JPS61230419A - Two-port idt excitation type resonator and resonance filter - Google Patents

Abstract

PURPOSE:To reduce remarkably the spurious radiation due to the standing wave of the 2nd order mode by making the center of any one of input/output interdigital transducers (IDTs) coincident with nearly the center of the reflector interval. CONSTITUTION:The interval between an input IDT2 provided on a crystal piezoelectric substrate 1 and the reflector adjacent thereto and that of input and output IDT2, IDT3 are selected as 3/8lambda-1lambda the same as a conventional two-port SAW resonator, where is the excited SAW wavelength, and the output IDT3 is arranged while its center line is made nearly coincident with the center of the inner interval (l) of the reflectors 4, 4'. The output IDT3 collects the 1st order mode electric charge from the charge at the hatched parts and outputs it as an electric signal, but as to the 2nd order mode electric charge, it is cancelled because the polarity of the generated charge is inverted in left and right sides and no electric signal output is obtained. That is, no electric signal with respect to the 2nd order mode is outputted, no spurious/response is caused.

Description

【発明の詳細な説明】 （産業上の利用分野） 本発明は弾性表面波（ＳＡＷ）共振器の如きＩＤＴ励振
型の２ポート共振器、殊にスプリアスを抑圧した２ポー
トＩＤＴ励振型共撮共振電極構造に関する。Detailed Description of the Invention (Industrial Application Field) The present invention relates to an IDT-excited two-port resonator such as a surface acoustic wave (SAW) resonator, and particularly to a two-port IDT-excited co-photographed resonator with spurious suppression. Regarding electrode structure.

（従来技術） ＩＤＴ励振型の２ポート共振器９例えば２ポートＳＡＷ
共振器は第２図に示す如く圧電基板１上に入力インタデ
ィジタル・トランスジェーサ（ＩＤＴ）電極２及び出力
ＩＤＴ電極３ｔ−倶えると共にその両側に周期的金属ス
トリップを用いた反射器４．４”ｉ配置し前記入力ＩＤ
Ｔ２　　によって励起した５ＡＷ−ｉ前記反射器４，４
の間に定在波として閉じ込め前記出力ＩＤＴ３に励起す
る電荷を電気信号として取り出すものであって、前記反
射器４と前記ＩＤＴ２又は３或はＩＤＴ２．３相互の間
隔はいずれも励起するＳＡＷ波長波長対して３／８λ乃
至１λになるよう等しく設定するのが一般的であった。(Prior art) IDT excitation type two-port resonator 9 For example, two-port SAW
As shown in FIG. 2, the resonator includes an input interdigital transducer (IDT) electrode 2 and an output IDT electrode 3t on a piezoelectric substrate 1, and a reflector 4.4 using periodic metal strips on both sides thereof. ”I place the input ID
5AW-i said reflector 4, 4 excited by T2
The electric charge excited in the output IDT 3 is extracted as an electric signal by confining it as a standing wave between them, and the distance between the reflector 4 and the IDT 2 or 3 or IDT 2.3 is equal to the wavelength of the exciting SAW wavelength. However, it was common to set the distance equally between 3/8λ and 1λ.

しかしながら上述の如く構成する共振器に於いては反射
器間に第３図（ａｔに示す如く基本（１次）モードのみ
ならず２次、３次・・・の高次エネルギー閉じ込めモー
ドが発生してこれがスプリアスの原因となり、殊に２次
モードは８ｇ３図（ｂｌに示す如く基本モードによるレ
スポンス５と同程度の顕著なレスポンス６を呈するので
発振回路全構成した場合に異常発振を起こすという欠陥
があった。又、このような２ポート共振器により構成し
たＳＡＷ共振器フィルタに於いては２次モードによるス
プリアスが顕著なスプリアス・レスポンスを呈するとい
う欠陥があった。However, in the resonator configured as described above, not only the fundamental (first-order) mode but also higher-order energy confinement modes such as second order, third order, etc. occur between the reflectors as shown in Figure 3 (at). This causes spurious response, and especially the secondary mode, as shown in Figure 8g3 (bl), exhibits a remarkable response 6 that is comparable to the response 5 in the fundamental mode, so there is a defect that abnormal oscillation occurs when the entire oscillation circuit is configured. In addition, the SAW resonator filter constructed from such two-port resonators has a defect in that spurious responses due to secondary modes are significant.

