JPH071859B2 - Surface acoustic wave filter - Google Patents
Surface acoustic wave filterInfo
- Publication number
- JPH071859B2 JPH071859B2 JP63056245A JP5624588A JPH071859B2 JP H071859 B2 JPH071859 B2 JP H071859B2 JP 63056245 A JP63056245 A JP 63056245A JP 5624588 A JP5624588 A JP 5624588A JP H071859 B2 JPH071859 B2 JP H071859B2
- Authority
- JP
- Japan
- Prior art keywords
- mode
- idt
- surface acoustic
- acoustic wave
- logarithm
- 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.)
- Expired - Lifetime
Links
- 238000010897 surface acoustic wave method Methods 0.000 title claims description 61
- 239000000758 substrate Substances 0.000 claims description 23
- 230000009977 dual effect Effects 0.000 claims description 19
- WSMQKESQZFQMFW-UHFFFAOYSA-N 5-methyl-pyrazole-3-carboxylic acid Chemical compound CC1=CC(C(O)=O)=NN1 WSMQKESQZFQMFW-UHFFFAOYSA-N 0.000 claims description 4
- 239000010408 film Substances 0.000 description 25
- 238000006073 displacement reaction Methods 0.000 description 10
- 238000009826 distribution Methods 0.000 description 10
- 238000010586 diagram Methods 0.000 description 9
- 230000007423 decrease Effects 0.000 description 7
- 229910013641 LiNbO 3 Inorganic materials 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000000737 periodic effect Effects 0.000 description 2
- 239000010453 quartz Substances 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- PIGFYZPCRLYGLF-UHFFFAOYSA-N Aluminum nitride Chemical compound [Al]#N PIGFYZPCRLYGLF-UHFFFAOYSA-N 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- PSHMSSXLYVAENJ-UHFFFAOYSA-N dilithium;[oxido(oxoboranyloxy)boranyl]oxy-oxoboranyloxyborinate Chemical compound [Li+].[Li+].O=BOB([O-])OB([O-])OB=O PSHMSSXLYVAENJ-UHFFFAOYSA-N 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 230000005624 perturbation theories Effects 0.000 description 1
- 230000001902 propagating effect Effects 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
Landscapes
- Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
Description
【発明の詳細な説明】 （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、特にエネルギー
閉じ込め形２端子対弾性表面波共振子の多重モード共振
を利用した広い通過帯域特性を有する弾性表面波フィル
タに関するものである。Description: TECHNICAL FIELD The present invention relates to a surface acoustic wave filter, and more particularly to an elastic surface having wide pass band characteristics utilizing multimode resonance of an energy trap type two-terminal surface acoustic wave resonator. The present invention relates to a surface wave filter.
（従来の技術） 圧電基板上のすだれ状変換器（Interdigital Transduce
r,以下IDTと略記する）の両側に、格子状反射器を有す
るエネルギー閉じ込め形弾性表面波共振子およびフィル
タは、摂動論とモード結合理論に基づいて設計される。
このようなエネルギー閉じ込め形弾性表面波共振子は、
通常第１図(a)に示すように、圧電基板１の表面中央部
に設けられたIDT2の両側に周期的構造の格子状のグレー
ティング（格子状）反射器３が配置された構成を有して
いる。このような構成において、IDT2によって励振され
た弾性表面波は、両側の格子状反射器３によって多重反
射されて定在波となり、そのエネルギーの大部分が両側
の格子状反射器３の間に閉じ込められる。このとき弾性
表面波の伝搬方向（縦方向、矢印で図に示す）にキャビ
ティが構成されているため、例えば、定在波の包絡線が
第１図(b)の４に示すような変位分布をもつ縦０次共振
モードが励起される。７は１端子対（1port）の入力端
子である。IDT2の対数は、通常、数10対以上多数設けら
れるが第１図の場合省略して２対のみ示してある。第１
図以降の図面も対数を省略して示す。(Prior Art) Interdigital Transduce on a Piezoelectric Substrate
r, abbreviated as IDT hereinafter), energy trapped surface acoustic wave resonators and filters having grating reflectors on both sides are designed based on perturbation theory and mode coupling theory.
Such an energy trap type surface acoustic wave resonator is
Usually, as shown in FIG. 1 (a), a structure in which a grating-shaped grating (grid-shaped) reflector 3 having a periodic structure is arranged on both sides of an IDT2 provided in the central portion of the surface of the piezoelectric substrate 1 is provided. ing. In such a configuration, the surface acoustic wave excited by the IDT 2 is multiple-reflected by the grating reflectors 3 on both sides to become a standing wave, and most of its energy is confined between the grating reflectors 3 on both sides. To be At this time, because the cavity is formed in the propagation direction of the surface acoustic wave (longitudinal direction, indicated by an arrow), for example, the envelope of the standing wave has a displacement distribution as shown by 4 in FIG. 1 (b). The longitudinal 0th-order resonance mode with is excited. Reference numeral 7 is an input terminal of one terminal pair (1 port). The number of logarithms of the IDT2 is usually several tens or more, but in FIG. 1 it is omitted and only two pairs are shown. First
The figures after the figure are also shown with the logarithm omitted.
圧電基板１の材料は、通常、タンタル酸リチウム(LiTaO
3)，ニオブ酸リウチウム(LiNbO3)，水晶等の圧電単結晶
基板,PZT系圧電セラミックス基板、又は例えばシリコン
基板上に酸化亜鉛（ZnO），窒化アルミ（AlN）等の圧電
薄膜をスパッタリング等で形成したものが用いられ、ID
T2およびグレーティング反射器３の電極材料には、通常
アルミニュウム（Al）等が使用される。The material of the piezoelectric substrate 1 is usually lithium tantalate (LiTaO
3 ), Lithium niobate (LiNbO 3 ), a piezoelectric single crystal substrate such as quartz, a PZT-based piezoelectric ceramic substrate, or a piezoelectric thin film such as zinc oxide (ZnO) or aluminum nitride (AlN) on a silicon substrate by sputtering, etc. What is formed is used, ID
Aluminum (Al) or the like is usually used for the electrode material of the T2 and the grating reflector 3.
弾性表面波共振子でフィルタを構成する場合、第１図に
示した１端子対弾性表面波共振子のIDT2を２つ、または
それ以上に分割して入力IDTと出力IDTとにした単一の共
振モードを有する２端子対共振子を、複数個縦続接続す
る構成が知られている。即ち弾性表面波共振子を２端子
対とし段単接続する構成である。When configuring a filter with a surface acoustic wave resonator, the IDT2 of the one-terminal-pair surface acoustic wave resonator shown in FIG. 1 is divided into two or more to form a single input IDT and output IDT. A configuration is known in which a plurality of two-terminal pair resonators having a resonance mode are connected in cascade. That is, the surface acoustic wave resonator has a structure in which two terminal pairs are used and single-stage connection is made.
まず、単一共振モードを有する２端子対共振子は、次の
ような電極構成と共振モードを有する。First, a two-terminal pair resonator having a single resonance mode has the following electrode configuration and resonance mode.
第２図(a)は、IDTを２分割した形で電極対数の相等しい
入力IDT2Aと出力IDT2Bとを格子反射器３の間に設けた２
端子対弾性表面波共振子の電極構成例であり、７は入力
端子、８は出力端子である。なお、第２図以降では、圧
電基板１の図示は省略する。第２図(b)は、第１図(b)と
同様に変位分布を示す。In FIG. 2 (a), an input IDT2A and an output IDT2B having the same number of electrode pairs are provided between the grating reflectors 3 in a form in which the IDT is divided into two.
It is an example of an electrode structure of a terminal pair surface acoustic wave resonator, 7 is an input terminal, and 8 is an output terminal. Note that the illustration of the piezoelectric substrate 1 is omitted in FIGS. FIG. 2 (b) shows the displacement distribution as in FIG. 1 (b).
一般に、エネルギー閉じ込め形２端子対共振子におい
て、格子状反射器３の間のIDT対数を多くすると共振子
の容量比γ（共振周波数と反共振周波数の差の逆数に比
例する値）が小さくなり、フィルタを構成した時に通過
帯域幅が広くとれることが知られている。Generally, in the energy trap type two-terminal pair resonator, when the number of IDT pairs between the lattice reflectors 3 is increased, the capacitance ratio γ of the resonator (a value proportional to the reciprocal of the difference between the resonance frequency and the anti-resonance frequency) becomes small. It is known that a wide pass band can be obtained when a filter is constructed.
