JPH07226643A - Elastic wave element - Google Patents

Abstract

PURPOSE:To prevent the crossing part of the same center frequency from continuing to provide required characteristics by providing an area where the ratio of an electrode finger width and the gap length of adjacent electrode fingers is changed in a part where the electrode fingers with different potentials of an interdigital electrode cross. CONSTITUTION:The electrode finger arraying gap of an input side interdigital electrode 1a is gradually made small towards an output side electrode 1b and the electrode 1b is turned to be in a shape symmetrical to the la as well. In the area 11 where the gap is small, the ratio of the width and the gap of the respective electrode fingers 2 is changed, the crossing part provided with the same constitution is eliminated in the entire crossing parts and the center frequencies of the respective crossing parts constituted of the adjacent electrode fingers 2 are made different. Since the propagation speeds of elastic waves in the electrode finger 2 and a gap part are different, by changing the ratio of the electrode finger width and the gap length, delay time between the electrode fingers 2 is changed and the center frequency is changed. Thus, by attaining such constitution, the delay time in respective crossing points is effectively made small and the degradation of the characteristics due to continuance in the crossing parts of the same delay time is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter, a delay line and a dispersion type delay line using elastic waves.

[0002]

2. Description of the Related Art An elastic wave element is one that filters an analog signal or delays it by generating an elastic wave on the surface of a piezoelectric material.

FIG. 36 shows a conventional wide band type acoustic wave device disclosed in Japanese Utility Model Publication No. 60-66118. In the figure, a pair of interdigital (or comb-shaped) electrodes are formed on the upper surface of the piezoelectric material in opposite directions, that is, the interdigital electrode 1a as an input electrode and the interdigital electrode 1b as an output electrode. Are formed.
Each interdigital electrode is composed of a plurality of rectangular electrode fingers 2 formed in parallel with each other at a predetermined interval, and a pair of extraction electrodes 3 commonly connected to the base ends of the electrode fingers 2. As shown, one of the pair of extraction electrodes is connected to the electric terminal 4, and the other is connected to the ground terminal 5.

In such an elastic wave element, for example, an elastic wave is generated at the left input-side interdigital electrode 1a, and the elastic wave is received by the right output-side interdigital electrode 1b. More specifically, a portion where the electrode finger 2 connected to the electric terminal 4 and the electrode finger 2 connected to the ground terminal 5 intersect with each other by an electric signal applied to the electric terminal 4 (hereinafter, referred to as an intersecting portion). ) Generates an electric field. Since the interdigital transducer 1 is formed on the surface of the piezoelectric material, the piezoelectric material causes a strain in the piezoelectric material, which is excited as an elastic wave and propagates in a direction perpendicular to the intersection. To do. Then, the elastic wave propagating to the output-side interdigital transducer 1b is converted into an electric signal again through a process reverse to the excitation,
The electric signal is taken out from the electric terminal 4.

Here, the electrode finger number is i, and the electrode finger i
Is L _i , the distance between the centers of the electrode fingers i and i + 1 is D _i (hereinafter referred to as the electrode finger arrangement interval), and the length of the gap between the electrode fingers i and i + 1 is S _i . Then, there is the following relationship between them, as is clear from FIG.

D _i = S _i + (L _i + L _{i + 1} ) / 2 (Equation 1) At each intersection, a frequency f _i at which the electrode finger arrangement interval D _i becomes a half wavelength (hereinafter referred to as the center The elastic wave is excited most strongly when it reaches the frequency. Therefore, the interdigital transducer 1 of FIG. 36 gradually changes the electrode finger arrangement interval D _i so that the interdigital transducer 1 can convert an electric signal and an elastic wave over a wide frequency range. That is, if such a comb-shaped electrode 1 is used, a pass band over a wide frequency range can be obtained.

FIG. 37 shows the output-side interdigital transducer 1b.
The relationship between the position X _i of the intersection and the center frequency f _{i at} each intersection i is illustrated. Here, the intersecting portion i means an intersecting portion constituted by the electrode finger i and the electrode finger i + 1, and the position X _i thereof is an intermediate position between the center position of the electrode finger i and the center position of the electrode finger i + 1. . In the figure, the horizontal axis is the position X _i of the intersection _i , and the vertical axis is the center frequency f of the intersection i.
_i .

As shown in FIG. 37, for position X _i ,
The center frequency f _i changes linearly. In other words, based on the left end of the output-side interdigital electrode 1b of FIG. 36, the delay time until the acoustic wave center frequency f _i reaches the intersection i When tau _i, with respect to the center frequency f _i, Delay time τ
_i changes linearly.

In the acoustic wave device shown in FIG. 36, the input-side interdigital transducer 1a and the output-side interdigital transducer 1b are arranged in line symmetry with each other, so that the delay time varies depending on the frequency. Operates as a delay line. The amount of change in the delay time τ _i over the bandwidth Δf _{IDT at} this time is the dispersion time, and the sum of the respective dispersion times of the input / output interdigital transducer 1 is the dispersion time Δτ as the acoustic wave device.

Although not shown in the figure, if the input / output interdigital transducers 1 are arranged in the same direction so that the changes in the electrode finger arrangement intervals are in the same direction, the dispersion characteristics of the input interdigital transducer 1a will be changed to the output side. Since the interdigital transducers 1b operate so as to cancel each other, the acoustic wave device operates as a wide band filter having a constant delay time regardless of frequency or as a delay line. Now, it is assumed that the center frequency f _i changes with respect to the position X _{i of the} intersection in the relationship of the following Expression 2.

F _i = H (X _i ) ... (Formula 2) For example, if the position of the crossing portion exciting the frequency f _{L of the} pass band is X _L , the center frequency f _i as shown in FIG.
The relationship in the case where changes linearly with respect to the position X _i is expressed by the following Expression 3.

F _i = f _L + α (X _i −X _L ) (Equation 3) Here, α is a constant and is an amount that determines the dispersion characteristics of the interdigital transducer. The electrode finger arrangement interval D _i has a relationship with the center frequency f _i as shown in the following Expression 4 with the sound velocity being V _S.

F _i = V _S / (2D _i ) ... (Formula 4) The relationship between the electrode finger arrangement interval D _i and the position X _i of the intersection i is
For example, when the above Expression 3 is satisfied, the following Expression 5 is obtained, and a change as shown in FIG. 38 is shown.

D _i = (1/2) × V _S / (F _L + α (X _i −X _L )) (Equation 5) In FIGS. 37 and 38, the graphs are continuously drawn as lines, but in reality, At the intersection X _i and the next intersection X
_{i + 1} is separated from the electrode finger arrangement interval D _i , and the position X _{i at} each intersection is a discrete quantity. Here, in order to realize the favorable characteristics of the acoustic wave device shown in FIG. 36, that is, the characteristics in which there is no unnecessary ripple in the in-band pass characteristic and the group delay time characteristic, the discrete crossover as described above is performed. The center frequency f _i and the electrode finger arrangement interval D _i with respect to the position X _i of the part are shown in FIG.
It is necessary that the graph can be regarded as a continuous graph as shown in Nos. 7 and 38. That is, it is necessary that the center frequency f i of each intersection _i and the electrode finger arrangement interval D _i gradually change.

In this case, when the electrode index of the interdigital transducer 1 is small such that the dispersion time required for the acoustic wave element is small, the change amount of the electrode finger arrangement interval D _i becomes large,
Smooth dispersion characteristics cannot be realized.

When the dispersion time required for the elastic wave element is long, the area where the high frequency of the interdigital transducer 1 is excited, that is, the area where the electrode finger arrangement interval D _i is small, is provided between the adjacent intersections i. The structure has a small difference in the electrode finger arrangement interval D _i . However, when manufacturing the acoustic wave device, the size of the interdigital transducer is set as an integral multiple of the minimum size unit Q due to manufacturing requirements. In that case, the minimum size unit Q should be reduced. Is a high-precision manufacturing process and causes an increase in manufacturing cost, so Q is limited.

For example, FIG. 39 shows the electrode finger arrangement interval D _i when the minimum dimension value D _min is set. In the figure,
The horizontal axis represents the electrode finger number i, and the vertical axis represents the electrode finger arrangement interval D _i of each electrode finger i. The thin line is the electrode finger arrangement interval D _i 6 that is continuously changed as shown in FIG. 38, and the closer to the electrode finger arrangement interval D _i 6, the better the characteristics. The step-like thick line is the electrode finger arrangement interval D _i 7 when the minimum dimension value is D _min . In the case of the interdigital electrode 1 shown in FIG. 36, the electrode finger width L _i and the gap S _i between the electrode fingers are
Since each of them is a quarter of the wavelength λ _i of the elastic wave of the center frequency f _i and the electrode finger arrangement interval D _i is ½ of the wavelength λ _i , the minimum dimension value D _min for the electrode is basically Is twice the minimum size unit Q.

For example, as shown in FIG. 49, when the width of each adjacent electrode finger 2 and the gap between the electrode fingers 2 are the same, when the electrode finger arrangement interval D _i is changed from 6Q to 8Q. Consider changes in the values of the electrode finger width, the gap length, and the electrode finger arrangement interval. As shown in the figure, the array A,
There are two possible changes like B. Transiently, there is a portion where the electrode finger arrangement interval is an intermediate value between 6Q and 8Q, and in this portion, the ratio of the width and the gap length of each adjacent electrode finger 2 is different from the other portions. This inevitably occurs when the electrode finger arrangement interval is gradually changed,
This site does not exist continuously. That is, as shown in FIG. 4, when the electrode finger arrangement interval when the dimension minimum unit is not taken into consideration is 6, the electrode finger arrangement interval when the smallest dimension unit Q is taken into consideration has a value such as 7. It becomes a stepwise value at 2Q intervals. P ₁ , P ₂ , and P ₃ are regions where the same electrode finger arrangement intervals are continuous, and transiently at the transition points from P ₁ to P ₂ and from P ₂ to P ₃ .
There is an electrode finger arrangement interval different from P ₁ , P ₂ , and P ₃ . For example, assuming that the electrode finger arrangement interval at P ₂ is 8Q, each dimension at the portion where P ₂ moves to P ₃ is
The values are shown in FIG.

It can be seen from FIG. 39 that the smaller the electrode finger arrangement interval D _{i, the} larger the electrode index for the same electrode finger arrangement interval. As the electrode finger arrangement interval D _i is closer to the minimum electrode finger arrangement interval D _min , a certain electrode finger arrangement interval D
or adding a minimum electrode finger arrangement interval D _{mi n} to _i, because the rate of change in the center frequency f _i in the case of pulling increases.

Electrode fingers N in which the same electrode finger arrangement interval D is continuous
A pair, that is, a comb-shaped electrode 1 having an electrode index of 2N + 1
However, the efficiency G (f) of converting an electric signal into an elastic wave is described in the literature (hereinafter referred to as the literature A) “Surface Acoustic Wave Engineering”, published by The Institute of Electronics and Communication Engineers, June 1985, pp. Equation 6 as described in 62-66.

[0021]

[Equation 1] Here, f ₀ is the center frequency, Δf is the difference between the frequency f and the center frequency f _0, which is obtained from the electrode finger arrangement interval D _i using Equation 4, and G ₀ is the center frequency f at the frequency f
The conversion efficiency when it is equal to ₀ . As can be seen from Expression 6, in the interdigital transducer 1 having a region in which the same electrode finger arrangement period D is continuous, there is a frequency at which the electric signal and the elastic wave are not converted periodically, and is shown in Expression 7. Thus, the greater the electrode index N, the smaller the frequency interval Δfz in which the electric signal and the elastic wave are not converted, and the narrower the band.

Δfz = f ₀ / N (Equation 7) The conversion efficiency between the electric signal of the interdigital transducer 1 and the elastic wave when the electrode finger arrangement interval D _i is continuously changed is as shown in FIG. become. In the figure, the horizontal axis represents frequency and the vertical axis represents conversion efficiency. Reference numeral 8 is a conversion efficiency for each intersection where the electrode finger arrangement interval D _i is different, and 9 is a conversion efficiency for the entire interdigital transducer 1 in which the conversion efficiency 8 for each intersection is added.

The conversion efficiency 8 at each intersection i is maximized at the center frequency f _i obtained from the electrode finger arrangement interval D _i at the intersection i from the equation 6. Further, since the electrode finger arrangement interval D _i is different for each intersection i, the number N of electrode finger pairs is set to 0.5.
It has an extremely wide band characteristic. Therefore, the conversion efficiency 9 of the entire interdigital transducer 1 is a characteristic obtained by summing up the conversion efficiencies 8 of the intersections _{i in} which the center frequency f _i changes little by little for all the intersections. As a whole, a flat conversion efficiency can be realized over the required band.

On the other hand, for example, when the same electrode finger arrangement interval is continuous at a high frequency (when the intersections of the same structure are continuous), the characteristics shown in FIG. 41 are obtained. In the figure, the horizontal axis and the vertical axis are the same as in the case of FIG. Similar to FIG. 40, 8 is the conversion efficiency of each intersection where the electrode finger arrangement interval D _i is different, and 10 is the conversion efficiency of the intersection where the same electrode finger arrangement interval is continuous.

The conversion efficiency 10 at the intersection where the same electrode finger arrangement interval is continuous has a narrow band, and the center frequency of the intersection where the same electrode finger arrangement interval is continuous has a difference between adjacent electrode finger arrangement intervals D _i. The difference from the center frequency of the part becomes large.
As a result, the conversion efficiency 9 of the interdigital transducer 1 as a whole, which is the sum of the conversion efficiencies 8 and 10 at each intersection, causes a large ripple in the band. Since the fluctuation of the conversion efficiency is directly reflected on the pass characteristic when the elastic wave element as shown in FIG. 36 is configured, the elastic wave element has a large in-band ripple.

