JPH06196964A - Surface acoustic wave element - Google Patents

Abstract

(57) [Abstract] [Purpose] The convolution output has been sufficiently reduced by improving the confinement effect of surface acoustic waves in the output electrode and suppressing surface acoustic wave leakage from the output electrode. A surface acoustic wave device is provided. [Structure] A first surface acoustic wave that excites first and second surface acoustic waves propagating in opposite directions on the surface of a piezoelectric substrate 1.
And the second input electrodes 2 and 3 and the non-linearity of the piezoelectric substrate 1 between the first and second input electrodes 2 and 3 is used to extract the convolution signal of the two surface acoustic wave signals. And an output electrode 4. The output electrode portion of the piezoelectric substrate 1 is formed by removing the surface portion of the piezoelectric substrate 1 on both sides of the output electrode 4 along the propagation directions of the first and second surface acoustic waves to form a step 10. Are formed in a convex shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave device for taking out a convolution signal of two surface acoustic wave signals propagating in opposite directions by utilizing the physical nonlinear effect of a piezoelectric substrate.

[0002]

2. Description of the Related Art A surface acoustic wave element, particularly a surface acoustic wave convolver for extracting a convolution signal of two surface acoustic wave signals, has recently been increasing in importance as a key device for performing spread spectrum communication. Has been actively studied.

FIG. 11 is a schematic view showing an example of such a conventional surface acoustic wave element. FIG. 12 is a schematic view showing another example of the conventional surface acoustic wave element, and FIG. 13 is a sectional view taken along the line AA ′.

In these figures, 1 is a piezoelectric substrate made of Y-cut (Z propagation) lithium niobate or the like, 2 and 3 are comb-shaped input electrodes formed on the surface of the piezoelectric substrate 1, and 4 is piezoelectric. An output electrode is formed on the surface of the substrate 1, and an output take-out tap 5 is formed on the surface of the piezoelectric substrate 1 in contact with the output electrode 4. These electrodes and taps are made of a conductive material such as aluminum and are usually formed directly on the surface of the piezoelectric substrate 1 by using a photolithography technique.

In the surface acoustic wave device having such a structure,
When an electric signal of carrier angular frequency ω is input to the comb-shaped input electrode 2, the surface acoustic wave is excited by the piezoelectric effect of the substrate. Similarly, when an electric signal having the carrier angular frequency ω is input to the comb-shaped input electrode 3, the surface acoustic wave is excited by the piezoelectric effect of the substrate. These two surface acoustic waves propagate in opposite directions on the piezoelectric substrate 1 while being confined in the output electrode 4 by the output electrode 4 acting as a waveguide. This waveguide is Δ
Known as a v / v waveguide. The Δv / v waveguide is
By electrically short-circuiting the surface of the substrate, the propagation velocity of the surface acoustic wave is made lower than that of the free surface, and by totally reflecting the surface acoustic wave at the boundary between the free surface and the short-circuited portion, the surface acoustic wave is guided by the waveguide. It is something that is locked inside. The Δv / v waveguide is described in detail, for example, in “Acoustic Wave Element Technology Handbook, edited by Ohmsha, p180-181”.

In this way, the two surface acoustic waves collide with each other on the output electrode 4, so that the convolution signal (carrier angular frequency 2ω) of the two input signals is generated by the physical nonlinear effect of the piezoelectric substrate 1. Occurs and is taken out. Note that this signal extraction can be performed through a bonding wire or the like (not shown) connected to the tap 5 in the elements of FIGS.

That is, two surface acoustic waves are F (tx / v) exp {j
If (ωt-kx)}, G (t + x / v) exp {j (ωt + kx)}, then the product F (t-
x / v) ・ G (t + x / v) exp (2jωt) surface acoustic wave is generated. This signal is integrated in the electrode length region by providing a uniform output electrode, and letting the interaction region length be L, S (t) = Kexp (2jωt) ∫ _{-L / 2} ^{L / 2} F (tx / v) ・ G (t + x / v) dx ・ ・ ・ ・ ・ ・ Extracted as the signal represented by (1). Here, the integration range may be substantially −∞ to + ∞ when the interaction region length L is sufficiently larger than the signal length. If τ = tx / v, the above equation (1) is S (t) =-vKexp (2jωt) ∫ _-I ^I F (τ) ・ G (2t-τ) dτ ··· (2) (where I in the integration range indicates ∞), and the signal has two elasticity. It becomes a convolution of surface waves. Such a convolution mechanism is described in, for example, “Shibayama,“ Application of Surface Acoustic Wave ”, Television, 30, 45.
7 (1976) ”and the like.