第２図に示す２端子対弾性表面波共振子の利用する共振
モードは、第１図の場合と同様に縦０次モード４である
が、通過帯域幅を広くするためにIDT2Aおよび2Bの対数
を多くすると、第２図(b)の５に示すような非調和高次
の縦１次モードが存在するようになり、フィルタを構成
したときにスプリアスとなって帯域を広くするにも限界
があり、圧電基板がXcut−112゜Ｙ伝搬LiTaO3の場合、
最大比帯域幅が約0.26％程度であった。The resonance mode used by the two-terminal surface acoustic wave resonator shown in FIG. 2 is the vertical zeroth-order mode 4 as in the case of FIG. 1, but the logarithm of the IDTs 2A and 2B is set to widen the pass band width. When the number of the filters is increased, there exists an anharmonic higher-order longitudinal first-order mode as shown by 5 in FIG. 2 (b), and there is a limit to widen the band as spurious when the filter is configured. Yes, if the piezoelectric substrate is Xcut-112 ° Y propagating LiTaO 3 ,
The maximum specific bandwidth was about 0.26%.
第３図は、格子状反射器３の間のIDTを３分割した形
で、その中央のIDTを入力IDT2Dとし、その両側の電極対
数が相等しいIDT2Cと2Eは電気的に並列接続して出力IDT
とした入力端子７と出力端子８を有する２端子対弾性表
面波共振子の電極構成例と、縦方向共振モードの変位分
布である。第３図の場合、出力IDT2Cと2Eが中央の入力I
DT2Dに対して対称に配置させることによって、第２図
(b)に示した縦１次モード５を抑圧し、利用する縦０次
モード４だけを励起しようとしたものである。この単一
共振モード２端子対共振子は、弾性表面波フィルタとし
て用いられる。しかし、このような３つのIDTを有する
弾性表面波フィルタを、さらに通過帯域幅を広くするた
め、両側の格子状反射器３の相互間隔を広げてIDTの電
極対数を多くすると図に示すような縦２次共振モード６
が現れ、これがスプリアスとなってフィルタの広帯域化
に限界があり、圧電基板がXcut−112゜Ｙ伝搬LiTaO3の
場合、最大比帯域幅が約0.29％程度であった。Fig. 3 shows the IDT between the grid reflectors 3 divided into three parts. The IDT at the center is the input IDT2D, and the IDTs 2C and 2E on both sides of which have the same number of electrode pairs are electrically connected in parallel and output. IDT
2 is an electrode configuration example of a two-terminal surface acoustic wave resonator having the input terminal 7 and the output terminal 8 and the displacement distribution of the longitudinal resonance mode. In the case of FIG. 3, the output IDTs 2C and 2E are the central input I.
By arranging them symmetrically with respect to DT2D,
It is intended to suppress the longitudinal first-order mode 5 shown in (b) and excite only the vertical zero-order mode 4 to be used. This single resonance mode two-terminal pair resonator is used as a surface acoustic wave filter. However, in order to further widen the pass band width of the surface acoustic wave filter having such three IDTs, the mutual spacing of the grating reflectors 3 on both sides is widened to increase the number of electrode pairs of the IDT as shown in the figure. Vertical secondary resonance mode 6
Appears, and there is a limit to widening the band of the filter as a spurious, and when the piezoelectric substrate is Xcut-112 ° Y-propagating LiTaO 3 , the maximum specific bandwidth is about 0.29%.
次に、上述した単一モード２端子対共振子を複数個縦続
接続して弾性表面波フィルタを構成する場合の従来例を
説明する。Next, a conventional example in which a plurality of single mode two-terminal pair resonators described above are connected in cascade to form a surface acoustic wave filter will be described.
第４図は、第３図の単一モード弾性表面波共振子を２段
縦続接続した２重モードフィルタの構成例を示す。接続
段数は２段に限らずそれ以上でもよい。第４図におい
て、2C,2D,2E,3,7,8は第３図の場合と同じである。FIG. 4 shows a configuration example of a dual mode filter in which the single mode surface acoustic wave resonators of FIG. 3 are cascade-connected in two stages. The number of connection stages is not limited to two and may be more. In FIG. 4, 2C, 2D, 2E, 3, 7, 8 are the same as in FIG.
第４図のように同一圧電基板１（図示は略）上に同一構
造の単一モード共振子２個を弾性表面波の伝搬方向で平
行でかつ互いに音響結合しないような間隔で並設し、中
央のIDT2Dをそれぞれ入力IDT,出力IDTとし、その両側の
IDT2C,2Eをすべて電気的に並列接続した場合、それぞれ
の２端子対共振子の伝搬方向と直角な方向（横方向）
に、IDTの電極指が交叉する領域で周期的電極指による
反射と摂動によって弾性表面波の伝搬速度がその両側の
領域より低下して弾性表面波導波路が構成されて、第４
図(c)に示すような共振モードを有し、それぞれ対称モ
ード９と反対称モード10が互いに独立して存在する。こ
のような構成では、対称モード９と縦０次モード４との
組み合せによる対称縦０次モードと、反対称モード10と
縦０次モード４との組み合わせによる反対称縦０次モー
ドとの２重モードが利用され、しかも反対称縦０次モー
ドの反共振周波数と、対称縦０次モードの共振周波数が
一致するため、特別な周波数合わせをしなくても、反対
称縦０次モードの共振周波数から対称縦０次モードの反
共振周波数までを通過帯域とする２重モード弾性表面波
フィルタが実現できる。しかし、この２重モード弾性表
面波フィルタの通過帯域を広げるため、両側の格子状反
射器３の相互間隔を広げてIDT対数をさらに多くする
と、第３図と同様に縦２次モード６が存在するようにな
り、このモードに起因するスプリアスが発生するためフ
ィルタの広帯域化には限界があった。As shown in FIG. 4, two single mode resonators having the same structure are arranged on the same piezoelectric substrate 1 (not shown) in parallel with each other in the propagation direction of the surface acoustic wave and at intervals such that they are not acoustically coupled to each other. The IDT2D in the center is used as the input IDT and output IDT, and
When IDT2C and 2E are all electrically connected in parallel, the direction (transverse direction) perpendicular to the propagation direction of each 2-terminal pair resonator
In addition, in the area where the electrode fingers of the IDT intersect, the propagation velocity of the surface acoustic wave becomes lower than the areas on both sides thereof due to the reflection and perturbation by the periodic electrode fingers, and the surface acoustic wave waveguide is constructed.
It has a resonance mode as shown in FIG. 3C, and a symmetric mode 9 and an antisymmetric mode 10 exist independently of each other. In such a configuration, there are doubled a symmetric longitudinal 0th order mode which is a combination of the symmetric mode 9 and the longitudinal 0th order mode, and an antisymmetric longitudinal 0th order mode which is a combination of the antisymmetric mode 10 and the longitudinal 0th order mode 4. Since the mode is used and the anti-resonance frequency of the anti-symmetric longitudinal zero-order mode and the resonance frequency of the symmetrical longitudinal zero-order mode match, the resonance frequency of the anti-symmetric longitudinal zero-order mode does not have to be adjusted. It is possible to realize a dual-mode surface acoustic wave filter having a pass band from to the anti-resonance frequency of the symmetric longitudinal zero-order mode. However, in order to widen the pass band of this dual-mode surface acoustic wave filter, if the mutual interval between the grating reflectors 3 on both sides is widened and the IDT logarithm is further increased, the longitudinal secondary mode 6 exists as in FIG. As a result, spurious signals are generated due to this mode, and there is a limit to widening the band of the filter.
（発明の目的） 本発明の目的は、従来スプリアスとして扱われていた縦
２次モードを利用し周波数合わせを行うことにより、通
過帯域幅の広い２重モード弾性表面波フィルタ、および
４重モード弾性表面波フィルタを提供することにある。(Object of the Invention) An object of the present invention is to use a longitudinal secondary mode, which has been conventionally treated as a spurious, to perform frequency matching, thereby providing a dual mode surface acoustic wave filter having a wide pass band width and a quadruple mode elasticity. It is to provide a surface wave filter.
（発明の構成と作用） 本発明は、縦０次モードを利用する単一モード２端子対
弾性表面波フィルタの両側の格子状反射器の相互間隔を
広げてその間のIDT対数を多くし、ある対数以上になっ
たとき新たに励起される縦２次モードを有効活用する手
段を設定して通過帯域幅の広い２重モード２端子対弾性
表面波フィルタを実現したものであり、圧電基板と、該
圧電基板の中央に配置された入力側IDTと、該入力側IDT
の両側に配置され並列接続された前記入力側IDTとほぼ
等しい電極対数を有する出力側IDTと、該出力側IDTの両
側に配置された格子状反射器とを備えて、弾性表面波の
伝搬方向に励起される縦０次共振モードを利用するエネ
ルギー閉じ込め形２端子対弾性表面波フィルタにおい
て、 前記入力側IDTおよび２つの出力側IDTの全体の電極対数
を縦２次共振モードが励起される対数以上に設定し、か
つ、前記反射器の格子ピッチＰに対する電極膜厚Ｈの比
（H/P）を前記縦０次共振モードの共振周波数と前記縦
２次共振モードの反共振周波数の正規化周波数差が0.00
05より小さくなるように設定したことを特徴とするもの
である。(Structure and Action of the Invention) The present invention increases the mutual distance between the grating reflectors on both sides of the single-mode two-terminal pair surface acoustic wave filter using the 0th-order longitudinal mode to increase the number of IDT pairs therebetween. A dual mode two terminal pair surface acoustic wave filter having a wide pass band width is realized by setting means for effectively utilizing a longitudinal second-order mode that is newly excited when the number of logarithms or more is achieved. The input-side IDT arranged in the center of the piezoelectric substrate and the input-side IDT
The output-side IDT, which is arranged on both sides of the output-side IDT and has substantially the same number of electrode pairs as the input-side IDT, and the grid-shaped reflectors arranged on both sides of the output-side IDT. In an energy confinement type two-terminal-pair surface acoustic wave filter utilizing a longitudinal zeroth-order resonance mode excited to the above, the total number of electrode pairs of the input-side IDT and the two output-side IDTs is defined as a logarithm in which the longitudinal second-order resonance mode is excited. The ratio (H / P) of the electrode film thickness H to the grating pitch P of the reflector is set as described above, and the resonance frequency of the longitudinal zero-order resonance mode and the anti-resonance frequency of the longitudinal secondary resonance mode are normalized. Frequency difference is 0.00
It is characterized by being set to be smaller than 05.