In practice, since the structure is composed of far more electrode fingers than in the case shown in FIGS. 40 and 41, for example, the elastic wave element in which the electrode finger arrangement interval as shown in FIG. 36 gradually changes. If the ideal passage characteristic of is as shown in FIG. 42, there is a minimum value D _min in the electrode finger arrangement interval, and as shown in FIG. In some cases, in-band ripple as shown in FIG. 44 occurs in both the passing power and the group delay time, and there is a problem that the performance as the acoustic wave device is deteriorated.

Therefore, there has been a demand for a structure capable of avoiding the coincidence of the center frequencies of the intersections under the constraint of the minimum dimension value.

A conventional interdigital electrode is disclosed in Japanese Patent Laid-Open No.
There is a configuration of FIG. 45 shown in Japanese Patent No. 132208 and a configuration of FIG. 46 shown in Japanese Patent Laid-Open No. 62-200811. 45 and 46 show the electrode finger 2 in which the center frequency of a part of the interdigital electrode is f ₀ and the wavelength of the elastic wave at the center frequency f ₀ is λ ₀ . IDT acoustic wave device of FIG. 45, the electrode finger 2 with a width of lambda _0/8
When the width is composed of lambda _0/4 of the electrode fingers 2 which, as one cycle lambda ₀ interval, the electrode fingers 2 and the width of the width of λ _0/8 λ ₀ /
Each one of the four electrode fingers 2 is arranged at the same potential and adjacent to each other. Interdigital transducers of FIG. 46, the width is composed of the electrode fingers 2 of lambda _0/8, 2 present among the three electrode fingers 2 which are arranged in positions next to each other at the same potential, the connecting electrode Connected at 12.

The elastic wave elements shown in FIGS. 45 and 46 are
And using the electrode fingers 2 in the width lambda _0/8, determine the wavelength lambda ₀ of the acoustic wave of the center frequency f ₀ is not an array interval of the electrode fingers 2, 4 in the wavelength lambda ₀ spacing elastic wave This is the electrode finger arrangement period for each electrode finger 2 of the book. In this structure, when the dimension unit of each electrode finger 2 is Q, the minimum value of the arrangement period of the electrode fingers 2 is 6Q, which is more than that of the conventional acoustic wave device of this type shown in FIG. The performance of the acoustic wave element is deteriorated because it is more affected by the minimum dimension unit Q of.

Further, as a conventional interdigital electrode, there is a configuration shown in FIG. 47 shown in Japanese Patent Application Laid-Open No. 3-228418 and Japanese Patent Application Laid-Open No. 1-166609. In the figure, 13 is a pair of electrode fingers having the same potential, and each electrode finger pair has a structure intersecting. 2 times the arrangement spacing of the electrode fingers 13 is center distance D _i of a pair of electrode fingers 13, twice this center distance D _i is the wavelength lambda _i of the acoustic wave at the center frequency f _i. In addition, in order to vary the excitation intensity of the elastic wave at the intersection of each electrode finger 13 pair, the center distance D
_Although the electrode finger width with respect to _i is made variable, it is irrelevant to the center distance D _i of the electrode finger 13 and the ratio of the electrode finger width to the center distance D _i .

In the elastic wave device of FIG. 47, the center distance D _i of the electrode fingers 13 determines the center frequency f _i of the elastic wave. The minimum value of the center distance D _i of the electrode fingers 13 is four times the minimum dimension unit Q of the electrode fingers 13, which is smaller than that of the acoustic wave device shown in FIG. 36. Since the unit Q is more affected, the performance as the acoustic wave device is deteriorated.

FIG. 48 is a diagram showing a conventional acoustic wave device disclosed in Japanese Patent Laid-Open No. 56-149817. FIG. 48
Then, among the lead-out electrodes of the interdigital transducer 1, the outer lead-out electrode 3a is connected to the electric terminal 4 and the inner lead-out electrode 3b is connected to the ground terminal when viewed from each input / output interdigital intermediary electrode 1. . Electrode finger 2 is elastic wave propagation path 1
Since a so-called slant electrode, which is arranged so as to be displaced in a direction perpendicular to 4, is used, the boundary 15 between the electrode finger 2 and the inner extraction electrode 3b is inclined at an angle θ _IDT with respect to the propagation path 14 of the elastic wave. Have. By adopting such an inclined structure, the number of electrode fingers 2 traversed by elastic waves propagating in an arbitrary propagation path 14 is reduced, and adverse effects such as reflection of elastic waves at the electrode fingers 2 and excitation of unnecessary waves are reduced. can do. At this time, an arbitrary propagation path 14 of the elastic wave and the input-side interdigital transducer 1a closest to the output-side interdigital transducer 1b.
The intersection point with the perpendicular line from the electrode finger 2 to the propagation path 14 of the elastic wave is A, the intersection point with the boundary 15 between the electrode finger 2 and the inner extraction electrode 3b is B, and the end surface 16 of the inner extraction electrode 3b is In the conventional acoustic wave device of this type shown in FIG. 48, the shape of the end face 16 of the inner extraction electrode 3b is determined so as to satisfy the expression 8.

X _BC / X _AB = V _m / (V _f −V _m ) × (V _f / V _IDT −1) (Equation 8) where X _AB is the distance between the points AB and X _BC is the point The distance between BCs, V _f is the propagation velocity of the elastic wave on the free surface, V _m is the propagation velocity of the elastic wave on the extraction electrode, and V _IDT is the propagation of the elastic wave in the region where the electrode fingers 2 are arranged. It's speed. Figure 4
As shown in FIG. 8, the electrode finger 2 and the inner extraction electrode 3b
When the boundary 15 between the and is linear, the end face 16 of the inner extraction electrode 3b has a linear structure. By determining the shape of the end face 16 of the inner extraction electrode 3b so as to satisfy Expression 8, the propagation velocities V _f , V _m , and V of the elastic wave are determined.
Disturbances in the wavefront of elastic waves due to different _IDTs can be prevented.

In the conventional elastic wave device of this type, the disturbance of the wavefront of the elastic wave due to the different propagation speeds V _f , V _m and V _IDT of the elastic wave is prevented by the formula (8). Equation 8 is uniquely determined by determining the propagation velocities V _f , V _m , and V _IDT of the elastic wave and the shape of the boundary 15 between the electrode finger 2 and the inner extraction electrode 3b, and uniquely the end surface of the inner extraction electrode 3b. Sixteen shapes have been determined. Therefore, the propagation velocity V _f of the elastic wave,
If V _m , V _{IDT and the} like differ depending on the material, an error occurs in the value on the right side of Expression 8, and the condition of Expression 8 cannot be satisfied. As a result, the wavefront of the elastic wave is disturbed and the characteristics of the elastic wave element are deteriorated.

[0035]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and even if the minimum dimension unit is set in the configuration of the interdigital electrode to reduce the manufacturing cost, each intersection is formed. It is an object of the present invention to provide an acoustic wave device capable of improving the properties of the entire device by avoiding the matching of the properties of 1.

Further, the present invention has been made to solve the above problems, and provides an acoustic wave device capable of achieving the required characteristics even when the electrode index for achieving the required dispersion characteristics is large. Especially.

The present invention has been made to solve the above problems, and provides an acoustic wave device capable of achieving the required characteristics even when the electrode index for achieving the required dispersion characteristics is small. Especially.

The present invention has been made to solve the above problems, and provides an elastic wave element which can realize the required characteristics even if there is an error in the propagation velocity of the elastic wave used at the time of design. Especially.

[0039]

In the acoustic wave device according to the first aspect of the present invention, the electrode finger width adjacent to the electrode finger width of the electrode finger adjacent to the electrode finger width is partially or wholly intersected with the electrode fingers of the interdigital electrode having different potentials. An area having a different ratio to the gap length was provided.

In the acoustic wave device according to the second aspect of the invention, the electrode finger sequence in which the electrode finger arrangement intervals of the interdigital electrodes are gradually reduced is provided in a part or the whole of the portion where the electrode fingers of the interdigital electrodes having different potentials intersect. In the direction of, the ratio of the electrode finger width to the gap length between adjacent electrode fingers was gradually decreased.

In the acoustic wave device according to the third aspect of the invention, the ratio of the electrode finger width to the gap length of the adjacent electrode fingers is set to a random number in a part or the whole of the portion where the electrode fingers of the interdigital electrode having different potentials intersect. Changed.

In the acoustic wave device according to the fourth aspect of the present invention, the ratio of the electrode finger width to the gap length of adjacent electrode fingers changes at a part or the whole of the portion where the electrode fingers of the interdigital electrode having different potentials intersect. It has a stepped electrode finger.

In the acoustic wave device according to the fifth aspect of the present invention, the ratio of the electrode finger width to the gap length of adjacent electrode fingers changes in a part or the whole of the portion where the electrode fingers of the interdigital electrode having different potentials intersect. In the direction of the electrode finger sequence in which the electrode finger arrangement interval of the interdigital electrode is gradually reduced, the ratio of the electrode finger width to the gap length of the adjacent electrode fingers in each electrode finger is large. The ratio of the total length in the cross width direction of the region where the ratio of the electrode fingers to the gap length of the adjacent electrode fingers is small to the total length in the cross width direction of the regions is gradually increased.

In the acoustic wave device according to the sixth aspect of the present invention, the ratio of the electrode finger width to the gap length of adjacent electrode fingers changes at a part or the whole of the portion where the electrode fingers of the interdigital electrode having different potentials intersect. Having a stepped electrode finger, the sum of the lengths in the cross width direction of the region having a large ratio of the electrode finger width to the gap length of the adjacent electrode fingers in each of the electrode fingers and the interval length of the adjacent electrode fingers. The ratio with respect to the total of the lengths in the cross width direction of the region where the ratio of the electrode finger width is small was randomly changed.

In the acoustic wave device according to the seventh aspect of the present invention, at least one non-piezoelectric thin film having elastic wave dispersion characteristics is formed on the surface of the piezoelectric substrate, and the surface of any of the above thin films or the above thin film is formed. On the boundary surface between the thin film and the piezoelectric substrate, the interdigital electrode having the electrode finger arrangement interval gradually changed was provided.

In the acoustic wave device according to the eighth aspect of the present invention, at least one non-piezoelectric thin film having elastic wave dispersion characteristics is formed on the surface of the piezoelectric substrate, and the surface of any thin film or the above thin film is formed. An electrode of the interdigital transducer is provided on the boundary surface between the thin film and the piezoelectric substrate, which is provided with the interdigital electrode with the electrode finger arrangement interval gradually changed, and is formed on a piezoelectric substrate having no dispersibility. Made the index smaller.

In the elastic wave device according to the ninth aspect of the present invention, at least one non-piezoelectric thin film having elastic wave dispersion characteristics is formed on the surface of the piezoelectric substrate, and the surface of any of the above thin films or the above thin film is formed. An electrode of the interdigital transducer is provided on the boundary surface between the thin film and the piezoelectric substrate, which is provided with the interdigital electrode with the electrode finger arrangement interval gradually changed, and is formed on a piezoelectric substrate having no dispersibility. Increased the index.

In the elastic wave device according to the tenth aspect of the present invention, at least one piezoelectric thin film having elastic wave dispersion characteristics is formed on the surface of the non-piezoelectric substrate, and the surface of any thin film of the above thin films or the above thin film is formed. The interdigital electrodes having the electrode finger arrangement intervals gradually changed were provided on the boundary surface between the thin film and the non-piezoelectric substrate.

In the elastic wave element according to the eleventh aspect of the present invention, at least one piezoelectric thin film having elastic wave dispersion characteristics is formed on the surface of the non-piezoelectric substrate, and the surface of any thin film or the above thin film is formed. On the boundary surface between the thin film and the non-piezoelectric substrate, the interdigital electrode with the electrode finger array spacing gradually changed is provided, and the interdigital electrode has a more interleaved shape than that of the non-dispersive piezoelectric substrate. The electrode index was reduced.

In the acoustic wave device according to the twelfth aspect of the invention, at least one piezoelectric thin film having elastic wave dispersion characteristics is formed on the surface of the non-piezoelectric substrate, and the surface of any thin film or the above thin film is formed. On the boundary surface between the thin film and the non-piezoelectric substrate, the interdigital electrode with the electrode finger array spacing gradually changed is provided, and the interdigital electrode has a more interleaved shape than that of the non-dispersive piezoelectric substrate. The electrode index was increased.

In the elastic wave element according to the thirteenth invention, the lower limit frequency of the pass band of the elastic wave element is f ₁ and the upper limit frequency is f ₁ .
₂ and the cross width of the interdigital electrodes of the acoustic wave device is W ₀
And the propagation velocity of the elastic wave in the interdigital transducer is V _IDT
And when the angle formed by the electrode fingers of the output-side interdigital transducer and the wavefront of the elastic wave excited by the input-side interdigital transducer is θ, then f ₂ <V _IDT / (W ₀ · sin θ) (Equation 9) Alternatively, where n is an integer, the extraction electrode may satisfy f ₂ / n <V _IDT / (W ₀ · sin θ) <f ₁ / (n−1) (Equation 10) The shape of the electrodes facing each other was determined.

In the elastic wave element according to the fourteenth invention, the lower limit frequency of the pass band of the elastic wave element is f ₁ and the upper limit frequency thereof is f ₁ .
₂ and the cross width of the interdigital electrodes of the above acoustic wave device is W
_0, and the propagation velocity of the elastic wave in the interdigital transducer is V
_{The angle} between the _IDT and the electrode finger of the output-side interdigital electrode and the wavefront of the elastic wave when the elastic wave excited by the input-side offset electrode reaches the output-side interdigital electrode is θ. At this time, the shape of the shield electrode was determined so as to satisfy the condition represented by the formula 9 or the condition represented by the formula 10 with n being an integer.