[0008]

However, in the above conventional example, since the output electrode is used as the Δv / v waveguide, the waveguiding effect is not sufficient, and the surface acoustic wave excited from the input electrode is output. There is a surface acoustic wave in the radiation mode that leaks without entering the (waveguide) or leaks to the outside of the output electrode while propagating on the output electrode (waveguide),
There is a problem that the convolution output is reduced by that much. Such leakage of the surface acoustic wave is remarkable when the output electrode width is, for example, about 3 wavelengths or less of the input surface acoustic wave so that the single mode surface acoustic wave propagates.

Further, when using a beam focusing means such as an arc-shaped input electrode or a parabolic horn type waveguide, it does not enter the waveguide at the entrance of the output electrode (waveguide) but leaks as it is. Since there are more surface acoustic waves, there is a problem that the angle of incidence of the surface acoustic waves on the waveguide is limited and the shape of the focusing means is limited.

Further, in the conventional example shown in FIGS. 12 and 13, the output electrode and the output take-out tap are formed of the same conductive material such as aluminum and have the same film thickness. Since a protrusion is attached to the output electrode, there is a radiation mode surface acoustic wave leaking from the tap to the outside of the output electrode, and there is a problem that the convolution output is reduced by that amount. Such a problem is particularly remarkable in the case of an output electrode width which propagates a single mode surface acoustic wave, for example, about 3 wavelengths or less of the input surface acoustic wave.

Therefore, the present invention improves the confinement effect (waveguiding effect) of the surface acoustic wave in the output electrode and suppresses the surface acoustic wave from leaking from the output electrode (waveguide).
An object of the present invention is to provide a surface acoustic wave device in which the reduction in convolution output is sufficiently reduced.

Furthermore, the present invention provides a surface acoustic wave element in which the reduction of the convolution output is sufficiently reduced by suppressing the leakage of the surface acoustic wave from the output extraction tap formed in contact with the output electrode. The purpose is to do.

[0013]

According to the present invention, on the surface of a piezoelectric substrate, the following objects can be achieved.
Utilizing the nonlinearity of the piezoelectric substrate between the first and second input electrodes that excite the first and second surface acoustic waves propagating in opposite directions and the first and second input electrodes, respectively. A surface acoustic wave element having an output electrode for taking out a convolution signal of the two surface acoustic wave signals from each other, on both sides of the output electrode along the propagation directions of the first and second surface acoustic waves. There is provided a surface acoustic wave device, characterized in that an output electrode portion of the piezoelectric substrate is formed in a convex shape by removing a surface portion of the piezoelectric substrate to form a step.

Further, according to the present invention, in order to achieve the above object, the first and second surface acoustic waves, which respectively propagate in opposite directions to each other, are excited on the surface of the piezoelectric substrate. It has a second input electrode and an output electrode for extracting the convolution signal of the two surface acoustic wave signals by utilizing the nonlinearity of the piezoelectric substrate between the first and second input electrodes. In the surface acoustic wave element, there is provided a surface acoustic wave element characterized in that grooves are formed in the piezoelectric substrate on both sides of the output electrode along the propagation directions of the first and second surface acoustic waves. It Here, the width of the groove can be made larger than a distance capable of generating electromagnetic induction from the output electrode to the opposite side across the groove.

In the present invention as described above, the width of the output electrode can be set so that the multi-mode surface acoustic wave can propagate.

Further, in the present invention as described above, the width of the output electrode can be set so that a single mode surface acoustic wave can propagate. Here, each of the first and second input electrodes may have a shape that focuses the first and second surface acoustic waves on an inlet end surface of the output electrode. Further, between the first and second input electrodes and the output electrode, it is possible to provide means for focusing the first and second surface acoustic waves on the inlet end faces of the output electrodes.

