JP3107392B2 - Vertically coupled dual mode leaky SAW filter - Google Patents
Vertically coupled dual mode leaky SAW filterInfo
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- JP3107392B2 JP3107392B2 JP02337281A JP33728190A JP3107392B2 JP 3107392 B2 JP3107392 B2 JP 3107392B2 JP 02337281 A JP02337281 A JP 02337281A JP 33728190 A JP33728190 A JP 33728190A JP 3107392 B2 JP3107392 B2 JP 3107392B2
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- idt
- filter
- dual mode
- electrode
- coupled dual
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Description
【発明の詳細な説明】 （産業上の利用分野）本発明はSAWフィルタ、殊に広
帯域で低損失な縦結合二重モードリーキSAWフィルタに
関する。Description: FIELD OF THE INVENTION The present invention relates to a SAW filter, and more particularly to a wide band, low loss longitudinally coupled dual mode leaky SAW filter.
（従来の技術）従来、VHF〜UHF帯の高周波領域に於け
る広帯域低損失フィルタには一方向性IDTを用いたトラ
ンスバーサル型SAWフィルタやマルチIDTを用いたSAWフ
ィルタが広く用いられている。2. Description of the Related Art Conventionally, a transversal SAW filter using a unidirectional IDT and a SAW filter using a multi-IDT have been widely used as a wideband low-loss filter in a high-frequency region of a VHF to UHF band.
一方向性IDTを用いたトランスバーサル型SAWフィルタ
は周波数特性に対する設計の自由度が大きいという利点
はあるが、グループ型一方向性IDT或は３相一方向性IDT
を用いるフィルタは外部に移相器を必要とし、浮き電極
内部反射型一方向性IDTを用いるものは移相器は必要と
しないものの中心周波数が高くなると電極線幅が極めて
細くなり製造困難であるという欠点があり、しかも、方
向性損失を完全に除去することは難しく低損失化が未だ
不十分であった。A transversal SAW filter using a unidirectional IDT has the advantage that the degree of freedom in designing frequency characteristics is large, but a group type unidirectional IDT or a three-phase unidirectional IDT.
A filter that uses an external phase shifter requires an external electrode, and a type that uses a floating electrode internal reflection type one-way IDT does not require a phase shifter, but when the center frequency increases, the electrode line width becomes extremely thin, making it difficult to manufacture. However, it is difficult to completely remove the directional loss, and the reduction of the loss is still insufficient.
又、マルチIDTを用いたSAWフィルタは、９トランスジ
ューサ以上の電極数ならばその方向性損失は1dB以下と
なり低損失化が可能であるが、電極数が多くなる為チッ
プサイズが大きくなる上に、IDT内部の反射によるスプ
リアスが多く現われ阻止域の減衰量が不十分であるとい
う欠点があった。In addition, a SAW filter using a multi-IDT can reduce the directional loss to 1 dB or less if the number of electrodes is 9 or more, and it is possible to reduce the loss.However, since the number of electrodes increases, the chip size increases, and There is a drawback that many spurious components due to reflection inside the IDT appear and the attenuation of the stop band is insufficient.
これに対して共振子フィルタ、殊に縦結合二重モード
SAWフィルタ［文献：田中ら、第15回EMシンポジウム、p
p.5−10（1986）．］は低損失化の点で前述した２種の
フィルタよりも優れてはいるが、通過帯域幅を決定する
共振子の容量比が大きい為、広帯域フィルタへの適用は
難しかった。In contrast, resonator filters, especially longitudinally coupled dual modes
SAW filter [Literature: Tanaka et al., 15th EM Symposium, p
p.5-10 (1986). ] Is superior to the above two types of filters in terms of low loss, but it has been difficult to apply to a broadband filter because the capacitance ratio of the resonator that determines the passband is large.
例えば結合係数が５％と大きい36゜Ｙカット、Ｘ伝搬
LiTaO3基板を用いて縦結合二重モードSAWフィルタを構
成しても高々比帯域幅2.1％のフィルタしか得られず、
縦結合二重モードSAWフィルタは中帯域のフィルタに適
用し得るに過ぎず2.5％以上の比帯域幅を必要とする広
帯域フィルタには適用し得なかった。For example, 36 ゜ Y cut, X propagation with a large coupling coefficient of 5%
Even if a longitudinally-coupled dual-mode SAW filter is configured using a LiTaO 3 substrate, only a filter with a fractional bandwidth of at most 2.1% can be obtained.