（発明の目的） 本発明は上述の如き従来の２ポートＳＡＷ共撮器の欠点
を除去する為になされたものであって、２次高次モード
によるスプリアス・レスポンスを除去した２ポートＩＤ
Ｔ励振型共振器及びスプリアス特性の良好な共振器フィ
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 to eliminate the drawbacks of the conventional 2-port SAW common camera as described above, and is a 2-port ID system that eliminates spurious responses due to secondary higher-order modes.
It is an object of the present invention to provide a T-excitation type resonator and a resonator filter with good spurious characteristics.

（発明の１！要） 上述の目的を達成する為１本発明に於いては入出力ＩＤ
Ｔのいずれか一方の中央を反射器間隔のは寸中心に一致
せしめるようにしたものである。(1! Essentials of the invention) In order to achieve the above-mentioned purpose, 1. In the present invention, input/output ID
The center of either one of the T's is made to coincide with the center of the reflector interval.

（発明の実施例） 以下９本発明を図面に示す実施例に基づいて詳細に説明
する。(Embodiments of the Invention) The present invention will be described below in detail based on embodiments shown in the drawings.

第１図（ａ）及び（ｂｌは夫々本発明に係る２ポ一トＳ
ＡＷ共機器の電極構成の一実施例を示す概念園及び原理
説明図である。FIGS. 1(a) and (bl) are two-point S according to the present invention, respectively.
FIG. 2 is a concept diagram and principle explanatory diagram showing an example of an electrode configuration of an AW common device.

本図（ａｌに於いて水晶等圧電基板１上に設ける入力Ｉ
ＤＴ　２とこれに隣接する反射器４との間隔及び入力Ｉ
ＤＴ　２と出力ＩＤＴ　３とのそれは従来の２ポートＳ
ＡＷ共撮器と同様励１ｓＡＷ波長λに対して３／８λ乃
至１λに設定するが出力ＩＤＴ３の配置をその中心線が
前記反射器４．４′の内側端間隔ｌのはソ中心と一致す
るようにし友ものである。In this figure (al), the input I provided on the crystal piezoelectric substrate 1
Distance between DT 2 and adjacent reflector 4 and input I
With DT 2 and output IDT 3, it is the traditional 2-port S
Similar to the AW co-imager, the excitation 1s AW wavelength λ is set to 3/8λ to 1λ, but the output IDT 3 is arranged so that its center line coincides with the center of the reflector 4.4' with an inner end interval l. It's a good friend.

斯くの如きＩＤＴ電極構成を採用した場合同図（ｂ）に
示す如き現象が生ずる。When such an IDT electrode configuration is adopted, a phenomenon as shown in FIG. 2(b) occurs.

即ち、前記入力ＩＤＴ　２によって励起したＳＡＷのエ
ネルギは前記反射器４，４′内に閉じ込められ図に示す
如く励起したＳＡＷ伝搬方向に沿ってはソサイン又はコ
サインカーヴ状の変位分布を有する定在波を生ずるが前
記反射器間管半波長とする１次モードから２次、３次、
・・・Ｋ至る多数のエネルギ閉じ込めモードの振動が混
在するものと考えてよい。That is, the energy of the SAW excited by the input IDT 2 is confined within the reflectors 4, 4' and forms a standing wave having a sosine or cosine curve displacement distribution along the propagation direction of the excited SAW as shown in the figure. is generated, but from the first mode to the half wavelength of the inter-reflector tube, the second, third,
. . . It can be considered that vibrations of many energy trapping modes up to K are mixed.

又、これら各次モードの変位分布は圧電基板１上に発生
する電荷量と夫々相似であると考えてよい。Further, it may be considered that the displacement distribution of each of these order modes is similar to the amount of charge generated on the piezoelectric substrate 1.

尚、斯る構造の共振器に於いては前記ＳＡＷ伝殻方向に
直角力方向にも同様の変位分布含有するエネルギ閉じ込
めモードが存在するが、これに基づくスプリアスは例え
ばＩＤＴに重み付は全村するといった手段で抑圧し得る
のでこれ以上の言及を避ける。In addition, in a resonator having such a structure, there is an energy confinement mode containing a similar displacement distribution in the force direction perpendicular to the SAW transmission direction, but the spurious based on this, for example, is weighted to the IDT. Since this could be suppressed by means such as

従って前記発生電荷を蒐集する前記出力ＩＤＴ３を前記
第１図（ａ）に示す如く配置すれば当該電極は同図（ｂ
ｌに於いてハツチングを施した部分の電荷を集めること
になる。Therefore, if the output IDT 3 that collects the generated charge is arranged as shown in FIG. 1(a), the electrode will be
The charges in the hatched portion of 1 will be collected.

