JP2003243963A - Surface acoustic wave filter device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface acoustic wave (SAW) filter device in which filter characteristics can be improved. <P>SOLUTION: A SAW element 8 has an input side IDT16 combining a comb- line electrode connected to an input terminal 20 and a comb-line electrode connected to a ground terminal and an output side IDT15 combining a comb-line electrode connected to an output terminal 21-1 and a comb-line electrode connected to the ground terminal. An electrode finger 16A-EL for input of the comb-line electrode connected to the input terminal, an electrode finger 15B-EL for output of the comb-line electrode connected to the output terminal and electrode fingers 15A-EL and 16B-EL for grounding of the comb-line electrodes connected to the ground terminal are arranged practically at equal intervals. The electrode fingers for input and the electrode fingers for output are adjacently arranged at prescribed intervals to cancel an acoustic response out of a prescribed band by electric coupling between them without interposing the electrode fingers for grounding. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave filter device used in mobile communication equipment and the like.
The present invention relates to a pattern of electrode fingers forming a surface acoustic wave element.

[0002]

2. Description of the Related Art A surface acoustic wave filter device is an interdigital converter made of a thin film metal provided on a piezoelectric body:
It is a device that transmits and receives signals by converting an electric signal and a surface acoustic wave (SAW) by an IDT, and is used in a surface acoustic wave filter element, a surface acoustic wave resonator, a delay circuit, and the like. This surface acoustic wave filter device has come to be widely used in the field of mobile communication such as a mobile phone because of its merit that it can be made thin and compact.

In recent years, there have been remarkable advances in the field of mobile communication, and the surface acoustic wave filter devices used therein are required to have higher performance year by year.

The characteristics required for the surface acoustic wave filter device are roughly classified into two: a small amount of attenuation within a predetermined band and a large amount of attenuation outside the predetermined band. An RF surface acoustic wave filter device used in a mobile communication device includes a multimode resonator filter using longitudinal mode multiple coupling, that is, an LMMS (Longitudin).
The general type is an al multi mode SAW type or a ladder type in which resonators are arranged in series and parallel.

Among them, in the multimode resonator filter, since the balanced and unbalanced output is easy, the surface acoustic wave filter device using this structure has been frequently used in recent years. However, in the case of the multimode resonator filter, since the acoustic response exists near the high frequency side of the predetermined band, the out-of-band attenuation on the high frequency side becomes a problem as a filter characteristic.

As a surface acoustic wave filter, there is a trade-off relationship between decreasing the in-band attenuation amount and increasing the out-of-band attenuation amount, and increasing the out-band attenuation amount results in sacrificing the in-band attenuation amount. I have to Therefore, when designing the filter, the desired filter characteristics are designed based on these points.

There are some other causes for reducing the out-of-band attenuation. One of them is electrical coupling. In a surface acoustic wave filter, an input terminal, an output terminal, and a ground terminal are supposed to be connected only by acoustic coupling, but in reality, electrical coupling always exists between the terminals. In general, the greater this coupling, the smaller the out-of-band attenuation of the surface acoustic wave filter. Therefore, normally, wiring is made so that this coupling is as small as possible to increase the total out-of-band attenuation. However, even in that case, since the acoustic response in the vicinity of the high frequency side of the predetermined band remains, the required out-of-band attenuation may not be obtained.

For example, in Japanese Unexamined Patent Publication No. 2001-230657, in order to sufficiently secure the out-of-band attenuation amount extremely close to the low band side and the high band side of the pass band, the frequency very close to the pass band is reversed. A configuration is disclosed in which a surface acoustic wave resonator having a resonance frequency is electrically connected between input and output terminals.

[0009]

In a normal surface acoustic wave filter, since an acoustic response exists near the high frequency side of a predetermined band, there is a problem that it is not possible to secure sufficient out-of-band attenuation. .

Further, according to the surface acoustic wave filter disclosed in Japanese Patent Laid-Open No. 2001-230657, the amount of attenuation near the high frequency side of the predetermined band can be increased, but at the same time, the amount of in-band attenuation also increases. Therefore, there is a problem that the flatness of the frequency characteristic in the band is impaired.

