JPS6145620A - Delay line - Google Patents

Abstract

PURPOSE:To reduce the level of a direct wave propagated electrically directly by arranging a transmission parallel stripe form electrodes and a 2-wire said form reception electrode so as to cause a signal in different phase by 180 deg. and outputting a reception signal difference of the 2-wire reception reed screen electrode. CONSTITUTION:The transmission parallel stripe form electrodes 2 exciting a surface acoustic wave and the two sets of reception said form electrodes 3 receiving the surface acoustic wave are arranged on a piezoelectric base 1 so that the signal phase difference received by the electrodes 3 is 180 deg.. The signal received by the electrodes 3 is outputted through a differential circuit 5. Then, the surface acoustic wave signal excited by the electrode 2 and received by the electrodes 3 is overlapped in phase at an output terminal of the delay line and outputted with a large level. Thus, the level of the direct wave is decreased than the conventional level.

Description

【発明の詳細な説明】 〔発明の技術分野〕 本発明は弾性表面波を用いた遅延線に関するものである
。DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a delay line using surface acoustic waves.

〔従来技術〕[Prior art]

従来のこの種の遅延線は、例えば第２図に示すように、
弾性表面波を伝播させる圧電体基板（１）上に、弾性表
面波を励振する送信用すだれ状電極（２）と弾性茨面波
を受信する受信用すだれ状電極（３）とを設けて構成さ
れていた。しかして、この種の遅延線における遅延時間
は、送信用すだれ状電極（２）と受信用すだれ状電極（
８）との間の中心間距離を、弾性表面波の伝播速度で割
った値となる。したがって、上記中心間距離を弾性表面
波の伝播速度と所要遅延時間との積で与えられる値に設
定することにより所要の遅延線が得られる。A conventional delay line of this type is, for example, as shown in FIG.
A transmitting interdigital electrode (2) for exciting surface acoustic waves and a receiving interdigital electrode (3) for receiving elastic thorny waves are provided on a piezoelectric substrate (1) for propagating surface acoustic waves. It had been. Therefore, the delay time in this type of delay line is the same as that between the transmitting interdigital electrode (2) and the receiving interdigital electrode (2).
8) divided by the propagation speed of the surface acoustic wave. Therefore, by setting the center-to-center distance to a value given by the product of the propagation velocity of the surface acoustic wave and the required delay time, the required delay line can be obtained.

ところで、この種の遅延線では、送信用すだれ状電極（
２）と受信用すだれ状電極（８）との間を、弾性表面波
を介さず浮遊容量等を介して直接電気的に伝播する、所
謂直達波がＩＣ１このレベルが所要の値まで十分抑圧さ
れている必要がある。従来のこの種の遅延線では、この
ため、送信用すだれ状電極（２）と受信用すだれ状電極
（８）との間に、７−ルド電極（４）を設けていた。By the way, in this type of delay line, the transmitting interdigital electrode (
2) and the reception interdigital electrode (8), the so-called direct wave that propagates directly electrically through stray capacitance, etc., without going through surface acoustic waves, is sufficiently suppressed to the required level. need to be. For this reason, in the conventional delay line of this type, a seven-lead electrode (4) is provided between the transmitting interdigital electrode (2) and the receiving interdigital electrode (8).

しかし、従来のこの種の遅延線において、所要遅延時間
が小さい場合には、上述したことから、送信用すだれ状
電極（匍と受信用すだれ状電極（８）との間の距離が短
くなる友め、シールド電極（４）の幅が狭くなる。この
ため、シールド電極（４）の効果が　゛小さくなシ直達
波のレベルを所要の値まで抑圧できない欠点があった。However, in a conventional delay line of this kind, if the required delay time is small, from the above-mentioned reasons, the distance between the transmitting interdigital electrode (the scowl and the receiving interdigital electrode (8) is shortened). Therefore, the width of the shield electrode (4) becomes narrower.Therefore, the shield electrode (4) has the disadvantage that the level of the direct wave cannot be suppressed to the required value due to its small effect.

〔発明の概要〕[Summary of the invention]

本発明は、圧電体基板上に、弾性表面波を励振する送信
用すだれ状電極と弾性表面波を受信する２組の受信用す
だれ状電極とを、上記２組の受信用すだれ状電極により
受信される信号の位相差が１８０度となるように配置し
、上記２組の受信用すだれ状電極によ−る受信信号の差
を出力するようにして遅延線を構成することにより、上
述の従来の欠点を除去したものである。The present invention provides a piezoelectric substrate with transmitting interdigital electrodes for exciting surface acoustic waves and two sets of receiving interdigital electrodes for receiving surface acoustic waves. By configuring the delay line so that the phase difference between the received signals is 180 degrees and outputting the difference between the signals received by the two sets of receiving interdigital electrodes, This eliminates the drawbacks of

〔発明の実施例〕[Embodiments of the invention]

以下、第１図に示す一実施例を用いて詳細に説明する。 Hereinafter, a detailed explanation will be given using an example shown in FIG.