以下図面により本発明を詳細に説明する。The present invention will be described in detail below with reference to the drawings.
第５図(a),(b)は、本発明による２重モード２端子対弾
性表面波フィルタの実施例の電極の構成例と、縦０次モ
ード(M0)4と縦２次モード(M2)6の変位分布を示す。FIGS. 5 (a) and 5 (b) show an example of the electrode configuration of the embodiment of the dual mode two-terminal pair surface acoustic wave filter according to the present invention, and the vertical zero-order mode (M 0 ) 4 and the vertical secondary mode ( The displacement distribution of M 2 ) 6 is shown.
第５図(a)において、格子状反射器３の間の７を入力端
子とする入力IDT2Gと、８を出力端子とする並列接続さ
れた出力IDT2Fと2Hの電極対数は、第４図に示した従来
のIDTの電極対数より多いので第５図では３対ずつで示
してあるが、実際には多数対形成される。また、IDT電
極指のピッチ11は反射器３の格子ピッチ12より若干小さ
く設定される。すなわち、IDTの放射コンダクタンスが
最大になる周波数と反射器のストップバンド（反射器が
反射し得る周波数帯域幅）の中心周波数とが一致するよ
うなピッチに設定される。さらに、両側反射器３の相互
間隔Ｌの中心に関して左右対称の電極構成とするため、
IDTの相互間隔14およびIDTと反射器３の相互間隔13はそ
れぞれ等しく形成される。また、IDTと反射器３の間隔1
3は、通常反射器３の格子ピッチ12と等しく設定され
る。第５図(c),(d)は、第５図(a)に示した実施例のIDT
電極部の他の変形例を示す。第５図(c)は、IDT間隔14が
０の場合すなわち互いに近接する接地側電極指を共通電
極指とした場合の例であり、第５図(d)は、IDT間隔14が
IDT電極指ピッチ11の２倍になるように共通接続された
接地側電極指を１本増やした場合の例を示す。この場合
接地側電極指を１本増やす代りに全面電極指としてもよ
い。In Fig. 5 (a), the number of electrode pairs of the input IDT2G having the input terminal 7 between the grid-shaped reflectors 3 and the output IDT2F and 2H connected in parallel having the output terminal 8 are shown in Fig. 4. Since the number of electrode pairs is larger than that of the conventional IDT, three pairs are shown in FIG. 5, but a large number of pairs are actually formed. The pitch 11 of the IDT electrode fingers is set to be slightly smaller than the grid pitch 12 of the reflector 3. That is, the pitch is set so that the frequency at which the radiative conductance of the IDT becomes maximum and the center frequency of the stop band (frequency bandwidth in which the reflector can reflect) of the reflector match. Furthermore, since the electrode configuration is left-right symmetric with respect to the center of the mutual distance L between the two-side reflectors 3,
The mutual spacing 14 of the IDT and the mutual spacing 13 of the IDT and the reflector 3 are formed equal to each other. Also, the space between the IDT and reflector 3 1
3 is usually set equal to the grating pitch 12 of the reflector 3. 5 (c) and 5 (d) are the IDTs of the embodiment shown in FIG. 5 (a).
The other modification of an electrode part is shown. FIG. 5 (c) is an example when the IDT interval 14 is 0, that is, when the ground-side electrode fingers that are close to each other are used as the common electrode finger, and FIG. 5 (d) shows that the IDT interval 14 is
An example is shown in which one ground-side electrode finger commonly connected is increased so as to have twice the IDT electrode finger pitch 11. In this case, instead of adding one ground side electrode finger, a full surface electrode finger may be used.
第６図は、第５図の実施例における２つのモードM0とM2
のそれぞれ共振周波数(fr)16,18と反共振周波数(fa)15,
17の両反射器間の全体のIDT対数に対する関係を示す。
この時の正規化膜厚H/P（H:電極の膜厚,P:反射器３の格
子ピッチ12）は0.06である。また縦軸はf0＝v/2P（v:自
由表面の表面波速度）で正規化した周波数であり、横軸
のIDT対数は両反射器の間隔Ｌに入り得る最大のIDT対数
である。即ち、言い換えれば、両反射器の間隔Ｌを全体
のIDT対数で表したものである。以下特に断らない限り
この意味で使用する。第６図に於いて、IDT対数が約70
対以下では、第５図の共振子は縦０次モードM0のみの単
一モードであり、約70対以上では縦２次モードM2が現れ
てくる。また縦０次モードM0の共振周波数16と縦２次モ
ードM2の反共振周波数17との差はIDT対数が多くなるに
従って小さくなる。FIG. 6 shows two modes M 0 and M 2 in the embodiment shown in FIG.
Resonant frequency (f r ) 16, 18 and anti-resonant frequency (f a ) 15,
The relationship between the total IDT logarithm between the two 17 reflectors is shown.
At this time, the normalized film thickness H / P (H: film thickness of the electrode, P: grating pitch 12 of the reflector 3) is 0.06. The vertical axis is the frequency normalized by f 0 = v / 2P (v: surface wave velocity of the free surface), and the IDT logarithm on the horizontal axis is the maximum IDT logarithm that can be in the interval L between both reflectors. That is, in other words, the distance L between the two reflectors is represented by the total IDT logarithm. The term will be used in this sense unless otherwise specified. In Fig. 6, the IDT logarithm is about 70.
Below the pair, the resonator of FIG. 5 is a single mode with only the longitudinal zero-order mode M 0 , and above about 70 pairs, the longitudinal secondary mode M 2 appears. Further, the difference between the resonance frequency 16 of the longitudinal 0th order mode M 0 and the antiresonance frequency 17 of the longitudinal 2nd order mode M 2 becomes smaller as the logarithm of the IDT increases.
第７図は、第５図の実施例における縦０次モードM0と縦
２次モードM2のそれぞれの共振周波数(fr)16,18と反共
振周波数(fa)15,17の膜厚依存度を示したものでIDT対数
は150対の場合である。第７図において、電極膜厚が厚
くなる（H/Pが大きくなる）につれて、それぞれのモー
ドM0,M2の容量比が小さくなり、共振周波数frと反共振
周波数faとの差が大きくなるとともに、それぞれの周波
数は低くなる傾向を示す。FIG. 7 shows a film of the resonance frequency (f r ) 16 and 18 and the anti-resonance frequency (f a ) 15 and 17 of the longitudinal zero-order mode M 0 and the longitudinal second-order mode M 2 in the embodiment of FIG. The thickness dependence is shown, and the IDT logarithm is 150 pairs. In FIG. 7, as the electrode film thickness increases (H / P increases), the capacitance ratio between the modes M 0 and M 2 decreases, and the difference between the resonance frequency f r and the anti-resonance frequency f a becomes smaller. As the frequency increases, the respective frequencies tend to decrease.
本発明では、第６図と第７図の特性で示される縦２次モ
ードM2の反共振周波数17と縦０次モードM0の共振周波数
16の周波数差が小さくなることに着目し、例えば、正規
化膜厚（H/P）を0.06に設定し、その値における両反射
器間の全IDT対数を第６図に示したように240対に設定す
ることにより、縦０次モードM0の共振周波数frと縦２次
モードM2の反共振周波数faを近づけて正規化周波数の周
波数差が0.0005以下になるようにする。このように、ID
T対数と膜厚を予め設定することによってスプリアスと
して扱われていた縦２次モードM2を通過帯域幅を広げる
ために有効活用できることを発見したのである。In the present invention, the anti-resonance frequency 17 of the longitudinal second-order mode M 2 and the resonance frequency of the vertical 0th-order mode M 0 shown in the characteristics of FIGS. 6 and 7
Focusing on the fact that the frequency difference of 16 becomes small, for example, the normalized film thickness (H / P) is set to 0.06, and the total IDT logarithm between both reflectors at that value is set to 240 as shown in FIG. by setting the pair, a frequency difference between the normalized frequency close the anti-resonance frequency f a of the resonance frequency f r and the vertical second mode M 2 of the longitudinal zero-order mode M 0 is set to be 0.0005 or less. Thus, the ID
It was discovered that the longitudinal second-order mode M 2 that was treated as a spurious can be effectively used to widen the pass bandwidth by setting the T logarithm and the film thickness in advance.