而して前記出力ＩＤＴ３は１次モードの電荷に関しては
ハツチングを施した部分を集めて電気信号とて出力する
が２次モードのそれについては発生電荷の極性が左右反
転している為相殺し電気信号として出力することがない
。即ち２次モードに関する電気信号は出力されないので
スプリアス・レスポンスも発生しないと考えられる。The output IDT 3 collects the hatched portion of the charge in the first mode and outputs it as an electric signal, but in the second mode, since the polarity of the generated charge is reversed left and right, it cancels out the electric signal. There is no output as a signal. That is, since no electrical signal related to the secondary mode is output, it is considered that no spurious response occurs.

第４図は上述の原理に基づいて製作した共振周波数１ｏ
ｏＭＨｚの２ポートＳＡＷ共撮共振特性を測定した結果
金示すものであって９９．８　ＭＨｚ付近に出現する２
次モードのスプリアスは従来は基本波のそれと同レベル
であったのに比べ約ｘｓｄＢ低く現れ著しい効果のある
ことが立証された。Figure 4 shows the resonance frequency 1o manufactured based on the above principle.
The results of measuring the oMHz 2-port SAW co-resonance characteristics show that the resonance characteristics appear around 99.8 MHz2.
The spurious of the next mode was at the same level as that of the fundamental wave in the past, but appeared lower by about xsdB and was proved to have a remarkable effect.

ところで、前記出力ＩＤＴ３を上述の如く偏った位置に
配置しこれと前記反射器４′　との間に空間を設けるこ
とは小型化が厳しく要求される共振器にとって不都合で
ある。従ってスプリアスの要求規格との関係で前記空間
をどの程度まで減少し得るか検討する。By the way, arranging the output IDT 3 at a biased position as described above and providing a space between it and the reflector 4' is inconvenient for a resonator that is strictly required to be miniaturized. Therefore, we will examine to what extent the space can be reduced in relation to the required standards for spurious components.

第５図（ａｌ及び（ｂ）は反射器４．４′の間隔ｌの中
心線に対する出力ＩＤＴ３の中心線の偏りｚ’６バラメ
ータとした場合１次モードの共振と２次モードのそれと
のレスポンスの差がどのように変化するかｋａｌｌべた
もので前記偏りχが大きくなれば２次モードによるスプ
リアスも大きくなるがχが１／８Ｎλ乃至１／４Ｎλ程
度であれば規格によってはこのような値を適用し共振器
を小型化し得ることが理解されよう。Figure 5 (al and (b)) shows the response between the resonance of the first mode and that of the second mode when the deviation of the center line of the output IDT 3 with respect to the center line of the reflector 4.4' with the spacing l is set as a parameter z'6. How does the difference between It will be appreciated that the present invention can be applied to reduce the size of the resonator.

以上入出力ＩＤＴの電極指対数Ｎが同一の場合及び出力
ＩＤＴ中央を反射器間隔の中心に概ね一致せしめる場合
についてのみ説明したが本発明は必ずしもこれにのみ限
定する必要はなく入出力ＩＤＴの対数は互に異ったもの
でもよく又、出力ＩＤＴと入力ＩＤＴとを交換してもよ
い。この場合には反射器間隔のはマ中夫に入力ＩＤＴの
中心が位置することになる為偶数次モードの定在波は極
めて発生し難く、仮に発生したとしても例えば第６図に
示す如く出力ＩＤＴ３及び３′ヲ前記入力ＩＤＴ２　′
ｔ−はさんで反射器間隔中央に対称となる如く配置すれ
ば実質的にキャンセルされ出力として現れることがない
。Although only the case where the number N of electrode finger pairs of the input/output IDTs is the same and the case where the center of the output IDT is made to roughly coincide with the center of the reflector spacing have been described above, the present invention is not necessarily limited to this, and the number of pairs of electrode fingers of the input/output IDT is may be different from each other, or the output IDT and input IDT may be exchanged. In this case, since the center of the input IDT is located at the center of the reflector spacing, it is extremely difficult for even-order mode standing waves to occur, and even if they occur, the output will be as shown in Figure 6. IDT3 and 3' the input IDT2'
If they are arranged symmetrically at the center of the reflector interval across the t-axis, they will be substantially canceled and will not appear as an output.