図中、（１）は圧電体基板、（２）は送信用すだれ状電
極、（８）は２組の受信用すだれ状電極で、上記送信用
すだれ状電極（２）と、２組の受信用すだれ状電極（８
）との間のそれぞれの中心間距離は同一であるが、２組
の受信用すだれ状電極（８」における信号用引出し線と
接地用引出し線とは図示するように互いに逆の関係にな
るように引出している。したがって２組の受信用すだれ
状電極（８）によりそれぞれ受信される弾性表面波信号
の間には位相差１８０度が生じる。一方、第１図に示す
ように、２組の受信用すだれ状電極（８）により受信さ
れた信号は差分回路（６ンを通して璽を遅延線の出力と
なっているから、送信用すだれ状電極（２）により励振
され、２組の受信用すだれ状電極（８）で受信された弾
性表面波信号は遅延線の出力端では同相で重なり合い大
きなレベルで出力される。このときの遅延時間は、従来
　　゛と同様に上述した送信用すだれ状電極（２）と受
信用すだれ状電極（８）との間の中心間距離により決ま
る。In the figure, (1) is a piezoelectric substrate, (2) is a transmitting interdigital electrode, and (8) is two sets of receiving interdigital electrodes. interdigital electrode (8
) are the same, but the signal lead wire and ground lead wire in the two sets of receiving interdigital electrodes (8") are in an inverse relationship to each other as shown in the figure. Therefore, a phase difference of 180 degrees occurs between the surface acoustic wave signals received by the two sets of receiving interdigital electrodes (8).On the other hand, as shown in FIG. The signal received by the receiving interdigital electrode (8) is passed through the differential circuit (6) and becomes the output of the delay line, so it is excited by the transmitting interdigital electrode (2) and sent to the two sets of receiving interdigital electrodes. The surface acoustic wave signals received by the shaped electrode (8) are overlapped in phase at the output end of the delay line and output at a large level.The delay time at this time is determined by the above-mentioned transmitting interdigital electrode (8) as in the conventional case. 2) and the receiving interdigital electrode (8).

ところ力ζ弾性表面波を介さず、浮遊容量を介して直接
、送信用すだれ状電極（２）と受信用すだれ状電極（８
）との間を電気的に伝播した直達波は、２組の受信用す
だれ状電極（８）には同相で到達するが、差分回路（６
）全通して遅延線の出力端にあられれるから、相殺され
、レベルが小さくなる。However, the transmitting interdigital electrode (2) and the receiving interdigital electrode (8
), the direct wave electrically propagates between the two receiving interdigital electrodes (8) in the same phase, but the differential circuit (6
) are all applied to the output end of the delay line, so they cancel each other out and the level becomes smaller.

すなわち、該構成に係る遅延線では、直達波のレベルを
従来に比べ小さくできる。なお、第１図中、（４）は従
来と同様のシールド電極であシ、直達波レベルをさらに
抑圧するため、第１図に示す一実施例では設けているが
、シールド電極（４）は設けなくてもよい。That is, in the delay line according to this configuration, the level of the direct wave can be made smaller than that of the conventional one. Note that in Fig. 1, (4) is a shield electrode similar to the conventional one.In order to further suppress the direct wave level, it is provided in the embodiment shown in Fig. 1, but the shield electrode (4) is It does not need to be provided.

以上は第１図に示す一実施例の場合について説明したが
、本発明はこれに限らず、２組の受信用すだれ状電極（
８）を送信用すだれ状電極（２）の両側に配置した構成
に適用してもよい。また、受信用すだれ状電極（８）を
弾性表面波の伝播路上に多数設けたタップ付遅延線の場
合に適当にしてもよい。The above description has been made regarding the case of one embodiment shown in FIG.
8) may be applied to a configuration in which the transmitting interdigital electrodes (2) are arranged on both sides. Further, it may be suitable for a tapped delay line in which a large number of receiving interdigital electrodes (8) are provided on the propagation path of surface acoustic waves.

〔発明の効果〕〔Effect of the invention〕

以上のように、本発明に係る遅延線では、弾性表面波を
励振する送信用すだれ状電極と、弾性表面波を受信する
２組の受信用すだれ状電極とを、上記２組の受信用すだ
れ状電極により受信される１１号の位相差が１８０度と
なるように配置し、上記２組の受信用すだれ状電極によ
る受信信号の差を出力するようになしたことにより、従
来に比べ、弾性表面波を介さず直接電気的に伝播する直
達波のレベルを小さくできる利点がめる。As described above, in the delay line according to the present invention, the transmitting interdigital electrode that excites surface acoustic waves and the two sets of receiving interdigital electrodes that receive surface acoustic waves are connected to the two sets of receiving interdigital electrodes. By arranging the signals so that the phase difference of No. 11 received by the interdigital electrodes is 180 degrees, and outputting the difference between the signals received by the two sets of receiving interdigital electrodes, the elasticity is improved compared to the conventional method. The advantage is that the level of direct waves that propagate electrically without going through surface waves can be reduced.

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

第１図は本発明に係る遅延線の一実施例を示す構成図、
第２図は従来の遅延線の構成図である。 （１ン・・圧電体基板 （２）・・送信用すだれ状電極 （８）・・受信用すだれ状電極 （４）・・シールド電’＠　　（５）・・差分回路なお
、図中、同一あるいは相当部分には同一符号を付して示
しである。FIG. 1 is a configuration diagram showing an embodiment of a delay line according to the present invention,
FIG. 2 is a block diagram of a conventional delay line. (1) Piezoelectric substrate (2) Transmitting interdigital electrode (8) Receiving interdigital electrode (4) Shield electrode (5) Differential circuit Alternatively, corresponding parts are indicated by the same reference numerals.

Claims (1)

【特許請求の範囲】[Claims] 圧電体基板上に、弾性表面波を励振する送信用すだれ状
電極と、弾性表面波を受信する２組の受信用すだれ状電
極とを、上記２組の受信用すだれ状電極により受信され
る信号の位相差が１８０度となるように配置し、上記２
組の受信用すだれ状電極により受信される信号の差を出
力するようになしたことを特徴とする遅延線。A transmitting interdigital electrode that excites surface acoustic waves and two sets of receiving interdigital electrodes that receive surface acoustic waves are arranged on a piezoelectric substrate, and signals received by the two sets of receiving interdigital electrodes are arranged on the piezoelectric substrate. are arranged so that the phase difference is 180 degrees, and the above 2
1. A delay line characterized in that the difference between signals received by a pair of reception interdigital electrodes is output.