IDT対数と膜厚の選定はいずれを先に設定してもよい。
第７図でH/Pを0.07に設定すれば、第６図でのIDT対数が
210程度となることが示されている。Either the IDT logarithm or the film thickness may be selected first.
If H / P is set to 0.07 in Fig. 7, the logarithm of IDT in Fig. 6 becomes
It is shown to be around 210.
即ち、圧電基板の材質，種類にそれぞれ対応するIDT対
数と電極膜厚を設定することにより、縦０次モードM0の
共振周波数frと縦２次モードM2の反共振周波数faの周波
数差を小さくし、通過帯域幅の広い２重モード２端子対
弾性表面波フィルタを実現したのである。That is, by setting the IDT logarithm and the electrode film thickness corresponding to the material and type of the piezoelectric substrate, respectively, the resonance frequency f r of the vertical zero-order mode M 0 and the anti-resonance frequency f a of the vertical secondary mode M 2 are set. The difference was reduced and a dual mode dual terminal pair surface acoustic wave filter with a wide pass band was realized.
本実施例では圧電基板はXcut−112゜回転Ｙ伝搬LiTaO3
を用いた場合、比帯域幅が約0.40％得られた。In this embodiment, the piezoelectric substrate is Xcut-112 ° rotated Y-propagating LiTaO 3
A bandwidth of about 0.40% was obtained with.
さらに、本発明では、以上の技術思想に基づき、上述の
２重モード２端子対弾性表面波フィルタ２個を同一の圧
電基板上に並設し、電気的に縦続接続することによって
４つの共振モードを組み合わせて有効活用する手段を設
定し、通過帯域幅が広く、帯域外減衰量の優れた４重モ
ード弾性表面波フィルタを実現したものであり、前述の
２重モード２端子対弾性表面波フィルタの電極構成を有
する第１の電極構造列と、該第１の電極構造列と線対称
の電極構造を有し弾性表面波の伝搬方向が平行でかつ互
いに音響結合しないように弾性表面波の波長の３倍以上
の間隔で同一圧電基板上に並設された第２の電極構造列
とから構成され、 前記第１の電極構造列の中央のIDTを入力変換器とし、
前記第１の電極構造列の前記入力側IDTの両側の出力側I
DTと前記第２の電極構造列の両側の出力側IDTのそれぞ
れ相対する電極が共通接続され、前記第２の電極構造列
の中央のIDTを出力IDTとし、 弾性表面波の伝搬方向に励起される縦２次共振モード，
縦０次共振モードと、弾性表面波の伝搬方向と直角方向
に生ずる反対称モード，対称モードとが組み合わされ周
波数の低い方から順次配列される反対称縦２次モード，
対称縦２次モード，反対称縦０次モード，対称縦０次モ
ードの４つのモードの隣りあう３箇所のそれぞれ反共振
周波数と共振周波数との正規化周波数差を、前記第１お
よび第２の電極構造列のそれぞれに対して、全体のIDT
対数，正規化膜厚，全体のIDT対数に対する中央のIDT対
数の割合,IDTの相互間隔を設定することによって0.0005
より小さくしたことを特徴とするものである。Further, according to the present invention, based on the above technical idea, two above-mentioned dual mode two-terminal pair surface acoustic wave filters are arranged side by side on the same piezoelectric substrate and electrically connected in cascade to thereby obtain four resonance modes. The present invention realizes a quadruple-mode surface acoustic wave filter having a wide pass band width and an excellent out-of-band attenuation by setting a means for effectively utilizing the combination of the two modes described above. And a wavelength of the surface acoustic wave so that the propagation directions of the surface acoustic waves are parallel to each other and are not acoustically coupled to each other. And a second electrode structure row arranged side by side on the same piezoelectric substrate at an interval of three times or more, and the central IDT of the first electrode structure row is used as an input converter,
Output sides I on both sides of the input side IDT of the first electrode structure row
The opposing electrodes of the DT and the output-side IDTs on both sides of the second electrode structure row are commonly connected, and the central IDT of the second electrode structure row is used as the output IDT and is excited in the propagation direction of the surface acoustic wave. Vertical secondary resonance mode,
An antisymmetric longitudinal quadratic mode in which a longitudinal zero-order resonance mode, an antisymmetric mode generated in a direction orthogonal to the propagation direction of a surface acoustic wave, and a symmetric mode are combined and sequentially arranged from the lower frequency side,
The normalized frequency difference between the anti-resonance frequency and the resonance frequency at three adjoining points of the four modes of the symmetric longitudinal second-order mode, the anti-symmetric longitudinal zero-order mode, and the symmetric longitudinal zero-order mode is calculated as follows. The total IDT for each of the electrode structure rows
0.0005 by setting logarithm, normalized film thickness, ratio of central IDT logarithm to total IDT logarithm, mutual interval of IDT
It is characterized by being made smaller.
以下図面により本発明による４重モード弾性表面波フィ
ルタについて詳細に説明する。Hereinafter, a quadruple mode surface acoustic wave filter according to the present invention will be described in detail with reference to the drawings.
第８図は、本発明による４重モード弾性表面波フィルタ
の実施例で、その電極構成と縦０次モード4,縦２次モー
ド６および対称モード9,反対称モード10の変位分布を示
した。第８図(a)に示した電極構成例は、図の上側の電
極構造列は第５図の本発明による２重モード２端子対弾
性表面波フィルタの構成と全く同じであり、下側の電極
構造列は、上側の構成と同一の形でもよいが、フィルタ
としての入力側と出力側のインピーダンス終端条件が等
しくなるような形として、２つの電極構造列の間の中心
線に関して線対称になるような電極構成を採用してい
る。そして２つの電極構造列は、平行でかつ、互いに音
響結合しない間隔（弾性表面波の波長の約３倍程度以
上）で揃えて配設される。即ち、上側の電極構造列の両
反射器３の間の中央にある入力IDT2Gを入力端子７から
励振し、その両側の電極対数のほぼ等しい（約１％程度
の差）IDT2Fと2Hとを並列接続した上側電極構造列の出
力側と、下側電極構造列の３組のIDTの両側のIDTを並列
に接続した入力側とを電気的に共通接続し、中央のIDT
の出力が出力端子８から取り出される。なお、IDTと反
射器の間隔13とIDT相互の間隔14は第５図同様それぞれ
相等しく、第５図(c),(d)に示した変形例と同様なIDT電
極構成を形成することもできる。FIG. 8 shows an embodiment of a quadruple mode surface acoustic wave filter according to the present invention, and shows the electrode configuration and the displacement distributions of the longitudinal 0th mode 4, the longitudinal 2nd mode 6, the symmetrical mode 9, and the antisymmetrical mode 10. . In the electrode configuration example shown in FIG. 8 (a), the electrode structure row on the upper side of the figure is exactly the same as the configuration of the dual mode 2-terminal pair surface acoustic wave filter according to the present invention of FIG. The electrode structure row may have the same shape as that of the upper side structure, but the shape is such that the impedance termination conditions on the input side and the output side of the filter are equal, and the electrode structure row is line-symmetric with respect to the center line between the two electrode structure rows. The following electrode configuration is adopted. The two electrode structure rows are arranged parallel to each other at intervals (about three times the wavelength of the surface acoustic wave or more) that do not acoustically couple with each other. That is, the input IDT2G located in the center between the two reflectors 3 in the upper electrode structure row is excited from the input terminal 7, and the IDT2F and 2H having the same number of electrode pairs on both sides thereof (the difference of about 1%) are arranged in parallel. The output side of the connected upper electrode structure row and the input side where the IDTs on both sides of the three IDTs of the lower electrode structure row are connected in parallel are electrically connected in common, and the central IDT
Is taken out from the output terminal 8. The distance 13 between the IDT and the reflector and the distance 14 between the IDTs are the same as in FIG. 5, and it is possible to form an IDT electrode structure similar to that of the modification shown in FIGS. 5 (c) and 5 (d). it can.
第８図に示す本発明による構成例では、縦０次モード４
及び縦２次モード６とは独立に対称モード９と反対称モ
ード10が存在し、これらの４つのモードを組合わせた反
対称縦２次モード(M2a)，対称縦２次モード(M2s)，反対
称縦０次モード(M0a)および対称縦０次モード(Mos)が存
在する。第４図の従来の方法では、M0aモードとMosモー
ドを利用し周波数合わせを必要としない２重モード弾性
表面波共振子フィルタであったが、前記４つのモードで
はM2aモードの反共振周波数faとM2sモードの共振周波数
fr、M2sモードの反共振周波数faとM0aモードの共振周波
数frおよびM0aモードの反共振周波数faとM0sモードの共
振周波数frをそれぞれ一致させる周波数合わせを必要と
する。従って、第８図の構成例にて、前記３組の周波数
合わせを行うことにより、４重モード弾性表面波共振子
フィルタを実現することができる。In the configuration example according to the present invention shown in FIG.
