JPH0758581A - Surface acoustic wave resonator filter - Google Patents
Surface acoustic wave resonator filterInfo
- Publication number
- JPH0758581A JPH0758581A JP19734993A JP19734993A JPH0758581A JP H0758581 A JPH0758581 A JP H0758581A JP 19734993 A JP19734993 A JP 19734993A JP 19734993 A JP19734993 A JP 19734993A JP H0758581 A JPH0758581 A JP H0758581A
- Authority
- JP
- Japan
- Prior art keywords
- acoustic wave
- surface acoustic
- electrode finger
- idts
- wave resonator
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Landscapes
- Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、圧電基板上にＩＤＴと
反射器とを備えてなる弾性表面波共振子フィルタに関す
るものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave resonator filter having an IDT and a reflector on a piezoelectric substrate.
【０００２】[0002]
【従来の技術】近年、各種通信機器に弾性表面波共振子
フィルタが使われるようになり、小形化、無調整化に一
役を担っている。そして、通信機器の高周波数化、高機
能化の進展にともない、弾性表面波共振子フィルタの広
帯域化の要求が益々増大してきている。例えば、９００
ＭＨｚ帯携帯電話用フィルタとしては、実効通過帯域幅
２０ＭＨｚ以上の高性能な広帯域フィルタが要求されて
いる。2. Description of the Related Art In recent years, surface acoustic wave resonator filters have come to be used in various communication devices and play a role in miniaturization and non-adjustment. With the progress of higher frequency and higher functionality of communication equipment, the demand for wide band of the surface acoustic wave resonator filter is increasing more and more. For example, 900
As a filter for a mobile phone of MHz band, a high performance wide band filter having an effective pass bandwidth of 20 MHz or more is required.
【０００３】広帯域化を実現するために、従来から様々
な方法が提案されている。広帯域化の１つの手法とし
て、３個のＩＤＴを設け、縦０次モードと縦２次モード
を利用した２重モード弾性表面波共振子フィルタがあ
る。従来の２重モード弾性表面波共振子フィルタでは、
圧電基板として、Ｘカット−１１２゜回転Ｙ伝搬ＬｉＴ
ａＯ3 基板を用いた場合、比帯域幅（中心周波数に対す
る通過帯域幅の値）は約０．４０％（特開平１−２３１
４１７）が得られるに過ぎず、また、電気機械結合係数
の大きい３６゜Ｙ回転カットのＬｉＴａＯ3 基板を用
い、ＩＤＴと電気的に並列となる結合容量を設け、広帯
域化を実現した場合でも、比帯域幅は、高々２％程度し
か得られていない（特開平４−４０７０５）。Various methods have heretofore been proposed to realize a wide band. As one method of widening the band, there is a dual-mode surface acoustic wave resonator filter in which three IDTs are provided and a longitudinal zero-order mode and a longitudinal second-order mode are used. In the conventional dual mode surface acoustic wave resonator filter,
As a piezoelectric substrate, X cut-112 ° rotation Y propagation LiT
When the aO 3 substrate is used, the specific bandwidth (the value of the pass bandwidth with respect to the center frequency) is about 0.40% (JP-A-1-231).
417) is obtained, and even when a 36 ° Y rotation cut LiTaO 3 substrate having a large electromechanical coupling coefficient is used and a coupling capacitance electrically provided in parallel with the IDT is provided to realize a wide band, The specific bandwidth has been obtained at most about 2% (Japanese Patent Laid-Open No. 40705/1992).
【０００４】そこで、圧電基板として、さらに電気機械
結合係数の大きい６４゜Ｙ回転カットのＬｉＮｂＯ3 基
板を用いることにより、比帯域幅３．２〜４．０％程度
の広帯域の弾性表面波共振子フィルタが実現できている
（特開平４−２０７６１５、特開平４−１１３７１
２）。Therefore, by using a 64 ° Y rotation cut LiNbO 3 substrate having a larger electromechanical coupling coefficient as the piezoelectric substrate, a broadband surface acoustic wave resonator having a specific bandwidth of about 3.2 to 4.0% is obtained. A filter has been realized (Japanese Patent Laid-Open No. 4-207615, Japanese Patent Laid-Open No. 4-11371).
2).