That is, in the conventional technique, it is difficult to increase the attenuation outside the band (particularly on the high frequency side) while reducing the attenuation within the band (or flattening the frequency characteristic within the band). Occurs.

The present invention has been made in view of the above problems, and an object thereof is to provide a surface acoustic wave filter device capable of improving filter characteristics.

[0013]

A surface acoustic wave filter device according to a first aspect of the present invention comprises a piezoelectric substrate and a surface acoustic wave element formed on the piezoelectric substrate. The element is an input-side interdigital converter combining at least a comb-teeth electrode connected to the input terminal and a comb-teeth electrode connected to the ground terminal, and a comb-teeth electrode connected to the output terminal and the ground. An output side interdigital converter in which a comb-teeth-shaped electrode connected to the terminal is combined,
An input electrode finger of a comb tooth-shaped electrode connected to the input terminal, an output electrode finger of a comb tooth-shaped electrode connected to the output terminal, and a comb tooth-shaped electrode connected to the ground terminal. The grounding electrode fingers of the electrodes are arranged at substantially equal intervals, and the input electrode finger and the output electrode finger cancel an acoustic response outside a predetermined band due to electrical coupling between them. It is characterized in that they are arranged adjacent to each other at such a predetermined interval without interposing the grounding electrode finger.

A surface acoustic wave filter device according to a second aspect of the present invention includes a piezoelectric substrate and a surface acoustic wave element formed on the piezoelectric substrate, and the surface acoustic wave element is at least an input device. An input side interdigital converter in which a comb-shaped electrode connected to a terminal and a comb-shaped electrode connected to a ground terminal are combined, and a comb-shaped electrode connected to an output terminal and a comb connected to a ground terminal An output side interdigital converter in combination with a tooth-shaped electrode, and a coupling means for providing an electrical coupling between the input side interdigital converter and the output side interdigital converter. A specific portion of a high frequency signal component outside a predetermined band that acoustically propagates between the input side interdigital converter and the output side interdigital converter by a surface acoustic wave. , Characterized in that it is configured to cancel the high-frequency signal component outside the predetermined band for electrically propagated by said coupling means.

According to this surface acoustic wave filter device, the input electrode fingers, the output electrode fingers, and the ground electrode fingers are arranged at substantially equal intervals. Therefore, the in-band attenuation amount can be reduced (or the frequency characteristic in the band can be flattened).

Further, according to this surface acoustic wave filter device, the input electrode fingers and the output electrode fingers are arranged adjacent to each other at a predetermined interval without the grounding electrode fingers interposed therebetween. . That is, the input electrode finger and the output electrode finger are outside the predetermined band due to electrical coupling between them.
In particular, they are arranged at predetermined intervals so as to cancel the acoustic response on the high frequency side.

That is, the electrical coupling between the input electrode finger and the output electrode finger is intentionally increased, and the signal component corresponding to the acoustic response is propagated through the electrical coupling. The input electrode fingers and the output electrode fingers are arranged at predetermined intervals such that the phase of the signal component is shifted by 180 degrees. As a result, the acoustic response can be canceled, and the amount of attenuation outside the band, particularly near the high band side of the predetermined band, can be increased.

Therefore, it is possible to increase the amount of attenuation outside the band (particularly on the high frequency side) while reducing the amount of attenuation within the band (or flattening the frequency characteristic within the band), and greatly improve the filter characteristics. It becomes possible.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION A surface acoustic wave filter device according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view schematically showing the structure of a surface acoustic wave filter device 100 according to an embodiment of the present invention. FIG. 2 is a plan view schematically showing the structure of the device chip 1 applied to this surface acoustic wave filter device 100.

This surface acoustic wave filter device 100 includes a device chip 1 and a substrate made of resin or ceramics (package of the surface acoustic wave filter device 100).
3 and 3 are provided. A wiring pattern 4 is formed at a predetermined position on the upper surface of the substrate 3. This wiring pattern 4
Are connected to the lead pattern 41 and the like on the lower surface of the substrate 3 via the via holes 31. Further, a functional portion 8 having a predetermined function is formed at a predetermined position on the device chip 1. In the case of the surface acoustic wave filter device, the surface acoustic wave element having the interdigital converter: IDT formed on the piezoelectric substrate 1 corresponds to the functional unit 8 having a predetermined function.

