JPH02237211A - Surface acoustic wave filter - Google Patents
Surface acoustic wave filterInfo
- Publication number
- JPH02237211A JPH02237211A JP5626989A JP5626989A JPH02237211A JP H02237211 A JPH02237211 A JP H02237211A JP 5626989 A JP5626989 A JP 5626989A JP 5626989 A JP5626989 A JP 5626989A JP H02237211 A JPH02237211 A JP H02237211A
- Authority
- JP
- Japan
- Prior art keywords
- input
- coils
- surface acoustic
- acoustic wave
- wave 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.)
- Pending
Links
- 238000010897 surface acoustic wave method Methods 0.000 title claims abstract description 15
- 239000003990 capacitor Substances 0.000 claims abstract description 9
- 239000000758 substrate Substances 0.000 abstract description 2
- 238000010586 diagram Methods 0.000 description 7
- 238000003780 insertion Methods 0.000 description 5
- 230000037431 insertion Effects 0.000 description 5
- 230000000694 effects Effects 0.000 description 2
- 238000013459 approach Methods 0.000 description 1
Landscapes
- Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
Abstract
Description
【発明の詳細な説明】
［産業上の利用分野コ
本発明は弾性表面波フィルタに関し、特に広帯域弾性表
面波フィルタに関する。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a surface acoustic wave filter, and particularly to a broadband surface acoustic wave filter.
［従来の技術］
従来、弾性表面波フィルタに用いる整合回路は、入・出
力電極の一方あるいは両方に、コイルを並列あるいは直
列に接続した構成となっていた。[Prior Art] Conventionally, a matching circuit used in a surface acoustic wave filter has a configuration in which a coil is connected in parallel or in series to one or both of input and output electrodes.
［発明が解決しようとする課題］
まず、広帯域フィルタ、特に入出力電極にチャープ電極
を用いた場合において、整合回路を使用せずに通過帯域
内を平坦にする場合を考える。この場合、入・出力電極
の並列容量が大きい為、入拳出力側からみたインピーダ
ンスを終端インピーダンスに対してほぼ一定とみなせる
様にするには、終端インピーダンスに対して充分小さい
か大きい値としなければならない。このため、第３図の
様に挿入損失が大きくなるという欠点がある。[Problems to be Solved by the Invention] First, consider the case of flattening the passband without using a matching circuit in a broadband filter, particularly in a case where chirp electrodes are used as input and output electrodes. In this case, since the parallel capacitance of the input and output electrodes is large, in order to make the impedance seen from the input output side almost constant with respect to the terminal impedance, it must be set to a sufficiently small or large value with respect to the terminal impedance. No. For this reason, there is a drawback that the insertion loss becomes large as shown in FIG.
整合回路に、第４図に示すよう人出力電極３２，３３に
並列コイル３４．３５を用いて、入・出力電極３２．３
３の並列容量を共役整合により相殺する場合には、中心
周波数近傍においては、挿入損失の改善を図る事が出来
る。しかしながら、電極の並列容量と外付並列コイルと
で構成された回路のフィルタ特性が並列容量が大きいた
めに、弾性表面波によるフィルタ特性と比較して狭帯域
となり、全体のフィルタ特性は、第５図に示す様に単峰
性となるという欠点がある。In the matching circuit, as shown in FIG.
When the parallel capacitances of 3 are offset by conjugate matching, insertion loss can be improved near the center frequency. However, since the parallel capacitance of the circuit composed of the parallel capacitance of the electrode and the external parallel coil is large, the filter characteristic of the circuit composed of the parallel capacitance of the electrode and the external parallel coil is narrow compared to the filter characteristic of surface acoustic waves, and the overall filter characteristic is As shown in the figure, it has the disadvantage of being unimodal.
本発明の課題は、上述した欠点を除去し、挿入損失を少
くし、通過帯域内特性を平坦とした弾性表面波フィルタ
を提供することにある。An object of the present invention is to provide a surface acoustic wave filter that eliminates the above-mentioned drawbacks, reduces insertion loss, and has flat passband characteristics.
［課題を解決するための手段コ
本発明の弾性表面波フィルタは、入・出力電極の少くと
も一方に、コイルを並列に、かつ、コイル及びコンデン
サを直列に接続したことを特徴とする。[Means for Solving the Problems] The surface acoustic wave filter of the present invention is characterized in that a coil is connected in parallel to at least one of the input and output electrodes, and a coil and a capacitor are connected in series.
［実施例］ 次に本発明について図面を参照して説明する。[Example] Next, the present invention will be explained with reference to the drawings.
第１図は、本発明の実施例の回路図である。FIG. 1 is a circuit diagram of an embodiment of the present invention.
入力電極１２及び出力電極１３は、圧電基盤１１上に設
けられ、整合回路１４及び１５は、それぞれ入力電極１
２及び出力電極１３に接続されている。また、整合回路
１４．１５は、入出力電極１２．１３に並列にコイル１
６，１９、直列にコイル１．７．１．９及びコンデンサ
１８，２］が接続されている。The input electrode 12 and the output electrode 13 are provided on the piezoelectric substrate 11, and the matching circuits 14 and 15 are connected to the input electrode 1, respectively.
2 and the output electrode 13. In addition, the matching circuit 14.15 connects the coil 1 in parallel to the input/output electrode 12.13.
6, 19, a coil 1.7.1.9 and a capacitor 18, 2] are connected in series.