[0053]

In the elastic wave device according to the first aspect of the present invention, the intersection group having the same electrode finger arrangement interval has the regions in which the ratio of the electrode finger width and the gap length of the adjacent electrode fingers is changed. Since the propagation speed of the elastic wave is different between the electrode finger portion and the gap portion between the electrode fingers, even if the electrode finger arrangement spacing is the same, the ratio between the electrode finger width and the gap length between adjacent electrode fingers is changed. As a result, the center frequency of the elastic wave can be changed. Further, by changing the ratio between the electrode finger width and the gap length between adjacent electrode fingers, the electrode finger arrangement interval can be changed at the minimum value of the electrode finger arrangement interval which is the same as the minimum dimension unit of the electrode finger. For this reason, it is possible to prevent the electrode finger arrangement intervals of the same center frequency from continuing, and to obtain an acoustic wave device having required characteristics.

In the acoustic wave device according to the second aspect of the invention, the electrode finger sequence in which the electrode finger arrangement interval of the interdigital electrodes gradually decreases is partially or wholly at the portion where the electrode fingers of the interdigital electrodes having different potentials intersect. In the direction of, the ratio of the electrode finger width to the gap length between adjacent electrode fingers was gradually decreased. Since the propagation speed of the elastic wave is slower in the electrode finger portion than in the gap portion between the electrode fingers, even if the electrode finger arrangement spacing is the same, the ratio between the electrode finger width and the gap length between adjacent electrode fingers is small. By doing so, the center frequency can be equivalently increased. The direction of the electrode finger sequence in which the electrode finger arrangement interval gradually decreases is the direction in which the center frequency gradually increases. Therefore, in the same direction, gradually increase the center frequency of the portion where the electrode finger arrangement interval is the same. Therefore, it is possible to prevent the electrode finger arrangement intervals of the same center frequency from continuing, and it is possible to obtain an acoustic wave device having required characteristics.

In the acoustic wave device according to the third aspect of the present invention, the ratio of the electrode finger width to the gap length of the adjacent electrode fingers is set to a part or the whole of the portion where the electrode fingers of the interdigital electrode having different potentials intersect. It was changed randomly. Part of the electrode finger,
Since the propagation speed of the elastic wave is different from that of the gap between the electrode fingers, even if the electrode finger arrangement interval is the same, by changing the ratio between the electrode finger width and the gap length of the adjacent electrode fingers, the elastic wave The center frequency can be changed. For this reason,
By randomly changing the ratio of the electrode finger width to the gap length of adjacent electrode fingers, it is possible to prevent the electrode finger arrangement intervals of the same center frequency from continuing and obtain an acoustic wave device having the required characteristics. it can.

In the elastic wave device according to the fourth aspect of the present invention, the ratio of the electrode finger width to the gap length of the adjacent electrode fingers is part or all of the portion where the electrode fingers of the interdigital electrode having different potentials intersect. Having varying electrode fingers. Since the propagation speed of the elastic wave is different between the electrode finger portion and the gap portion between the electrode fingers, even if the electrode finger arrangement spacing is the same, the ratio between the electrode finger width and the gap length between adjacent electrode fingers changes. .
That is, when the stepped electrode fingers whose electrode finger widths change are used, they operate equivalently as if the intersecting portions having different center frequencies are connected in parallel. Therefore, by using the stepped electrode fingers in which the ratio of the electrode finger width to the gap length of the adjacent electrode fingers changes, it is possible to prevent the electrode finger arrangement intervals of the same center frequency from continuing and to achieve elasticity having the required characteristics. A wave element can be obtained.

In the acoustic wave device of the fifth invention, the ratio of the electrode finger width to the gap length of adjacent electrode fingers changes at a part or the whole of the portion where the electrode fingers of the interdigital electrode having different potentials intersect. In the direction of the electrode finger sequence in which the electrode finger arrangement interval of the interdigital electrode is gradually reduced, the ratio of the electrode finger width to the gap length of the adjacent electrode fingers in each electrode finger is large. The ratio of the total length in the cross width direction of the region having a small ratio of the electrode finger width to the gap length of the adjacent electrode fingers to the total length in the cross width direction of the regions was gradually increased. The propagation speed of the elastic wave is slower in the electrode finger portion than in the gap portion between the electrode fingers. Therefore, even if the electrode finger arrangement intervals are the same, the ratio between the electrode finger width and the gap length between adjacent electrode fingers is small. That is, when an electrode finger having a narrow electrode finger width is used, the operation equivalently increases the center frequency. Therefore, the sum of the lengths in the cross width direction of the regions in which the ratio of the electrode finger width to the gap length of the adjacent electrode fingers in each electrode finger is large and the ratio of the electrode finger width to the gap length of the adjacent electrode fingers. By gradually decreasing the ratio of the area of small area to the total length in the cross width direction, the center frequency is equivalently increased gradually. As a result, it is possible to prevent the electrode finger arrangement intervals of the same center frequency from continuing, and to obtain an acoustic wave device having required characteristics.

In the acoustic wave device of the sixth aspect of the present invention, the ratio of the electrode finger width to the gap length of adjacent electrode fingers changes at a part or the whole of the portion where the electrode fingers of the interdigital electrode having different potentials intersect. Having a stepped electrode finger, the total of the lengths in the cross width direction of the region having a large ratio of the electrode finger width to the gap length of the adjacent electrode fingers in each of the electrode fingers and the gap length of the adjacent electrode fingers The total ratio of the lengths in the cross width direction of the region having a small electrode finger width ratio was randomly changed. In the part of the electrode finger and the part of the gap between the electrode fingers,
Since the propagation speeds of elastic waves are different, even if the electrode finger arrangement intervals are the same, the ratio between the electrode finger width and the gap length between adjacent electrode fingers changes. That is, when the electrode fingers whose electrode finger widths change are used, they operate equivalently as if the intersections having different center frequencies are connected in parallel. Therefore, by using the electrode fingers in which the ratio of the electrode finger width to the gap length of the adjacent electrode fingers changes randomly, it is possible to prevent the electrode finger arrangement intervals of the same center frequency from continuing and to have the required characteristics. An acoustic wave device can be obtained.

In the acoustic wave device according to the seventh aspect of the present invention, at least one non-piezoelectric thin film having elastic wave dispersion characteristics is formed on the surface of the piezoelectric substrate, and the surface of any thin film of the above thin films or On the boundary surface between the thin film and the piezoelectric substrate, the interdigital electrode having the electrode finger arrangement interval gradually changed was provided. Due to the dispersion characteristics of the thin film, the propagation path of the elastic wave has a characteristic that the propagation velocity varies depending on the frequency. Therefore, even if the electrode index of the drooping electrode required to achieve the required characteristics is too small or too large to achieve good characteristics, by using the dispersion characteristics of the thin film, By sharing the dispersion characteristics of the wave element with both the interdigital electrodes and the dispersion characteristics of the thin film, it is possible to obtain an acoustic wave element having the required characteristics. Further, even if the same electrode finger arrangement interval is continuous due to the minimum dimension unit of the electrode fingers, the group delay characteristics can be changed by the frequency due to the dispersion characteristics of the thin film. An element can be obtained.

In the elastic wave device of the eighth aspect of the invention, at least one non-piezoelectric thin film having elastic wave dispersion characteristics is formed on the surface of the piezoelectric substrate, and the surface of any thin film or the above thin film is formed. An electrode of the interdigital transducer is provided on the boundary surface between the thin film and the piezoelectric substrate, which is provided with the interdigital electrode having the electrode finger arrangement interval gradually changed, and is formed on a piezoelectric substrate having no dispersibility. Made the index smaller. For this reason, at an intersection where the frequency is high, it is possible to increase the value of the required electrode finger arrangement interval difference between adjacent intersections, and even if the electrode finger dimension has the minimum dimension unit, the same electrode finger arrangement interval can be set. Can be prevented, and an acoustic wave element having required characteristics can be obtained.

In the elastic wave device according to the ninth aspect of the present invention, at least one non-piezoelectric thin film having elastic wave dispersion characteristics is formed on the surface of the piezoelectric substrate, and the surface of any thin film of the above thin films or On the boundary surface between the thin film and the piezoelectric substrate, the interdigital electrode having the electrode finger array spacing gradually changed is provided, and the interdigital electrode is formed more than the case where the interdigital electrode is formed on the piezoelectric substrate having no dispersibility. The electrode index was increased. For this reason, since the electrode index is small, it is possible to prevent the amount of change in the adjacent electrode finger arrangement interval from becoming large, which makes it impossible to realize smooth dispersion characteristics, and it is possible to obtain an acoustic wave element having the required characteristics.

In the elastic wave element according to the tenth invention,
At least one piezoelectric thin film having elastic wave dispersion characteristics is formed on the surface of the non-piezoelectric substrate, and an electrode is formed on the surface of any of the thin films or on the boundary surface between the thin film and the non-piezoelectric substrate. The above-mentioned interdigital electrodes in which the finger arrangement interval was gradually changed were provided. Due to the dispersion characteristics of the thin film, the propagation path of the elastic wave has a characteristic that the propagation velocity varies depending on the frequency. Therefore, even if the electrode index of the drooping electrode required to achieve the required characteristics is too small or too large to achieve good characteristics, by using the dispersion characteristics of the thin film, By sharing the dispersion characteristics of the wave element with both the interdigital electrodes and the dispersion characteristics of the thin film, it is possible to obtain an acoustic wave element having the required characteristics. Further, even if the same electrode finger arrangement interval is continuous due to the minimum dimension unit of the electrode fingers, the group delay characteristics can be changed by the frequency due to the dispersion characteristics of the thin film. An element can be obtained.

In the elastic wave element of the eleventh aspect of the invention, at least one piezoelectric thin film having elastic wave dispersion characteristics is formed on the surface of the non-piezoelectric substrate, and the surface of any thin film or the above thin film is formed. On the boundary surface between the thin film and the non-piezoelectric substrate, the interdigital electrodes with the electrode finger arrangement interval gradually changed are provided, and the interdigital electrodes are arranged more than the case where the interdigital electrodes are formed on a non-dispersive piezoelectric substrate. The electrode index was reduced. Therefore, at an intersection where the frequency is high, it is possible to increase the value of the required electrode finger arrangement interval difference between adjacent intersections, and even if the electrode finger dimension has the minimum unit, the same electrode finger arrangement interval is maintained. It is possible to prevent continuous occurrence and obtain an acoustic wave device having required characteristics.

In the elastic wave element according to the twelfth invention,
At least one piezoelectric thin film having elastic wave dispersion characteristics is formed on the surface of the non-piezoelectric substrate, and an electrode finger is formed on the surface of any of the thin films or on the boundary surface between the thin film and the non-piezoelectric material. The interdigital electrodes having the arrangement intervals gradually changed were provided to increase the electrode index of the interdigital electrodes as compared with the case where the interdigital electrodes were formed on a non-dispersive piezoelectric substrate. For this reason, since the electrode index is small, it is possible to prevent the amount of change in the adjacent electrode finger arrangement interval from becoming large, which makes it impossible to realize smooth dispersion characteristics, and it is possible to obtain an acoustic wave element having the required characteristics.

In the elastic wave element according to the thirteenth invention,
The lower limit frequency of the pass band of the elastic wave element is f ₁ , the upper limit frequency is f ₂ , the cross width of the interdigital electrodes of the elastic wave element is W _0, and the propagation speed of the elastic wave in the interdigital electrode is V.
_{Let IDT} be the angle between the electrode finger of the output-side interdigital electrode and the wavefront of the above-mentioned elastic wave when the elastic wave excited by the input-side interdigital electrode reaches the output-side interdigital electrode. The shape of the extraction electrode end face was determined so as to satisfy the condition represented by the formula 9 or the condition represented by the formula 10 with n being an integer. The angle θ formed by the electrode fingers of the output-side interdigital transducer and the wavefront of the elastic wave is uniquely determined by the structure of the extraction electrode of the input-side interdigital electrode and the shape of the extraction electrode of the output-side interdigital electrode. The condition of the angle θ formed by the electrode fingers of the output-side interdigital transducer and the wavefront of the elastic wave has a range, which allows the shape of each extraction electrode of the input / output interdigital transducer to have a range. That is. Therefore, even if the propagation velocity of the elastic wave varies depending on the material, it is possible to obtain the acoustic wave element having the required characteristics by appropriately determining the shape of the extraction electrode corresponding to the range of the variation. it can.

In the elastic wave device of the fourteenth invention, the lower limit frequency of the pass band of the elastic wave device is f ₁ , and the upper limit frequency thereof is f ₁ .
₂ and the cross width of the interdigital electrodes of the above acoustic wave device is W
_0, and the propagation velocity of the elastic wave in the interdigital transducer is V
_IDT , when the angle formed between the electrode finger of the output-side interdigital electrode and the wavefront of the elastic wave when the elastic wave excited by the input-side interdigital electrode reaches the electrode in the output-side interdigital shape is θ Further, the shape of the shield electrode was determined so as to satisfy the condition represented by the formula 9 or the condition represented by the formula 10 with n being an integer. The angle θ formed by the electrode fingers of the output-side interdigital transducer and the wavefront of the elastic wave is unique depending on the structure of each extraction electrode of the input / output interdigital transducer and the shape of the shield electrode arranged between the input / output interdigital transducer. Since the condition of the angle θ formed by the electrode finger of the output-side interdigital transducer and the wavefront of the elastic wave has a range, it means that the shape of the shield electrode can have a range. is there. Therefore, even if the propagation velocity of the elastic wave varies depending on the material, it is possible to obtain the acoustic wave element having the required characteristics by appropriately determining the shape of the shield electrode corresponding to the range of the variation. it can.

[0067]

【Example】

Example 1. 1 is a diagram showing an acoustic wave device according to a first embodiment of the present invention.

An input side interdigital electrode 1a and an output side interdigital electrode 1b are formed on the upper surface of the piezoelectric material, and each interdigital electrode is common to a plurality of electrode fingers 2 and the base ends of those electrode fingers 2. It is composed of a pair of extraction electrodes 3 connected to each other. The electric terminal 4 is connected to one of the extraction electrodes, and the ground terminal 5 is connected to the other extraction electrode. The plurality of electrode fingers 2 connected to the electric terminal 4 and the plurality of electrode fingers 2 connected to the ground terminal intersect each other, and the elastic wave propagates in a direction perpendicular to each intersection. The electrode finger arrangement interval of the input-side interdigital transducer 1a is gradually reduced from the far side to the output-side interdigital electrode 1b,
The electrode finger arrangement interval of the output-side interdigital transducer 1b is symmetrical with the input-side interdigital transducer 1a. Here, it is the same as the conventional acoustic wave element of this type that the width of each adjacent electrode finger 2 and the gap between the electrode fingers 2 are configured to be substantially the same.