The longitudinally-coupled dual-mode SAW filter was only applicable to a medium-band filter, but could not be applied to a wide-band filter requiring a specific bandwidth of 2.5% or more.
即ち、縦結合二重モードフィルタの帯域幅を広げるに
は容量比の小さい共振子を用いればよく、それには結合
係数の極めて大きい基板材料が必要である。That is, in order to widen the bandwidth of the longitudinally coupled dual mode filter, a resonator having a small capacitance ratio may be used, which requires a substrate material having an extremely large coupling coefficient.
ところで、容量比の小さい共振子としては清水らが発
明したラブ波共振子がある［文献：信学技報、US86−37
（1986）。］。By the way, as a resonator having a small capacitance ratio, there is a love wave resonator invented by Shimizu et al. [Reference: IEICE Technical Report, US86-37]
(1986). ].
これはＹカット、Ｘ伝搬LiNbO3基板上にAu電極のIDT
を構成してラブ波共振子としたもので、結合係数が約30
％と極めて大きい為共振子の容量比を約３と極めて小さ
くし得ることが判っている。This is an IDT of Au electrode on Y-cut, X-propagating LiNbO 3 substrate.
And a Love wave resonator with a coupling coefficient of about 30
%, It is known that the capacitance ratio of the resonator can be made as small as about 3.
しかしながらこのラブ波共振子を用いて縦結合二重モ
ードフィルタを構成しようとすると、結合係数が過大な
為、IDT対数が少なくても入力及び出力IDTそれ自体の中
でエネルギーが閉じこもってしまい、入出力IDT間の結
合が十分とれず帯域が広がらないということが明らかと
なった。However, if an attempt is made to construct a longitudinally coupled double mode filter using this Love wave resonator, the coupling coefficient will be too large, and even if the IDT logarithm is small, the energy will be trapped in the input and output IDTs themselves, and the input will be confined. It became clear that the coupling between the output IDTs was not sufficient and the bandwidth was not widened.
一方、上述のラブ波共振子には劣るもののやはり11％
程度の結合係数を有する共振子として、柴山らは64゜Ｙ
カット、Ｘ伝搬LiNbO3基板にリーキーSAWを励起する共
振子の存在を理論と計算によって見出している［文献:
J.Appl.Phys.,vol.43,No.3,pp.856−862（1972）．］。
しかし、この基板を用いてマルチIDTのフィルタを構成
した例はあるが、共振子に適用した例は目下のところ見
当らず、勿論これを縦結合二重モードフィルタに使用す
る場合いかなる電極構成をとるべきかについては全く明
らかとなっていなかった。On the other hand, 11%
Shibayama et al. Have a 64 Y
Cut and X-propagation LiNbO 3 substrate has been found through the theory and calculation of the existence of a resonator that excites leaky SAW [Literature:
J. Appl. Phys., Vol. 43, No. 3, pp. 856-862 (1972). ].
However, although there is an example in which a multi-IDT filter is configured using this substrate, an example applied to a resonator is not found at present, and of course, any electrode configuration is used when this is used for a longitudinally coupled dual mode filter. It was not clear at all what to do.
（発明の目的）本発明は上述した如き従来の各種のフィ
ルタが容量比の制限、音響結合の過剰等々の理由により
低損失且つ広帯域のフィルタを実現し得なかった事実に
鑑みなされたものであって、高周波領域に於いて2.5％
以上の比帯域幅を有し且つ低損失な縦結合二重モードリ
ーキーSAWフィルタを提供することを目的とする。(Object of the Invention) The present invention has been made in view of the fact that various conventional filters as described above cannot realize a low-loss and wide-band filter due to the limitation of the capacitance ratio, excessive acoustic coupling, and the like. 2.5% in high frequency range
An object of the present invention is to provide a low-loss longitudinally coupled dual-mode leaky SAW filter having the above fractional bandwidth.
（発明の概要）上述の目的を達成する為、本発明に於い
ては64゜Ｙカット、Ｘ伝搬LiNbO3基板を用い、入出力ID
T対数を各々５〜18対、IDT周期LTと反射器周期LRの比を
LT/LR＝0.995〜0.975,電極膜厚を３±1.5％λとし、
又、両IDT間隔ｌを （n/2−1/4）λ≦ｌ＜（n/2−1/8）λ （但しｎ＝２〜８） とした構成をとる。(Summary of the Invention) In order to achieve the above object, in the present invention, a 64 ° Y-cut, X-propagation LiNbO 3 substrate is used and an input / output ID is used.