【０００５】[0005]
【発明が解決しようとする課題】しかしながら、上記の
方法では、基板に６４゜Ｙ回転カットのＬｉＮｂＯ3 基
板を用いるので、基板の温度特性の影響を受け、使用温
度範囲１００℃内でフィルタの中心周波数が、約０．７
％も変動する。このため、フィルタとしての実使用上の
実効的な通過帯域幅が狭くなり、さらに通過帯域近傍の
選択度が不足するという問題があった。However, in the above method, since the LiNbO 3 substrate of 64 ° Y rotation cut is used as the substrate, it is affected by the temperature characteristics of the substrate and the center of the filter is within the operating temperature range of 100 ° C. Frequency is about 0.7
% Also fluctuates. Therefore, there is a problem in that the effective pass band width in actual use as a filter becomes narrow and the selectivity near the pass band becomes insufficient.
【０００６】また、３６゜Ｙ回転カットのＬｉＴａＯ3
基板を用い、従来の設計手法よれば、温度による周波数
変動は、６４゜Ｙ回転カットのＬｉＮｂＯ3 基板に比べ
約１／２に抑えられるが、前記したように、通過帯域幅
が不足するという問題から、広い通過帯域幅が必要な携
帯電話等の通信機器への適用には問題があった。Also, 36 ° Y rotation cut LiTaO 3
According to the conventional design method using the substrate, the frequency fluctuation due to the temperature can be suppressed to about 1/2 as compared with the LiNbO 3 substrate having the 64 ° Y rotation cut, but as described above, the pass band width is insufficient. Therefore, there is a problem in application to communication devices such as mobile phones that require a wide pass bandwidth.
【０００７】そこで、本発明の目的は、３６゜Ｙ回転カ
ットのＬｉＴａＯ3 基板を用い、温度特性が良好で、か
つ通過帯域幅の広い弾性表面波共振子フィルタを提供す
ることにある。Therefore, an object of the present invention is to provide a surface acoustic wave resonator filter which uses a 36 ° Y rotation cut LiTaO 3 substrate and has good temperature characteristics and a wide pass band width.
【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、本発明は、３６゜Ｙ回転カットのＬｉＴａＯ3 圧電
基板上に３個のＩＤＴが近接配置され、かつ前記ＩＤＴ
の両側に反射器が配置されてなる弾性表面波共振子フィ
ルタにおいて、前記ＩＤＴ及び前記反射器の電極膜厚を
ｈ、表面波の波長をλ、前記ＩＤＴの総電極指対数をＮ
ｔとしたとき、 ｈ／λ≧０．０６ ４６≦Ｎｔ≦７１．５ に設定され、かつ、ＩＤＴの同電位側電極指周期をＬ、
電極指交さ幅をＷ、としたとき、 ４２×５０／ＲL ≦Ｗ／Ｌ≦１１０×５０／ＲL に設定されたことを特徴とするものである。但し、ＲL
は、弾性表面波共振子フィルタに接続される負荷インピ
ーダンスの大きさであり、単位はΩである。また、前記
ＩＤＴの各々の電極指中心間隔をｄとしたとき、 ０．２４≦ｄ／Ｌ≦０．３０ に設定されたことを特徴とするものである。In order to achieve the above object, the present invention provides three IDTs closely arranged on a 36 ° Y rotation cut LiTaO 3 piezoelectric substrate.
In a surface acoustic wave resonator filter in which reflectors are arranged on both sides of the IDT, the electrode film thickness of the IDT and the reflector is h, the wavelength of the surface wave is λ, and the total number of electrode finger pairs of the IDT is N.
When t is set, h / λ ≧ 0.06 46 ≦ Nt ≦ 71.5, and the electrode potential period on the same potential side of the IDT is L,
When the electrode finger crossing width is W, it is set to 42 × 50 / RL ≦ W / L ≦ 110 × 50 / RL . However, R L
Is the magnitude of the load impedance connected to the surface acoustic wave resonator filter, and the unit is Ω. Further, when the center distance between the electrode fingers of the IDT is d, 0.24 ≦ d / L ≦ 0.30 is set.
【０００９】[0009]
【作用】上記の構成によれば、温度特性の良い３６゜Ｙ
回転カットのＬｉＴａＯ3 基板を用いることで、温度に
よる周波数変動等を低減でき、また、ＩＤＴ及び反射器
の電極膜厚を従来の膜厚の約２倍の厚さとすることで、
最大通過帯域幅を決定する反射器のストップバンド幅を
拡大し、さらに、電極指対数や電極指交さ幅等を実験的
に確認し、具体的に最適な値に設定することで、通過帯
域内でのリップルを低減するができる。According to the above construction, the temperature characteristic is 36 ° Y.
By using a rotation-cut LiTaO 3 substrate, frequency fluctuations due to temperature can be reduced, and by making the electrode film thickness of the IDT and the reflector about twice the conventional film thickness,
By increasing the stop band width of the reflector that determines the maximum pass band width, and experimentally confirming the number of electrode finger pairs and the electrode finger cross width, etc., and setting it to a specific optimum value, the pass band The internal ripple can be reduced.