However, as in the conventional acoustic wave device, if the width of each adjacent electrode finger 2 and the gap between the electrode fingers 2 are substantially the same at a place where the electrode finger arrangement interval is small, the minimum dimension value of the electrode finger width is obtained. Therefore, the same electrode finger arrangement interval increases, so that in the acoustic wave device according to the first embodiment of the present invention, the area 1
1, the width of each adjacent electrode finger 2 and the ratio of the gap between the electrode fingers 2 are changed.

That is, in the acoustic wave device of this embodiment,
Assuming that the electrode finger width and the electrode finger spacing are both set to an integral multiple of the minimum dimension unit, the combination of the electrode finger width and the size of the electrode finger spacing at each intersection at the same array spacing is mutually Different. As a result, it is possible to prevent the occurrence of intersecting portions having the same geometrical configuration in the entire intersecting portions, and it is possible to make the center frequencies of the intersecting portions formed by the adjacent electrode fingers different from each other. Become.

FIG. 2 shows a first embodiment of the present invention shown in FIG.
A region 11 in which the electrode finger arrangement interval of the input-side interdigital transducer 1a of the elastic wave element shown in FIG. 2 is reduced and the ratio of the width of each adjacent electrode finger 2 and the gap between the electrode fingers 2 is changed is enlarged. ing. In the figure, the electrode finger number is i, the width of the electrode finger 2 of the electrode finger number i is L _i , and the electrode finger number i and the electrode finger number i +
The distance between the electrode finger centers between 1 is D _i, and the gap length between the electrode finger number i and the electrode finger number i + 1 is S _i . The minimum unit of the electrode finger width is Q, which is indicated by a broken line. Each electrode finger 2 has an edge on the broken line.

Here, the relationship between the electrode finger arrangement interval D _i and the center frequency f _i will be described in detail. The propagation velocity of the elastic wave between the electrode fingers 2 differs between the electrode finger 2 portion and the gap between the electrode fingers. The propagation velocity of the elastic wave at the electrode finger 2 is V
₁ , the propagation velocity of the elastic wave in the gap between the electrode fingers is V ₂
Then, the delay time τ _i required to propagate the electrode finger arrangement interval D _i is given by the following Expression 11.

Τ _i = 1/2 × ((L _i + L _{i + 1} ) / V ₁ ) + S _i / V ₂ (Equation 11) Then, the delay time required to propagate the electrode finger arrangement interval D _i The center frequency f _i when τ _i is given by Expression 12.

F _i = 1 / (2τ _i ) (Equation 12) As can be seen from Equations 11 and 12, the propagation velocity V ₁ of the elastic wave at the electrode finger 2 and the gap between the electrode fingers are Since the propagation velocity V ₂ of the elastic wave is different, the delay time τ _i between the electrode fingers 2 is changed and the center frequency f _i is changed by changing the ratio of the electrode finger width L _i and the gap length S _i. be able to. The propagation velocity V ₁ of the elastic wave at the electrode finger 2 is equal to the propagation velocity V _m when the surface of the substrate is covered with a conductor, and the propagation velocity V ₂ of the elastic wave at the gap between the electrode fingers is _If it is equal to the propagation velocity V _f on the free surface, the propagation velocity V ₁ ,
Between V ₂ and the electromechanical coupling coefficient k ² of the substrate, equation 1
It is shown in the above mentioned document A that there is a relationship of 3.

K ² = 2 (V ₂ −V ₁ ) / V ₂ (Equation 13) When Equation 13 is rewritten, Equation 14 is obtained.

[0076] When the ^{_{V 1 = (1-k 2}} /2) V 2 ... ( Equation 14) Equation 14 is organized into equation 11 to obtain an expression 15.

[0077]

[Equation 2] Equation 15 shows that if the ratio of (L _i + L _{i + 1} ) / 2 and S _i changes, the sum of the electrode finger arrangement intervals D _i is constant,
It shows that the delay time τ _i between the electrode fingers changes.
Therefore, the electrode finger widths L _i and L _{i + 1} and the electrode fingers L _i and L _i
By changing the ratio with the gap length S _i between _{i + 1,} the center frequency f _i of the intersection i can be changed. As shown in FIG. 1, for example, the electrode finger arrangement interval of the input-side interdigital transducer 1a is equal to the output-side interdigital transducer 1b.
In the area 11 where the same electrode finger arrangement interval is continuous due to the minimum dimension unit Q, the ratio of the electrode finger width L _i and the gap length S _i between the electrode fingers is set to the output side interdigital shape when If the distance is made closer to the electrode 1b, the delay time τ _i at each intersection is effectively decreased little by little, so that the deterioration of the characteristics due to continuous intersections having the same delay time is prevented. You can

Example 2. (Specific Example of First Embodiment) FIG. 3 is an example showing an electrode finger arrangement interval in an acoustic wave device of a second embodiment of the present invention. FIG. 3 shows, as an example, the selectable electrode finger width L _i and the gap length S _i between the electrode fingers when the electrode finger arrangement interval D _i is from 8Q to 6Q. All the numerical values in the figure indicate values divided by the minimum dimension unit Q.
In the figure, the electrode finger width indicates the sum (L _i + L _{i + 1} ) of two electrode finger widths across the intersection, and for example, the electrode finger width sum (L _i + L _{i + 1} ) is 4. Denoting the combination of L _i and L _{i + 1} when a _{(L i, L i + 1} ), the sum of the electrode finger _L i +
When L _{i + 1} is 4, (1, 3), (2, 2), (3,
There are three possibilities of 1). Thus, the combination of the gap length S _i between the electrode fingers L _i, L _{i + 1} and the electrode finger L _i, L _{i + 1} is greater than in the case shown in FIG.

In the example of the electrode finger arrangement interval which can be realized by the acoustic wave device of the second embodiment of the present invention shown in FIG. 3, the electrode finger arrangement interval D _i is 0.5 Q interval with respect to the minimum dimension unit Q. Can be set at any interval. On the other hand, FIG.
The electrode finger arrangement interval that can be realized by the conventional acoustic wave device shown in (1) can be transiently set to 0.5Q, but this transitional electrode finger arrangement interval cannot be made continuous, The actually realizable electrode finger arrangement interval D _i is a value every 2Q. That is, in the elastic wave device of the second embodiment of the present invention, since the ratio change between the width size and the gap length is utilized, the electrode finger arrangement interval D is four times finer than the conventional elastic wave device of this type. _i can be set.

FIG. 4 is a diagram showing the electrode finger arrangement interval D _i when the acoustic wave device of the second embodiment of the present invention is used, for example. In the figure, the horizontal axis is the electrode finger number i, and the vertical axis is the electrode finger arrangement interval D _i . 6 is the electrode finger arrangement interval D of the conventional acoustic wave device of this type when the minimum dimension unit Q is not set.
_i is 17 and 17 is an electrode finger arrangement interval D _{i according} to the acoustic wave device of the second embodiment of the present invention.

Compared with the conventional electrode finger arrangement interval D _i 7 of this type of acoustic wave device, the electrode finger arrangement interval D _i 17 according to the elastic wave device of the second embodiment of the present invention is equal to the electrode finger arrangement interval D _{i. i}
Shows a change close to the continuous electrode finger arrangement interval D _i 6 when the minimum size unit Q is not set.
As a result, the acoustic wave device according to the second embodiment of the present invention can obtain good characteristics with less in-band ripple.

FIG. 5 shows the delay time τ _i between the electrode fingers in the electrode finger arrangement interval shown in FIG. 3 when the Y-cut Z-propagating lithium niobate is used as the substrate material. Figure, the horizontal axis represents the respective electrode finger arrangement interval D _i shown in FIG. 3, the electrode sum of finger width (L _i of in each electrode finger arrangement interval D _i
+ L _{i + 1} ) and the gap length S _i between the electrode fingers are shown for each combination. The vertical axis shows the delay time τ between the electrode fingers
_i is shown. The electromechanical coupling coefficient k ² was set to 4.9%. The black squares are values that can be conventionally achieved by this type of acoustic wave device, and the white squares are values that can be achieved by the acoustic wave device of Example 2 of the present invention.

As shown in FIGS. 3 and 4, in the acoustic wave device according to the second embodiment of the present invention, the electrode finger arrangement interval D is set.
It is possible to set i at intervals of 0.5Q, where _i is the minimum size unit. Further, as shown in the elastic wave element according to the first embodiment of the present invention, since the propagation speed of the elastic wave in the electrode fingers and the propagation speed of the elastic wave in the gap between the electrode fingers are different, Sum of (L _i + L
_The delay time τ _i can be changed little by little by changing the ratio of ( _{i + 1} ) to the gap length S _i between the electrode fingers.
By utilizing this slight change, the interdigital transducer 1
It is possible to change the electrode finger arrangement interval D _{i in} the inside more continuously than in the conventional acoustic wave device of this type. For example, when the electrode finger arrangement interval D _i is 7Q, the sum of the electrode finger widths (L _i + L _{i + 1} ) is 6, and the gap length S _i between the electrode fingers is S _i.
With 1, the electrode finger arrangement interval D _i is as most delay time tau _i becomes longer when 7Q, when the electrode finger arrangement interval D _i is 7.5Q, the sum of the electrode finger width (L _i + L
_{i + 1} ) is set to 1.5 and the gap length S _i between the electrode fingers is set to 6.5, so that the delay time τ _i is set to be the shortest when the electrode finger arrangement interval D _i is 7.5Q. By doing
As shown in FIG. 5, the delay time difference can be set to 0.39Q / V ₂ . In the conventional acoustic wave device of this type, the difference in delay time τ _i is 2.03Q / V ₂ , so that the elastic wave device of the second embodiment of the present invention can realize a much smaller delay time difference. It is possible to arrange the electrode fingers 2.

Example 3. FIG. 6 is a view showing a part of the interdigital transducer 1 of the acoustic wave device according to the third embodiment of the present invention. In the figure, 2 is an electrode finger, and a broken line is a dimensional position that is an integral multiple of the minimum unit Q. Each electrode finger 2 has an arrangement interval D
arranged by _i .

The elastic wave element according to the third embodiment of the present invention shown in FIG. 6 has a minimum dimension unit Q in the area 11 where the electrode finger arrangement intervals D _i are the same. , The electrode finger width L _i is randomly changed. By changing the ratio of the electrode finger width L _i and the gap length S _i between the electrode fingers, the delay time τ _i between the electrode fingers can be changed as shown in an example in FIG. Delay time between electrode fingers τ
By changing _i at random, the center frequency f _i at each intersection also changes at random. The sum of the conversion efficiencies at the intersections is the sum of the characteristics in which the center frequency f _i changes in a random number, and the frequencies at which the conversion efficiencies are maximum do not overlap. As a result, the bandwidth of the sum of the conversion efficiencies of each intersection becomes wider than that in the case where the intersections having the same delay time τ _i between the electrode fingers are continuous, and the conversion efficiency of the adjacent intersections smoothly overlaps. Therefore, the ripples that occur in the characteristics of the interdigital transducer 1 can be reduced, and an acoustic wave device with excellent characteristics can be obtained.

Example 4. FIG. 7 is a diagram for explaining the operation of the acoustic wave device according to the fourth embodiment of the present invention. In the figure,
Reference numeral 18 is a stepped electrode finger in which the electrode finger width is partially changed, 19 is a thick portion of the electrode finger width, and the electrode finger width is M
_i is a portion having a narrow electrode finger width, and the electrode finger width is L _i . W ₀ is the length of the intersecting portion of the electrode fingers 18. In FIG. 7, the broken line indicates the position of an integral multiple of the minimum dimension unit Q.

The characteristic between the electrode fingers 18 is determined by the delay time τ _i for the elastic wave to propagate through the electrode finger arrangement interval D _i . Since the propagation velocity at the electrode finger 18 portion and the propagation velocity at the gap between the electrode fingers are slightly different, the delay time at the narrow electrode finger width portion 20 and the delay time at the thick electrode finger width portion 19 are increased. Have different values. When the same electrode finger 18 has a narrow electrode finger width portion 20 and a thick electrode finger width portion 19, each electrode finger 18 has the same potential, so that equivalently, the thin electrode finger width portion 20 and intersections made of the electrode fingers of the same electrode finger width L _i and, be regarded as a cross-section consisting of electrode fingers of the same electrode finger width M _i and the thick portion 19 of the electrode finger width is electrically connected in parallel You can That is, the characteristics of the intersections, and the characteristics of the cross-section consisting of electrode fingers of the same electrode finger width L _i a narrow portion 20 of the electrode finger width, thick portion of the electrode finger width 19
Can be regarded as the sum of the characteristics of the intersection portion formed by the electrode fingers having the same electrode finger width M _i . Therefore, for each intersection, by the ratio of the sum of the intersection widths of the portions where the thin electrode finger widths 20 intersect and the sum of the intersection widths of the portions where the thick electrode finger widths 19 intersect, The characteristics of the intersecting portion can be changed, and even if the electrode finger arrangement interval D _i is the same, it is possible to equivalently obtain the intersecting portion having different delay times, and the intersecting width W ₀ is equal to each electrode finger width. Since the ratio is usually considerably large, the ratio of the thin electrode finger width portion 20 to the thick electrode finger width portion 19 can be set almost continuously. Therefore, at a certain electrode finger arrangement interval D _i , the electrode finger width is reduced to the limit. The delay time in the case of the above can be set almost continuously from the delay time in the case of widening the electrode finger width to the limit. As a result, it is possible to obtain an acoustic wave device having good characteristics with little ripple.