T each 5-18 versus log, the IDT period L T to the ratio of the reflector period L R
L T / L R = 0.995 ~ 0.975, electrode thickness is 3 ± 1.5% λ,
Also, a configuration is adopted in which both IDT intervals 1 are (n / 2−1 / 4) λ ≦ l <(n / 2−1 / 8) λ (where n = 2 to 8).
（発明の実施例）以下、本発明を図面に示した実施例に
基づいて詳細に説明する。(Embodiments of the Invention) Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.
第１図は本発明に係る縦結合二重モードリーキーSAW
フィルタの電極パターンを示す構成図であって、64゜Ｙ
カットLiNbO3基板１の表面にリーキSAWを励振する為の
入力IDT2とこれを受信するための出力IDT3及びその両側
に反射器４、４を伝搬方向がＸ軸方向になるように配置
する。本図に於いて２つのIDT2及び３の対数を各々N1及
びN2対、電極（Al）膜圧をＨ、IDTの周期をLT、反射器
の周期をLR（ピッチの２倍）、両IDT間隔（最内側電極
指の中心間々隔）をｌとする。FIG. 1 shows a longitudinally coupled dual mode leaky SAW according to the present invention.
FIG. 4 is a configuration diagram showing an electrode pattern of a filter, wherein 64 ° Y
Propagation direction a reflector 4, 4 outputs IDT3 and on both sides for receiving this and input IDT2 for exciting a leaky SAW on the surface of the cut LiNbO 3 substrate 1 is arranged such that the X-axis direction. Each N 1 and N 2 pairs two IDT2 and 3 logarithm In this figure, the electrode (Al) the film thickness H, the IDT of the period L T, the period of the reflectors L R (2 times the pitch) And the IDT interval (interval between the centers of the innermost electrode fingers) is l.
以上の如きフィルタの電極構成に於いて各パラメータ
の最適値を求めるため次下に示す如き実験を行った。In order to obtain the optimum value of each parameter in the electrode configuration of the filter as described above, the following experiment was performed.
先ず、二重モードフィルタの終端抵抗Reは２つの近接
配置したIDTの音響結合の結果発生する対称モード及び
反対称モードの２つの共振モード（共振周波数は夫々fs
及びfa）の内前者のモードの共振に於ける等価インダク
タンスL1とこのフィルタの帯域幅の積に比例すると共に
前記等価インダクタンスL1は入出力IDTの電極対数と密
接な関係を有することから、入出力IDT2及び３の電極対
数の和Ｎ＝N1＋N2とL1との関係を実験によって調べたと
ころ第２図に示す如き結果を得た。First, the terminating resistor Re of the double mode filter has two resonance modes of a symmetric mode and an antisymmetric mode generated as a result of acoustic coupling of two closely arranged IDTs (the resonance frequency is f s, respectively).
And f a ) are proportional to the product of the equivalent inductance L 1 in the resonance of the former mode and the bandwidth of this filter, and the equivalent inductance L 1 has a close relationship with the number of electrode pairs of the input / output IDT. to obtain such results shown in Figure 2 was examined by the relationship of the experiments with the sum N = N 1 + N 2 and L 1 of the electrode pairs input IDT2 and 3.
即ち、IDT電極指交叉長Ｗを100λと十分大きな値に設
定してもIDT対数Ｎが８以下となると等価インダクタン
スL1は急増する。Ｎ＝８に於けるL1の値は既ね1KΩの終
端抵抗Reに相当するが、高周波領域に於けるフィルタの
終端抵抗Reは実用上1KΩ以下に設定するのが一般的であ
るからIDT対数Ｎは10対以上必要（入出力IDTについて夫
々N1≧５、N2≧５）であることが判る。That is, even by setting the IDT electrode fingers crossing length W in 100λ sufficiently large value IDT log N 8 hereinafter become the equivalent inductance L 1 increases rapidly. The value of L 1 at N = 8 already corresponds to the terminating resistor Re of 1 KΩ. However, since the terminating resistor Re of the filter in the high frequency region is generally set to 1 KΩ or less in practice, the IDT logarithm is used. It can be seen that N requires 10 pairs or more (N 1 ≧ 5 and N 2 ≧ 5 for the input and output IDTs, respectively).
