JP3137392B2 - One-way SAW filter - Google Patents
One-way SAW filterInfo
- Publication number
- JP3137392B2 JP3137392B2 JP03305435A JP30543591A JP3137392B2 JP 3137392 B2 JP3137392 B2 JP 3137392B2 JP 03305435 A JP03305435 A JP 03305435A JP 30543591 A JP30543591 A JP 30543591A JP 3137392 B2 JP3137392 B2 JP 3137392B2
- Authority
- JP
- Japan
- Prior art keywords
- idt
- internal reflection
- reflection type
- excitation electrode
- saw filter
- 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 - Fee Related
Links
Landscapes
- Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
Description
【０００１】[0001]
【産業上の利用分野】本発明はＳＡＷフィルタ、殊に浮
き電極をもつ内部反射型一方向性ＩＤＴを用いた低損失
ＳＡＷフィルタに関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a SAW filter, and more particularly to a low-loss SAW filter using an internal reflection type unidirectional IDT having a floating electrode.
【０００２】[0002]
【従来技術】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としてトランスバーサル型Ｓ
ＡＷフィルタが広く用いられてきた。しかしながら、ト
ランスバーサル型ＳＡＷフィルタは双方向性損失のため
に挿入損失が大きくなる欠点があり、低損 化を図るた
めには一方向性ＩＤＴを用いる必要がある。この一方向
性ＩＤＴとして広く使われている方法には３相一方向性
ＩＤＴやグループ型一方向性ＩＤＴがある。しかしなが
ら、製造が困難である叉は複雑な外部回路が必要で使用
し難いという問題があった。2. Description of the Related Art Conventionally, a transversal type S has been used as a wideband low-loss filter in a high frequency range of the VHF to UHF bands.
AW filters have been widely used. However, the transversal SAW filter has a drawback that insertion loss becomes large due to bidirectional loss, and it is necessary to use a unidirectional IDT in order to reduce the loss. Methods widely used as the one-way IDT include a three-phase one-way IDT and a group-type one-way IDT. However, there is a problem that manufacturing is difficult or a complicated external circuit is required and it is difficult to use.
【０００３】これに対して山之内らはＩＤＴの正負電極
指の間に開放型及び短絡型の浮き電極を入れることによ
り一方向性が得られることを示した。（文献〜電子通信
学会超音波研究会技術報告、ＵＳ８４−１８、ｐ．９５
（１９８４）．）この浮き電極をもつ内部反射型一方向
性ＩＤＴは通常のＳＡＷフィルタと同様に唯１回の蒸着
とフォトエッチング加工で電極形成ができ製造が容易で
あるという利点があるが、ＩＤＴ電極の線幅が通常の双
方向性ＩＤＴの１／３となり製造困難となり高周波化に
は向いていない。On the other hand, Yamanouchi et al. Have shown that unidirectionality can be obtained by inserting open and short-type floating electrodes between the positive and negative electrode fingers of the IDT. (Literature-Technical Report of the Institute of Ultrasonics, IEICE, US84-18, p.95
(1984). The internal reflection type unidirectional IDT having the floating electrode has an advantage that the electrode can be formed by only one evaporation and photoetching as in the case of the ordinary SAW filter and the manufacturing is easy. The width is 1/3 that of a normal bidirectional IDT, making it difficult to manufacture, and is not suitable for higher frequencies.
【０００４】更に、山之内らは図２に示すようにＩＤＴ
の正負電極指８、８’の間に開放型の浮き電極１０と前
記電極の３倍の幅を有する負電極指９を配置すると一方
向性が得られ、また２倍倍調波で動作させることが出来
ることを見いだした。（文献〜電子通信学会超音波研究
会技術報告、ＵＳ８９−９０、ｐ．２１（１９９
０）．）この内部反射型一方向性ＩＤＴは、２倍倍調波
で動作させる場合には通常の双方向性ＩＤＴ線幅の０．
８倍の線幅となり高周波化に向いている。しかしなが
ら、通過帯域を平坦にするための交差幅重み付けを双方
向性ＩＤＴに施し、その両側に前記２倍倍調波動作の内
部反射型一方向性ＩＤＴを配置したＳＡＷフィルタに於
いては、通過帯域が平坦にならず傾斜するという欠点が
あった。Further, Yamanouchi et al., As shown in FIG.