Example 5. FIG. 8 is a diagram showing an acoustic wave device according to a fifth embodiment of the present invention. In the figure, the electrode finger number is i
The larger the electrode finger number, the thicker the electrode finger 1
The ratio of the narrow portion 20 of the electrode finger width to 9 is large. The broken line indicates a position that is an integral multiple of the minimum dimension unit Q, and a part of the electrode finger 18 having a width 4Q is thicker from the electrode finger i to i + 2, and the electrode finger i + 4 has a width 4Q.
Some of the electrode fingers are thin.

The crossing portion composed of electrode fingers having a narrow electrode finger width is
Than intersections consisting thick electrode finger 18 of the electrode finger width, the delay time tau _i when propagating through the electrode finger arrangement interval D _i is small. That is, the center frequency f _i becomes high. Therefore, the larger the ratio of the narrow electrode finger width portion 20 to the thicker electrode finger width portion 19 is, the higher the center frequency is. In the example of the acoustic wave device according to the fifth embodiment of the present invention shown in FIG. 8, the larger the electrode finger number i, the larger the ratio of the narrow electrode finger portion 20 to the thick electrode finger portion 19 is. Therefore, as the electrode finger number i increases, the center frequency f _i at each intersection increases. Therefore, as the electrode finger number i increases,
As the electrode finger number i as shown in FIG. 8 increases in a part or the whole of the interdigital electrode 1 in which the electrode finger arrangement interval is small, the electrode finger width with respect to the thicker electrode finger width 19 is increased. By using the electrode fingers 18 in which the ratio of the narrow portion 20 of the electrode finger is large, the center frequency can be changed even in the portion 11 where the electrode finger arrangement intervals of the same value are continuous, and a good acoustic wave element with less ripples can be obtained. Can be obtained.

Example 6. FIG. 9 is a diagram showing an acoustic wave device according to Example 6 of the present invention. In the figure, the electrode finger number is i
Then, the ratio of the thin portion 20 of the electrode finger to the thick portion 19 of the electrode finger width is randomly changed by the electrode finger 18. The broken line indicates the position of an integral multiple of the minimum dimension unit Q.

The delay time τ _i between the electrode fingers can be changed by changing the ratio of the narrow electrode finger width portion 20 to the wide electrode finger width portion 19. By randomly changing the delay time τ _i between the electrode fingers, the center frequency f _i at each intersection changes randomly. The sum of the conversion efficiencies at the intersections is the sum of the characteristics in which the center frequency f _i changes in a random number, and the frequencies at which the conversion efficiencies are maximum do not overlap. As a result, the bandwidth of the sum of the conversion efficiencies of each intersection becomes wider than that in the case where the intersections having the same delay time τ _i between the electrode fingers are continuous, and the conversion efficiency of the adjacent intersections smoothly overlaps. Therefore, the ripples that occur in the characteristics of the interdigital transducer 1 can be reduced, and an acoustic wave device with excellent characteristics can be obtained.

Example 7. 10 and 11 are diagrams showing elastic wave blocking according to the seventh embodiment of the present invention. FIG. 10 is a top view of an acoustic wave device according to Example 7 of the present invention,
FIG. 11 is a cross-sectional view taken along the line AB shown in FIG. In the figure, 21 is a piezoelectric substrate, and 22 is a non-piezoelectric thin film having dispersibility. As the input side interdigital transducer 1a is closer to the output side interdigital transducer 1b, the electrode finger arrangement interval increases, and the output side interdigital transducer 1b has a shape symmetrical to the input side interdigital transducer 1a. . For this reason,
The acoustic wave devices shown in FIGS. 10 and 11 show the characteristic that the delay time increases as the frequency increases. FIG. 12 is a diagram showing the dispersion characteristics of elastic waves in the thin film configuration including the non-piezoelectric thin film 22 and the piezoelectric substrate 21 shown in FIG. In the figure, the horizontal axis represents frequency and the vertical axis represents the propagation velocity of elastic waves. When the thin film 22 is provided,
Reference (hereinafter referred to as Reference B) "Surface Acoustic Wave Engineering", published by The Institute of Electronics and Communication Engineers, June 1985, pp. 82-90, the higher the frequency, the smaller the propagation velocity. The value of the propagation velocity with respect to frequency is
It is determined by the material of the substrate 21 and thin film 22 used, the thickness of the thin film, and the like.

As shown in FIG. 12, since the propagation velocity V decreases as the frequency f increases, the delay time also increases in the propagation path between the input / output interdigital transducers 1 as the frequency increases. Therefore, the delay time difference to be realized in the interdigital transducer 1 is obtained by subtracting the delay time difference in the propagation path. That is, in the interdigital transducer 1, the change amount of the delay time when the frequency changes by Δf is Δτ _IDT , the target value is Δτ, and the change in the delay time in the propagation path between the input / output interdigital transducer 1 is set. Δτ
_{If dly} , the relation of Expression 16 is obtained.

Δτ _IDT = Δτ−Δτ _dly (Equation 16) In the conventional elastic wave device of this type, the input / output interdigital transducer 1
Since there is no delay time difference due to the frequency in the propagation path between them, the interdigital transducer 1 of the acoustic wave device according to the seventh embodiment of the present invention.
Can reduce the delay time variation Δτ _IDT by the amount obtained by subtracting the delay time variation Δτ _dly on the propagation path. Reducing the delay time change amount Δτ _IDT in the interdigital transducer 1 means that the electrode index of the interdigital electrode 1 can be reduced, and the difference in the electrode finger arrangement interval between adjacent crossing portions is large. Therefore, even if there is the minimum dimension unit Q, it is possible to prevent the same electrode finger arrangement interval from continuing. As a result, in the conventional acoustic wave device of this type, even when the electrode index of the interdigital transducer 1 becomes too large and the same electrode finger arrangement interval is continuous in the region where high frequency is excited, the same electrode fingers are arranged. Since the range of the region where the finger arrangement intervals are continuous can be reduced, it is possible to suppress the occurrence of ripples to a low level. Further, even in the region where the same electrode finger arrangement interval is continuous, the delay time changes depending on the frequency, so that a better delay time characteristic than that of the conventional acoustic wave device of this type can be realized.

Example 8. 13 and 14 are views showing an acoustic wave device according to Example 8 of the present invention. 13 is a top view of an acoustic wave device according to Example 8 of the present invention, and FIG.
FIG. 14 is a cross-sectional view taken along the line AB shown in FIG. 13. 2 in the figure
Reference numeral 1 is a piezoelectric substrate, and 22 is a "non-piezoelectric" thin film having dispersibility. As the input side interdigital transducer 1a is closer to the output side interdigital transducer 1b, the electrode finger arrangement interval becomes smaller, and the output side interdigital transducer 1b is symmetrical to the input side interdigital transducer 1a. . For this reason, the elastic wave elements shown in FIGS. 13 and 14 show the characteristic that the delay time becomes smaller as the frequency becomes higher. The characteristic of the propagation path composed of the piezoelectric substrate 21 and the non-piezoelectric thin film 22 is such a characteristic that the propagation velocity decreases as the frequency increases, as shown in FIG.

Since the elastic wave elements shown in FIGS. 13 and 14 have the characteristic that the delay time decreases as the frequency increases, the delay time difference Δτ _IDT of the interdigital transducer 1 when the frequency is changed is This is the delay time difference Δτ required for the element plus the delay time difference Δτ _dly in the propagation path between the input / output interdigital transducers 1. The interdigital transducer 1 of the acoustic wave device according to the eighth embodiment of the present invention can increase the delay time change amount Δτ _IDT by an amount corresponding to the addition of the delay time change amount Δτ _dly in the propagation path. Increasing the delay time variation Δτ _IDT at the interdigital transducer 1 means
It is possible to increase the number of the interdigital electrodes 1, and it is possible to reduce the difference between the adjacent electrode finger arrangement intervals so that the characteristics of each intersection smoothly change. As a result, in the conventional acoustic wave device of this type, the electrode index of the interdigital electrode 1 becomes too small, the adjacent electrode finger arrangement interval difference becomes small, and the characteristics of each intersection smoothly change. Therefore, it is possible to suppress the occurrence of ripples to a low level.

Example 9. 15 and 16 are diagrams showing an acoustic wave device according to a ninth embodiment of the present invention. FIG. 15 is a top view of an acoustic wave device according to Example 7 of the present invention,
16 is a cross-sectional view taken along the line AB shown in FIG. In the figure, 23 is a non-piezoelectric substrate, and 24 is a "piezoelectric" thin film having dispersibility. Input side interdigital transducer 1a
, The electrode finger arrangement interval becomes larger as it gets closer to the output-side interdigital transducer 1b, and the output-side interdigital transducer 1b is symmetrical with the input-side interdigital transducer 1a.
For this reason, the acoustic wave devices shown in FIGS. 15 and 16 show the characteristic that the delay time increases as the frequency increases. Dispersion characteristics of elastic waves in the thin film configuration including the piezoelectric thin film 24 and the non-piezoelectric substrate 23 shown in FIG. June 1985, pp. 69
As shown by -74, as the frequency becomes higher, the propagation velocity becomes smaller, which is the characteristic shown in FIG. The value of the propagation velocity with respect to the frequency is determined by the material of the substrate 23 and thin film 24 used, the thickness of the thin film, and the like.

The interdigital transducer 1 of the acoustic wave device according to the ninth embodiment of the present invention has a delay time variation Δτ in the propagation path between the input / output interdigital transducers 1 as compared with the conventional acoustic wave device of this type.
The delay time change amount Δτ _IDT of the interdigital transducer 1 can be reduced by the amount obtained by subtracting _dly . Decreasing the delay time variation Δτ _IDT at the interdigital transducer 1 means
Since the electrode index of the interdigital electrode 1 can be reduced, the difference in the electrode finger arrangement interval between adjacent crossing portions becomes large, and the same electrode finger arrangement interval is continuous even if the minimum dimension unit Q exists. Can be prevented. As a result, in the conventional acoustic wave device of this type, even when the electrode index of the interdigital transducer 1 becomes too large and the same electrode finger arrangement interval is continuous in the region where high frequency is excited, the same electrode fingers are arranged. Since the range of the region where the finger arrangement intervals are continuous can be reduced, it is possible to suppress the occurrence of ripples to a low level. Further, even in the region where the same electrode finger arrangement interval is continuous, the delay time changes depending on the frequency, so that a better delay time characteristic than that of the conventional acoustic wave device of this type can be realized.

Example 10. 17 and 18 show
It is a figure which shows the acoustic wave element which concerns on Example 10 of this invention. 17 is a top view of an acoustic wave device according to a tenth embodiment of the present invention, and FIG. 18 is a cross-sectional view taken along the line AB of FIG. In the figure, 23 is a non-piezoelectric substrate, and 24 is a "piezoelectric" thin film having dispersibility. As the input side interdigital transducer 1a is closer to the output side interdigital transducer 1b, the electrode finger arrangement interval becomes smaller, and the output side interdigital transducer 1b is symmetrical to the input side interdigital transducer 1a. . For this reason, the acoustic wave devices shown in FIGS. 17 and 18 show the characteristic that the delay time decreases as the frequency increases. The characteristics of the propagation path composed of the non-piezoelectric substrate 23 and the piezoelectric thin film 24 are as shown in FIG.
The characteristic is that the propagation velocity decreases as the frequency increases.

Since the elastic wave elements shown in FIGS. 17 and 18 have the characteristic that the delay time decreases as the frequency increases, the delay time difference Δτ _IDT of the interdigital transducer 1 when the frequency is changed is It is the delay time difference Δτ required for the element plus the delay time difference Δτ _dly in the transmission line between the input / output interdigital transducers 1. Embodiment 10 of the present invention
Interdigital transducer 1 of the acoustic wave element according to the amount corresponding to plus delay time variation .DELTA..tau _{dl y} in the transmission path, it is possible to increase the delay time change dormitory .DELTA..tau _IDT. Interdigital transducer 1
It is possible to increase the electrode index of, and it is possible to make the difference between the adjacent electrode finger arrangement intervals small so that the characteristics of each crossing change smoothly. As a result, in the conventional acoustic wave device of this type, the electrode index of the interdigital electrode 1 becomes too small, the adjacent electrode finger arrangement interval difference becomes small, and the characteristics of each intersection smoothly change. Therefore, it is possible to suppress the occurrence of ripples to a low level.

Example 11. FIG. 19 is a diagram showing an acoustic wave device according to Example 11 of the present invention. In the figure, 25 is an end surface of the extraction electrode 3b for refraction correction, 26 is a direction perpendicular to the wavefront of the elastic wave, and 27 is a tangent line of the extraction electrode end surface 25 for refraction correction. A boundary surface 15 between the electrode finger 2 and the inner extraction electrode 3b has an inclination of an angle θ _IDT with respect to the propagation direction of the elastic wave. FIG. 20 is a diagram for explaining the operation when an obliquely incident elastic wave is received at the intersection of the electrode fingers 2. In the figure, 28 is the wavefront of the elastic wave, which is shown at intervals of half the wavelength λ. Wavefront 28
The perpendicular line 26 has an inclination of an angle θ with the X axis which is the propagation direction. Reference numeral 29 shows the intersection of the interdigital electrode 1 as a line wave source, and the integrated potential of the elastic wave along the line wave source 29 is proportional to the electric power received by the line wave source 29. The angle θ formed by the perpendicular line 26 of the wavefront 28 and the X axis, which is the propagation direction, is determined by the wavefront 28 and the line wave source 2
It is the same as the angle formed by 8.