ところで二重モードSAWフィルタに於いて入出力IDTの
電極対数N1、N2を大きくすると夫々のIDT内での振動エ
ネルギ閉込め率が過大となり相互の間の音響結合が弱ま
る結果フィルタの通過帯域が狭くなることは周知である
から入出力IDT対数N1、N2の上限を検討する必要があ
る。そこで入出力IDT対数の和Ｎと1dB比帯域幅Δf/f
o（fo:中心周波数）との関係を実験によって調べたとこ
ろ第３図の如き結果を得た。By the way, in the dual mode SAW filter, when the number of electrode pairs N 1 and N 2 of the input and output IDTs is increased, the vibration energy confinement rate in each IDT becomes excessive and the acoustic coupling between the IDTs is weakened. that becomes narrower, it is necessary to consider the upper limit of the output IDT log N 1, N 2 because it is well known. Therefore, the sum N of the logarithms of the input and output IDTs and the 1 dB relative bandwidth Δf / f
When the relationship with o (f o : center frequency) was examined by an experiment, the result as shown in FIG. 3 was obtained.
本図を検討するにＮが既ね38でΔf/foは2.5％である
からこれがIDT対数の上限であることが判る。以上の結
果より入出力IDTの対数は夫々５乃至18の間で適宜選択
すれば適正な終端抵抗Reと所望の比帯域を得ることがで
きよう。Δf / f o N is in the already ne 38 to consider this figure it can be seen that is this because it is 2.5%, which is the upper limit of the IDT logarithm. From the above results, if the logarithm of the input / output IDT is appropriately selected from 5 to 18 respectively, an appropriate termination resistor Re and a desired fractional band can be obtained.
次にIDTと反射器とのAl膜厚について検討するに、一
般に膜厚Ｈが大となる程反射器のストップバンドの幅が
広がる為fs−fa（≒Δｆ）が大きくなるが共振子のＱは
低下する。Next to be discussed Al film thickness of the IDT and the reflector, generally to a thickness H of broadening of the stop band of the reflector enough to become large f s -f a (≒ Δf) increases resonator Q decreases.
従って電極膜厚Ｈには適性値が存在するはずである。 Therefore, there should be an appropriate value for the electrode film thickness H.
そこで入出力IDT対数をN1＝N2＝10に設定し電極膜厚
Ｈと（fs−fa）/fsとの関係及びＨとＱとの関係を実験
により調べたところ夫々第４図及び第５図の如き結果を
得た。Therefore the input and output IDT log N 1 = N 2 = 10 set the electrode thickness H to (f s -f a) / f s and the relationships and were examined by relationship experiments with H and Q, respectively fourth The results shown in FIG. 5 and FIG. 5 were obtained.
これらの結果を勘案するに電極膜厚Ｈが励起するリー
キーSAWの波長λの１％以下ではストップバンドの幅が
狭くフィルタ比帯域幅f/foは2.5％以下となり、Ｈがλ
の4.5％以上となるとＱが150以下となり挿入損失が増大
するのみならず、電極をエッチングによって形成する際
サイドエッチが大きくなるという製造上の問題も発生す
ることから電極膜厚Ｈはλの３±1.5％の範囲が適当と
考えられる。Is narrow filter fractional bandwidth f / f o of the stop band is 1% or less of the wavelength λ of the leaky SAW the electrode film thickness H in consideration of these results is excited becomes 2.5% or less, H is λ
Is 4.5% or more, the Q becomes 150 or less, not only the insertion loss increases, but also there is a manufacturing problem that the side etch becomes large when the electrode is formed by etching. A range of ± 1.5% is considered appropriate.
ところで、一般によく知られているようにSAW共振子
に於いては、IDTの放射コンダクタンスが最大となる周
波数fTと反射器のストップバンドの中心周波数fRの間に
はfR＞fTなる関係がある。これを補正しＱの高い共振子
を得るには両者の周期LTとLRを違えてfTとfRを一致せし
めるべきである。By the way, as is generally well known, in a SAW resonator, f R > f T between the frequency f T at which the radiation conductance of the IDT is maximum and the center frequency f R of the stop band of the reflector. Have a relationship. Thereto obtain a high resonator of corrected Q should allowed to match the f T and f R are Chigae the period of both L T and L R.