【００１０】[0010]
【実施例】図１は、本発明の一実施例による弾性表面波
共振子フィルタの構成を示す平面図である。図１におい
て、弾性表面波共振子フィルタ１０は、３６°Ｙ回転カ
ットのＬｉＴａＯ3 基板１１上に、反射器１４、１５が
形成され、反射器１４と反射器１５の間には３個のＩＤ
Ｔ１２ａ、１２ｂ、１３が形成されている。そして、両
側のＩＤＴ１２ａとＩＤＴ１２ｂは、電気的に並列接続
され、入出力端子２２と接続される。一方、中央のＩＤ
Ｔ１３は、入出力端子２３に接続される。これらの反射
器１４、１５及びＩＤＴ１２ａ、１２ｂ、１３は、すべ
て３６°Ｙ回転カットのＬｉＴａＯ3 基板１１上にＡｌ
の薄膜を成膜した後、フォトエッチング工程を経て形成
される。1 is a plan view showing the structure of a surface acoustic wave resonator filter according to an embodiment of the present invention. In FIG. 1, a surface acoustic wave resonator filter 10 has reflectors 14 and 15 formed on a 36 ° Y rotation cut LiTaO 3 substrate 11, and three IDs are provided between the reflectors 14 and 15.
T12a, 12b, 13 are formed. The IDTs 12a and 12B on both sides are electrically connected in parallel and connected to the input / output terminal 22. On the other hand, the central ID
T13 is connected to the input / output terminal 23. These reflectors 14 and 15 and IDTs 12a, 12b and 13 are all made of Al on a LiTaO 3 substrate 11 of 36 ° Y rotation cut.
After the thin film is formed, it is formed through a photo-etching process.
【００１１】上記構成において、ＩＤＴ１２ａ、１２
ｂ、１３の同電位側電極指周期（以下、電極指周期と記
す）Ｌの１／２周期を反射器１４、１５の格子周期に対
し、約１〜２％程度小さくすることによって、共振子の
Ｑが向上することは周知であり、本実施例及び以下の実
験においても、従来どうりとしてある。In the above structure, the IDTs 12a, 12
The resonator is obtained by reducing the 1/2 period of the same potential side electrode finger period of b and 13 (hereinafter referred to as electrode finger period) L by about 1 to 2% with respect to the grating period of the reflectors 14 and 15. It is well known that Q is improved, and in the present embodiment and the following experiments, it is the same as before.
【００１２】以下、本発明にかかる弾性表面波共振子フ
ィルタについて、各種実験の結果に基づいて説明する。
図２は、従来の設計値に基づいて作成した弾性表面波共
振子フィルタの一例の特性図である。具体的には、表面
波の波長λに対する電極膜厚ｈの比率である電極膜厚比
ｈ／λ＝０．０３、総電極指対数Ｎｔ＝７０．５、電極
指周期Ｌに対する電極指交さ幅Ｗの比Ｗ／Ｌ＝２０とし
たときのフィルタ特性である。The surface acoustic wave resonator filter according to the present invention will be described below based on the results of various experiments.
FIG. 2 is a characteristic diagram of an example of a surface acoustic wave resonator filter created based on conventional design values. Specifically, the electrode film thickness ratio h / λ = 0.03, which is the ratio of the electrode film thickness h to the wavelength λ of the surface wave, the total number of electrode finger pairs Nt = 70.5, and the electrode finger crossing for the electrode finger period L. It is a filter characteristic when the ratio W / L of the width W is 20.
【００１３】ここで、９００ＭＨｚ帯の携帯電話では、
２０ＭＨｚの通過帯域幅が必須であり、これに温度変動
分、経時変動分、さらに製造上の公差を含めると、フィ
ルタとしては最低でも３０ＭＨｚの帯域幅が必要とな
る。また、携帯電話等の用途には、省電力化のために低
損失化が必須であり、フィルタとしては挿入損失３ｄＢ
以内を要求されている。しかし、図２においては、挿入
損失３ｄＢ帯域幅（以下、３ｄＢ帯域幅と略す）は２０
ＭＨｚ程度であり、携帯電話用フィルタとしては実用上
適さないことが明らかである。Here, in a 900 MHz band mobile phone,
A pass band width of 20 MHz is indispensable, and if a temperature variation amount, a temporal variation amount, and manufacturing tolerances are included in the pass bandwidth, the filter needs a minimum bandwidth of 30 MHz. In addition, low loss is indispensable for power saving in applications such as mobile phones, and the insertion loss is 3 dB as a filter.