If an open floating electrode 10 and a negative electrode finger 9 having a width three times the width of the electrode are arranged between the positive and negative electrode fingers 8 and 8 ', unidirectionality can be obtained, and operation is performed with double harmonics. I found that I could do that. (Literature-IEICE Technical Report on Ultrasonics, US89-90, p.21 (199
0). This internal reflection type unidirectional IDT has a normal bidirectional IDT line width of 0.1 mm when operated at the double harmonic.
The line width is 8 times, which is suitable for higher frequency. However, in the SAW filter in which the bidirectional IDT is weighted to make the passband flat and the internal reflection type unidirectional IDT for the double harmonic operation is arranged on both sides of the bidirectional IDT, There is a disadvantage that the band is not flat but inclined.
【０００５】[0005]
【発明の目的】本発明は上述した如き従来の内部反射型
一方向性ＩＤＴを用いたＳＡＷフィルタの欠点を除去す
るためになされたものであって、高周波領域で平坦な通
過帯域をもつ低損失ＳＡＷフィルタを提供することを目
的とする。SUMMARY OF THE INVENTION The present invention has been made in order to eliminate the drawbacks of the conventional SAW filter using the internal reflection type unidirectional IDT as described above, and has a low loss having a flat pass band in a high frequency region. It is an object to provide a SAW filter.
【０００６】[0006]
【発明の概要】上述の目的を達成する為、本発明に於い
ては内部反射型一方向性ＩＤＴと双方向性ＩＤＴとのピ
ッチの倍率を整数倍より所要量異ならしめた構成をと
る。SUMMARY OF THE INVENTION In order to achieve the above object, the present invention employs a configuration in which the required magnification of the pitch between the internal reflection type unidirectional IDT and the bidirectional IDT is different from an integral multiple.
【０００７】[0007]
【実施例】以下、本発明を実施例を示す図面によって詳
細に説明する。実施例の説明に先立ち、本発明の理解を
助ける為、従来の内部反射型一方向性ＩＤＴを用いたＳ
ＡＷフィルタの構成について説明する。図２は従来の内
部反射型一方向性ＩＤＴを用いたＳＡＷフィルタの構成
を示す図であって、圧電基板１表面に正負電極指５、
５’と、正負電極指８、８’の間に負電極指９及び開放
型浮き電極１０を配置し、電極５、５のライン幅と電極
間のスペース幅を全てλ／４（λは励振されたＳＡＷの
波長）、電極９のライン幅を３Ｐ’／１０（Ｐ’はピッ
チ）、残りの電極のライン幅と電極間のスペース幅を全
てＰ’／１０とする。このように電極８、８’、９、１
０より構成された内部反射型一方向性ＩＤＴ１１におい
ては、ＳＡＷの伝搬速度をＶとした場合に、Ｖ／Ｐ’で
決まる周波数の基本波以外に、２Ｖ／Ｐ’の周波数であ
る２倍倍調波をも励振可能である。電極線幅が太くなり
製造上有利な２倍倍調波で動作させる場合には、Ｐ’＝
２λとする。更に、通過帯域を平坦にするために電極
５、５’により構成される双方向性ＩＤＴ７に交差幅重
み付けを施す。このような構成のフィルタを１２８゜Ｙ
カットＸ伝搬ＬｉＮｂＯ3 基板を用いて試作してその特
性を調べた結果、図３に示すように通過帯域が設計値と
異なり傾斜した特性となった。DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing embodiments. Prior to the description of the embodiment, in order to assist the understanding of the present invention, the S using a conventional internal reflection type unidirectional IDT has been described.
The configuration of the AW filter will be described. FIG. 2 is a diagram showing a configuration of a conventional SAW filter using an internal reflection type one-way IDT.