Further, according to the present invention, in order to achieve the above-mentioned object, the first and second surface acoustic waves, which propagate in opposite directions on the surface of the piezoelectric substrate, are excited respectively. And a second input electrode, an output electrode for obtaining a convolution signal of the two surface acoustic wave signals by utilizing the non-linearity of the piezoelectric substrate between the first and second input electrodes, and the output electrode In a surface acoustic wave element having an output extraction tap for extracting the convolution signal formed in contact with, the mass per unit area of the substrate surface of the conductive material forming the output electrode is calculated as the output extraction. There is provided a surface acoustic wave element, characterized in that the conductive material forming the tap is made larger than the mass per unit area of the substrate surface.

In the present invention as described above, the output electrode and the output take-out tap are made of the same conductive material, and the thickness of the output electrode is made larger than that of the output take-out tap. The mass of the conductive material forming the output electrode per unit area of the substrate surface may be larger than the mass of the conductive material forming the output take-out tap per unit area of the substrate surface. Here, the film thickness of the output electrode can be formed so as to gradually decrease from the central portion to both side portions in a cross section orthogonal to the propagation directions of the first and second surface acoustic waves.

Further, in the present invention as described above, the film thickness of the output electrode and the film thickness of the output take-out tap are made the same, and the output electrode is made of a conductive material having a larger density than that of the output take-out tap. By doing so, the mass of the conductive material forming the output electrode per unit area of the substrate surface can be made larger than the mass of the conductive material forming the output take-out tap per unit area of the substrate surface.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] FIG. 1 is a schematic view showing a first embodiment of a surface acoustic wave element according to the present invention, and FIG. 2 is a sectional view taken along the line AA '. In these figures, 1 is a piezoelectric substrate such as Y-cut (Z-propagation) lithium niobate,
Reference numeral 3 is a first and second comb-shaped input electrode formed on the surface of the piezoelectric substrate 1, and 4 is an output electrode formed on the surface of the piezoelectric substrate 1. These electrodes are made of a conductive material such as aluminum, and are usually formed directly on the surface of the piezoelectric substrate 1 using a photolithography technique.

In this embodiment, the propagation direction of the surface acoustic wave excited by the first and second input electrodes 2 and 3 (piezoelectric substrate 1
Of the piezoelectric substrate 1 on both sides of the output electrode 4 when viewed along the direction AA 'in the plane of FIG. By forming 10, the portion of the output electrode 4 of the piezoelectric substrate 1 is formed in a convex shape.

In the surface acoustic wave device having such a structure,
When an electric signal having the carrier angular frequency ω is input to the comb-shaped input electrode 2, the first surface acoustic wave is excited by the piezoelectric effect of the substrate. Similarly, when an electric signal having the carrier angular frequency ω is input to the comb-shaped input electrode 3, the second surface acoustic wave is excited by the piezoelectric effect of the substrate. These two surface acoustic waves propagate in opposite directions on the piezoelectric substrate 1 while being confined in the output electrode 4 by the output electrode 4 acting as a Δv / v waveguide.

In this embodiment, since the piezoelectric substrate 1 is stepped and the output electrode 4 is formed in a convex shape as described above, it functions as a so-called topographic waveguide and confines the surface acoustic wave. The effect is improved. Topographic waveguides utilize the fact that surface acoustic waves propagate through the convex portions of the substrate as waveguides, and there are ridge types and wedge types, and surface acoustic waves are confined compared to Δv / v waveguides. It is known that the effect is great. Regarding the topographic waveguide, "Ohm Co., Ltd., Elastic Wave Element Technology Handbook, p181" and "Michio Suzuki, Technical Report of IEICE, MW75-23, p35-44 (197).
5) ”, etc., for detailed description.

With such a structure, the effect of confining the surface acoustic wave in the waveguide (output electrode 4) is improved as compared with the conventional one, and therefore two surface acoustic waves colliding on the output electrode 4 are improved. Convolution signal (carrier angular frequency 2
ω) is taken out from the output electrode 4 without loss.

The effect of this embodiment as described above is obtained by the output electrode 4
Is particularly remarkable when the width of a single-mode surface acoustic wave propagates on the output electrode (waveguide), for example, a width of three wavelengths or less of the input surface acoustic wave. The effect can be obtained even in the case of an output electrode (waveguide) having a width such that a wave propagates.