The functional portion 8 has a lead wiring pattern 81.
A plurality of bonding pads are connected via.
In the examples shown in FIGS. 1 and 2, four bonding pads are arranged. These four bonding pads and predetermined portions (four portions) of the lead-out wiring pattern 81 on the substrate 3 are arranged to face each other via the conductive metal bumps 2 made of, for example, gold or gold alloy. At this time, the functional unit 8 of the device chip 1 is connected to the substrate 3
Is arranged so as to face the upper surface of and substantially parallel to this upper surface.

Here, the functional unit 8 of the device chip 1 and
A hollow portion (space portion) 7 is provided between the surfaces facing the substrate 3. This is because, in the case of the surface acoustic wave filter device, it has an attribute of propagating surface acoustic waves in terms of its function, and it is not possible to closely contact mutually opposing surfaces.

The hollow portion 7 is formed as follows. That is, one main surface of the substrate 3, that is, the surface provided with the wiring pattern 4, or one main surface of the device chip 1,
That is, a frame 72 provided so as to surround the functional portion 8 is formed on the surface provided with the functional portion 8. When the frame body 72 is formed on one main surface of the device chip 1, the frame body 72
The hollow portion 7 is formed inside the frame 72 by contacting the main surface of the substrate 3 with the main surface of the substrate 3. Note that the frame 72 may not be used as long as the space 7 is formed.

The device chip 1 and the substrate 3 as described above are connected via the metal bumps 2. That is, the metal bumps 2 between the device chip 1 and the substrate 3 are pressurized, heated, and ultrasonically applied to partially melt them (flip chip bonding or face down bonding). When the pressurization / heating / application of ultrasonic waves is completed, the melted portion of the metal bump 2 is cooled and solidified.
As a result, the four bonding pads connected to the functional portion 8 and the predetermined four positions of the wiring pattern 4 on the substrate 3 are electrically and mechanically connected via the four metal bumps 2, respectively.

Thereafter, as shown in FIG. 1, the entire device chip 1 is sealed with a sealing resin (protective material) 5 having an appropriate viscosity.
Overwrap with. Then, the encapsulating resin 5 is cured. The sealing resin 5 is made of epoxy resin or the like.

By the way, the functional unit 8 shown in FIG. 1 and FIG.
Is configured as follows. That is, the surface acoustic wave element 8 as the functional portion, that is, the multimode resonator filter is formed on the piezoelectric substrate 1 made of, for example, lithium tetraborate or lithium tantalate, as shown in FIG.

1 and 2, the surface acoustic wave filter device 10 is flip-chip bonded or face-down bonded and sealed with resin.
0 has been described, the surface acoustic wave element 8 of the present invention is
It goes without saying that the present invention is not limited to the structure of the surface acoustic wave filter device 100, and can be applied to a surface acoustic wave filter device having another structure such as being sealed by a metal cap or a ceramic cap.

The surface acoustic wave elements 8 are IDTs arranged in a line.
15 to 17, and the reflectors 11 and 12 provided at both ends of the IDTs 15 to 17 in the arrangement direction.

In the example shown in FIG. 3, the IDT 15 is the ID
It has the same electrode pattern as T17. IDT16
Has an electrode pattern which is upside down from the IDT 15 in the figure. The IDTs 15 to 17 and the reflector 11
The electrode patterns Nos. 12 to 12 are made of, for example, an aluminum alloy or a copper alloy.

ID sandwiched between IDT15 and IDT17
The first comb-teeth electrode 16A of T16 is connected to the signal port 20, and the second comb-teeth electrode 16B facing the first comb-teeth electrode 16A is electrically grounded. The first comb-shaped electrode 15A of the IDT 15 is grounded, and the first comb-shaped electrode 1
The second comb-shaped electrode 15B facing 5A is connected to the signal port 21-1. First comb-shaped electrode 1 of the IDT 17
7A is grounded, and the second comb-shaped electrode 17B facing the first comb-shaped electrode 17A is connected to the signal port 21-2.