Also, there are a symmetric mode 9 and an antisymmetric mode 10 independently of the longitudinal quadratic mode 6, and an antisymmetric longitudinal quadratic mode (M 2a ), a symmetric longitudinal quadratic mode (M 2s ) that combines these four modes. ), An antisymmetric longitudinal zero-order mode (M 0a ) and a symmetrical longitudinal zero-order mode (M os ). In the fourth view of a conventional method, although there was a M 0a mode and M os mode double mode SAW resonator filter which does not require a frequency matching using the anti-resonance of the M 2a modes in four modes Frequency f a and resonance frequency of M 2s mode
f r, require frequency adjustment to match respectively the resonance frequency f r of the anti-resonance frequency f a and M 0 s-mode resonance frequency f r and M 0a mode antiresonance frequency f a and M 0a mode M 2s Mode . Therefore, in the configuration example of FIG. 8, a quadruple mode surface acoustic wave resonator filter can be realized by performing the three sets of frequency matching.
第９図は、４つの共振モードのリアクタンス特性例図で
ある。第９図に示すように、M2aモード22の反共振周波
数とM2sモード21の共振周波数fr（Ｂ点の近傍）、M2sモ
ード21の反共振周波数faとM0aモード20の共振周波数fr
（Ｃ点の近傍）、M0aモード20の反共振周波数faとM0sモ
ード19の共振周波数fr（Ｄ点の近傍）がそれぞれ一致す
れば、M2aモード（周波数が最も低いモード）22の共振
周波数Ａ点からM0sモード（周波数が最も高いモード）1
9の反共振周波数Ｅ点までを通過帯域とする４重モード
フィルタが実現できることがイメージパラメータ理論に
より明らかである。FIG. 9 is a diagram showing an example of reactance characteristics of four resonance modes. As shown in FIG. 9, the anti-resonance frequency of the M 2a mode 22 and the resonance frequency f r of the M 2s mode 21 (near point B), the anti-resonance frequency f a of the M 2s mode 21 and the resonance of the M 0a mode 20. Frequency f r
(Near the point C), if the anti-resonance frequency f a of the M 0a mode 20 and the resonance frequency f r of the M 0s mode 19 (near the point D) match, the M 2a mode (the lowest frequency mode) 22 Resonance frequency from point A to M 0s mode (highest frequency mode) 1
It is clear from the image parameter theory that a quadruple mode filter having a pass band up to point 9 of anti-resonance frequency can be realized.
従来から行われている第４図の２重モードフィルタに於
いては、縦２次モード６はスプリアスとして扱われてお
り、これらのモードの影響を減らすようにフィルタの設
計が行われていた。このスプリアスとして扱われていた
縦２次モード６を、IDT対数，入出力IDT対数の割合,IDT
間隔及び膜厚の条件を見い出すことによって、周波数合
わせを行い、縦０次モード４と縦２次モード６の両方を
利用した４重モードフィルタを実現したのが本発明であ
る。In the conventional dual mode filter shown in FIG. 4, the longitudinal secondary mode 6 is treated as spurious, and the filter is designed to reduce the influence of these modes. The vertical secondary mode 6 that was treated as this spurious, IDT logarithm, ratio of input / output IDT logarithm, IDT
The present invention realizes a quadruple mode filter using both vertical 0th order mode 4 and vertical 2nd order mode 6 by performing frequency matching by finding the conditions of the interval and the film thickness.
第８図および第９図におけるM2a,M2s,M0a,M0sの各モー
ドの共振周波数frと反共振周波数faは、IDT対数,IDT間
隔，入出力IDT対数の割合〔第５図に於いて中央のIDTの
対数が全体のIDT対数に占める割合（但し、中央に対し
左右対称とする。）すなわち２つの共振子の結合の度合
いを示すことになる。〕および膜厚に依存する。以下、
各要素の依存度について説明する。The resonance frequency f r and anti-resonance frequency f a of each mode of M 2a , M 2s , M 0a , and M 0s in FIGS. 8 and 9 are the IDT logarithm, the IDT interval, and the ratio of the input / output IDT logarithm [5th In the figure, the ratio of the logarithm of the central IDT to the total logarithm of the IDT (however, it is symmetrical with respect to the center), that is, the degree of coupling of two resonators is shown. ] And the film thickness. Less than,
The dependency of each element will be described.
第10図は、膜厚H/P＝0.06,全体のIDT対数に対する中央
のIDT対数の比が0.29,IDT間隔14をIDT電極指のピッチ11
の４倍の場合の全体のIDT対数に対する前記４つのモー
ドの共振，反共振周波数の関係を示す。この図からM2s
モードとM2aモードの変化率はM0sモードとM0aモードの
変化率に比べて大きく、IDT対数を243対とすれば、M2s
モードの反共振周波数27とM0aモードの共振周波数26を
一致させることができる。即ち、図で示されるように全
体のIDT対数が215〜275対のときM0aモードの共振周波数
26とM2sモードの反共振周波数27の正規化周波数の差が
0.0005以内となり実用領域であることがわかる。Figure 10 shows the film thickness H / P = 0.06, the ratio of the central IDT logarithm to the total IDT logarithm is 0.29, the IDT interval 14 is the IDT electrode finger pitch 11
4 shows the relationship between the resonance and anti-resonance frequencies of the above four modes with respect to the total IDT logarithm in the case of 4 times. From this figure M 2s
The rate of change between the mode and M 2a mode is larger than the rate of change between the M 0s mode and M 0a mode, and if the IDT logarithm is 243 pairs, M 2s
The mode anti-resonance frequency 27 and the M 0a mode resonance frequency 26 can be matched. That is, as shown in the figure, when the total number of IDT pairs is 215 to 275, the resonance frequency of the M 0a mode is
26 and the normalized frequency difference between the antiresonance frequency 27 of the M 2s mode 27
It is within 0.0005, which is a practical area.
第11図は、全体のIDT対数が180対のとき膜厚を変えて周
波数合わせをするときの特性を示すものであり、全体の
IDT対数に対する中央のIDT対数の比が0.33,IDT間隔14が
IDT電極指のピッチ11の４倍の時の膜厚に対する各モー
ドの共振，反共振周波数の関係を示しており、膜厚が厚
くなると前記４つのモードの周波数は低下し、M2sモー
ドの反共振周波数27とM0aモードの共振周波数26の周波
数差が小さくなる傾向を示す。FIG. 11 shows the characteristics when the frequency is adjusted by changing the film thickness when the total number of IDT pairs is 180 pairs.
The ratio of the central IDT logarithm to the IDT logarithm is 0.33, and the IDT interval 14 is
The relationship between the resonance and anti-resonance frequencies of each mode with respect to the film thickness when the pitch of the IDT electrode fingers is 4 times is shown. As the film thickness increases, the frequencies of the four modes decrease, and the M 2s mode anti-resonance decreases. The frequency difference between the resonance frequency 27 and the resonance frequency 26 of the M 0a mode tends to decrease.
この図から、全体のIDT対数を200以上にすれば、正規化
膜厚が0.07のときM0aモードの共振周波数26とM2sモード
の反共振周波数27の正規化周波数の差が0.0005程度の実
用領域になることがわかる。From this figure, if the overall IDT logarithm is set to 200 or more, the difference between the normalized frequencies of the resonance frequency 26 of the M 0a mode and the antiresonance frequency 27 of the M 2s mode is about 0.0005 when the normalized film thickness is 0.07. It turns out that it becomes an area.
第12図は、全体のIDT対数が180対のときの中央のIDT対
数の全体のIDT対数に対する割合を変えたときの特性を
示すものであり、正規化膜厚H/P＝0.06,IDT間隔14がIDT
電極指のピッチ11の４倍のときの、中央のIDT対数が全
体のIDT対数に占める割合と、前記４つのモードの共
振，反共振周波数との関係を示す。この図によって、中
央のIDT対数の全体のIDT対数に占める割合が0.27〜0.31
のとき、M2aモードの反共振周波数29とM2sモードの共振
周波数28,M0aモードの反共振周波数25とM0sモードの共
振周波数24とをそれぞれ近づけて正規化周波数の差が実
用領域になることがわかる。Figure 12 shows the characteristics when the ratio of the central IDT logarithm to the total IDT logarithm was changed when the total IDT logarithm was 180 pairs. The normalized film thickness H / P = 0.06, IDT interval 14 is IDT
The relationship between the ratio of the central IDT logarithm to the total IDT logarithm and the resonance and anti-resonance frequencies of the four modes when the pitch of the electrode fingers is four times is shown. This figure shows that the central IDT log accounts for 0.27 to 0.31 of the total IDT log.