The elastic wave excited at the intersection of the electrode fingers 2 of the input-side interdigital electrode 1a propagates in the direction perpendicular to the intersection, and the elastic wave reaching the output-side interdigital electrode 1b is output again. It is converted into an electric signal at the intersection of each electrode finger 2 of the side-comb-shaped electrode 1b. At this time, elastic waves obliquely enter the boundary surface 15 between the electrode finger 2 and the inner extraction electrode 3b and the end surface 25 of the inner extraction electrode 3b.
Refraction occurs according to the values of the propagation velocity V _IDT in a certain region, the propagation velocity V _m at the extraction electrode 3b, and the propagation velocity V _f at the free surface. Usually, the elastic wave changes its propagation direction by refraction, but in a piezoelectric material such as Y-cut Z-propagation lithium niobate, the wavefront of the elastic wave 28 is not changed in the propagation direction.
There are things that only turn. Angle θ shown in FIG.
₁ , θ ₂ , θ ₃ , θ ₄ , θ ₅ , θ ₆ , θ ₇ , and θ ₈ are the normal line of the wavefront 28 of the elastic wave and the normal line of each boundary surface having points B, C, D, and E. It is an angle. These angles satisfy Snell's law at each point B, C, D, and E, and satisfy the following four expressions.

Sin (θ ₂ ) / sin (θ ₁ ) = V _m / V _IDT (Equation 17) sin (θ ₄ ) / sin (θ ₃ ) = V _f / V _m (Equation 18) sin (θ) ₆ ) / sin (θ ₅ ) = V _m / V _f (Equation 19) sin (θ ₈ ) / sin (θ ₇ ) = V _IDT / V _m (Equation 20) In addition, the interdigital transducer 1 and the inside The inclination angle θ _IDT of the boundary 15 with the extraction electrode 3b, the inclination angle θp of the tangent line 27 in an arbitrary propagation path of the elastic wave of the inner extraction electrode end surface 25, and θ ₁ , θ ₂ , θ ₃ , θ ₄ , θ. ₅ , θ ₆ ,
There is a geometrical relationship between θ ₇ and θ ₈ as follows.

Θ ₁ + θ _IDT = 90 ° (Equation 21) θ ₂ -θ ₃ = θ _p -θ _IDT (Equation 22) θ ₄ + θ ₅ +2 θ _p = 180 ° (Equation 23) θ ₇ -θ ₆ = Θ _p −θ _IDT (Equation 24) Further, the angle θ formed by the perpendicular of the wavefront 28 and the elastic wave propagation direction has the relationship of Equation 25 between the angle θ ₈ .

Θ = θ ₈ + θ _IDT −90 ° (Equation 25) By using Equation 17 to Equation 25, the inclination angle θ _IDT of the boundary surface 15 between the electrode finger 2 and the inner extraction electrode 3b, and Inclination angle θp of the tangent to the extraction electrode end surface 25 of
Is determined, the angle θ between the wavefront 28 of the elastic wave reaching the output-side interdigital transducer 1b and the linear wave source 29 is uniquely determined. That is, the inclination angle θ _IDT of the boundary surface 15 between the electrode finger 2 and the inner extraction electrode 3b, and the wavefront 28 and the line wave source 29 of the elastic wave reaching the output-side interdigital electrode 1b.
It is also possible to uniquely determine the inclination angle θ _p of the tangent line of the end surface 25 of the inner extraction electrode by determining the angle θ formed by In the conventional elastic wave element of this type, only the condition that the angle θ formed by the wavefront 28 of the elastic wave reaching the output-side interdigital transducer 1b and the linear wave source 29 is zero is used.

Next, the influence when the wavefront 28 and the linear wave source 29 have an angle θ will be described. Assuming that the direction parallel to the line wave source 29 is the Y axis, the potential φ (X, X,
Y) is given by the following equation.

Φ (X, Y) = φ ₀ e ^{j (ωt-k (Xcos θ-Y sin θ))} (Equation 26) Here, φ ₀ indicates the amplitude of the propagating elastic wave, and k indicates the wave number. I shall. The received power P _i at the line wave source 29 is φ
Since (X, Y) is integrated over the intersection width W, the result of Expression 27 is obtained.

[0108]

[Equation 3] Here, θ is given by Equation 28.

Θ = (kW / 2) sin θ (Equation 28) The received power P of the interdigital transducer 1 is given by Equation 29 in which the received power P _i at the intersection _i is summed over all the intersections.

[0110]

[Equation 4] Expression 29 becomes zero when the condition of Expression 30 is satisfied. This corresponds to the zero point where the loss of the acoustic wave element becomes extremely large.

Θ = (kW / 2) sin θ = nπ (n is an integer) (Equation 30) Since the wave number k has the relationship of Equation 31 using the propagation velocity V _IDT frequency f of the elastic wave, elasticity The frequency f at which the zero point occurs in the pass characteristic of the wave element is given by equation 32.

K = 2πf / V _IDT (Equation 31) f = V _IDT / (W · sin θ) × n (n is an integer) (Equation 32) From Equation 32, the wavefront 28 of the elastic wave is in the form of a comb on the output side. Electrode 1
When incident on b with a cross width and an inclination of an angle θ, the pass characteristic of this acoustic wave element causes a zero point at a frequency that satisfies Expression 32. Here, if the lower frequency of the pass band of the acoustic wave element is f ₁ and the higher frequency thereof is f ₂ , the inner extraction electrode is arranged so that the zero point does not occur at a frequency lower than the frequency f _2. By determining the shape of 3b, even if the wavefront 28 of the elastic wave is inclined with respect to the intersection, its influence can be reduced.

[0113]

[Equation 5] Alternatively, by determining the shape of the inner extraction electrode 3b so as to satisfy Expression 34 with respect to the integer n, it is possible to prevent a zero point from occurring in the pass band of the acoustic wave device.

[0114]

[Equation 6] For example, in an acoustic wave device having a pass band of 500 MHz to 1 GHz, the propagation velocity V _f on the free surface is 3500 (m / s
ec), and the propagation velocity V _m at the extraction electrode 3b is 34
14 (m / sec), and the propagation velocity V _IDT in the region where the electrode finger 2 is present is a value between 3500 and 3414, 3457.
(M / sec) constant, the cross width W of the electrode fingers 2 is 100
.mu.m, and the inclination angle _.theta.IDT is 30.degree. From Equation 33, the inclination angle θ of the wavefront 28 of the elastic wave is calculated by Equation 3
It is necessary to satisfy 5.

[0115]

[Equation 7] On the other hand, using Equation 17 to Equation 25 with θ _p as a variable,
Is obtained, the result shown in FIG. 21 is obtained. In the figure, the horizontal axis is the inclination angle θ _p of the extraction electrode 3b, and the vertical axis is the inclination angle θ of the wavefront 28 of the elastic wave reaching the output-side interdigital transducer 1b. When the inclination angle θ _p of the extraction electrode 3b that satisfies the condition of Expression 35 is obtained, it becomes 25 ° <θ _p <96 ° (Expression 36). When the boundary surface 15 between the electrode finger 2 and the inner extraction electrode 3b is linear and the propagation velocity V _IDT in a certain area of the electrode finger 2 is constant, the inner extraction electrode 3
The shape of the end surface 25 of b is linear. The shape of the inner extraction electrode 3b is set to a tilt angle θ _p within a range that satisfies Expression 36.
By having the above, it is possible to obtain an acoustic wave device having required characteristics.

FIG. 22 shows the inclination angle θ of the wavefront 28 of the elastic wave calculated by using Equations 17 to 25 with the propagation velocity V _IDT of the elastic wave in a certain area of the electrode finger 2 changed and θ _p as a variable.
Is. The numerical values used for the calculation are the same as those in the case of FIG. 21, except for the propagation velocity V _IDT of the elastic wave in the region where the electrode finger is present. From FIG. 22, when the range of the inclination angle θ _p of the extraction electrode on the inside which satisfies the expression 35 is obtained, it becomes 29 ° <θ _p <86 ° (Expression 37). Even if the variation in the propagation velocity V _IDT of the elastic wave in the region where the electrode finger 2 is present is 3460 ± 10 (m / sec), the shape of the inner extraction electrode end face 25 is set so as to satisfy Expression 37. As a result, the acoustic wave device can realize the required characteristics.

Example 12. FIG. 23 is a diagram showing an acoustic wave device according to Example 12 of the present invention. In the figure, 30 is a shield electrode arranged between the input / output interdigital electrodes 1,
Reference numeral 31 is an end face on which the elastic wave is incident. Each end face 31 has an inclination of an angle θ _s with respect to the elastic wave propagation direction. Angle θ
_a , θ _b , θ _c , and θ _d are the wavefronts 28 of the elastic waves, respectively.
Is the angle formed by the vertical line 26 and the vertical line of the end face 31. Points E and F are points on the end face 31 of the shield electrode 30 through which the elastic wave propagating through the points B, C, D, and E passes.

The elastic wave element according to the twelfth embodiment of the present invention shown in FIG. 23 uses refraction of the elastic wave at the end face 31 of the shield electrode 30 arranged between the input / output interdigital transducers 1 to obtain the required characteristics. Obtain an acoustic wave device. The relational expressions of the refraction of the elastic wave at the points B, C, D and E are the same as the expressions 17 to 20. Further, the equations 21, 22, 24, and 25 are similarly established. Relational expression of refraction at points E and F and angles θ _a and θ
The relational expressions of _b , θ _c and θ _d and the angles θ ₄ , θ ₅ and θ _s are obtained by the equations 38 to 42.

Sin θ _b / sin θ _a = V _m / V _f (Equation 38) sin θ _d / sin θ _c = V _f / V _m (Equation 39) θ _a = θ ₄ + θ _p −θ _s (Equation 40) θ _b + θ _c +2 θ _s = 180 ° (Formula 41) θ ₅ = θ _d + θ _s −θ _p (Formula 42) Formula 17 to Formula 20, Formula 21, 22, 24, 25, and Formula 38 to Formula When 42 is used, the inclination angle θ _s of the shield electrode end face 31 and the inclination angle θ of the wavefront 28 of the elastic wave reaching the output-side interdigital transducer 1b are used as in FIGS.
You can ask for a relationship with. On the other hand, since the conditional expression for obtaining the required characteristics of the elastic wave element is Expression 33 or Expression 34, from the range of the inclination angle θ of the wavefront 28 of the elastic wave reaching the output-side interdigital transducer 1b, The range of the tilt angle θ _s of the shield electrode end face 31 can be determined.
That is, by determining the shape of the shield electrode end face 31 so as to satisfy Expression 33 or Expression 34, it is possible to obtain an elastic wave element having a required characteristic even if the propagation speed of the elastic wave varies. .

Next, a modified example will be described.

In all of the acoustic wave devices shown in Examples 1 to 6 of the present invention, the cross widths of the electrode fingers 2 were the same,
The present invention is not limited to this, and the same effect is obtained even if the cross width of the electrode fingers 2 is changed. Further, in all of the elastic wave elements shown in Examples 1 to 6 of the present invention, the electrode fingers 2 are arranged along the propagation direction of the elastic wave, but the present invention is not limited to this, and for example, as shown in FIG. The same effect can be obtained by applying the electrode finger 2 as shown in 24 to a slant electrode that is displaced in the direction perpendicular to the propagation direction of the elastic wave. Furthermore, Example 1 of the present invention
The elastic wave elements shown in 6 to 6 are effective even if they are applied when the delay time becomes shorter as the frequency becomes higher or when the delay time becomes longer as the frequency becomes higher. Are the same. Further, as shown in FIG. 25, the same effect can be obtained even if the input / output interdigital transducers 1 are arranged in the same direction and applied to an acoustic wave device having a constant delay time regardless of frequency. is there. further,
A region where the ratio of the electrode finger width L _{i to} the electrode finger arrangement interval D _i is changed and a region where the electrode finger width is changed for each electrode finger are limited to the narrow electrode finger region 11 in the interdigital transducer 1. However, it may be applied to any region in the interdigital transducer 1.

The elastic wave elements shown in Embodiments 7 and 8 of the present invention are composed of a single layer of non-piezoelectric thin film 22 on a piezoelectric substrate 21.
And the interdigital transducer 1 on the non-piezoelectric thin film 22.
However, the present invention is not limited to this, and as shown in FIG. 26, the effect is the same even if the interdigital electrode 1 is formed at the boundary between the piezoelectric substrate 21 and the non-piezoelectric thin film 22. Further, as shown in FIG. 27, the non-piezoelectric thin film 22 may be formed on the piezoelectric substrate 21, and the thin film 32 may be further formed on it. The thin film 32 has the same effect whether it is piezoelectric or non-piezoelectric. Further, as shown in FIG. 28, the thin film 3
2 can also be applied to the case where the region is limited, such as being formed only on the interdigital transducer 1. Further, the thin film 3
2 may be formed between the piezoelectric substrate 21 and the non-piezoelectric thin film 22. The position of the interdigital transducer 1 is the piezoelectric substrate 2
1, the boundary of the non-piezoelectric thin film 22, the thin film 32, or
It may be formed on the surface.

Similarly, the ninth and tenth embodiments of the present invention.
In the acoustic wave device shown in FIG. 1, one layer of the piezoelectric thin film 24 is formed on the non-piezoelectric substrate 23, and the interdigital electrode 1 is formed on the piezoelectric thin film 24. Not limited to this, as shown in FIG. 29, the same effect can be obtained even if the interdigital electrode 1 is formed at the boundary between the non-piezoelectric substrate 23 and the piezoelectric thin film 24. Further, as shown in FIG. 30, the non-piezoelectric substrate 2
3, a piezoelectric thin film is formed on top of which a thin film 32 is further formed.
May be configured. The thin film 32 has the same effect whether it is piezoelectric or non-piezoelectric. Furthermore, as shown in FIG. 31, the present invention can be applied to the case where the region is limited such that the thin film 32 is formed only on the interdigital transducer 1, for example. further,
The thin film 32 may be formed between the non-piezoelectric substrate 23 and the piezoelectric thin film 24. The position of the interdigital transducer 1 is at the boundary of the non-piezoelectric substrate 23, the piezoelectric thin film 24, and the thin film 32,
Alternatively, it may be formed on the surface.