Is required within. However, in FIG. 2, the insertion loss 3 dB bandwidth (hereinafter, abbreviated as 3 dB bandwidth) is 20.
It is about MHz, and it is clear that it is not suitable for practical use as a filter for mobile phones.
【００１４】弾性表面波共振子フィルタでは、帯域幅の
上限は、反射器のストップバンド幅（反射器が反射し得
る周波数帯域幅）で制限される。上記図２の特性図での
反射器の反射係数｜Ｒ｜は、図３に示すような周波数特
性であり、図２での通過帯域幅が図３に示すストップバ
ンド幅によって制限されていることがわかる。In the surface acoustic wave resonator filter, the upper limit of the bandwidth is limited by the stop bandwidth of the reflector (the frequency bandwidth that the reflector can reflect). The reflection coefficient | R | of the reflector in the characteristic diagram of FIG. 2 has the frequency characteristic as shown in FIG. 3, and the pass band width in FIG. 2 is limited by the stop band width shown in FIG. I understand.
【００１５】電極膜厚比ｈ／λを増大させることによ
り、ストップバンド幅を広くすることができる。図４
は、図２における他の設定値を変えず、電極膜厚ｈを２
倍とし、ストップバンド幅の拡大を狙ったものの特性図
である。図４の特性から明らかなように、電極膜厚ｈの
増大だけでは、リップルが大きくなり良好な通過帯域特
性は得られない。The stop band width can be widened by increasing the electrode film thickness ratio h / λ. Figure 4
Does not change other setting values in FIG.
FIG. 6 is a characteristic diagram of the doubled structure aiming at widening the stop band width. As is clear from the characteristics of FIG. 4, an increase in the electrode film thickness h alone results in large ripples, and good pass band characteristics cannot be obtained.
【００１６】そこで、本発明は、弾性表面波共振子フィ
ルタの通過帯域内のリップルを抑え、通過帯域幅を１．
５倍以上に拡大するためには、いかなる設計値に設定す
べきかという点を示す。以下、本発明に係る弾性表面波
共振子フィルタの設計条件について、その設定理由を説
明する。Therefore, according to the present invention, the ripple in the pass band of the surface acoustic wave resonator filter is suppressed and the pass band width is 1.
The following shows the design value that should be set in order to increase the size five times or more. The reasons for setting the design conditions of the surface acoustic wave resonator filter according to the present invention will be described below.
【００１７】図５は、電極膜厚比ｈ／λを変化させ、反
射器のストップバンド幅を測定した実験結果である。こ
こで、３ｄＢ帯域幅を図２で示した２０ＭＨｚに対し
１．５倍以上とするには、まず反射器のストップバンド
幅を１．５倍以上にする必要がある。電極膜厚比ｈ／λ
＝０．０３のとき３ｄＢ帯域幅は２０ＭＨｚであり、図
５に示すように、このときのストップバンド比帯域幅は
０．０３であり、このストップバンド比帯域幅の１．５
倍は０．０４５となり、電極膜厚比ｈ／λは０．０６と
なっている。以上のことから、３ｄＢ帯域幅を３０ＭＨ
ｚ以上とするには、電極膜厚比ｈ／λを０．０６以上に
設定すればよいことがわかる。FIG. 5 shows the experimental results of measuring the stop band width of the reflector while changing the electrode film thickness ratio h / λ. Here, in order to make the 3 dB bandwidth 1.5 times or more of 20 MHz shown in FIG. 2, the stop band width of the reflector needs to be 1.5 times or more. Electrode film thickness ratio h / λ
= 0.03, the 3 dB bandwidth is 20 MHz, and as shown in FIG. 5, the stop band ratio bandwidth at this time is 0.03, and the stop band ratio bandwidth is 1.5.
The doubled value is 0.045, and the electrode film thickness ratio h / λ is 0.06. From the above, a 3 dB bandwidth of 30 MH
It can be seen that the electrode film thickness ratio h / λ may be set to 0.06 or more in order to obtain z or more.