At this time, the anti-resonance frequency 29 of the M 2a mode, the resonance frequency 28 of the M 2s mode, the anti-resonance frequency 25 of the M 0a mode and the resonance frequency 24 of the M 0s mode are brought close to each other, and the difference between the normalized frequencies becomes the practical range. You can see.
第13図は、膜厚H/P＝0.06,IDT対数250対，全体のIDT対
数に対する中央のIDT対数の比が0.28の場合、IDT間隔
（第８図の14）と前記４つのモードの共振，反共振周波
数の関係を示しており、IDT間隔14が４〜８（×Ｐ）の
とき、M2sモードの反共振周波数27とM0aモードの共振周
波数26との周波数合わせができて実用領域になることが
わかる。Fig. 13 shows the film thickness H / P = 0.06, IDT logarithm 250 pairs, and the ratio of the central IDT logarithm to the total IDT logarithm is 0.28, the IDT interval (14 in Fig. 8) and the resonance of the four modes. , Shows the relation of anti-resonance frequency, and when the IDT interval 14 is 4 to 8 (× P), the anti-resonance frequency 27 of the M 2s mode and the resonance frequency 26 of the M 0a mode can be matched and the practical range can be achieved. It turns out that
以上まとめると、M2sモードの反共振周波数27とM0aモー
ドの共振周波数26との周波数を一致させるには、IDT対
数，膜厚,IDT間隔の３つの要素が条件となり、M2aモー
ドの反共振周波数29とM2sモードの共振周波数28およびM
0aモードの反共振周波数25とM0sモードの共振周波数24
の周波数を一致させるには、中央のIDT対数が全体のIDT
対数に占める割合が条件となる。In summary, to match the frequency of the resonant frequency 26 of the anti-resonance frequency 27 and M 0a mode M 2s mode, IDT logarithmic, thickness, three elements of the IDT interval is a condition, the anti of M 2a Mode Resonant frequency 29 and M 2s mode resonant frequency 28 and M
0a mode anti-resonance frequency 25 and M 0s mode resonance frequency 24
To match the frequencies of, the central IDT logarithm is
The condition is the ratio to the logarithm.
従って、フィルタの設計に於いて、前記３組の周波数合
わせを行うための条件は多様になるが、膜厚を厚くした
場合、第11図によってM2sモードの反共振周波数27とM0a
モードの共振周波数26はそれぞれ低下する傾向にある
が、その周波数差は縮まる傾向にあるため、その分IDT
対数は少なくてよいことがわかる。また、第12図により
M2aモードの反共振周波数29とM2sモードの共振周波数2
8、およびM0aモードの反共振周波数25とM0sモードの共
振周波数24は入出力IDTの割合を0.27〜0.31変えること
により行えばよいことがわかる。Therefore, in the design of the filter, the conditions for performing the above three sets of frequency matching are varied, but when the film thickness is increased, the anti-resonance frequency 27 and M 0a of the M 2s mode are shown in FIG.
The resonance frequency 26 of each mode tends to decrease, but the frequency difference tends to decrease.
It turns out that the logarithm is small. Also, according to FIG.
M 2a mode anti-resonance frequency 29 and M 2s mode resonance frequency 2
8 and the anti-resonance frequency 25 of the M 0a mode and the resonance frequency 24 of the M 0s mode can be determined by changing the ratio of input / output IDTs by 0.27 to 0.31.
前記の周波数合わせの条件は、第12図の２組24と25およ
び28と29と第13図の１組26と27合計３組の周波数がそれ
ぞれ全て一致した時がフィルタの最適条件であるが、多
少ずれた場合は帯域内のリップルとして現れる。しか
し、そのリップルが許容範囲以内であれば、その分ずれ
ても差し支えない。また、帯域内リップルは入出力終端
インピーダンスによってもある程度調整できることは云
うまでもない。The optimum conditions for the above-mentioned frequency adjustment are the optimum conditions of the filter when the two groups 24 and 25 and 28 and 29 in FIG. 12 and the one group 26 and 27 in FIG. , If there is a slight shift, it appears as a ripple within the band. However, if the ripple is within the allowable range, it may be offset by that amount. Further, it goes without saying that the in-band ripple can be adjusted to some extent also by the input / output termination impedance.
従って、第８図の構成に於いて、フィルタの構成要素で
ある第５図の２重モード共振子では、実用上の膜厚がH/
P＝0.005〜0.08の場合全体のIDT対数は、90対以上必要
であるが、この２重モード共振子を２段縦続接続した第
８図の４重モードフィルタでは、おおむね120対以上は
必要となる。Therefore, in the configuration of FIG. 8, in the dual mode resonator of FIG. 5 which is a constituent element of the filter, the practical film thickness is H /
When P = 0.005 to 0.08, the total number of IDT pairs is required to be 90 pairs or more, but in the quadruple mode filter of FIG. 8 in which the double mode resonators are connected in two stages, approximately 120 pairs or more are required. Become.
第14図は、本発明による第８図の４重モード弾性表面波
フィルタの伝送特性例を示す。比帯域幅が約0.40％であ
り、従来の約0.26％に比べて約1.5倍の帯域幅が得られ
た。この場合の４つの条件は、膜厚H/P＝0.06,IDT対数
＝240対，入出力IDTの割合＝0.29,IDT間隔＝4Pである。FIG. 14 shows an example of transmission characteristics of the quadruple mode surface acoustic wave filter of FIG. 8 according to the present invention. The specific bandwidth is about 0.40%, which is about 1.5 times the conventional bandwidth of about 0.26%. The four conditions in this case are film thickness H / P = 0.06, IDT logarithm = 240 pairs, input / output IDT ratio = 0.29, and IDT interval = 4P.
以上の実施例は、Xcut−112゜回転Ｙ伝搬LiTaO3（タン
タル酸リチウム）での例であるが、伝搬媒質である圧電
基板がLiNbO3（ニオブ酸リチウム），水晶等の場合、そ
れぞれ材料定数が異なるため、最適な膜厚,IDT対数,IDT
間隔，入出力IDT対数の割合の値は変わるが、第５図の
２重モード２端子対弾性表面波フィルタ及び第８図の構
成のような４重モード共振子フィルタが実現できること
は明らかである。The above example is an example of Xcut-112 ° rotation Y-propagation LiTaO 3 (lithium tantalate), but when the piezoelectric substrate that is a propagation medium is LiNbO 3 (lithium niobate), quartz, etc. The optimum film thickness, IDT logarithm, IDT
Although the values of the spacing and the ratio of the number of input / output IDT pairs change, it is clear that the dual mode two-terminal pair surface acoustic wave filter of FIG. 5 and the quadruple mode resonator filter having the configuration of FIG. 8 can be realized. .
（発明の効果） 以上詳細に説明したように、スプリアスとなる縦２次モ
ードのためにIDT対数が制限された単一モード共振子を
２個縦続接続した従来の構成による２重モードフィルタ
では、比帯域幅を広くとることができず、約0.26％程度
が限界であったのに比べて、本発明によれば、１つの共
振子を２重モードフィルタとし、またそれを２段縦続接
続することによって４重モード弾性表面波フィルタと
し、従来スプリアスとして扱われてきたモードを積極的
に利用してこれらのモードの周波数合わせをすることに
より、従来の約1.5倍，約0.4％の広い通過帯域をもつフ
ィルタが実現でき、しかも小形になるため実用上の効果
は大きいことは明らかである。(Effect of the Invention) As described in detail above, in the dual mode filter according to the conventional configuration in which two single mode resonators in which the IDT logarithm is limited due to the longitudinal secondary mode that is a spurious, are cascade-connected, According to the present invention, one resonator is used as a dual mode filter, and it is connected in two stages in cascade, in comparison with the fact that the specific bandwidth cannot be wide and the limit is about 0.26%. As a result, a quadruple mode surface acoustic wave filter is used, and the modes that have been treated as spurs are actively used to tune the frequencies of these modes. It is obvious that the practical effect is large because a filter having the above can be realized and the size becomes small.