本発明に係る縦結合二重モードリーキーSAWフィルタ
共振子の場合も同様に両者の周波数を合わせる必要があ
る。但し、この場合LT/LRの値が１に近いと反対称モー
ド共振周波数（fa）のＱが小さく、逆にLT/LRが小さい
と対称モード（共振周波数fS）のＱが小さくなってしま
う。このLT/LRの最適値についての実験結果は煩雑を避
けるため図示を省略するが前述の最適膜厚Ｈ＝３±1.5
％λ、最適値IDT対数N1＝N2＝５〜18対の下ではLT/LR＝
0.995〜0.975の範囲とすれば十分であることが明らかと
なった。Similarly, in the case of the longitudinally coupled dual mode leaky SAW filter resonator according to the present invention, it is necessary to match both frequencies. However, in this case, if the value of L T / L R is close to 1, the Q of the anti-symmetric mode resonance frequency (f a ) is small, and if L T / L R is small, the Q of the symmetric mode (resonance frequency f S ) is small. Becomes smaller. The experimental results on the optimum value of L T / L R are not shown in order to avoid complication, but the above-mentioned optimum film thickness H = 3 ± 1.5.
% Λ, optimal value IDT logarithm N 1 = N 2 = L T / L R = 5-18 pairs below
It has been found that a range of 0.995 to 0.975 is sufficient.
また、２つのIDTの間隔ｌは、両IDTが周期的に配置さ
れているならばｌ＝ｎλ２（但しｎは正の整数）とな
る。しかしながら入出力IDTをこのように配置するとfS
とfaとの差（ほぼΔｆに等しい）は小さいので、２ポー
トSAW共振子に於いて一般的に行われているように間隔
ｌを周期的配置から若干狭くするとfSのみが広域側へシ
フトしΔｆが広がっていく。第６図はこのΔｆの変化を
示した実験結果の図であって、入出力IDT最内側の電極
指間隔ｌを周期的配置に対して−λ/4としたときΔｆは
最大となる。The interval 1 between two IDTs is 1 = nλ2 (where n is a positive integer) if both IDTs are arranged periodically. However, if the input / output IDT is arranged in this way, f S
And the difference between f a (substantially equal to Delta] f) is small, only f S when slightly reduce the distance l as is commonly done from periodically arranged at the two-port SAW resonators to the wide area side The shift shifts to increase Δf. FIG. 6 is a diagram of an experimental result showing the change of Δf. When the innermost electrode finger interval l of the input / output IDT is −λ / 4 with respect to the periodic arrangement, Δf becomes maximum.
従って、ｌの値は実用的に （n/2−1/4）λ≦ｌ＜（n/2−1/8）λ とするのが妥当であろう。ここで、ｎの値を10以上とす
ると、少ない対数のIDTが互いに離れすぎてしまい、結
合が弱くなって帯域が減少してしまうのでｎは２乃至８
とするのが適当である。Therefore, it would be reasonable to make the value of l practically (n / 2−1 / 4) λ ≦ l <(n / 2−1 / 8) λ. Here, if the value of n is 10 or more, the IDTs with small logarithms are too far apart from each other, weakening the coupling and reducing the band.
Is appropriate.
第７図は上述した如きパラメータを有する縦結合二重
モードリーキーSAWフィルタを２個縦続接続したフィル
タの構成を示す図であって、基板は64゜Ｙ−Ｘ LiNb
O3、２つのIDTの電極対数は共に10対でCOS型の重みづけ
を施してあり、LTは15.6μｍ、交叉長Ｗは50λ、反射器
は両側とも80本、IDT間隔ｌは３λ/4、LT/LRは0.985、
膜厚Ｈは３％λである。FIG. 7 is a diagram showing a configuration of a filter in which two longitudinally coupled dual mode leaky SAW filters having the above-described parameters are cascaded, and the substrate is 64 ゜ YX LiNb
O 3, 2 two IDT electrodes logarithm has been applied weighting COS type in both 10 pairs, L T is 15.6, crossover length W is 50Ramuda, reflector 80 present both sides, IDT interval l is 3 [lambda] / 4, L T / L R is 0.985,
The film thickness H is 3% λ.
第８図は第７図の示した縦結合二重モードリーキーSA
Wフィルタの周波数特性を示す図であり、中心周波数fo
＝281MHz、1dB比帯域幅9.2MHz（Δf/fo＝3.2％）、挿入
損失は約2dBであった。FIG. 8 shows the longitudinally coupled dual mode leaky SA shown in FIG.