Here, for example, the signal port 20 functions as an input terminal, and in that case, the signal ports 21-1 and 21-2 function as output terminals. (Conversely, when the signal ports 21-1 and 21-2 function as input terminals, the signal port 20 functions as output terminals.) The IDTs 15 to 17 and the reflectors 11 to 12 are arranged substantially parallel to each other. And a bus bar that connects the plurality of electrode fingers in common. For example, the reflector 11 includes a plurality of electrode fingers 11EL and a bus bar 11BB. Similarly, the reflector 12 includes a plurality of electrode fingers 12EL and a bus bar 12BB. In this embodiment, the reflectors 11 and 12
Are, for example, 100 electrode fingers 11EL and 12 respectively.
Equipped with EL.

The first comb-teeth-shaped electrode 15A of the IDT 15 is composed of a plurality of electrode fingers 15A-EL and bus bars 15A-BB. The second comb-shaped electrode 15 of the IDT 15
B is a plurality of electrode fingers 15B-EL and a bus bar 15B-B.
It is composed of B and. In this embodiment, the first comb tooth-shaped electrode 15A has, for example, 12 electrode fingers 15A−.
The second comb-teeth-shaped electrode 15B includes EL, for example, 13 electrode fingers 15B-EL. In addition, in this embodiment, the electrode fingers 15A-EL of the first comb-teeth-shaped electrode 15A are used.
Acts as a grounding electrode finger connected to the grounding terminal,
The electrode finger 15B-EL of the second comb tooth-shaped electrode 15B functions as an output electrode finger connected to the output terminal 21-1.

The first comb-teeth electrode 16A of the IDT 16 is composed of a plurality of electrode fingers 16A-EL and bus bars 16A-BB. The second comb-teeth electrode 16 of the IDT 16
B is a plurality of electrode fingers 16B-EL and a bus bar 16B-B.
It is composed of B and. In this embodiment, the first comb-shaped electrode 16A has, for example, 16 electrode fingers 16A−.
The second comb-teeth-shaped electrode 16B includes EL, and includes, for example, 15 electrode fingers 16B-EL. In addition, in this embodiment, the electrode fingers 16A-EL of the first comb-teeth-shaped electrode 16A are used.
Functions as an input electrode finger connected to the input terminal 20, and the electrode finger 16B-EL of the second comb-shaped electrode 16B functions as a ground electrode finger connected to the ground terminal.

The first comb tooth-shaped electrode 17A of the IDT 17 is composed of a plurality of electrode fingers 17A-EL and bus bars 17A-BB. The second comb-shaped electrode 17 of the IDT 17
B is a plurality of electrode fingers 17B-EL and a bus bar 17B-B.
It is composed of B and. In this embodiment, the first comb-shaped electrode 17A has, for example, 12 electrode fingers 17A-.
The second comb-teeth-shaped electrode 17B includes EL, for example, 13 electrode fingers 17B-EL. In addition, in this embodiment, the electrode fingers 17A-EL of the first comb tooth-shaped electrode 17A are used.
Acts as a grounding electrode finger connected to the grounding terminal,
The electrode finger 17B-EL of the second comb-shaped electrode 17B functions as an output electrode finger connected to the output terminal 21-2.

Input electrode fingers 16A-EL, output electrode fingers 15B-EL and 17B-EL, and ground electrode finger 1
The 5A-EL, 16B-EL and 17A-EL are formed to have substantially the same width and the same length. That is, these electrode fingers have a width of, for example, λ / 4, where λ is the wavelength of the surface acoustic wave. In this embodiment, each electrode finger has a width of about 1.15 μm and a length of about 0.2 mm.

The electrode fingers forming the IDTs 15 to 17 are arranged at substantially equal intervals. That is,
The intervals between the electrode fingers of the first comb-teeth-shaped electrode and the electrode fingers of the second comb-teeth-shaped electrode that configure each IDT are the same. For example,
In the IDT 15, the electrode finger 1 of the first comb-shaped electrode 15A
5A-EL center and electrode finger 1 of the second comb-teeth-shaped electrode 15B
The distance from the center of the 5B-EL is set to λ / 2.