コイル１６．１９は、入・出力電極：ｌ−２．１３の並
列容量を共役整合により相殺する様選ばれ、挿入損失が
低減される。The coils 16.19 are selected so as to cancel the parallel capacitance of the input/output electrodes: 1-2.13 by conjugate matching, thereby reducing insertion loss.
また、コイル１７．２０及びコンデンサ１８，２１は、
通過帯域内の低域側及び高城側の入出力端から見たイン
ピーダンスを中心周波数近傍のインピーダンスに近づけ
る様に選ばれ、通過帯域内は平坦になる。In addition, the coil 17.20 and the capacitors 18, 21 are
It is selected so that the impedance seen from the input/output end on the low frequency side and the high frequency side within the passband approaches the impedance near the center frequency, and the inside of the passband becomes flat.
第２図は第１図に示す実施例のフィルタ特性図である。FIG. 2 is a filter characteristic diagram of the embodiment shown in FIG. 1.
第５図の従来の整合回路によるフィルタ特性と比較して
、通過帯域内が平坦になっている事がわかる。In comparison with the filter characteristics of the conventional matching circuit shown in FIG. 5, it can be seen that the pass band is flat.
［発明の効果コ
以上説明したように本発明は、入出力電極に並列にコイ
ルを、直列にコイル及びコンデンサを接続した、整合ロ
路を用いる事により、弾性表面波フィルタの挿入損失が
少く、通過帯域内特性を平坦にできる効果がある。[Effects of the Invention] As explained above, the present invention uses a matching loop in which a coil is connected in parallel to the input and output electrodes, and a coil and a capacitor are connected in series, thereby reducing the insertion loss of the surface acoustic wave filter. This has the effect of flattening the characteristics within the passband.
第１図は本発明の一実施例による弾性表面波フィルタの
回路図、第２図は第１図の弾性表面波フィルタのフィル
タ特性図、第３図は従来の弾性表面波フィルタのフィル
タ特性図、第４図は従来の別の弾性表面波フ、ｆルタの
回路図、第５図は第４図の弾性表面波フィルタのフィル
タ特性図である。
１１．３１・・・圧電基盤、１２，
１３．３３・・・出力電極、１４，１
１６， １７， １９， ２０， ３４，１．８．２１
・・・コンデンサ。
３２・・・人力電極、
５・・・整合回路、
３５・・・コイル、Fig. 1 is a circuit diagram of a surface acoustic wave filter according to an embodiment of the present invention, Fig. 2 is a filter characteristic diagram of the surface acoustic wave filter of Fig. 1, and Fig. 3 is a filter characteristic diagram of a conventional surface acoustic wave filter. , FIG. 4 is a circuit diagram of another conventional surface acoustic wave filter, and FIG. 5 is a filter characteristic diagram of the surface acoustic wave filter of FIG. 4. 11.31... Piezoelectric base, 12, 13.33... Output electrode, 14, 1 16, 17, 19, 20, 34, 1.8.21
...Capacitor. 32... Human electrode, 5... Matching circuit, 35... Coil,
Claims (1)
おいて、入・出力電極の少くとも一方に、コイルを並列
に、かつ、コイル及びコンデンサを直列に接続したこと
を特徴とする弾性表面波フィルタ。1. A surface acoustic wave filter having a pair of input and output electrodes, characterized in that a coil is connected in parallel to at least one of the input and output electrodes, and a coil and a capacitor are connected in series.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5626989A JPH02237211A (en) | 1989-03-10 | 1989-03-10 | Surface acoustic wave filter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5626989A JPH02237211A (en) | 1989-03-10 | 1989-03-10 | Surface acoustic wave filter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH02237211A true JPH02237211A (en) | 1990-09-19 |
Family
ID=13022368
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP5626989A Pending JPH02237211A (en) | 1989-03-10 | 1989-03-10 | Surface acoustic wave filter |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH02237211A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5592135A (en) * | 1994-01-20 | 1997-01-07 | Matsushita Electric Industrial Co., Ltd. | Surface acoustic wave filter with different filter portions satisfying complex conjugate relationship of impedances |
| US6121859A (en) * | 1998-03-26 | 2000-09-19 | Nec Corporation | Surface acoustic wave filter with stacked impedance matching coils for discharging static electricity |
| JP2001185990A (en) * | 1999-11-09 | 2001-07-06 | Motorola Inc | Integrated filter having improved i/o matching |
| JP2007174713A (en) * | 2001-03-30 | 2007-07-05 | Hitachi Media Electoronics Co Ltd | High-frequency filter, high-frequency circuit, antenna duplexer, and radio terminal |
-
1989
- 1989-03-10 JP JP5626989A patent/JPH02237211A/en active Pending
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5592135A (en) * | 1994-01-20 | 1997-01-07 | Matsushita Electric Industrial Co., Ltd. | Surface acoustic wave filter with different filter portions satisfying complex conjugate relationship of impedances |
| US6121859A (en) * | 1998-03-26 | 2000-09-19 | Nec Corporation | Surface acoustic wave filter with stacked impedance matching coils for discharging static electricity |
| JP2001185990A (en) * | 1999-11-09 | 2001-07-06 | Motorola Inc | Integrated filter having improved i/o matching |
| JP4700184B2 (en) * | 1999-11-09 | 2011-06-15 | フリースケール セミコンダクター インコーポレイテッド | Integrated filter with improved I / O matching and method of manufacturing the same |
| JP2007174713A (en) * | 2001-03-30 | 2007-07-05 | Hitachi Media Electoronics Co Ltd | High-frequency filter, high-frequency circuit, antenna duplexer, and radio terminal |
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