A negative electrode finger 9 and an open floating electrode 10 are arranged between 5 ′ and the positive and negative electrode fingers 8, 8 ′, and the line width of the electrodes 5, 5 and the space width between the electrodes are all λ / 4 (where λ is the excitation Of the electrode 9), the line width of the electrode 9 is 3P '/ 10 (P' is a pitch), and the line width of the remaining electrodes and the space width between the electrodes are all P '/ 10. Thus, the electrodes 8, 8 ', 9, 1
In the internal reflection type one-way IDT 11 composed of 0, when the propagation speed of the SAW is V, in addition to the fundamental wave of the frequency determined by V / P ′, the frequency of 2V / P ′ is doubled. Harmonics can also be excited. In the case where the electrode line width is widened and the device is operated at the double harmonic which is advantageous in manufacturing, P ′ =
2λ. Further, in order to flatten the pass band, the bidirectional IDT 7 constituted by the electrodes 5 and 5 'is weighted with a cross width. A filter having such a configuration is used for 128 ゜ Y
As a result of examining the characteristics of a prototype manufactured using a cut X-propagation LiNbO3 substrate, as shown in FIG.
【０００８】この原因について調べるために内部反射型
一方向性ＩＤＴ１１、１１’及び双方向性ＩＤＴ７の放
射コンダクタンス−周波数特性を調べた結果、図４に示
すようにＩＤＴ７の放射コンダクタンス１２に対しＩＤ
Ｔ１１、１１’の放射コンダクタンス１３が周波数の高
い方にずれている。ＩＤＴ１１、１１’のグループ数１
０乃至２０の範囲で実験した結果では、両者の周波数差
はほぼ０．３乃至２％の範囲にある。この結果より、こ
の周波数差に相当する量、両者ＩＤＴのピッチを補正す
れば設計通りの通過帯域特性が得られると考えられる。
そこで図１に示すように、内部反射型一方向性ＩＤＴ
６、６’のピッチＰを双方向性ＩＤＴ７のピッチλの２
倍より０．４５％大きくした構成としたフィルタを試作
して、その伝送特性を測定した。その結果、図５に示す
ように平坦な通過帯域特性が得られた。この結果より本
発明による構成により、設計値通りの良好な通過帯域特
性のフィルタが得られることが示された。尚、両者ＩＤ
Ｔのピッチの補正量をどの程度とするのが最適であるか
については要求仕様により異なるが、前述の放射コンダ
クタンスの実験結果より０．３乃至２％程度であろう。As a result of examining the radiation conductance-frequency characteristics of the internal reflection type unidirectional IDTs 11 and 11 'and the bidirectional IDT 7 to investigate the cause, as shown in FIG.
The radiation conductance 13 of T11, 11 'is shifted to a higher frequency. Number of groups 1 for IDTs 11 and 11 '
According to the results of experiments in the range of 0 to 20, the frequency difference between the two is approximately in the range of 0.3 to 2%. From this result, it is considered that a passband characteristic as designed can be obtained by correcting the pitch of both IDTs by an amount corresponding to the frequency difference.
Therefore, as shown in FIG.
The pitch P of 6, 6 ′ is 2 of the pitch λ of the bidirectional IDT 7.
A filter having a configuration 0.45% larger than the doubled filter was prototyped, and its transmission characteristics were measured. As a result, a flat passband characteristic was obtained as shown in FIG. The results show that the configuration according to the present invention can provide a filter having good passband characteristics as designed. In addition, both ID
The optimal amount of the correction of the pitch of T differs depending on the required specifications, but will be about 0.3 to 2% based on the above-described experimental results of the radiation conductance.
【０００９】[0009]
【発明の効果】本発明は以上説明したように構成するの
で、高周波領域に於いて通過帯域の平坦な低損失のＳＡ
Ｗフィルタを得る上で著しい効果がある。Since the present invention is constructed as described above, a low-loss SA having a flat pass band in a high-frequency region is provided.
There is a remarkable effect in obtaining a W filter.
【００１０】[0010]
【図１】本発明に係る内部反射型一方向性ＩＤＴを用い
たＳＡＷフィルタの構成を示す図。FIG. 1 is a diagram showing a configuration of a SAW filter using an internal reflection type unidirectional IDT according to the present invention.
【図２】従来の内部反射型一方向性ＩＤＴを用いたＳＡ
Ｗフィルタの構成を示す図。FIG. 2 shows a SA using a conventional internal reflection type unidirectional IDT.
The figure which shows the structure of a W filter.
【図３】従来の内部反射型一方向性ＩＤＴを用いたＳＡ
Ｗフィルタの周波数伝送特性を示す実験データの図。FIG. 3 shows a SA using a conventional internal reflection type one-way IDT.
FIG. 4 is a diagram of experimental data showing frequency transmission characteristics of a W filter.