The IDTs 15 to 17 are also arranged at substantially equal intervals. That is, IDT15-IDT
The interval between 16 and the interval between IDT16 and IDT17 are equal. For example, IDT15-IDT16
And the center of the electrode finger 15A-EL arranged at the position closest to the IDT 16 of the IDT 15, I
The distance from the center of the electrode finger 16B-EL arranged closest to the IDT 15 of the DT 16 is set to λ / 2.

Similarly, the distance between the IDT 16 and the IDT 17, that is, the center of the electrode finger 16A-EL arranged at the position closest to the IDT 17 of the IDT 16 and the IDT1.
The distance from the center of the electrode finger 17B-EL arranged in the position 7 closest to the IDT 16 is also set to λ / 2.

As described above, by making the width and length of each electrode finger equal and arranging each electrode finger at substantially equal intervals, the amount of attenuation can be reduced within a predetermined band (or within the predetermined band). The frequency characteristic can be flattened), and the filter characteristic can be improved.

Further, in the surface acoustic wave filter device 100 according to this embodiment, the input electrode fingers and the output electrode fingers are arranged adjacent to each other at a predetermined interval between them without the grounding electrode fingers interposed therebetween. ing. In the example shown in FIG. 3, I
Input electrode finger 16 closest to IDT 15 of DT 16
The A-EL is the IDT1 without using the grounding electrode finger.
Output electrode finger 15B-E closest to the IDT 16 of 5
It is arranged adjacent to L. Further, the input electrode finger 16A-EL closest to the IDT 17 of the IDT 16 does not have the grounding electrode finger, and the input electrode finger 16A-EL of the IDT 17 has the highest IDT.
It is arranged adjacent to the output electrode finger 17 </ b> B-EL that is in close proximity to 16.

The predetermined distance between the input electrode finger and the output electrode finger is set so that the acoustic response outside the predetermined band is canceled by the electrical connection between the electrode fingers. That is, the input electrode fingers and the output electrode fingers, which are arranged at a predetermined interval, function in the same manner as a parallel plate capacitor as a coupling means for providing electrical coupling between them.

In order to effectively cancel the acoustic response outside the predetermined band, the predetermined interval between the center of the input electrode finger and the center of the output electrode finger is λ, which is the wavelength of the surface acoustic wave. At this time, it is substantially set to λ / 2. In this embodiment, the predetermined distance between the center of the input electrode finger and the center of the output electrode finger is substantially 1 μm.

As described above, by arranging the input electrode finger and the output electrode finger adjacent to each other without interposing the grounding electrode finger therebetween, the input electrode finger and the output electrode finger are separated from each other. Electrical coupling between them can be intentionally increased. Moreover, the input electrode fingers and the output electrode fingers are arranged at predetermined intervals such that the phase of the signal component propagated via electrical coupling is 180 degrees out of phase with the signal component corresponding to the acoustic response. .

Therefore, the IDT 16 including the input electrode fingers
Between the IDTs 15 and 17 including the output electrode finger and a specific portion of the high-frequency signal component outside the predetermined band that acoustically propagates by surface acoustic waves (that is, the acoustic response existing near the high-frequency side of the predetermined band). ) Can be canceled by a high-frequency signal component outside a predetermined band that is electrically propagated through electrical coupling (that is, electrostatic coupling) between the input electrode finger and the output electrode finger. As a result, the amount of attenuation can be increased outside the band, particularly near the high band side of the predetermined band, and the filter characteristics can be improved.

The surface acoustic wave filter device according to this embodiment is not limited to the arrangement of the electrode fingers as shown in FIG. 3 and can be variously modified. That is, in the example shown in FIG. 3, the input electrode finger connected to the input terminal 20 is the first comb tooth-shaped electrode 16A arranged on the upper side of the IDT 16 in the drawing, and the output terminals 21-1 and 21.
The output electrode fingers respectively connected to -2 correspond to the second comb tooth-shaped electrodes 15B and 17B arranged below the IDTs 15 and 17 in the figure. In this way, the input electrode fingers and the output electrode fingers, which function as the coupling means for providing electrical coupling, extend in different directions.