第１図は１端子対弾性表面波共振子の電極構成例図、第
２図は従来の２端子対単一モード弾性表面波フィルタの
電極構成例図、第３図は従来の２端子対単一モード弾性
表面波共振子の電極構成例図、第４図は従来の単一モー
ド弾性表面波共振子を２個縦続接続した２重モード弾性
表面波フィルタの構成例図、第５図は本発明の２端子対
２重モード弾性表面波フィルタの電極構成例図、第６図
は第５図の構成による２端子対弾性表面波共振子におけ
るモードとIDT対数の特性図、第７図は第５図の構成に
よる２端子対弾性表面波共振子におけるモードの膜厚依
存特性図、第８図は本発明の４重モード弾性表面波フィ
ルタの電極構成例図、第９図は第８図の構成におけるリ
アクタンス特性図、第10図は第８図の構成における４つ
のモードの共振周波数，反共振周波数のIDT対数依存特
性例図、第11図は第８図の構成における４つのモードの
共振周波数，反共振周波数の膜厚依存特性図、第12図は
第８図の構成における４つのモードの共振周波数，反共
振周波数の入出力IDT対数割合依存特性図、第13図は第
８図の構成における４つのモードの共振，反共振周波数
のIDT間隔依存特性図、第14図は本発明の４重モード弾
性表面波フィルタの伝送特性例図である。 １……圧電基板、2,2A〜2H……IDT（Interdigital Tran
sducer,すだれ状変換器）、３……グレーティング（格
子状）反射器、４……縦０次モード変位分布(M0)、５…
…縦１次モード変位分布(M1)、６……縦２次モード変位
分布(M2)、７……入力端子、８……出力端子、９……対
称モード変位分布、10……反対称モード変位分布、11…
…IDT電極指のピッチ、12……反射器の格子ピッチ、13
……反射器とIDTとの間隔、14……IDT相互間隔、15……
縦０次モード反共振周波数、16……縦０次モード共振周
波数、17……縦２次モード反共振周波数、18……縦２次
モード共振周波数、19……対称縦０次モードリアクタン
ス特性、20……反対称縦０次モードリアクタンス特性、
21……対称縦２次モードリアクタンス特性、22……反対
称縦２次モードリアクタンス特性、23……対称縦０次モ
ード反共振周波数、24……対称縦０次モード共振周波
数、25……反対称縦０次モード反共振周波数、26……反
対称縦０次モード共振周波数、27……対称縦２次モード
反共振周波数、28……対称縦２次モード共振周波数、29
……反対称縦２次モード反共振周波数、30……反対称縦
２次モード共振周波数。FIG. 1 is a diagram showing an electrode configuration example of a one-terminal-pair surface acoustic wave resonator, FIG. 2 is a diagram showing an electrode configuration example of a conventional two-terminal pair single-mode surface acoustic wave filter, and FIG. FIG. 4 is a diagram showing a configuration example of a double-mode surface acoustic wave filter in which two conventional single-mode surface acoustic wave resonators are cascade-connected, and FIG. FIG. 6 is a characteristic diagram of modes and IDT logarithms in the two-terminal pair surface acoustic wave resonator according to the constitution of FIG. 5, FIG. FIG. 5 is a film thickness-dependent characteristic diagram of modes in a two-terminal surface acoustic wave resonator having the configuration of FIG. 5, FIG. 8 is an electrode configuration example diagram of a quadruple mode surface acoustic wave filter of the present invention, and FIG. 9 is of FIG. Fig. 10 shows the reactance characteristics of the configuration, and Fig. 10 shows the resonance frequencies of the four modes in the configuration of Fig. 8. , IDT logarithmic dependence characteristic example of anti-resonance frequency, FIG. 11 is a resonance frequency of four modes in the configuration of FIG. 8, film thickness dependence characteristic of anti-resonance frequency, FIG. 12 is 4 in the configuration of FIG. Input / output IDT logarithmic ratio dependence characteristic diagram of one mode resonance frequency, anti-resonance frequency, Fig. 13 shows four mode resonance and anti-resonance frequency IDT interval dependence characteristic diagram in Fig. 8, Fig. 14 shows this It is a transmission characteristic example figure of a quadruple mode surface acoustic wave filter of the invention. 1 ... Piezoelectric substrate, 2,2A-2H ... IDT (Interdigital Tran)
sducer, interdigital transducer, 3 ... Grating (lattice) reflector, 4 ... Vertical zeroth-order mode displacement distribution (M 0 ), 5 ...
… Vertical first-order mode displacement distribution (M 1 ), 6 …… Vertical second-order mode displacement distribution (M 2 ), 7 …… input terminal, 8 …… output terminal, 9 …… symmetric mode displacement distribution, 10 …… opposite Nominal mode displacement distribution, 11 ...
… IDT electrode finger pitch, 12 …… Reflector grating pitch, 13
...... Reflector-IDT spacing, 14 …… IDT mutual spacing, 15 ……
Longitudinal zero-order mode anti-resonance frequency, 16 ... Longitudinal zero-order mode resonance frequency, 17 ... Longitudinal second-order mode anti-resonance frequency, 18 ... Longitudinal second-order mode resonance frequency, 19 ... Symmetrical longitudinal zero-order mode reactance characteristic, 20 …… Antisymmetric vertical zeroth-order mode reactance characteristics,
21 …… Symmetric vertical second-order mode reactance characteristics, 22 …… Anti-symmetric vertical second-order mode reactance characteristics, 23 …… Symmetric vertical zero-order mode anti-resonance frequency, 24 …… Symmetric vertical zero-order mode resonance frequency, 25 …… Opposite Nominal longitudinal 0th-order mode anti-resonance frequency, 26 ... Anti-symmetric longitudinal 0th-order mode resonance frequency, 27 ... Symmetrical longitudinal 2nd-order mode antiresonance frequency, 28 ... Symmetrical longitudinal 2nd-order mode resonance frequency, 29
…… Antisymmetric longitudinal secondary mode antiresonance frequency, 30 …… Antisymmetric longitudinal secondary mode resonance frequency.
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 昭58−3307（ＪＰ，Ａ) 特開 昭61−144910（ＪＰ，Ａ) 江畑奏男、越野昌芳「四ホウ酸リチウム 基板を用いたＳＡＷ共振フィルタ」電子情 報通信学会創立70周年記念総合全国大会 （昭和62年）93，ＰＰ．１−93 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-58-3307 (JP, A) JP-A-61-144910 (JP, A) Norio Ebata, Masayoshi Koshino “SAW using lithium tetraborate substrate "Resonant filter" Electronic Information and Communication Engineers 70th Anniversary General Conference (1987) 93, PP. 1-93
Claims (4)
た入力側IDTと、該入力側IDTの両側に配置され並列接続
された前記入力側IDTとほぼ等しい電極対数を有する出
力側IDTと、該出力側IDTの両側に配置された格子状反射
器とを備えて、弾性表面波の伝搬方向に励起される縦０
次共振モードを利用するエネルギー閉じ込め形２端子対
弾性表面波フィルタにおいて、 前記入力側IDTおよび２つの出力側IDTの全体の電極対数
を縦２次共振モードが励起される対数以上に設定し、か
つ、前記反射器の格子ピッチＰに対する電極膜厚Ｈの比
（H/P）を前記縦０次共振モードの共振周波数と前記縦
２次共振モードの反共振周波数の正規化周波数差が0.00
05より小さくなるように設定したことを特徴とする２重
モード２端子対弾性表面波フィルタ。1. A piezoelectric substrate, an input-side IDT arranged in the center of the piezoelectric substrate, and output-side IDTs arranged on both sides of the input-side IDT and having substantially the same number of electrode pairs as the input-side IDTs connected in parallel. And a grating reflector disposed on both sides of the output-side IDT, and a vertical 0 excited in the propagation direction of the surface acoustic wave.
In an energy confinement type two-terminal pair surface acoustic wave filter utilizing a secondary resonance mode, the total number of electrode pairs of the input-side IDT and the two output-side IDTs is set to be equal to or larger than the logarithm at which the longitudinal secondary resonance mode is excited, and , The ratio (H / P) of the electrode film thickness H to the grating pitch P of the reflector is 0.00 when the normalized frequency difference between the resonance frequency of the longitudinal zero-order resonance mode and the anti-resonance frequency of the longitudinal secondary resonance mode is 0.00.
A dual mode dual terminal pair surface acoustic wave filter characterized by being set to be smaller than 05.
タンタル酸リチウムで形成され、 前記全体のIDT対数を210対以上とし、 前記H/Pを0.05〜0.07の範囲にしたことを特徴とする請
求項１記載の２重モード２端子対弾性表面波フィルタ。2. The piezoelectric substrate is formed of an X-cut 112 ° rotated Y-propagating lithium tantalate, the total number of IDT pairs is 210 pairs or more, and the H / P is in a range of 0.05 to 0.07. The dual mode dual terminal pair surface acoustic wave filter according to claim 1.