【００１８】次に通過帯域内のリップルを抑えるため
に、ＩＤＴの電極指対数の検討を行った。電極膜厚比ｈ
／λ＝０．０６、電極指周期Ｌに対する電極指交さ幅Ｗ
の比Ｗ／Ｌ＝６５、電極指中心間隔ｄ＝０．２５Ｌとし
て、電極指対数を変えて、リップル及び３ｄＢ帯域幅を
測定した。その実験結果を図６に示す。図６において、
図１に示したＩＤＴ１２ａ、１２ｂの電極指対数をそれ
ぞれＮ１、ＩＤＴ１３の電極指対数をＮ２、これら３個
の電極指対数の総和をＮｔとしてある。Next, in order to suppress the ripple in the pass band, the number of electrode finger pairs of the IDT was examined. Electrode film thickness ratio h
/Λ=0.06, electrode finger intersection width W with respect to electrode finger period L
With the ratio W / L = 65 and the electrode finger center interval d = 0.25 L, the ripple and the 3 dB bandwidth were measured by changing the number of electrode finger pairs. The experimental results are shown in FIG. In FIG.
The number of electrode finger pairs of the IDTs 12a and 12b shown in FIG. 1 is N1, the number of electrode finger pairs of the IDT 13 is N2, and the total number of these three electrode finger pairs is Nt.
【００１９】前記したように３ｄＢ帯域幅は３０ＭＨｚ
以上必要であり、リップルは実用上１ｄＢ以下に抑える
必要がある。この条件を満たすＩＤＴの総電極指対数Ｎ
ｔは、図６より、４６≦Ｎｔ≦７１．５の範囲に設定し
なければならないことがわかる。As mentioned above, the 3 dB bandwidth is 30 MHz.
The above is necessary, and the ripple must be suppressed to 1 dB or less for practical use. Total number of electrode finger pairs of IDT satisfying this condition N
It can be seen from FIG. 6 that t must be set in the range of 46 ≦ Nt ≦ 71.5.
【００２０】また、３ｄＢ帯域幅とリップルはＩＤＴの
電極指交さ幅Ｗによっても変動する。そこで、電極膜厚
比ｈ／λ＝０．０６、電極指中心間隔ｄ＝０．２５Ｌ、
総電極指対数Ｎｔ＝５８として、交さ幅Ｗを変化させ
て、３ｄＢ帯域幅及びリップルを測定した。その実験結
果を図７に示す。図７において、リップルを１ｄＢ以内
に抑えるためには、電極指周期Ｌに対する電極指交さ幅
Ｗの比Ｗ／Ｌを、４２≦Ｗ／Ｌ≦１１０の範囲に設定し
なければならないことがわかる。なお、ここでは測定系
のインピーダンスＲL を５０Ωとして測定した。また、
電極指周期Ｌに対する電極指交さ幅Ｗの比Ｗ／Ｌは、弾
性表面波共振子フィルタの特性インピーダンスとほぼ逆
比例の関係にあることは周知であるので、異なるインピ
ーダンスＲL の場合を考慮すると、４２×５０／ＲL ≦
Ｗ／Ｌ≦１１０×５０／ＲL の範囲でなければならな
い。The 3 dB bandwidth and the ripple also vary depending on the electrode finger crossing width W of the IDT. Therefore, the electrode film thickness ratio h / λ = 0.06, the electrode finger center distance d = 0.25L,
With the total number of electrode finger pairs Nt = 58, the cross width W was changed and the 3 dB bandwidth and ripple were measured. The experimental results are shown in FIG. In FIG. 7, in order to suppress the ripple within 1 dB, it can be seen that the ratio W / L of the electrode finger cross width W to the electrode finger period L must be set within the range of 42 ≦ W / L ≦ 110. . In this case, the impedance R L of the measurement system was set to 50Ω. Also,
The ratio W / L of the electrode fingers interlinked width W to the electrode fingers period L, so that the relationship of approximately inversely proportional to the characteristic impedance of the surface acoustic wave resonator filter is well known, considering the case of a different impedance R L Then 42 × 50 / R L ≦
It must be within the range of W / L ≦ 110 × 50 / RL .
【００２１】さらに、ＩＤＴの電極指中心間隔ｄを変え
ることで、３ｄＢ帯域幅を拡大しリップルを低減するこ
とを検討した。電極膜厚比ｈ／λ＝０．０６、総電極指
対数Ｎｔ＝５８、電極指周期Ｌに対する電極指交さ幅Ｗ
の比Ｗ／Ｌ＝７０として、電極指中心間隔ｄを変化させ
て、３ｄＢ帯域幅及びリップルを測定した。その実験結
果を図８に示す。図８において、３ｄＢ帯域幅を３０Ｍ
Ｈｚ以上、リップルを１ｄＢ以内とするには、電極指周
期Ｌに対する電極指中心間隔ｄの比ｄ／Ｌは、０．２４
≦ｄ／Ｌ≦０．３０の範囲に設定しなければならないこ
とがわかる。Further, it was studied to increase the 3 dB bandwidth and reduce the ripple by changing the electrode finger center distance d of the IDT. Electrode film thickness ratio h / λ = 0.06, total number of electrode finger pairs Nt = 58, electrode finger crossing width W with respect to electrode finger period L
With the ratio W / L = 70, the electrode finger center interval d was changed and the 3 dB bandwidth and ripple were measured. The experimental results are shown in FIG. In FIG. 8, the 3 dB bandwidth is 30 M
In order to keep the ripple at 1 Hz or more and within 1 dB, the ratio d / L of the electrode finger center interval d to the electrode finger period L is 0.24.