For example, as shown in FIG. 7, the input terminal 20
The input electrode finger connected to is the IDT16 in the figure.
Is the first comb-shaped electrode 16A arranged on the upper side of the IDT, and the output electrode fingers respectively connected to the output terminals 21-1 and 21-2 are the second electrode arranged on the upper side of the IDTs 15 and 17 in the figure. You may comprise so that it may correspond to the comb-teeth-shaped electrodes 15A and 17A. In this way, even if the input electrode fingers and the output electrode fingers functioning as the coupling means for causing electrical coupling are extended in the same direction, they are equivalent to the electrode finger arrangement of the structure shown in FIG. Therefore, it is possible to obtain the same effect as that of the above-described embodiment.

Next, the frequency characteristics of the surface acoustic wave filter device manufactured by using the above structure will be described.

Here, the frequency characteristics were measured using a network analyzer manufactured by Hewlett Packard under the condition of input / output 50Ω termination. Further, as a comparative example, as shown in FIG. 4, grounding is performed between the input electrode finger connected to the input terminal 20 and the output electrode finger connected to the output terminal 21-1 (or 21-2). 1 connected to a terminal
The frequency characteristics of the surface acoustic wave filter device prototyped using the structure in which the two electrode fingers for grounding are arranged were also measured under the same conditions. Also in the structure shown in FIG. 4, the shape of each electrode finger and the interval between the electrode fingers are the same as those in the structure shown in FIG.

FIG. 5 shows an example of the measurement result of the frequency characteristic. The solid line (1) is the frequency characteristic of the surface acoustic wave filter device having the structure shown in FIG. 3, and the broken line (2) is
It is a frequency characteristic of the surface acoustic wave filter device of the structure shown in FIG. Further, FIG. 6 shows the measurement result of the frequency characteristic in which the vicinity of a predetermined band centered at about 881.5 MHz of the measurement result shown in FIG. 5 is enlarged.

As shown in FIGS. 5 and 6, in the structure shown in FIG. 3, the attenuation amount (or flatness) in the band is almost equal to that in the structure shown in FIG. It was possible to increase the amount of attenuation outside the band, especially on the high frequency side, while maintaining. In this measurement result, in the structure shown in FIG.
As compared with the structure shown in FIG. 4, it can be seen that the attenuation amount near the high frequency side of the predetermined band is increased by about 10 dB.

On the contrary, in the structure shown in FIG.
Compared with the structure as shown in FIG. 3, the electric coupling between the input and the output is large, and as a result, the total out-of-band attenuation amount is small. It is necessary to use these characteristics properly according to the requirements, but by using the method of this embodiment, the characteristics in the vicinity of the high frequency side are shown in FIG.
It was confirmed that the amount of attenuation was much larger than that of the structure shown in (4).

As described above, according to this embodiment, the input electrode fingers, the output electrode fingers, and the ground electrode fingers are arranged at substantially equal intervals, and furthermore, the input electrode fingers and the output electrode fingers are arranged. The working electrode fingers are arranged adjacent to each other at a predetermined interval such that an acoustic response outside a predetermined band is canceled by electrical coupling between them, without the grounding electrode finger being interposed.

As a result, the amount of attenuation outside the band, particularly on the high frequency side of the predetermined band, is increased without increasing the amount of in-band attenuation of the surface acoustic wave filter (or without impairing the flatness of the in-band frequency characteristics). Therefore, the filter characteristics can be significantly improved. As a result, it is possible to provide a surface acoustic wave filter device having higher performance and better filter characteristics than ever before.

The present invention is not limited to the above embodiments, and various modifications and changes can be made at the stage of carrying out the invention without departing from the spirit of the invention. Also,
The respective embodiments may be combined as appropriate as much as possible, and in that case, the effect of the combination can be obtained.