面波フィルタの電極構成を有する第１の電極構造列と、
該第１の電極構造列と線対称の電極構造を有し弾性表面
波の伝搬方向が平行でかつ互いに音響結合しないように
弾性表面波の波長の３倍以上の間隔で同一圧電基板上に
並設された第２の電極構造列とから構成され、 前記第１の電極構造列の中央のIDTを入力変換器とし、
前記第１の電極構造列の前記入力側IDTの両側の出力側I
DTと前記第２の電極構造列の両側の出力側IDTのそれぞ
れ相対する電極が共通接続され、前記第２の電極構造列
の中央のIDTを出力IDTとし、 弾性表面波の伝搬方向に励起される縦２次共振モード，
縦０次共振モードと、弾性表面波の伝搬方向と直角方向
に生ずる反対称モード，対称モードとが組み合わされ周
波数の低い方から順次配列される反対称縦２次モード，
対称縦２次モード，反対称縦０次モード，対称縦０次モ
ードの４つのモードの隣りあう３箇所のそれぞれ反共振
周波数と共振周波数との正規化周波数差を、前記第１お
よび第２の電極構造列のそれぞれに対して、全体のIDT
対数，正規化膜厚，全体のIDT対数に対する中央のIDT対
数の割合,IDTの相互間隔を設定することによって0.0005
より小さくしたことを特徴とする４重モード２端子対弾
性表面波フィルタ。3. A first electrode structure row having the electrode configuration of the dual mode dual terminal pair surface acoustic wave filter according to claim 1,
It has an electrode structure line-symmetrical to the first electrode structure row and is arranged on the same piezoelectric substrate at intervals of three times or more the wavelength of the surface acoustic waves so that the propagation directions of the surface acoustic waves are parallel and are not acoustically coupled to each other. And a second electrode structure row provided, wherein the central IDT of the first electrode structure row serves as an input converter,
Output sides I on both sides of the input side IDT of the first electrode structure row
The opposing electrodes of the DT and the output-side IDTs on both sides of the second electrode structure row are commonly connected, and the central IDT of the second electrode structure row is used as the output IDT and is excited in the propagation direction of the surface acoustic wave. Vertical secondary resonance mode,
An antisymmetric longitudinal quadratic mode in which a longitudinal zero-order resonance mode, an antisymmetric mode generated in a direction orthogonal to the propagation direction of a surface acoustic wave, and a symmetric mode are combined and sequentially arranged from the lower frequency side,
The normalized frequency difference between the anti-resonance frequency and the resonance frequency at three adjoining points of the four modes of the symmetric longitudinal second-order mode, the anti-symmetric longitudinal zero-order mode, and the symmetric longitudinal zero-order mode is calculated as follows. The total IDT for each of the electrode structure rows
0.0005 by setting logarithm, normalized film thickness, ratio of central IDT logarithm to total IDT logarithm, mutual interval of IDT
A quadruple-mode two-terminal pair surface acoustic wave filter characterized by being made smaller.
回転Ｙ伝搬タンタル酸リチウムで形成され、 前記全体のIDT対数を215〜275,前記正規化膜厚を0.05〜
0.07の範囲，前記全体のIDT対数に対する中央のIDT対数
の割合を0.27〜0.31の範囲，前記IDTの相互間隔を該IDT
の電極ピッチの４〜８倍の範囲にしたことを特徴とする
請求項３記載の４重モード２端子対弾性表面波フィル
タ。4. The piezoelectric substrate according to claim 3, which is formed of an X-cut 112 ° rotating Y-propagating lithium tantalate, the total IDT logarithm is 215 to 275, and the normalized film thickness is 0.05 to.
The range of 0.07, the ratio of the central IDT logarithm to the total IDT logarithm is in the range of 0.27 to 0.31, and the mutual interval of the IDTs is
4. The quadruple-mode two-terminal pair surface acoustic wave filter according to claim 3, wherein the electrode pitch is in the range of 4 to 8 times.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63056245A JPH071859B2 (en) | 1988-03-11 | 1988-03-11 | Surface acoustic wave filter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63056245A JPH071859B2 (en) | 1988-03-11 | 1988-03-11 | Surface acoustic wave filter |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH01231417A JPH01231417A (en) | 1989-09-14 |
| JPH071859B2 true JPH071859B2 (en) | 1995-01-11 |
Family
ID=13021709
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP63056245A Expired - Lifetime JPH071859B2 (en) | 1988-03-11 | 1988-03-11 | Surface acoustic wave filter |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH071859B2 (en) |
Families Citing this family (29)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA2062463C (en) * | 1991-03-29 | 1996-01-16 | Yoshio Satoh | Surface acoustic wave device for band-pass filter having small insertion loss and predetermined pass-band characteristics for broad band |
| JP3160023B2 (en) * | 1991-08-21 | 2001-04-23 | 東洋通信機株式会社 | Vertically coupled dual mode SAW filter |
| JP2800905B2 (en) | 1991-10-28 | 1998-09-21 | 富士通株式会社 | Surface acoustic wave filter |
| USRE40036E1 (en) | 1991-10-28 | 2008-01-29 | Fujitsu Limited | Surface acoustic wave filter |
| JPH05315886A (en) * | 1992-05-14 | 1993-11-26 | Matsushita Electric Ind Co Ltd | Surface acoustic wave filter |
| JPH0685605A (en) * | 1992-07-17 | 1994-03-25 | Nec Corp | Surface acoustic wave filter |
| JPH06232687A (en) * | 1992-08-24 | 1994-08-19 | Nec Corp | Surface acoustic wave resonator filter |
| JPH0648233U (en) * | 1992-11-27 | 1994-06-28 | 東光株式会社 | Resonator type surface acoustic wave filter |
| JP3001350B2 (en) * | 1993-05-19 | 2000-01-24 | 日本電気株式会社 | Surface acoustic wave filter |
| JPH06338756A (en) | 1993-05-27 | 1994-12-06 | Fujitsu Ltd | Resonator type surface acoustic wave filter |
| JPH0730362A (en) * | 1993-07-13 | 1995-01-31 | Mitsubishi Electric Corp | Surface acoustic wave device |
| JP3214226B2 (en) * | 1994-05-11 | 2001-10-02 | 株式会社村田製作所 | Surface acoustic wave resonator filter |
| JP4251409B2 (en) * | 1995-03-15 | 2009-04-08 | 京セラキンセキ株式会社 | Surface acoustic wave filter |
| JPH09167936A (en) | 1995-10-13 | 1997-06-24 | Fujitsu Ltd | Surface acoustic wave device |
| JPH09205342A (en) * | 1996-01-26 | 1997-08-05 | Matsushita Electric Ind Co Ltd | Surface acoustic wave filter |
| EP0800270B1 (en) * | 1996-04-02 | 2003-09-10 | Matsushita Electric Industrial Co., Ltd. | Surface acoustic wave filter |
| JP3739858B2 (en) * | 1996-06-14 | 2006-01-25 | 松下電器産業株式会社 | High frequency filter |
| US6107899A (en) * | 1996-10-21 | 2000-08-22 | Matsushita Electric Industrial Co., Ltd. | Surface acoustic wave filter with grounds not connected in the package or on the piezoelectric substrate |
| JP3224202B2 (en) * | 1996-11-28 | 2001-10-29 | 富士通株式会社 | Surface acoustic wave device |
| WO2004102797A1 (en) * | 1997-07-17 | 2004-11-25 | Michiaki Takagi | Two-port saw resonator |
| KR100341235B1 (en) * | 1997-07-18 | 2002-06-20 | 니시무로 타이죠 | Surface acoustic wave filter |
| JP3137064B2 (en) * | 1998-01-16 | 2001-02-19 | 日本電気株式会社 | Surface acoustic wave filter |
| JP2000059176A (en) * | 1998-08-06 | 2000-02-25 | Toshiba Corp | Surface acoustic wave device |
| WO2000013316A1 (en) | 1998-08-28 | 2000-03-09 | Seiko Epson Corporation | Multi-longitudinal mode saw filter |
| JP4145678B2 (en) | 2003-02-13 | 2008-09-03 | セイコーエプソン株式会社 | Vertical double mode SAW filter |
| CN100452650C (en) | 2003-07-02 | 2009-01-14 | 京瓷株式会社 | Surface acoustic wave device and communication device using the device |
| US7504911B2 (en) | 2005-05-27 | 2009-03-17 | Kyocera Corporation | Surface acoustic wave resonator, surface acoustic wave device, and communications equipment |
| JP2007189746A (en) * | 2007-04-13 | 2007-07-26 | Oki Electric Ind Co Ltd | Branching filter employing surface acoustic wave filter |
| JP5100890B2 (en) * | 2009-06-26 | 2012-12-19 | 京セラ株式会社 | Surface acoustic wave filter and duplexer using the same |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS583307A (en) * | 1981-06-29 | 1983-01-10 | Toyo Commun Equip Co Ltd | Surface acoustic wave multiplex mode filter |
| JPS61144910A (en) * | 1984-12-19 | 1986-07-02 | Toyo Commun Equip Co Ltd | Electrode structure of idt excitation energy confinement type piezoelectric device |
-
1988
- 1988-03-11 JP JP63056245A patent/JPH071859B2/en not_active Expired - Lifetime
Non-Patent Citations (1)
| Title |
|---|
| 江畑奏男、越野昌芳「四ホウ酸リチウム基板を用いたＳＡＷ共振フィルタ」電子情報通信学会創立７０周年記念総合全国大会（昭和６２年）９３，ＰＰ．１−９３ |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH01231417A (en) | 1989-09-14 |
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