In this embodiment, as shown in FIG. 2, the side surface of the output electrode portion of the piezoelectric substrate 1 formed in a convex shape is substantially perpendicular to the substrate surface. Besides, the surface of the piezoelectric substrate and the side surface of the output electrode portion may be inclined in the AA ′ cross section.

In this embodiment, only the waveguide region of the piezoelectric substrate 1 has a convex shape, but the piezoelectric substrate 1
The input electrode region may be formed in a convex shape.

Further, in this embodiment, the input electrodes 2 and 3 are
Although the example using the normal type comb-shaped electrode (IDT) is shown as the above, an apodized type or chirp type IDT may be used.

[Second Embodiment] FIG. 3 is a schematic view showing a second embodiment of a surface acoustic wave device according to the present invention, and FIG. 4 is a sectional view taken along line AA '. In these figures, the same members as the members in FIGS. 1 and 2 are designated by the same reference numerals.

In this embodiment, the grooves 11 are formed in the piezoelectric substrate 1 on both sides of the output electrode 4 along the propagation directions of the first and second surface acoustic waves. Here, the width of the groove 11 is set to be larger than at least the distance from the portion where the output electrode 4 is formed to the portion on both sides of the groove where electromagnetic induction is generated.

With this structure, the same effect as that of the first embodiment can be obtained. This effect is particularly remarkable when the width of the output electrode 4 is, for example, a width of 3 wavelengths or less of the input surface acoustic wave such that the single mode surface acoustic wave propagates on the output electrode (waveguide). The effect can be obtained even in the case of an output electrode (waveguide) having a width such that a multi-mode surface acoustic wave propagates.

In this embodiment, as shown in FIG. 4, the side surface of the groove 11 is substantially perpendicular to the surface of the substrate. The surface of the substrate and the side surface of the groove may be inclined.

In this embodiment, the groove 11 is formed only on both sides of the waveguide area of the piezoelectric substrate 1, but the groove 11 may be extended to both sides of the input electrode area of the piezoelectric substrate 1. .

Further, in this embodiment, the input electrodes 2 and 3 are
Although the example of using the normal type IDT is shown as above, an apodize type or chirp type IDT may be used.

[Third Embodiment] FIG. 5 is a schematic view showing a third embodiment of the surface acoustic wave device according to the present invention. In the figure, the same members as those in FIGS. 1 to 4 are designated by the same reference numerals. This embodiment differs from the first embodiment only in that the comb-shaped input electrodes 2 and 3 are arc-shaped.

With such a configuration, the conventional Δv /
In the case of a v-waveguide, surface acoustic waves excited by the arc-shaped electrode leak at the entrance of the output electrode (waveguide) without entering the output electrode (waveguide) depending on the angle of view of the arc-shaped input electrode (as it is The surface acoustic wave having a particularly large incident angle can be effectively confined in the output electrode (waveguide) 4. That is, in this embodiment, since the maximum incident angle of the surface acoustic wave confined in the output electrode (waveguide) 4 can be made larger than that in the conventional case, the degree of freedom in designing the input electrodes 2 and 3 is increased.

In this embodiment, the output electrode portion of the piezoelectric substrate 1 is formed in a convex shape as in the first embodiment, but the output of the piezoelectric substrate 1 is made in the same manner as in the second embodiment. Similar effects can be obtained by forming grooves on both sides of the electrode portion. The structure of the groove is as shown in the second embodiment.

In this embodiment, the side surface of the output electrode portion of the piezoelectric substrate 1 formed in a convex shape is substantially perpendicular to the substrate surface. However, the surface of the piezoelectric substrate and the side surface of the output electrode portion are shown. And may be slanted.

In this embodiment, the input electrodes 2 and 3 are
However, the shape may be formed by a plurality of curved lines, and any shape may be used as long as the surface acoustic wave is focused on the inlet of the output electrode 4.

In this embodiment, an arc type input electrode is used to focus the surface acoustic wave.
The same effect can be obtained by providing a surface acoustic wave focusing means such as a parabolic horn waveguide or a multi strip coupler between the input electrodes 2 and 3 and the output electrode 4.