In the acoustic wave device according to the eleventh embodiment of the present invention, the boundary 15 between the electrode finger 2 and the inner extraction electrode 3b is linear, but the present invention is not limited to this, and, for example,
As shown in FIG. 32, the electrode finger 2 and the inner extraction electrode 3
It is also applicable when the boundary 15 with b is a curve. In this case, regarding the propagation path of each elastic wave, the angle formed by the tangent of the boundary 15 between the electrode finger 2 and the inner extraction electrode 3b and the elastic wave propagation direction is θ _IDT , and the inner extraction electrode end surface 2
The angle θp formed by the tangent line 27 of 5 and the elastic wave propagation direction may be determined. At this time, the inner extraction electrode end surface 25 may also be a curve, and if the expression 33 or the expression 34 is satisfied, the inner extraction electrode end surface 25 may be linearly configured as shown in FIG. . Further, as shown in FIG. 33, the inner extraction electrode end surface 25 may be divided into a plurality of regions, and each region may be linearly configured. Furthermore, in the eleventh embodiment, the case where Expression 33 is satisfied has been described, but the present invention is not limited to this, and the inner extraction electrode end surface 25 may be determined so as to satisfy Expression 34. Further, the shape of the boundary 15 between the electrode finger 2 and the inner lead electrode 3b and the shape of the inner lead electrode end surface 25 may be changed between the input side interdigital electrode 1a and the output side interdigital electrode 1b.

The elastic wave element according to the twelfth embodiment of the present invention has a boundary 15 between the electrode finger 2 and the inner extraction electrode 3b.
The shapes of the inner extraction electrode end surface 25 and the shield electrode end surface 31 are linear, but the present invention is not limited to this, and for example, as shown in FIG. 34, the boundary between the electrode finger 2 and the inner extraction electrode 3b. 15, the inner extraction electrode end surface 25,
The shape of any part of the shield electrode end face 31 may be curved. In this case, the shape of the curved portion may be determined using the angle formed by the tangent line of the curved portion. Further, as shown in FIG. 35, the shield electrode end face 31 may be divided into a plurality of regions, and each of the divided portions may have a linear configuration.

Further, although the elastic wave elements shown in the eleventh and twelfth embodiments have been shown to have a configuration in which the delay time becomes shorter as the frequency becomes higher, the present invention is not limited to this, and the frequency becomes higher. Therefore, it can be applied even when the delay time becomes large. Further, the angle formed by the inner extraction electrode end face 25 with the elastic wave propagation direction and the angle formed by the shield electrode end face 31 with the elastic wave propagation direction are shown as acute angles, but they may be obtuse angles. These angle conditions are based on the results of Expression 33 and Expression 34.
Further, the output side interdigital transducer 1b is formed by the shapes of both the lead-out electrode end face 25 and the shield electrode end face 31 on the inner side.
You may control the wavefront of the elastic wave which reached | attained.

Example 2, Example 11, and Example 1
The acoustic wave device shown in 2 is shown for the case of a lithium niobate substrate, but the present invention is not limited to this, and the ratio of the electrode finger width L _i to the electrode finger arrangement interval D _i is changed, or each electrode finger is changed. The interdigital electrode 1 having a structure having a region for changing the electrode finger width can be applied to any substrate material and thin film material, and only the inside extraction electrode end face 25 and the shield electrode end face are inclined, and the elastic wave propagation direction The same can be applied as long as it is a substrate material or a material having a thin film structure, in which is substantially unchanged.

[0128]

As described above, according to the first aspect of the present invention, the electrode finger width and the gap length of the adjacent electrode finger are partially or entirely formed at the portion where the electrode fingers of the interdigital electrode having different potentials intersect. A region having a different ratio to is provided. For this reason,
It is possible to prevent continuous intersections having the same center frequency and obtain an acoustic wave device having required characteristics.

As described above, according to the second aspect of the present invention, the electrode finger arrangement interval of the interdigital electrode gradually decreases in a part or the whole of the portion where the interdigital electrode fingers of the interdigital electrode cross each other. In the direction of the finger order, the ratio of the electrode finger width to the gap length of the adjacent electrode fingers was gradually decreased. Therefore, the center frequency of the portion having the same electrode finger arrangement interval can be gradually increased, and the same center It is possible to prevent continuous frequency crossing portions and obtain an acoustic wave device having required characteristics.

As described above, according to the third aspect of the present invention, the ratio of the electrode finger width to the gap length of the adjacent electrode fingers is part or all of the portion where the electrode fingers of the interdigital electrode having different potentials intersect. Was randomly changed. Therefore, by randomly changing the ratio of the electrode finger width to the gap length of adjacent electrode fingers, it is possible to prevent the intersections of the same center frequency from continuing and obtain an acoustic wave device having the required characteristics. You can

As described above, according to the fourth aspect, the ratio of the electrode finger width to the gap length of the adjacent electrode fingers is partly or wholly at the portion where the electrode fingers of the interdigital electrode having different potentials intersect. To have stepped electrode fingers that vary. Therefore, by using a stepped electrode finger in which the ratio of the electrode finger width to the gap length of adjacent electrode fingers changes, it is possible to prevent continuous intersections of the same center frequency from continuing and to provide an acoustic wave device having the required characteristics. Can be obtained.

As described above, according to the fifth invention, the ratio of the electrode finger width to the gap length of the adjacent electrode fingers is partly or wholly at the portion where the electrode fingers of the interdigital electrode having different potentials intersect. In the direction of the electrode finger sequence in which the electrode finger arrangement interval of the interdigital electrode gradually decreases, the ratio of the electrode finger width to the gap length of the adjacent electrode fingers in each electrode finger. Of the total width in the cross width direction, the ratio of the total length in the cross width direction of the area having a small ratio of the electrode finger width to the gap length of the adjacent electrode fingers is gradually increased. did. Therefore, the sum of the lengths in the cross width direction of the regions in which the ratio of the electrode finger width to the gap length of the adjacent electrode fingers in each electrode finger is large and the ratio of the electrode finger width to the gap length of the adjacent electrode fingers. By gradually decreasing the ratio of the area of small area to the total length in the cross width direction, the center frequency is equivalently increased gradually. As a result, it is possible to prevent continuous intersections having the same center frequency and obtain an acoustic wave device having desired characteristics.

As described above, according to the sixth aspect of the present invention, the ratio of the electrode finger width to the gap length of the adjacent electrode fingers is part or all of the portion where the electrode fingers of the interdigital electrode having different potentials intersect. Has a stepped electrode finger that changes, the total of the lengths in the cross width direction of the region where the ratio of the electrode finger width to the gap length of the adjacent electrode finger in each electrode finger is large and the gap between the adjacent electrode fingers. The ratio of the region having a small ratio of the electrode finger width to the length to the total length in the cross width direction was randomly changed. Therefore, by using electrode fingers whose ratio of the electrode finger width to the gap length of adjacent electrode fingers changes in a random manner, it is possible to prevent continuous intersections of the same center frequency from continuing, and to obtain an elastic wave having the required characteristics. An element can be obtained.

As described above, according to the seventh aspect of the present invention, at least one non-piezoelectric thin film having elastic wave dispersion characteristics is formed on the surface of the piezoelectric substrate, and any one of the above thin films is formed. The interdigital electrodes with the electrode finger arrangement intervals gradually changed were provided on the surface or the boundary surface between the thin film and the piezoelectric substrate. Therefore, even if the electrode index of the drooping electrode required to achieve the required characteristics is too small or too large to achieve good characteristics, by using the dispersion characteristics of the thin film, By sharing the dispersion characteristics of the wave element with both the interdigital electrodes and the dispersion characteristics of the thin film, it is possible to obtain an acoustic wave element having the required characteristics. Further, even if the same crossing portion continues due to the minimum dimension unit of the electrode finger, the group delay characteristic can be changed depending on the frequency due to the dispersion characteristic of the thin film. Obtainable.

As described above, according to the eighth aspect of the present invention, at least one non-piezoelectric thin film having elastic wave dispersion characteristics is formed on the surface of the piezoelectric substrate, and any one of the above thin films is formed. On the surface or on the boundary surface between the thin film and the piezoelectric substrate, the interdigital electrodes having the electrode finger array spacing gradually changed are provided, and the interdigital pattern is formed on the piezoelectric substrate having no dispersibility. The electrode index of the electrode was reduced. Therefore, at a high frequency intersection, it is possible to increase the value of the required characteristic difference between the adjacent intersections, and even if the electrode finger dimension has a minimum dimension unit,
It is possible to prevent the same intersection from continuing and obtain an acoustic wave device having required characteristics.

As described above, according to the ninth invention, at least one non-piezoelectric thin film having elastic wave dispersion characteristics is formed on the surface of the piezoelectric substrate, and any of the above thin films is formed. On the surface or on the boundary surface between the thin film and the piezoelectric substrate, the interdigital electrodes having the electrode finger array spacing gradually changed are provided, and the interdigital pattern is formed on the piezoelectric substrate having no dispersibility. The electrode index of the electrode was increased. For this reason, since the electrode index is small, it is possible to prevent the amount of change in the adjacent electrode finger arrangement interval from becoming large, which makes it impossible to realize smooth dispersion characteristics, and it is possible to obtain an acoustic wave element having the required characteristics.

As described above, according to the tenth invention, at least one piezoelectric thin film having elastic wave dispersion characteristics is formed on the surface of the non-piezoelectric substrate, and the surface of any thin film among the above thin films is formed. Alternatively, the interdigital electrode having the electrode finger arrangement interval gradually changed is provided on the boundary surface between the thin film and the non-piezoelectric substrate. Therefore, the interdigital electrode required to realize the required characteristics is provided. Even when the electrode index is too small or too large to achieve good characteristics, the dispersion characteristics of the acoustic wave element can be used for both the interdigital electrode and thin film dispersion characteristics by utilizing the dispersion characteristics of the thin film. By sharing, it is possible to obtain an acoustic wave device having required characteristics. Further, even if the same crossing portion continues due to the minimum dimension unit of the electrode finger, the group delay characteristic can be changed depending on the frequency due to the dispersion characteristic of the thin film. Obtainable.

As described above, according to the eleventh invention, at least one piezoelectric thin film having elastic wave dispersion characteristics is formed on the surface of the non-piezoelectric substrate, and any one of the above thin films is formed. On the surface or on the boundary surface between the thin film and the non-piezoelectric substrate, the interdigital electrodes in which the electrode finger arrangement interval is gradually changed are provided, and the above-mentioned interlace is more than the case where the interdigital electrode is formed on a non-dispersive piezoelectric substrate. The electrode index of the strip electrodes was reduced. Therefore, at intersections with high frequencies,
It is possible to increase the value of the required electrode finger arrangement interval difference between adjacent intersections, and prevent the same intersection from continuing even if there is a minimum dimension unit in the electrode finger dimension, and it has the required characteristics. An acoustic wave device can be obtained.

As described above, according to the twelfth invention, at least one piezoelectric thin film having elastic wave dispersion characteristics is formed on the surface of the non-piezoelectric substrate, and any one of the above thin films is formed. On the surface or on the boundary surface between the thin film and the non-piezoelectric substrate, the interdigital electrodes in which the electrode finger arrangement interval is gradually changed are provided, and the above-mentioned interlace is more than the case where the interdigital electrode is formed on a non-dispersive piezoelectric substrate. The electrode index of the electrode is increased. For this reason, it is possible to prevent the change amount of adjacent crossing characteristics from increasing due to a small electrode index, and it is possible to prevent a smooth dispersion characteristic from being realized, and it is possible to obtain an acoustic wave device having required characteristics.

As described above, according to the thirteenth invention, the lower limit frequency of the pass band of the elastic wave element is f ₁ and the upper limit frequency is f _2, and the intersection width of the interdigital electrodes of the elastic wave element is W.
_0, and the propagation velocity of the elastic wave in the interdigital transducer is V
_{Let IDT} be the angle between the electrode finger of the output-side interdigital electrode and the wavefront of the above-mentioned elastic wave when the elastic wave excited by the input-side interdigital electrode reaches the output-side interdigital electrode. The shape of the lead-out electrode end face was determined so as to satisfy the condition expressed by Expression 9 or the condition expressed by Expression 10 with n being an integer. Therefore, even if the propagation velocity of the elastic wave varies depending on the material, it is possible to obtain the acoustic wave element having the required characteristics by appropriately determining the shape of the extraction electrode corresponding to the range of the variation. it can.

As described above, according to the fourteenth invention, the lower limit frequency of the pass band of the elastic wave element is f ₁ and the upper limit frequency is f _2, and the intersection width of the interdigital electrodes of the elastic wave element is W.
_0, and the propagation velocity of the elastic wave in the interdigital transducer is V
_{Let IDT} be the angle between the electrode finger of the output-side interdigital electrode and the wavefront of the elastic wave when the elastic wave excited by the input-side interdigital electrode reaches the output-side interdigital electrode and θ. Further, the shape of the shield electrode was determined so as to satisfy the condition represented by the formula 9 or the condition represented by the formula 10 with n being an integer. Therefore, even if the propagation velocity of the elastic wave varies depending on the material, it is possible to obtain the acoustic wave element having the required characteristics by appropriately determining the shape of the shield electrode corresponding to the range of the variation. it can.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a part of electrode fingers of the acoustic wave device shown in FIG.

FIG. 3 is a diagram showing an electrode finger width, a gap between electrode fingers, and an electrode finger arrangement gap of an acoustic wave device according to a second embodiment of the present invention.

FIG. 4 is a diagram showing electrode finger arrangement intervals of an acoustic wave device according to a second embodiment of the present invention.

FIG. 5 is a diagram showing an example of a delay time of the acoustic wave device according to the second embodiment of the present invention.

FIG. 6 is a diagram showing a part of a comb-shaped electrode according to a third embodiment of the present invention.

FIG. 7 is a diagram for explaining the operation of the acoustic wave device of the fourth embodiment of the present invention.

FIG. 8 is a diagram showing a part of a comb-shaped electrode according to a fifth embodiment of the present invention.

FIG. 9 is a diagram showing a part of a comb-shaped electrode according to a sixth embodiment of the present invention.

