図であって、交差長Ｗを６
０λ、ダミー電極長Ｄを５０λ（２５λ＋２５λ）とし
た以外は図７の諸パラメータと同一である。図３（ａ）
は通過域特性を、（ｂ）は減衰特性を、（ｃ）は位相特
性を示す。本発明の一実施例である図３に示す測定値と
図７に示した特性（Ｗ＝７５λ）の測定値とを一覧表に
纏めると図４に示す図となる。図４から明らかなように
電極指の交差長Ｗ、ダミー電極の長さＤを長くしても本
発明になる電極指構成手段を用いることによって、挿入
損失（Ｌｏｓｓ）は従来のものと同等に維持したまま、
位相直線性はほぼ３０％改善され、減衰傾度Ｂ3 3 ／Ｂ
5 もほぼ５．２％急峻な特性を得ることができる。FIG. 3 shows a transversal type S according to the present invention.
FIG. 4 is a diagram illustrating an example of characteristics of an AW filter, wherein an intersection length W is 6;
The parameters are the same as those in FIG. 7 except that 0λ and the dummy electrode length D are set to 50λ (25λ + 25λ). FIG. 3 (a)
Shows passband characteristics, (b) shows attenuation characteristics, and (c) shows phase characteristics. FIG. 4 is a table summarizing the measured values shown in FIG. 3 and the measured values of the characteristics (W = 75λ) shown in FIG. 7 according to an embodiment of the present invention. As is clear from FIG. 4, even when the intersection length W of the electrode fingers and the length D of the dummy electrode are increased, the insertion loss (Loss) is equal to that of the conventional one by using the electrode finger forming means according to the present invention. While maintaining
Phase linearity is improved approximately 30%, the attenuation slope B 3 3 / B
5 can also obtain a steep characteristic of almost 5.2%.
【００１４】以上の説明で圧電基板として水晶基板を用
いた場合を説明してきたが、水晶のみに限らずＬｉＴａ
Ｏ３、ＬｉＮｂＯ３、ＬＢＯその他表面波を励振できる
圧電材料であるなら、本発明が適用できることは言うま
でもない。また、連結電極として複数本の細い直線状の
導電パターンを用いた例を示したが必ずしも直線である
必要はなく、電極指のオーミックロスが改善でき、電極
指とダミー電極の音響的連続性を維持できるものであれ
ば、いかなる配置で構成してもよい。なお、連結電極５
の形成はＩＤＴ２、３のそれぞれの電極指を形成する際
に、フォトリソグラフィ技術で同時に形成するため余分
な工程は必要としない。In the above description, the case where a quartz substrate is used as the piezoelectric substrate has been described.
It is needless to say that the present invention can be applied to any piezoelectric material capable of exciting O3, LiNbO3, LBO, and other surface waves. In addition, an example in which a plurality of thin linear conductive patterns are used as the connection electrodes has been described, but it is not necessarily required to be a straight line. Any arrangement may be used as long as it can be maintained. The connection electrode 5
No extra step is required because the electrodes are formed by photolithography at the same time when the electrode fingers of the IDTs 2 and 3 are formed.
【００１５】また、本発明は２個のＩＤＴのトランスバ
ーサル型ＳＡＷフィルタのみに限らず、マルチＩＤＴ等
を含むＩＤＴが３個以上のトランスバーサル型ＳＡＷフ
ィルタにも適用できることは言うまでもない。更に、縦
結合型多重モード表面波フィルタにも適用が可能であ
る。また、電極指の幅がλ／４幅の以外の電極指で構成
された表面波デバイスに適用できる。例えばスプリット
電極を用い多表面波デバイス、表面波の一方向性を図る
ため電極指幅を変えたような表面波デバイスにも適用が
可能である。Further, it is needless to say that the present invention can be applied not only to a transversal SAW filter having two IDTs but also to a transversal SAW filter having three or more IDTs including a multi-IDT. Further, the present invention can be applied to a longitudinally coupled multi-mode surface wave filter. Further, the present invention can be applied to a surface acoustic wave device including an electrode finger having a width other than the λ / 4 width. For example, the present invention can be applied to a multi-surface wave device using a split electrode and a surface wave device in which the width of an electrode finger is changed in order to achieve unidirectional surface waves.