【図４】従来の双方向性ＩＤＴ及び内部反射型一方向性
ＩＤＴの放射コンダクタンス−周波数特性を示す実験デ
ータの図。FIG. 4 is a diagram of experimental data showing radiation conductance-frequency characteristics of a conventional bidirectional IDT and an internal reflection type unidirectional IDT.
【図５】本発明に係る内部反射型一方向性ＩＤＴを用い
たＳＡＷフィルタの周波数伝送特性を示す実験データの
図。FIG. 5 is a diagram of experimental data showing frequency transmission characteristics of a SAW filter using an internal reflection type one-way IDT according to the present invention.
１・・・圧電基板 ２、２’・・・正負電極指 ３・・・負電極指 ４・・・開放型浮き電極 ５、５’・・・正負電極指 ６、６’・・・内部反射型一方向性ＩＤＴ ７・・・双方向性ＩＤＴ ８、８’・・・正負電極指 ９・・・負電極指 １０・・・開放型浮き電極 １１、１１’・・・内部反射型一方向性ＩＤＴ １２・・・内部反射型一方向性ＩＤＴの放射コンダクタ
ンス １３・・・双方向性ＩＤＴの放射コンダクタンスDESCRIPTION OF SYMBOLS 1 ... Piezoelectric substrate 2, 2 '... Positive and negative electrode finger 3 ... Negative electrode finger 4 ... Open floating electrode 5, 5' ... Positive and negative electrode finger 6, 6 '... Internal reflection Mold unidirectional IDT 7 Bidirectional IDT 8, 8 '... Positive / negative electrode finger 9 ... Negative electrode finger 10 ... Open floating electrode 11, 11' ... Internal reflection type one direction 12: Radiation conductance of internal reflection type unidirectional IDT 13: Radiation conductance of bidirectional IDT
フロントページの続き (58)調査した分野(Int.Cl.7，ＤＢ名) H03H 9/145 H03H 9/64 Continuation of the front page (58) Field surveyed (Int.Cl. 7 , DB name) H03H 9/145 H03H 9/64
Claims (2)
に当該励振電極の３倍の幅を有する負励振電極を前記正
励振電極の直近に、前記正負励振電極と同じ幅を有する
開放型浮き電極を前記負励振電極の直近に配置した内部
反射型一方向性ＩＤＴを配置し、当該内部反射型一方向
性ＩＤＴを２倍倍調波にて動作させるべく、両者のＩＤ
Ｔピッチを整数倍より所要量異ならしめたことを特徴と
する一方向性ＳＡＷフィルタ。1. A negative excitation electrode having a width three times as large as the excitation electrode in the positive / negative excitation electrode on both sides of the bidirectional IDT, an opening having the same width as the positive / negative excitation electrode in the immediate vicinity of the positive excitation electrode. An internal reflection type unidirectional IDT in which a mold floating electrode is disposed immediately adjacent to the negative excitation electrode is arranged, and both IDs are operated so that the internal reflection type unidirectional IDT operates at a double harmonic.
A unidirectional SAW filter characterized in that a required amount of T pitch is made different from an integral multiple.
ＩＤＴとのピッチの倍率を整数倍より０．３乃至２．０
％異ならしめたことを特徴とする請求項１記載の一方向
性ＳＡＷフィルタ2. The pitch ratio between the bidirectional IDT and the internal reflection type unidirectional IDT is set to an integer multiple of 0.3 to 2.0.
2. The unidirectional SAW filter according to claim 1, wherein the SAW filters are different by%.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP03305435A JP3137392B2 (en) | 1991-10-24 | 1991-10-24 | One-way SAW filter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP03305435A JP3137392B2 (en) | 1991-10-24 | 1991-10-24 | One-way SAW filter |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH05121992A JPH05121992A (en) | 1993-05-18 |
| JP3137392B2 true JP3137392B2 (en) | 2001-02-19 |
Family
ID=17945104
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP03305435A Expired - Fee Related JP3137392B2 (en) | 1991-10-24 | 1991-10-24 | One-way SAW filter |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3137392B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1276235A1 (en) | 2001-07-13 | 2003-01-15 | Matsushita Electric Industrial Co., Ltd. | Surface acoustic wave filter and communication device using the filter |
-
1991
- 1991-10-24 JP JP03305435A patent/JP3137392B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH05121992A (en) | 1993-05-18 |
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