It can be seen that the range must be set to ≤d / L≤0.30.
【００２２】以上の実験結果を総括すると、３６゜Ｙ回
転カットのＬｉＴａＯ3 基板を用いて、広帯域で、かつ
低リップルの弾性表面波共振子フィルタを実現するに
は、限定された設計条件が必要である。その設計条件を
まとめると以下のようになる。To summarize the above experimental results, limited design conditions are required to realize a wide-band, low-ripple surface acoustic wave resonator filter using a 36 ° Y rotation cut LiTaO 3 substrate. Is. The design conditions are summarized below.
【００２３】表面波の波長λに対するＩＤＴ及び反射
器の電極膜厚ｈの比ｈ／λを ｈ／λ≧０．０６ ＩＤＴの総電極指対数Ｎｔを ４６≦Ｎｔ≦７１．５ ＩＤＴの電極指周期Ｌに対する電極指交さ幅Ｗの比Ｗ
／Ｌを ４２×５０／ＲL ≦Ｗ／Ｌ≦１１０×５０／ＲL ただし、ＲL は、負荷インンピーダンスの大きさ（単
位：Ω） ＩＤＴの電極指周期Ｌに対する電極指中心間隔ｄの比
ｄ／Ｌを ０．２４≦ｄ／Ｌ≦０．３０ に設定する。The ratio h / λ of the electrode film thickness h of the IDT and the reflector to the wavelength λ of the surface wave is h / λ ≧ 0.06 The total number Nt of electrode fingers of IDT is 46 ≦ Nt ≦ 71.5 The electrode finger of IDT Ratio W of electrode finger cross width W to period L
/ L is 42 × 50 / RL ≦ W / L ≦ 110 × 50 / RL , where RL is the magnitude of the load impedance (unit: Ω) of the electrode finger center distance d with respect to the electrode finger period L of the IDT. The ratio d / L is set to 0.24 ≦ d / L ≦ 0.30.
【００２４】以上の結果に基づいて作成した弾性表面波
共振子フィルタの特性の一例を図９に示す。図９は、前
記４つの設計条件を、ｈ／λ＝０．０６、Ｎｔ＝４
９．５、Ｗ／Ｌ＝６０、ｄ／Ｌ＝０．２７に設定
し、測定系の負荷インピーダンスＲL ＝５０Ωで測定し
た弾性表面波共振子フィルタの周波数特性である。３ｄ
Ｂ帯域幅は３５ＭＨｚあり、従来の設計値に対し１．５
倍以上に拡大されており、比帯域幅は、６４゜Ｙ回転カ
ットのＬｉＮｂＯ3 基板を用いて得られる弾性表面波共
振子フィルタと同等の３．７％が得られた。また、温度
特性は、３６゜Ｙ回転カットのＬｉＴａＯ3 基板を用い
た従来の弾性表面波共振子フィルタと同等であり、６４
゜Ｙ回転カットのＬｉＮｂＯ3 基板を用いた場合に比
べ、約１／２の良好な温度特性を得ることができた。FIG. 9 shows an example of the characteristics of the surface acoustic wave resonator filter produced based on the above results. FIG. 9 shows the four design conditions as h / λ = 0.06 and Nt = 4.
It is a frequency characteristic of the surface acoustic wave resonator filter measured with load impedance R L = 50Ω of the measurement system, setting 9.5, W / L = 60, d / L = 0.27. 3d
The B bandwidth is 35 MHz, which is 1.5 compared to the conventional design value.
It is more than doubled, and the specific bandwidth is 3.7%, which is equivalent to that of the surface acoustic wave resonator filter obtained by using the 64 ° Y rotation cut LiNbO 3 substrate. In addition, the temperature characteristic is equivalent to that of a conventional surface acoustic wave resonator filter using a 36 ° Y rotation cut LiTaO 3 substrate.
It was possible to obtain a good temperature characteristic of about 1/2 as compared with the case of using the LiNbO 3 substrate with the ° Y rotation cut.