[0056]

As described above, according to the present invention, it is possible to provide the surface acoustic wave filter device capable of improving the filter characteristics.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a structure of a surface acoustic wave filter device according to an embodiment of the present invention.

FIG. 2 is a plan view schematically showing the structure of a device chip applied to the surface acoustic wave filter device shown in FIG.

3 is a diagram schematically showing a structure of a surface acoustic wave element applied to the surface acoustic wave filter device shown in FIG.

FIG. 4 is a diagram schematically showing a structure of a surface acoustic wave element as a comparative example in which one grounding electrode finger is arranged between an input electrode finger and an output electrode finger.

FIG. 5 is a diagram showing an example of measurement results when measuring frequency characteristics of surface acoustic wave filter devices having various structures.

6 is a diagram showing a measurement result of frequency characteristics obtained by enlarging a vicinity of a predetermined band around a predetermined frequency of the measurement result shown in FIG.

7 is a diagram schematically showing another structure of a surface acoustic wave element applicable to the surface acoustic wave filter device shown in FIG.

[Explanation of symbols]

1. Device chip (piezoelectric substrate) 3 ... Substrate 8: Functional part (surface acoustic wave element) 15, 16, 17 ... IDT 15B-EL ... Output electrode finger 16A-EL ... Input electrode fingers 17B-EL ... Output electrode finger 15A-EL ... Electrode finger for grounding 16B-EL ... Grounding electrode finger 17A-EL ... Ground electrode finger 20 ... Input terminal 21-1, 2 ... Output terminals 100 ... Surface acoustic wave filter device

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yasuo Ebata             8th Shinsugita Town, Isogo Ward, Yokohama City, Kanagawa Prefecture             Ceremony company Toshiba Yokohama office F term (reference) 5J097 AA15 AA16 BB03 BB14 CC08                       JJ09 KK04 KK10

Claims (5)

[Claims] 1. A piezoelectric substrate, and a surface acoustic wave element formed on the piezoelectric substrate, wherein the surface acoustic wave element has at least a comb tooth-shaped electrode connected to an input terminal and a ground terminal. An input side interdigital converter in which comb-shaped electrodes connected to each other are combined, and an output-side interdigital converter in which comb-shaped electrodes connected to an output terminal and comb-shaped electrodes connected to a ground terminal are combined And an input electrode finger of a comb-shaped electrode connected to the input terminal,
An output electrode finger of a comb-shaped electrode connected to the output terminal,
And the ground electrode fingers of the comb-teeth-shaped electrode connected to the ground terminal are arranged at substantially equal intervals, and the input electrode finger and the output electrode finger are electrically connected between them. A surface acoustic wave filter device, wherein the surface acoustic wave filter devices are arranged adjacent to each other at predetermined intervals such that acoustic response outside a predetermined band is canceled by various couplings, without interposing the grounding electrode fingers. 2. The predetermined distance between the center of the input electrode finger and the center of the output electrode finger is substantially λ / 2, where λ is the wavelength of the surface acoustic wave. The surface acoustic wave filter device according to claim 1. 3. The surface acoustic wave filter device according to claim 1, wherein the predetermined distance between the center of the input electrode finger and the center of the output electrode finger is substantially 1 μm. . 4. The surface acoustic wave filter device according to claim 1, wherein the surface acoustic wave filter device is a multimode resonator filter. 5. A piezoelectric substrate, and a surface acoustic wave element formed on the piezoelectric substrate, wherein the surface acoustic wave element has at least a comb-teeth-shaped electrode connected to an input terminal and a ground terminal. An input side interdigital converter in which comb-shaped electrodes connected to each other are combined, and an output-side interdigital converter in which comb-shaped electrodes connected to an output terminal and comb-shaped electrodes connected to a ground terminal are combined And a coupling means for electrically coupling between the input side interdigital converter and the output side interdigital converter, and the input side interdigital converter and the input side interdigital converter. A specific portion of a high frequency signal component outside a predetermined band that acoustically propagates between the output side interdigital converter and a surface acoustic wave,
A surface acoustic wave filter device, characterized in that it is configured to be canceled by a high frequency signal component outside a predetermined band that is electrically propagated by the coupling means.