【００１６】[0016]
【発明の効果】本発明は、以上説明したように構成した
ので、トランスバーサル型ＳＡＷフィルタに本発明を適
用すると、挿入損失を劣化させることなく周波数−位相
特性の直線性を大幅にに改善すること可能となった。さ
らに低次モードの近接を交差長とダミー電極長で調整す
ることにより、挿入損失を損なうことなく該フィルタの
減衰傾度を改善できるという著しい効果を奏する。Since the present invention is configured as described above, when the present invention is applied to a transversal type SAW filter, the linearity of the frequency-phase characteristic is greatly improved without deteriorating the insertion loss. It became possible. Further, by adjusting the proximity of the low-order mode by the intersection length and the dummy electrode length, there is a remarkable effect that the attenuation gradient of the filter can be improved without impairing the insertion loss.
【図１】本発明に係るトランスバーサル型ＳＡＷフィル
タの実施の一形態例を示す平面図である。FIG. 1 is a plan view showing one embodiment of a transversal SAW filter according to the present invention.
【図２】トランスバーサル型ＳＡＷフィルタが低次のモ
ードのそれぞれの特性により合成されていることを説明
する図である。FIG. 2 is a diagram for explaining that a transversal SAW filter is synthesized according to the characteristics of each of low-order modes.
【図３】図（ａ）、（ｂ）、（ｃ）はそれぞれ本発明に
なるトランスバーサル型ＳＡＷフィルタの通過域特性、
減衰域特性及び位相特性である。3 (a), 3 (b) and 3 (c) show passband characteristics of a transversal SAW filter according to the present invention, respectively.
These are an attenuation region characteristic and a phase characteristic.
【図４】本発明のトランスバーサル型ＳＡＷフィルタと
従来のフィルタの比較した図である。FIG. 4 is a diagram comparing a transversal SAW filter of the present invention with a conventional filter.
【図５】従来のトランスバーサル型ＳＡＷフィルタの平
面図である。FIG. 5 is a plan view of a conventional transversal type SAW filter.
【図６】図（ａ）、（ｂ）、（ｃ）はそれぞれ従来のト
ランスバーサル型ＳＡＷフィルタの通過域特性、減衰域
特性及び位相特性である。FIGS. 6 (a), (b), and (c) show a pass band characteristic, an attenuation band characteristic, and a phase characteristic of a conventional transversal SAW filter, respectively.
【図７】図（ａ）、（ｂ）、（ｃ）はそれぞれ従来のト
ランスバーサル型ＳＡＷフィルタの通過域特性、減衰域
特性及び位相特性である。FIGS. 7 (a), (b) and (c) show a pass band characteristic, an attenuation band characteristic and a phase characteristic of a conventional transversal type SAW filter, respectively.
【図８】従来のトランスバーサル型ＳＡＷフィルタの交
差長を変えた場合の諸時性である。FIG. 8 shows various times when the cross length of a conventional transversal type SAW filter is changed.
【図９】（ａ）、（ｂ）は位相特性を説明する図であ
る。FIGS. 9A and 9B are diagrams illustrating phase characteristics.
【図１０】ＩＤＴの交差長を長くしたトランスバーサル
型ＳＡＷフィルタの平面図である。FIG. 10 is a plan view of a transversal type SAW filter having a longer IDT crossing length.