FIG. 4 is a diagram illustrating a frequency characteristic of a W filter, and illustrates a center frequency f o.
= 281 MHz, 1 dB relative bandwidth 9.2 MHz (Δf / f o = 3.2%), and insertion loss was about 2 dB.
以上述べた如く、64゜Ｙ−Ｘ LiNbO3基板を用いて縦
結合二重モードリーキーSAWフィルタを構成し広帯域低
損失フィルタを実現するには入出力IDT電極対数N1＝N2
＝５〜18対、電極膜厚Ｈ＝３±1.5％λ、LT/LR＝0.995
〜0.975、IDT間隔ｌについては （n/2−1/4）λ≦ｌ＜（n/2−1/8）λ （但し、ｎは２乃至８） とすればよいことが明らかとなった。As described above, the number of pairs of input / output IDT electrodes N 1 = N 2 is required to construct a longitudinally coupled dual mode leaky SAW filter using a 64 ° YX LiNbO 3 substrate and to realize a wideband low-loss filter.
= 5-18 pairs, electrode film thickness H = 3 ± 1.5% λ, L T / L R = 0.995
0.90.975, and the IDT interval l was found to be (n / 2−1 / 4) λ ≦ l <(n / 2−1 / 8) λ (where n is 2 to 8). .
（発明の効果）本発明は以上説明したように構成するの
で、結合係数が大きい64゜ＹカットＸ方向伝搬LiNbO3基
板を用いた容量費の小さいリーキSAW共振子により比帯
域幅が2.5％以上の広帯域で低損質な縦結合二重モード
フィルタを得ることが可能となるため近年実用化が急が
れている多チャンネル携帯電話の入出力RFフィルタなど
に適用する上で著しい効果がある。(Effect of the Invention) Since the present invention is configured as described above, the ratio bandwidth is 2.5% or more by a leaky SAW resonator having a small coupling cost using a 64 ° Y-cut X-propagation LiNbO 3 substrate having a large coupling coefficient. It is possible to obtain a low-loss longitudinally-coupled dual-mode filter with a wide bandwidth, which has a remarkable effect when applied to an input / output RF filter of a multi-channel mobile phone which has been urgently put into practical use in recent years.
第１図は本発明に係るリーキーSAW共振子による縦結合
二重モードフィルタの電極構造を示す図、第２図はリー
キーSAW共振子の対称モードの等価インダクタンスL1とI
DT対数Ｎとの関係を示す実験結果の図、第３図は縦結合
二重モードリーキーSAWフィルタの1dB比帯域幅とIDT対
数Ｎとの関係を示す実験結果の図、第４図は縦結合二重
モードリーキーSAWフィルタの２つの共振モードの周波
数差ｆと電極膜厚Ｈとの関係を示す実験結果の図、第５
図はリーキーSAW共振子のＱと電極膜厚Ｈとの関係を示
す実験結果の図、第６図はリーキーSAW共振子の２つ共
振モードの周波数差Δｆと入出力IDT間隔ｌとの関係を
示す実験結果の図、第７図は本発明に係る縦結合二重モ
ードリーキーSAWフィルタを２個縦続接続したフィルタ
の構成を示す図、第８図は第７図に示す縦結合二重モー
ドリーキーSAWフィルタの周波数特性を示す図である。 １……64゜ＹカットLiNbO3基板 ２……入力IDT、３……出力IDT ４……反射器Figure Figure 1 is showing an electrode structure of a longitudinally coupled double mode filter according leaky SAW resonator according to the present invention, the equivalent inductance L 1 and I of FIG. 2 symmetric mode leaky SAW resonator
FIG. 3 is a diagram of experimental results showing the relationship between DT logarithm N, FIG. 3 is a diagram of experimental results showing the relationship between 1 dB fractional bandwidth of longitudinally coupled dual mode leaky SAW filter and IDT logarithmic N, and FIG. FIG. 5 is a diagram of an experimental result showing the relationship between the frequency difference f between the two resonance modes of the dual mode leaky SAW filter and the electrode film thickness H.