【００２５】なお、上記実施例では、図１に示すよう
に、１セクションの共振子で構成したが、これに限るこ
とはなく、図１に示すような共振子を２個以上縦続接続
した弾性表面波共振子フィルタにも本発明を適用するこ
とができる。In the above embodiment, as shown in FIG. 1, the resonator is composed of one section. However, the invention is not limited to this, and it is possible to elastically connect two or more resonators as shown in FIG. The present invention can also be applied to a surface wave resonator filter.
【００２６】[0026]
【発明の効果】以上説明したように、本発明に係る弾性
表面波共振子フィルタは、温度特性のよい３６゜Ｙ回転
カットのＬｉＴａＯ3 基板を用いることで、温度による
周波数変動等を低減することができる。さらに、ＩＤＴ
及び反射器の電極膜厚を増大することにより、最大通過
帯域幅を決定する反射器のストップバンド幅を拡大し、
かつ、電極指対数、電極指交さ幅、電極指中心間隔等を
最適な値に設定することで、通過帯域内のリップルを低
減することにより、広帯域な通過帯域幅を得ることがで
きる。As described above, the surface acoustic wave resonator filter according to the present invention uses a 36 ° Y rotation cut LiTaO 3 substrate having good temperature characteristics to reduce frequency fluctuations due to temperature. You can Furthermore, IDT
And by increasing the electrode film thickness of the reflector, the stop band width of the reflector that determines the maximum pass band width is expanded,
In addition, by setting the number of electrode finger pairs, the electrode finger crossing width, the electrode finger center interval, etc. to optimum values, ripples in the pass band can be reduced, and a wide pass band width can be obtained.
【００２７】すなわち、本発明によれば、温度特性のよ
い、広帯域の弾性表面波共振子フィルタを、容易に実現
することができる。That is, according to the present invention, a wide-range surface acoustic wave resonator filter having good temperature characteristics can be easily realized.
【図１】本発明の一実施例による弾性表面波共振子フィ
ルタの構成を示す平面図である。FIG. 1 is a plan view showing the structure of a surface acoustic wave resonator filter according to an embodiment of the present invention.
【図２】従来の設計値による弾性表面波共振子フィルタ
の特性図である。FIG. 2 is a characteristic diagram of a surface acoustic wave resonator filter according to a conventional design value.
【図３】従来の設計値による弾性表面波共振子フィルタ
における反射器の反射係数の周波数特性図である。FIG. 3 is a frequency characteristic diagram of a reflection coefficient of a reflector in a surface acoustic wave resonator filter according to a conventional design value.
【図４】従来の設計値による弾性表面波共振子フィルタ
において、電極膜厚を２倍にしたときの特性図である。FIG. 4 is a characteristic diagram when the electrode film thickness is doubled in the surface acoustic wave resonator filter according to the conventional design value.
【図５】本発明の実験により得られた、電極膜厚と反射
器のストップバンド帯域幅の関係を示す図である。FIG. 5 is a diagram showing a relationship between an electrode film thickness and a stop band bandwidth of a reflector, which is obtained by an experiment of the present invention.
【図６】本発明の実験により得られた、ＩＤＴの電極指
対数と３ｄＢ帯域幅及びリップルの関係を示す図であ
る。FIG. 6 is a diagram showing the relationship between the number of electrode finger pairs of the IDT, the 3 dB bandwidth, and the ripple obtained by the experiment of the present invention.
【図７】本発明の実験により得られた、ＩＤＴの電極指
交さ幅と３ｄＢ帯域幅及びリップルの関係を示す図であ
る。FIG. 7 is a diagram showing the relationship between the electrode finger interdigitation width of the IDT, the 3 dB bandwidth, and the ripple obtained by the experiment of the present invention.
【図８】本発明の実験により得られた、ＩＤＴの電極指
中心間隔と３ｄＢ帯域幅及びリップルの関係を示す図で
ある。FIG. 8 is a diagram showing the relationship between the electrode finger center distance of the IDT, the 3 dB bandwidth, and the ripple, obtained by an experiment of the present invention.
【図９】本発明によって得られた設計範囲で作成した弾
性表面波共振子フィルタの特性図である。FIG. 9 is a characteristic diagram of a surface acoustic wave resonator filter created in the design range obtained by the present invention.