FIG. 10 is a top view showing a seventh embodiment of the present invention.

11 is a diagram showing a cross section of the acoustic wave device shown in FIG.

FIG. 12 is a diagram showing dispersion characteristics of elastic waves in a thin film configuration.

FIG. 13 is a top view showing an eighth embodiment of the present invention.

14 is a diagram showing a cross section of the acoustic wave device shown in FIG.

FIG. 15 is a top view showing a ninth embodiment of the present invention.

16 is a diagram showing a cross section of the acoustic wave device shown in FIG.

FIG. 17 is a top view showing a tenth embodiment of the present invention.

18 is a diagram showing a cross section of the acoustic wave device shown in FIG.

FIG. 19 is a diagram showing an eleventh embodiment of the present invention.

FIG. 20 is a diagram illustrating an operation when an elastic wave having an inclined wavefront is received at an intersection.

FIG. 21 is a diagram showing the calculation result of the relationship between the inclination angle of the end surface of the inner extraction electrode and the inclination angle of the wavefront of the elastic wave reaching the output-side interdigital electrode.

FIG. 22 is a calculation result of the relationship between the inclination angle of the end surface of the extraction electrode on the inner side and the inclination angle of the wave surface of the elastic wave reaching the output-side interdigital electrode when the propagation speed of the elastic wave in the region with the electrode finger is changed. FIG.

FIG. 23 is a diagram showing a twelfth embodiment of the present invention.

FIG. 24 is a diagram showing another embodiment of the present invention.

FIG. 25 is a diagram showing another embodiment of the present invention.

FIG. 26 is a diagram showing another embodiment of the present invention.

FIG. 27 is a diagram showing another embodiment of the present invention.

FIG. 28 is a diagram showing another embodiment of the present invention.

FIG. 29 is a diagram showing another embodiment of the present invention.

FIG. 30 is a diagram showing another embodiment of the present invention.

FIG. 31 is a diagram showing another embodiment of the present invention.

FIG. 32 is a diagram showing another embodiment of the present invention.

FIG. 33 is a diagram showing another embodiment of the present invention.

FIG. 34 is a diagram showing another embodiment of the present invention.

FIG. 35 is a diagram showing another embodiment of the present invention.

FIG. 36 is a diagram showing a conventional acoustic wave device of this type.

37 is a diagram showing positions of intersections of the output-side interdigital transducers shown in FIG. 36 and center frequencies at the respective intersections.

38 is a diagram showing positions of intersections of the output-side interdigital transducers shown in FIG. 37 and electrode finger arrangement intervals of the respective electrode fingers.

39 is a diagram showing electrode finger arrangement intervals when the minimum dimension unit is set to the electrode finger arrangement intervals of the electrode fingers shown in FIG. 37.

FIG. 40 is a diagram showing conversion efficiency of a comb-shaped electrode when the electrode finger arrangement interval is gradually changed.

FIG. 41 is a diagram showing conversion efficiency of a comb-shaped electrode in the case where there are intersections where the same electrode finger arrangement intervals are continuous.

FIG. 42 is a diagram showing an example of the pass characteristics of an acoustic wave device in which the electrode finger arrangement interval gradually changes.

FIG. 43 is a diagram showing an acoustic wave device having an intersection where the same electrode finger arrangement intervals are continuous.

FIG. 44 is a diagram showing an example of an acoustic wave element passage characteristic having an intersection where the same electrode finger arrangement intervals are continuous.

FIG. 45 is a diagram showing electrode fingers of a conventional acoustic wave device of this type.

FIG. 46 is a diagram showing electrode fingers of a conventional acoustic wave device of this type.

FIG. 47 is a diagram showing electrode fingers of a conventional acoustic wave device of this type.

FIG. 48 is a diagram showing electrode fingers of a conventional acoustic wave device of this type.

FIG. 49 shows the electrode finger width when the electrode finger arrangement interval is changed,
It is a figure which shows an example of the gap length between electrode fingers, and an electrode finger arrangement | positioning space | interval.

[Explanation of symbols]

 1 interdigital electrode 2 electrode finger 3 extraction electrode 3a outer extraction electrode 3b inner extraction electrode 4 electrical terminal 5 ground terminal 21 piezoelectric substrate 22 non-piezoelectric thin film 23 non-piezoelectric substrate 24 piezoelectric thin film 30 shield electrode 31 Shield electrode end face 32 Thin film 33 Area with electrode fingers

Continued Front Page (72) Inventor Shuzo Waka, 1-1 1-1 Ofuna, Kamakura-shi, Kanagawa Electronic Systems Research Center, Mitsubishi Electric Corporation

Claims (14)

[Claims] 1. An acoustic wave device having a configuration in which at least one of the interdigital electrodes for converting an electric signal and an elastic wave is configured such that the electrode finger arrangement interval is gradually changed, and the interdigital electrodes have different potentials. An acoustic wave device characterized in that it has a region where the ratio of the electrode finger width and the gap length between adjacent electrode fingers is changed, in a part or the whole of the portion where the electrode fingers intersect. 2. An elastic wave device having a configuration in which at least one of the interdigital electrodes for exchanging an electric signal and an elastic wave is configured such that the electrode finger arrangement interval is gradually changed, and the interdigital electrodes have different potentials. The ratio of the electrode finger width to the gap length of the adjacent electrode fingers is gradually increased in the direction of the electrode finger order in which the electrode finger arrangement interval of the interdigital electrode gradually decreases over a part or the whole of the area where the electrode fingers intersect. An acoustic wave device characterized by being made smaller. 3. An acoustic wave device having a configuration in which at least one of the interdigital electrodes for exchanging an electric signal and an elastic wave is configured such that the electrode finger arrangement interval is gradually changed, and the interdigital electrodes have different potentials. An acoustic wave device characterized in that the ratio of the electrode finger width to the gap length of adjacent electrode fingers is randomly changed in a part or the whole of the portion where the electrode fingers intersect. 4. In an acoustic wave device having a configuration in which at least one of the interdigital electrodes for converting an electric signal and an elastic wave is gradually changed in electrode finger arrangement interval, the interdigital electrodes have different potentials. An acoustic wave device comprising a stepped electrode finger in which the ratio of the electrode finger width to the gap length of adjacent electrode fingers changes in a part or the whole of the portion where the electrode fingers intersect. 5. An acoustic wave device having a configuration in which an electrode finger arrangement interval is gradually changed to at least one of interdigital electrodes for exchanging an electric signal and an elastic wave. Part or all of the portion where the different electrode fingers intersect has stepped electrode fingers in which the ratio of the electrode finger width to the gap length of the adjacent electrode fingers changes, and the electrode arrangement interval of the interdigital electrode gradually decreases. In the direction of the electrode finger sequence, the total length of the adjacent electrode fingers in the direction of the cross width of the region having a large ratio of the electrode finger width to the gap length of the adjacent electrode fingers in each of the electrode fingers is An acoustic wave device characterized in that the ratio of the total length in the cross width direction of the region where the ratio of the electrode fingers to the gap length is small is gradually increased. 6. An acoustic wave device having a configuration in which at least one of the interdigital electrodes for converting an electric signal and an elastic wave is configured such that the electrode finger arrangement interval is gradually changed, and the interdigital electrodes have different potentials. A part or the whole of the portion where the electrode fingers intersect has stepped electrode fingers in which the ratio of the electrode finger width to the gap length of the adjacent electrode fingers changes, and the gap length of the adjacent electrodes in each of the electrode fingers corresponds to the gap length. An elastic wave device, wherein the ratio of the total lengths in the cross width direction of the region having a small electrode width ratio is randomly changed. 7. An acoustic wave device having a configuration in which at least one of interdigital electrodes for converting an electric signal and an elastic wave is configured such that an electrode finger arrangement interval is gradually changed. Comprises at least one non-piezoelectric thin film having dispersion characteristics, and gradually changes the electrode finger arrangement interval on the surface of any thin film among the above thin films or on the boundary surface between the above thin film and the piezoelectric substrate. An elastic wave device characterized in that the electrode index of the interdigital transducer is smaller than that in the case where the interdigital transducer is provided on a piezoelectric substrate having no dispersibility. 8. An electrode finger arrangement interval is gradually changed to at least one of the interdigital electrodes for converting an electric signal and an elastic wave so that the group delay time increases as the frequency increases. In the elastic wave device having the above-mentioned structure, at least one non-piezoelectric thin film having elastic wave dispersion characteristics is formed on the surface of the piezoelectric substrate, and the surface of any thin film among the above thin films or the above thin film and the above piezoelectric film are formed. On the boundary surface between and, the interdigital electrodes with the electrode finger arrangement intervals gradually changed are provided, so that the electrode index of the interdigital electrodes becomes smaller than that in the case where the interdigital electrodes are formed on a non-dispersive piezoelectric substrate. An elastic wave device characterized by the above. 9. A structure in which the electrode finger arrangement interval is gradually changed to at least one of the interdigital electrodes for converting an electric signal and an elastic wave so that the delay time becomes smaller as the frequency becomes higher. In the elastic wave device described above, at least one non-piezoelectric thin film having elastic wave dispersion characteristics is formed on the surface of the piezoelectric substrate, and the surface of any thin film among the thin films or the thin film and the piezoelectric substrate At the boundary surface of the interdigital transducer, the interdigital electrodes with the electrode finger array spacing gradually changed were provided, and the interdigitated electrode index of the interdigital electrodes was set to be larger than that in the case where the interdigital electrodes were formed on the non-dispersive piezoelectric substrate. An elastic wave device characterized by the above. 10. An elastic wave device having a configuration in which an electrode finger arrangement interval is gradually changed to at least one of interdigital electrodes for converting an electric signal and an elastic wave, and the elastic wave is formed on a surface of a non-piezoelectric substrate. Comprises at least one piezoelectric thin film having dispersion characteristics, and gradually changes the electrode finger arrangement interval on the surface of any of the thin films or on the boundary surface between the thin film and the non-piezoelectric substrate. An acoustic wave device comprising the interdigital transducer. 11. A configuration in which an electrode finger arrangement interval is gradually changed on at least one or more interdigital electrodes for converting an electric signal and an elastic wave, and a delay time increases as the frequency increases. In the elastic wave device described above, at least one piezoelectric thin film having elastic wave dispersion characteristics is formed on the surface of the non-piezoelectric substrate, and the surface of any of the thin films or the thin film and the non-piezoelectric substrate are formed. On the boundary surface between the and the interdigital electrodes, the interdigital electrodes with the electrode finger arrangement intervals gradually changed are provided, so that the electrode index of the interdigital electrodes becomes smaller than that in the case where the interdigital electrodes are formed on a non-dispersive piezoelectric substrate. An elastic wave device characterized by the above. 12. A structure in which the electrode finger arrangement interval is gradually changed to at least one interdigital transducer for converting an electric signal and an elastic wave so that the delay time becomes smaller as the frequency becomes higher. In the elastic wave device described above, at least one piezoelectric thin film having elastic wave dispersion characteristics is formed on the surface of the non-piezoelectric substrate, and the surface of any of the thin films or the thin film and the non-piezoelectric material are formed. At the boundary surface of the interdigital transducer, the interdigital electrodes with the electrode finger arrangement interval gradually changed are provided, and the electrode index of the interdigital electrodes is made larger than that in the case where the interdigital electrodes are formed on the non-dispersive piezoelectric substrate. An elastic wave device characterized by the above. 13. The electrode index of a comb-shaped electrode for converting an electric signal and an elastic wave is shifted in a direction perpendicular to the elastic wave propagation direction to reduce the electrode exponent traversed by the elastic wave on an arbitrary elastic wave propagation path. Using at least one of the input and output electrodes of the slant electrode, the boundary between the slant electrode and the signal extraction electrode of the slant electrode, or by refraction at the end surface of the signal extraction electrode facing the electrode side. , The elastic wave element that corrects the deviation of the wavefront and propagation method of the elastic wave from the required direction by the shape of the electrode side facing the extraction electrode, the lower limit frequency of the pass band of the elastic wave element is f ₁ , the upper limit frequency. Is f ₂ , and the elasticity is the crossing width of the interdigital transducer of the element is W _0, and the propagation velocity of the elastic wave in the interdigital electrode is V 2.
And _IDT, an angle between the wavefront of the input-side interdigital acoustic wave excited by the electrodes is output interdigital electrode fingers of the electrode and the acoustic wave is taken as _{θ, f 2 <V IDT /} (W 0 · sin [theta) or, where n is an _{integer, f 2 / n <V IDT} / (W 0 · sinθ) <f 1
An elastic wave element, characterized in that the shape of the extraction electrode on the opposite electrode side is determined so as to satisfy / (n-1). 14. The electrode index of a comb-shaped electrode for converting an electric signal and an elastic wave is shifted in a direction perpendicular to the elastic wave propagation direction to reduce the electrode index crossed by the elastic wave on an arbitrary elastic wave propagation path. Using at least one of the input and output electrodes slant electrode aimed at, the boundary portion of the signal extraction electrode of the slant electrode and the slant electrode, by refraction at the end face on the opposite electrode side of the extraction electrode, In the elastic wave element that corrects the deviation of the wavefront and propagation method of the elastic wave from the required direction by the shape on the shield electrode side placed between the interdigital electrodes, the lower limit frequency of the pass band of the elastic wave element is f ₁ , The upper limit frequency is f ₂ , the cross width of the interdigital electrodes of the elastic wave element is W _0, and the propagation velocity of the elastic wave in the interdigital electrode is V
_IDT , when the angle formed between the electrode finger of the output-side interdigital electrode and the wavefront of the elastic wave when the elastic wave excited by the input-side interdigital electrode reaches the electrode in the output-side interdigital shape is θ And f ₂ <V _IDT / (W ₀ · sin θ) or, where n is an integer, f ₂ / n <V _IDT / (W ₀ · sin θ) <f ₁
An elastic wave device characterized in that the shape of the shield electrode is determined so as to satisfy / (n-1).