The figure shows the experimental results showing the relationship between the Q of the leaky SAW resonator and the electrode film thickness H. FIG. 6 shows the relationship between the frequency difference Δf between the two resonance modes of the leaky SAW resonator and the input / output IDT interval l. FIG. 7 is a view showing experimental results, FIG. 7 is a view showing a configuration of a filter in which two longitudinally coupled dual mode leaky SAW filters according to the present invention are cascaded, and FIG. 8 is a longitudinally coupled dual mode leaky shown in FIG. FIG. 3 is a diagram illustrating frequency characteristics of a SAW filter. 1... 64 ° Y-cut LiNbO 3 substrate 2... Input IDT 3... Output IDT 4... Reflector
フロントページの続き 合議体 審判長 川名 幹夫 審判官 吉見 信明 審判官 橋本 正弘 (56)参考文献 特開 昭53−123051（ＪＰ，Ａ) 特開 昭63−283309（ＪＰ，Ａ) 特開 昭64−19814（ＪＰ，Ａ) 特開 昭61−285814（ＪＰ，Ａ)Continuing from the front page Referee Mikio Kawana Judge Nobuaki Yoshimi Judge Masahiro Hashimoto (56) References JP-A-53-123051 (JP, A) JP-A-63-283309 (JP, A) JP-A 64-64 19814 (JP, A) JP-A-61-285814 (JP, A)
Claims (2)
上にリーキーSAWを励振、受信するための入出力インタ
デジタルトランスジューサ（IDT）電極をＸ軸に沿って
配置し、その両側に該リーキーSAWを閉じ込めて共振子
を構成するための反射器を持つ縦結合二重モードフィル
タに於いて、該IDTの電極対数が各々５〜18対、該IDTの
周期LTと反射器の周期LRとの比が LT/LR＝0.995〜0.975 であり、且つ、電極膜厚ＨがリーキーSAWの波長λに対
して３±1.5％であって、比帯域幅が2.5％以上であるこ
とを特徴とする縦結合二重モードリーキーSAWフィル
タ。1. An input / output interdigital transducer (IDT) electrode for exciting and receiving a leaky SAW on a 64 ° Y-cut LiNbO 3 substrate having a large coupling coefficient is arranged along the X axis, and the leaky SAW is disposed on both sides thereof. in the longitudinally-coupled dual mode filter having a reflector for forming a resonator confine the SAW, the period of the IDT of electrode pairs are each 5 to 18 pairs, the reflectors and the IDT of the period L T L R ratio of is L T / L R = 0.995~0.975, and, the electrode thickness H is a 3 ± 1.5% with respect to the wavelength λ of the leaky SAW, the fractional bandwidth is 2.5% or more Features a vertically coupled dual mode leaky SAW filter.
隔）ｌが、前記IDT周期LTに対して （n/2−1/4）λ≦ｌ＜（n/2−1/8）λ であってｎが２乃至８であることを特徴とする請求項
（１）記載の縦結合二重モードリーキーSAWフィルタ。Wherein said both IDT spacing (between the innermost electrode finger center s intervals) l is the relative IDT period L T (n / 2-1 / 4 ) λ ≦ l <(n / 2-1 / 8) The longitudinally coupled dual mode leaky SAW filter according to claim 1, wherein λ and n are 2 to 8.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP02337281A JP3107392B2 (en) | 1990-11-30 | 1990-11-30 | Vertically coupled dual mode leaky SAW filter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP02337281A JP3107392B2 (en) | 1990-11-30 | 1990-11-30 | Vertically coupled dual mode leaky SAW filter |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH04207615A JPH04207615A (en) | 1992-07-29 |
| JP3107392B2 true JP3107392B2 (en) | 2000-11-06 |
Family
ID=18307136
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP02337281A Expired - Fee Related JP3107392B2 (en) | 1990-11-30 | 1990-11-30 | Vertically coupled dual mode leaky SAW filter |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3107392B2 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH06338756A (en) * | 1993-05-27 | 1994-12-06 | Fujitsu Ltd | Resonator type surface acoustic wave filter |
| JP3068035B2 (en) * | 1997-05-26 | 2000-07-24 | 日本電気株式会社 | Surface acoustic wave device |
| JP3280617B2 (en) * | 1998-02-27 | 2002-05-13 | 東洋通信機株式会社 | Broadband surface wave filter |
| JP2000059176A (en) | 1998-08-06 | 2000-02-25 | Toshiba Corp | Surface acoustic wave element |
| US6472959B1 (en) * | 1999-03-11 | 2002-10-29 | Nortel Networks Limited | Longitudinally coupled double mode resonator filters using shallow bulk acoustic waves |
-
1990
- 1990-11-30 JP JP02337281A patent/JP3107392B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH04207615A (en) | 1992-07-29 |
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