In the present embodiment, only the waveguide region of the piezoelectric substrate 1 has a convex shape. However, the arc-shaped input electrodes 2 and 3 are changed to have a shape as shown in FIG. Even in the region up to the entrance of the output electrode 4, the piezoelectric substrate 1 may be formed in a convex shape by forming a step or forming a groove. According to this, the confinement effect can be further improved.

In the first to third embodiments, the side surface of the step portion and the groove is flat, but the rough side surface suppresses the spurious mode propagating on the side surface. can do.

In the first to third embodiments, the piezoelectric substrate 1 is not limited to a piezoelectric single crystal such as lithium niobate, but may be a semiconductor or a glass substrate on which a piezoelectric film is added. Any material and structure having a parametric mixing effect may be used.

Furthermore, by forming the comb-shaped electrodes 2 and 3 in the first to third embodiments as double electrodes (split electrodes), reflection of surface acoustic waves at the input electrodes can be suppressed and the characteristics of the device can be improved. It can be better.

The height of the stepped portion and the depth of the groove shown in the first to third embodiments may be within the range in which the output electrode forming portion of the piezoelectric substrate 1 acts as a topographic waveguide.

[Fourth Embodiment] FIG. 7 is a schematic view showing a fourth embodiment of the surface acoustic wave device according to the present invention, and FIG. 8 is a sectional view taken along the line AA '. In these drawings, the same members as those in FIGS. 1 to 6 are designated by the same reference numerals.

In the present embodiment, 5 is an output take-out tap formed on the surface of the piezoelectric substrate 1 in contact with the output electrode 4. The tap is made of a conductive material such as aluminum, and is usually formed directly on the surface of the piezoelectric substrate 1 using a photolithography technique. Here, the film thickness of the output electrode 4 is formed to be larger than the film thickness of the output take-out tap 5.

In the surface acoustic wave device having such a structure,
When an electric signal having the carrier angular frequency ω is input to the comb-shaped input electrode 2, the first surface acoustic wave is excited by the piezoelectric effect of the substrate. Similarly, when an electric signal having the carrier angular frequency ω is input to the comb-shaped input electrode 3, the second surface acoustic wave is excited by the piezoelectric effect of the substrate. These two surface acoustic waves propagate in opposite directions on the piezoelectric substrate 1 while being confined in the output electrode 4 by the output electrode 4 acting as a Δv / v waveguide.

When the output electrode 4 is provided with a protrusion such as the output tap 5, a surface acoustic wave leaking to the outside of the output electrode 4 exists. However, in this embodiment, since the film thickness of the output electrode 4 is formed larger than the film thickness of the tap 5, the mass per unit area of the output electrode 4 becomes larger than the mass per unit area of the tap 5,
The acoustic velocity of the surface acoustic wave at the output electrode 4 becomes slower than the acoustic velocity of the surface acoustic wave at the tap 5. In the Δv / v waveguide, the effect of confining the surface acoustic wave is larger as the velocity difference of the surface acoustic wave is larger. Therefore, the surface acoustic wave confining effect of the output electrode 4 is larger than that of the tap 5. This effect is called the mass loading effect and is described in "Ohm Co., Ltd., Acoustic Wave Device Technology Handbook,
p181 ”and the like.

Therefore, with the structure of this embodiment, the effect of confining the surface acoustic wave in the waveguide (output electrode 4) is improved as compared with the conventional structure shown in FIGS. The convolution signals (carrier angular frequency 2ω) of the two surface acoustic waves colliding on the electrode 4 are taken out from the tap 5 attached to the output electrode 4 via a wire bonding or the like (not shown) with an extremely small loss. .

In this embodiment, an example in which aluminum is used for the output electrode 4 and the output take-out tap 5 has been shown, but any other conductive material may be used.

[Fifth Embodiment] FIG. 9 is a sectional view showing a surface acoustic wave device according to a fifth embodiment of the present invention. In the figure, the same members as those shown in FIGS. 1 to 8 are designated by the same reference numerals.

In this embodiment, the film thickness of the output electrode 4 is gradually reduced from the central portion to both side portions in the width direction of the output electrode 4 (direction orthogonal to the propagation direction of surface acoustic waves). ing. By doing this,
The same effect as the fourth embodiment can be obtained.