従って入出力端子を交換すれば位相反転は自由であり使
用の自由度が大きいという特徴がある。Therefore, by exchanging the input/output terminals, the phase can be reversed freely, and the device has a feature that there is a high degree of freedom in use.

最后に本発明に係る２ポート　ＳＡＷ共撮共振利用した
共振器フィルタについて簡単に説明する。ｙａ７ｗは本
発明に係る同一共振周波数の２ポートＳＡＷ共振器を２
個接続した場合の実施例を示すものであって両共機器の
ＩＤ７間に挿人する容ｔ−＝ｉによって所要の通過帯域
を得ることはいうまでもないがこの容量はデスクリート
な部品で付してもよいし圧電基板１上にパターンで形成
してもよい。或はＩＤＴ自身が有する容量にて充分であ
ることもあろう。Finally, a resonator filter using two-port SAW shared resonance according to the present invention will be briefly explained. ya7w is a two-port SAW resonator with the same resonant frequency according to the present invention.
This shows an example in which two devices are connected, and it goes without saying that the required passband can be obtained by the capacitor t-=i inserted between ID7 of both devices, but this capacitance is a discrete component. It may be attached or may be formed in a pattern on the piezoelectric substrate 1. Alternatively, the capacity of the IDT itself may be sufficient.

デ 又、端子号及び孕はいずれを入出力側にしてもよいこと
も自明であろう。It is also obvious that either terminal number or pregnancy may be used as the input/output side.

上述した如きフィルタの特性は一般に第８図実線の如く
なる。即ち、従来一般に使用されていた２ポー）　ＳＡ
Ｗ共振器を用いたフィルりに於いては各共振器の２次以
上の高次モードに由来するスプリアス・レスポンスが通
過域近傍に発生しく同図点線の如し）これを除去するの
に苦慮していたものであるが本発明に係る共振器を用い
れば斯るスプリアス・レスポンスは充分抑圧されるので
極めて良好なフィルタ特性を得ることが可能となるもの
である。The characteristics of the filter as described above are generally as shown by the solid line in FIG. That is, the conventionally commonly used 2-port) SA
In filling using W resonators, spurious responses originating from the second and higher order modes of each resonator occur near the passband, and it is difficult to eliminate them (as shown by the dotted line in the figure). However, by using the resonator according to the present invention, such spurious responses can be sufficiently suppressed, making it possible to obtain extremely good filter characteristics.

以上２ポート　ＳＡＷ共振器を例に挙げて説明したが本
発明はＳＡＷ′ｔ−利用するものに限定する必要はなく
各種圧電基板上にＩＤＴを付着しこれに交番電界を印加
することによって励起し得るあらゆる波動１例えば漏洩
弾性表面波、ラブ波、すべり波或はＳＨ波等々を利用す
る共振器のいずれにも同様に適用可能であることはいう
までもない。Although the above description has been made using a two-port SAW resonator as an example, the present invention is not limited to those that use SAW't-, and can be excited by attaching an IDT on various piezoelectric substrates and applying an alternating electric field to it. It goes without saying that the present invention is equally applicable to any resonator that utilizes any type of wave 1 such as leaky surface acoustic waves, Love waves, shear waves, SH waves, etc.

又５本発明に係る電極構造は重み付けが施されたＩＤＴ
を使用する共振器９′　又はフィルタに適用してもその
効果に変わりはない。ただしこの場合、中央に配置する
ＩＤＴに重み付けを施すときは、２次モードの変位分布
（はぼサインカーブ）にＩＤＴに付し友重み付けに相応
する重み付けを乗じて求められる蒐集電荷ｉｔ相殺する
位置にＩＤＴを配置すればよい。Furthermore, the electrode structure according to the present invention is a weighted IDT.
Even if it is applied to a resonator 9' or a filter using the same, the effect remains the same. However, in this case, when weighting is applied to the IDT placed in the center, the position where the collected charge is offset is determined by applying weighting to the IDT and multiplying it by a weighting corresponding to the weighting of the second-order mode displacement distribution (Habo sine curve). The IDT may be placed at

（発明の効果） 本発明は以上説明した如く構成するものであるから従来
の２ポートよりＴ励振型共振器の欠陥たる高次モード、
殊に２次モードの定在波に由来するスプリアスを単にＩ
ＤＴ作成パターンを変更するのみで大幅に除去し得るの
で発振の容易性等から高周波領域で賞月されている２ポ
ートＳＡＷ共振器等の不要振動を除去しこれを利用した
フィルタの通過帯域特性を良好なものとする上で著しい
効果がある。(Effects of the Invention) Since the present invention is constructed as described above, the higher-order mode, which is a defect in the T-excitation type resonator, is eliminated from the conventional two-port resonator.
In particular, spurious waves originating from secondary mode standing waves can be simply
Since it can be largely removed just by changing the DT creation pattern, unnecessary vibrations such as those of 2-port SAW resonators, which are prized in the high frequency range due to their ease of oscillation, can be removed, and the passband characteristics of filters using this can be improved. It has a remarkable effect on making things better.