１・・・圧電基板 ２、３・・・ＩＤＴ ４・・・ダミー電極 ５・・・連結電極 ６・・・一体化電極指 Ｄ・・・ダミー電極長 Ｗ・・・交差長 Ｓ１、Ｓ２、Ｓ３・・・低次モード DESCRIPTION OF SYMBOLS 1 ... Piezoelectric substrate 2, 3 ... IDT 4 ... Dummy electrode 5 ... Connection electrode 6 ... Integrated electrode finger D ... Dummy electrode length W ... Intersection length S1, S2, S3: Low-order mode
Claims (2)
沿って少なくとも２個以上のＩＤＴを配置したトランス
バーサル型ＳＡＷフィルタにおいて、前記ＩＤＴにダミ
ー電極を形成すると共に該ダミー電極と電極指とを互い
に連結する連結電極を設けたことを特徴とするトランス
バーサル型ＳＡＷフィルタ。1. A transversal SAW filter in which at least two or more IDTs are arranged on a main surface of a piezoelectric substrate along a propagation direction of a surface wave, a dummy electrode is formed on the IDT, and the dummy electrode and the electrode are connected to each other. A transversal SAW filter comprising a connection electrode for connecting a finger to each other.
スに電極を付着し、両者を一体化した部分を少なくとも
一カ所もうけて電極指のオーミックロスを軽減したこと
を特徴とするトランスバーサル型ＳＡＷフィルタ。2. A transversal type wherein an electrode is attached to a space between the dummy electrode and the electrode finger, and at least one integrated portion is provided to reduce ohmic loss of the electrode finger. SAW filter.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP35287896A JPH10173467A (en) | 1996-12-13 | 1996-12-13 | Transversal saw filter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP35287896A JPH10173467A (en) | 1996-12-13 | 1996-12-13 | Transversal saw filter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH10173467A true JPH10173467A (en) | 1998-06-26 |
Family
ID=18427074
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP35287896A Withdrawn JPH10173467A (en) | 1996-12-13 | 1996-12-13 | Transversal saw filter |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH10173467A (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003087083A (en) * | 2001-07-04 | 2003-03-20 | Murata Mfg Co Ltd | Comb type electrode section, surface acoustic wave device and communications equipment for surface acoustic wave |
| EP1324489A1 (en) * | 2001-12-21 | 2003-07-02 | Temex | Method for realising surface acoustic wave filter arrangements and filter arrangement obtained in accordance to this method |
| KR100679195B1 (en) * | 2001-12-21 | 2007-02-07 | 후지쓰 메디아 데바이스 가부시키가이샤 | Surface acoustic wave resonator and surface acoustic wave filter |
| US7671705B2 (en) | 2006-09-29 | 2010-03-02 | Tdk Corporation | Surface acoustic wave filter and resonator utilizing a branch electrode with an electrically opened end |
| JPWO2016170982A1 (en) * | 2015-04-24 | 2017-05-18 | 株式会社村田製作所 | Elastic wave device |
| WO2020120153A1 (en) * | 2018-12-12 | 2020-06-18 | RF360 Europe GmbH | Electro acoustic resonator with suppressed transversal gap mode excitation and reduced transversal modes |
| WO2023286704A1 (en) * | 2021-07-16 | 2023-01-19 | 京セラ株式会社 | Elastic wave device, filter, splitter, and communication device |
-
1996
- 1996-12-13 JP JP35287896A patent/JPH10173467A/en not_active Withdrawn
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003087083A (en) * | 2001-07-04 | 2003-03-20 | Murata Mfg Co Ltd | Comb type electrode section, surface acoustic wave device and communications equipment for surface acoustic wave |
| EP1324489A1 (en) * | 2001-12-21 | 2003-07-02 | Temex | Method for realising surface acoustic wave filter arrangements and filter arrangement obtained in accordance to this method |
| KR100679195B1 (en) * | 2001-12-21 | 2007-02-07 | 후지쓰 메디아 데바이스 가부시키가이샤 | Surface acoustic wave resonator and surface acoustic wave filter |
| US7671705B2 (en) | 2006-09-29 | 2010-03-02 | Tdk Corporation | Surface acoustic wave filter and resonator utilizing a branch electrode with an electrically opened end |