[Sixth Embodiment] FIG. 10 is a sectional view showing a surface acoustic wave device according to a sixth embodiment of the present invention. In the figure,
The same members as those in FIGS. 1 to 9 are designated by the same reference numerals.

In this embodiment, the output electrode 4 and the tap 5 have the same film thickness, but the output electrode 4 is made of a material having a higher density than the tap 5. That is, the output electrode 4 is made of Au and the tap 5 is made of Al. This allows
Although the output electrode 4 and the tap 5 have the same film thickness, the mass loading effect of the output electrode 4 is larger than that of the output extraction tap 5, so that the same effect as the fourth embodiment can be obtained.

In this embodiment, the output electrode 4 is made of Au and the tap 5 is made of Al. However, if the material used for the output electrode has a higher density than the material used for the tap, other conductive materials are used. It may be a combination of materials.

The tap 5 is used in the fourth to sixth embodiments.
Although an example is shown in which the electrode is formed in contact with the central portion of the output electrode 4,
It may be formed at a position deviated from the center.

Although the taps 5 are provided at one place in the fourth to sixth embodiments, they may be provided at a plurality of places.

In the fourth to sixth embodiments, the tap 5 has a quadrangular shape. However, other shapes may be used, for example, a portion adjacent to the output electrode may have a constricted shape. Good.

Further, in the fourth to sixth embodiments, the example in which the output signal is taken out by directly wire-bonding to the tap 5 is shown. However, a strip pattern for taking out the output signal is formed on the piezoelectric substrate. May be formed.

Incidentally, also in the fourth to sixth embodiments,
As in the first to third embodiments, the piezoelectric substrate 1 is not limited to a piezoelectric single crystal such as lithium niobate, but may be a semiconductor or a structure in which a piezoelectric film is added on a glass substrate, for example.
Any material and structure having a parametric mixing effect may be used.

Also in the fourth to sixth embodiments, as in the first to third embodiments, the comb-shaped electrodes 2 and 3 are double electrodes (split electrodes) so that the input electrodes It is possible to suppress the reflection of the surface acoustic wave at, and to further improve the characteristics of the device.

Further, in the fourth to sixth embodiments, as in the first to third embodiments, a parabolic horn type waveguide or a multi-channel waveguide is provided between the input electrodes 2 and 3 and the output electrode 4. .The input electrode 2, by providing a surface acoustic wave focusing means such as a strip coupler or using an arc type IDT
Surface acoustic waves excited from 3 can be focused on the output electrode 4.

[0065]

As described above, according to the present invention, the first
And forming a step by removing the surface portion of the piezoelectric substrate on both sides of the output electrode along the propagation direction of the second surface acoustic wave, or forming the output electrode portion of the piezoelectric substrate in a convex shape, or
Since the grooves are formed in the piezoelectric substrate on both sides of the output electrode along the propagation directions of the first and second surface acoustic waves, the confinement effect (waveguiding effect) of the surface acoustic waves in the output electrode is improved. ,
Leakage of surface acoustic waves from the output electrode (waveguide) is suppressed, and the reduction in convolution output can be sufficiently reduced.

Further, according to the present invention, the mass of the conductive material forming the output electrode per unit area of the substrate surface is made larger than the mass of the conductive material forming the output take-out tap per unit area of the substrate surface. Therefore, the leakage of the surface acoustic wave from the output take-out tap is suppressed, and the decrease in the convolution output can be sufficiently reduced.

[Brief description of drawings]

FIG. 1 is a schematic view showing a first embodiment of a surface acoustic wave device according to the present invention.

FIG. 2 is a cross-sectional view taken along the line A-A ′ of FIG.

FIG. 3 is a schematic view showing a second embodiment of the surface acoustic wave device according to the present invention.

FIG. 4 is a cross-sectional view taken along the line A-A ′ of FIG.

FIG. 5 is a schematic view showing a third embodiment of the surface acoustic wave device according to the present invention.

FIG. 6 is a schematic view showing a modified example of the surface acoustic wave element of FIG.

FIG. 7 is a schematic view showing a fourth embodiment of the surface acoustic wave device according to the present invention.