【図面の簡単な説明】[Brief explanation of drawings]

第１図（ａｌ及び（ｂｌは夫々本発明に係る２ポートＳ
ＡＷ共撮器の一実施例を示す電極構成概念図及びその効
果を説明する原理説明図、第２図は従来の２ポー）ＳＡ
Ｗ共撮共振一般的構成を示す概念図、第３図（ａ）及び
（ｂ）は夫々従来の２ポートＳＡＷ共振器に於いて発生
するエネルギ・モードを示す図及びその特性図、第４図
は本発明に係るＳＡＷ共振器の特性に関する実現データ
の図、第５図（ａｔ及び（ｂｌは夫々ＩＤＴの中心線の
偏り量を示す図及び前記偏り量とスプリアスとの関係を
調べた実験データ図、第６図は本発明に係る２ポート共
振器の他の実施例を説明する概念図、早７図は本発明に
係る２ポートＳＡＷ共撮器を利用したフィルタの一実施
例を示す概念図、第８図はその一般的フィルタ特性を示
す説明図である。 １・・・・・・・・・圧電基板、　　２，３・・・・・
・・・・入出力ＩＤＴ、　　　４．４’・・・・・・・
・・反射器。 特許出願人　　東洋通信機株式会社 第　　１　　図 魁腎枢％ テ５！＋　　　　　　　ｙｐ、６　　　　　　　ｔａρ
　　　　　　ｙｔｐａ、ａ　　　　　　／’Ｊ　　ｑ＠
＠ＨＨｚン第　　り　　図 気（冑硬FIG. 1 (al and (bl are 2-port S according to the present invention, respectively)
A conceptual diagram of the electrode configuration showing an example of an AW co-camera and a principle explanatory diagram explaining its effects. Figure 2 is a conventional 2-port SA
A conceptual diagram showing the general configuration of W co-resonance; Fig. 3 (a) and (b) are diagrams showing the energy modes generated in a conventional 2-port SAW resonator, respectively, and their characteristic diagram; Fig. 4; 5 is a diagram showing realized data regarding the characteristics of the SAW resonator according to the present invention, and FIG. 6 is a conceptual diagram illustrating another embodiment of the 2-port resonator according to the present invention, and FIG. 7 is a conceptual diagram illustrating an embodiment of the filter using the 2-port SAW resonator according to the present invention. 8 are explanatory diagrams showing the general filter characteristics. 1...Piezoelectric substrate, 2, 3...
...Input/output IDT, 4.4'...
...Reflector. Patent applicant: Toyo Tsushinki Co., Ltd. + yp, 6 taρ
ytpa, a /'J q@
@HHHz

Claims (2)

【特許請求の範囲】[Claims] （１）圧電基板表面に設けた入出力インタディジタル・
トランスジューサ（ＩＤＴ）によって励起する波動のエ
ネルギをその両側に配置した反射器間に閉じ込める共振
器に於いて、前記入出力ＩＤＴのいずれか一方の中央を
前記反射器内側端間隔のほゞ中心に一致せしめたことを
特徴とする２ポートＩＤＴ励振型共振器。(1) Input/output interdigital installed on the surface of the piezoelectric substrate
In a resonator that confines the energy of waves excited by a transducer (IDT) between reflectors placed on both sides of the resonator, the center of one of the input and output IDTs is aligned approximately with the center of the inner end spacing of the reflectors. A 2-port IDT excitation type resonator characterized by the following characteristics: （２）前記特許請求の範囲（１）記載の２ポートＩＤＴ
励振型共振器を所要個数接続して所要の通過帯域を得る
ことを特徴とする２ポートＩＤＴ励振型共振器フィルタ
。(2) Two-port IDT according to claim (1)
A two-port IDT excitation type resonator filter characterized in that a required number of excitation type resonators are connected to obtain a required passband.