１０ 弾性表面波共振子フィルタ １１ ＬｉＴａＯ3 基板 １２ａ、１２ｂ、１３ ＩＤＴ １４、１５ 反射器10 Surface Acoustic Wave Resonator Filter 11 LiTaO 3 Substrate 12a, 12b, 13 IDT 14, 15 Reflector
─────────────────────────────────────────────────────
─────────────────────────────────────────────────── ───
【手続補正書】[Procedure amendment]
【提出日】平成６年７月１２日[Submission date] July 12, 1994
【手続補正１】[Procedure Amendment 1]
【補正対象書類名】図面[Document name to be corrected] Drawing
【補正対象項目名】図８[Correction target item name] Figure 8
【補正方法】変更[Correction method] Change
【補正内容】[Correction content]
【図８】 [Figure 8]
Claims (2)
基板上に３個のＩＤＴが近接配置され、かつ前記ＩＤＴ
の両側に反射器が配置されてなる弾性表面波共振子フィ
ルタにおいて、 前記ＩＤＴ及び前記反射器の電極膜厚をｈ、表面波の波
長をλ、前記ＩＤＴの総電極指対数をＮｔとしたとき、 ｈ／λ≧０．０６ ４６≦Ｎｔ≦７１．５ に設定され、かつ、ＩＤＴの同電位側電極指周期をＬ、
電極指交さ幅をＷ、としたとき、 ４２×５０／ＲL ≦Ｗ／Ｌ≦１１０×５０／ＲL に設定されたことを特徴とする弾性表面波共振子フィル
タ。但し、ＲL は、弾性表面波共振子フィルタに接続さ
れる負荷インピーダンスの大きさであり、単位はΩであ
る。1. IDTs are arranged in proximity to each other on a 36 ° Y rotation cut LiTaO 3 piezoelectric substrate, and the IDTs are arranged close to each other.
In a surface acoustic wave resonator filter in which reflectors are arranged on both sides of, when the electrode film thickness of the IDT and the reflector is h, the wavelength of the surface wave is λ, and the total number of electrode finger pairs of the IDT is Nt. , H / λ ≧ 0.06 46 ≦ Nt ≦ 71.5, and the electrode finger period on the same potential side of the IDT is L,
The surface acoustic wave resonator filter is set to 42 × 50 / RL ≦ W / L ≦ 110 × 50 / RL, where W is the electrode finger cross width. However, R L is the magnitude of the load impedance connected to the surface acoustic wave resonator filter, and the unit is Ω.
としたとき、 ０．２４≦ｄ／Ｌ≦０．３０ に設定されたことを特徴とする請求項１に記載の弾性表
面波共振子フィルタ。2. The center distance between the electrode fingers of each of the IDTs is d.
The surface acoustic wave resonator filter according to claim 1, wherein: 0.24 ≤ d / L ≤ 0.30.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP19734993A JP3225702B2 (en) | 1993-08-09 | 1993-08-09 | Surface acoustic wave resonator filter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP19734993A JP3225702B2 (en) | 1993-08-09 | 1993-08-09 | Surface acoustic wave resonator filter |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0758581A true JPH0758581A (en) | 1995-03-03 |
| JP3225702B2 JP3225702B2 (en) | 2001-11-05 |
Family
ID=16373010
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP19734993A Expired - Lifetime JP3225702B2 (en) | 1993-08-09 | 1993-08-09 | Surface acoustic wave resonator filter |
Country Status (1)
| Country | Link |
|---|---|
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5874869A (en) * | 1996-11-28 | 1999-02-23 | Fujitsu Limited | Surface acoustic wave filter device on 40° to 42° rotated Y-X LITAO3 |
| US7102468B2 (en) | 2003-07-02 | 2006-09-05 | Kyocera Corporation | Surface acoustic wave device and communication apparatus using the same |
| US7504911B2 (en) | 2005-05-27 | 2009-03-17 | Kyocera Corporation | Surface acoustic wave resonator, surface acoustic wave device, and communications equipment |
| JP2012049816A (en) * | 2010-08-26 | 2012-03-08 | Seiko Epson Corp | Surface acoustic wave resonator, and surface acoustic wave oscillator, and electronic apparatus |
-
1993
- 1993-08-09 JP JP19734993A patent/JP3225702B2/en not_active Expired - Lifetime
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5874869A (en) * | 1996-11-28 | 1999-02-23 | Fujitsu Limited | Surface acoustic wave filter device on 40° to 42° rotated Y-X LITAO3 |
| US7102468B2 (en) | 2003-07-02 | 2006-09-05 | Kyocera Corporation | Surface acoustic wave device and communication apparatus using the same |
| US7504911B2 (en) | 2005-05-27 | 2009-03-17 | Kyocera Corporation | Surface acoustic wave resonator, surface acoustic wave device, and communications equipment |
| JP2012049816A (en) * | 2010-08-26 | 2012-03-08 | Seiko Epson Corp | Surface acoustic wave resonator, and surface acoustic wave oscillator, and electronic apparatus |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3225702B2 (en) | 2001-11-05 |
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