8 is a cross-sectional view taken along the line A-A ′ of FIG.

FIG. 9 is a sectional view showing a surface acoustic wave device according to a fifth embodiment of the present invention.

FIG. 10 is a sectional view showing a surface acoustic wave device according to a sixth embodiment of the present invention.

FIG. 11 is a schematic view showing an example of a conventional surface acoustic wave element.

FIG. 12 is a schematic view showing another example of a conventional surface acoustic wave element.

13 is a cross-sectional view taken along the line A-A ′ in FIG.

[Explanation of symbols]

 1 Piezoelectric Substrate 2,3 Comb Input Electrode 4 Output Electrode 5 Output Extraction Tap 10 Step 11 Groove

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Norihiro Mochizuki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (11)

[Claims] 1. A first and second input electrode for exciting first and second surface acoustic waves propagating in opposite directions to each other on a surface of a piezoelectric substrate, and the first and second input electrodes. A surface acoustic wave device having an output electrode for extracting a convolution signal of the two surface acoustic wave signals by utilizing the non-linearity of the piezoelectric substrate between the first surface acoustic wave and the second surface acoustic wave. The surface electrode of the piezoelectric substrate is formed in a convex shape by removing the surface portion of the piezoelectric substrate on both sides of the output electrode along the propagation direction of the surface acoustic wave. element. 2. A first and a second input electrode for exciting first and second surface acoustic waves propagating in opposite directions to each other on the surface of a piezoelectric substrate, and the first and second input electrodes. A surface acoustic wave device having an output electrode for extracting a convolution signal of the two surface acoustic wave signals by utilizing the non-linearity of the piezoelectric substrate between the first surface acoustic wave and the second surface acoustic wave. A surface acoustic wave element, wherein grooves are formed in the piezoelectric substrate on both sides of the output electrode along the propagation direction of the surface acoustic wave element. 3. The surface acoustic wave device according to claim 2, wherein the width of the groove is larger than a distance capable of generating electromagnetic induction from the output electrode to the opposite side across the groove. 4. The surface acoustic wave device according to claim 1, wherein a width of the output electrode is a width in which a multi-mode surface acoustic wave can propagate. 5. The width of the output electrode is a width in which a single mode surface acoustic wave can propagate.
The surface acoustic wave device according to claim 1. 6. The first and second input electrodes are shaped so as to focus the first and second surface acoustic waves on an inlet end surface of the output electrode, respectively. The surface acoustic wave device according to claim 5. 7. A means for converging the first and second surface acoustic waves is provided between the first and second input electrodes and the output electrode at the entrance end face of the output electrode, respectively. The surface acoustic wave device according to claim 5, which is characterized in that: 8. A first and a second input electrode for exciting first and second surface acoustic waves propagating in opposite directions on a surface of a piezoelectric substrate, respectively, and the first and second input electrodes. An output electrode for obtaining a convolution signal of the two surface acoustic wave signals by utilizing the non-linearity of the piezoelectric substrate, and an output take-out tap for taking out the convolution signal formed in contact with the output electrode. In the surface acoustic wave element having, the mass per substrate surface unit area of the conductive material forming the output electrode is larger than the mass per substrate surface unit area of the conductive material forming the output tap. A surface acoustic wave device characterized by the above. 9. The output electrode is formed by forming the output electrode and the output extraction tap with the same conductive material and making the film thickness of the output electrode larger than the film thickness of the output extraction tap. 9. The surface acoustic wave device according to claim 8, wherein the mass of the conductive material per unit surface area of the substrate is larger than the mass of the conductive material forming the output taps per unit surface area of the substrate. . 10. The film thickness of the output electrode is formed so as to gradually decrease from the central portion to both side portions in a cross section orthogonal to the propagation directions of the first and second surface acoustic waves. The surface acoustic wave element according to claim 9. 11. The output electrode is formed by making the film thickness of the output electrode and the film thickness of the output extraction tap the same and forming the output electrode with a conductive material having a density higher than that of the output extraction tap. The elastic surface according to claim 8, wherein the mass of the conductive material to be formed per unit surface area of the substrate is larger than the mass of the conductive material to form the output tap per unit surface area of the substrate. Wave element.