| JPWO2016170982A1 (en) * | 2015-04-24 | 2017-05-18 | 株式会社村田製作所 | Elastic wave device |
| WO2020120153A1 (en) * | 2018-12-12 | 2020-06-18 | RF360 Europe GmbH | Electro acoustic resonator with suppressed transversal gap mode excitation and reduced transversal modes |
| US11876504B2 (en) | 2018-12-12 | 2024-01-16 | Rf360 Singapore Pte. Ltd. | Electro acoustic resonator with suppressed transversal gap mode excitation and reduced transversal modes |
| WO2023286704A1 (en) * | 2021-07-16 | 2023-01-19 | 京セラ株式会社 | Elastic wave device, filter, splitter, and communication device |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JPH06260876A (en) | Surface acoustic wave filter | |
| JP2003243965A (en) | Surface acoustic wave filter | |
| JPS62188512A (en) | Surface elastic wave resonator, surface elastic wave resonator filter and manufacture of them | |
| JP4100249B2 (en) | Surface acoustic wave device, communication device | |
| WO2000076067A1 (en) | Saw filter | |
| JP3929415B2 (en) | Surface acoustic wave device | |
| CN110048691B (en) | Acoustic resonator, filter and multiplexer | |
| JPH10173467A (en) | Transversal saw filter | |
| JP3890740B2 (en) | Surface acoustic wave waveguide structure and device using the same | |
| JP3918433B2 (en) | Horizontal double mode SAW filter | |
| JP3113199B2 (en) | Surface acoustic wave device | |
| JP3310132B2 (en) | Surface acoustic wave device and antenna duplexer using the same | |
| JP4821079B2 (en) | Comb electrode section for surface acoustic wave, surface acoustic wave device, communication device | |
| JP3154402B2 (en) | SAW filter | |
| JP4457914B2 (en) | Unidirectional surface acoustic wave transducer and surface acoustic wave device using the same | |
| KR102561687B1 (en) | Transducer structure for source suppression in SAW filter devices | |
| CN1551499B (en) | Surface acoustic wave device | |
| EP0255263A2 (en) | Transducer | |
| JPH1117493A (en) | Surface acoustic wave device | |
| WO2020020643A1 (en) | Saw device with a slanted resonator | |
| JP3436812B2 (en) | Surface acoustic wave converter | |
| JP3035085B2 (en) | Unidirectional surface acoustic wave converter | |
| GB2333196A (en) | Surface acoustic wave device | |
| JPH03295308A (en) | Surface acoustic wave resonator | |
| JP4454703B2 (en) | Surface acoustic wave filter |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20050704 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20050726 |
|
| A521 | Written amendment |
Effective date: 20050912 Free format text: JAPANESE INTERMEDIATE CODE: A523 |
|
| A02 | Decision of refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A02 Effective date: 20060117 |
|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20060209 |
|
| RD03 | Notification of appointment of power of attorney |
Free format text: JAPANESE INTERMEDIATE CODE: A7423 Effective date: 20060209 |
|
| A521 | Written amendment |
Effective date: 20060213 Free format text: JAPANESE INTERMEDIATE CODE: A523 |
|
| A911 | Transfer of reconsideration by examiner before appeal (zenchi) |
Free format text: JAPANESE INTERMEDIATE CODE: A911 Effective date: 20060216 |
|
| A912 | Removal of reconsideration by examiner before appeal (zenchi) |
Effective date: 20060428 Free format text: JAPANESE INTERMEDIATE CODE: A912 |
|
| RD04 | Notification of resignation of power of attorney |
Free format text: JAPANESE INTERMEDIATE CODE: A7424 Effective date: 20070410 |
|
| A761 | Written withdrawal of application |
Free format text: JAPANESE INTERMEDIATE CODE: A761 Effective date: 20080122 |