JP6387573B2 - Surface acoustic wave filter - Google Patents

Description

  The present invention relates to a surface acoustic wave filter.

  Conventionally, as this type of surface acoustic wave filter, an oblique electrode on the input side having a plurality of oblique electrode fingers that input an electric signal and generate a surface acoustic wave on a piezoelectric substrate and a surface acoustic wave are received. Output-side oblique electrodes having a plurality of oblique electrode fingers that are converted into electrical signals, and each of the input-side and output-side oblique electrode fingers has an interval between adjacent electrode fingers, the propagation direction of the surface acoustic wave What is formed so that it may change in the direction orthogonal to is known (patent document 1).

In a surface acoustic wave filter, in order to suitably separate signals whose frequencies are close to each other, a steep filter characteristic in which the amount of attenuation suddenly increases from the signal pass band to the stop band is required. Therefore, for example, a method of increasing the frequency characteristics (hereinafter referred to as “shoulder characteristics”) of the rising part and the falling part in the filter waveform by increasing the number of diagonal electrode fingers facing the diagonal electrodes on the input side and the output side. Is mentioned. In this case, due to the increase in the number of pairs of diagonal electrode fingers, the diagonal electrode on the input side and the diagonal electrode on the output side are close to each other, and electromagnetic coupling occurs between them.
Therefore, in the conventional device, if the shoulder characteristics are steep, it is necessary to suppress the electromagnetic coupling by separating the oblique electrode on the input side and the oblique electrode on the output side from each other, which increases the area of the substrate. There was a problem that miniaturization could not be achieved.

  In order to solve this problem, a structure that blocks a desired frequency characteristic, in which an integral reflector in which two kinds of reflectors having different center frequencies are electrically connected to each other is provided in a propagation path portion of an oblique electrode finger Has been proposed (Patent Document 2). FIG. 9 is a diagram for explaining a difference in shoulder characteristics of the surface acoustic wave filter before and after providing the integrated reflector in the propagation path portion of the oblique electrode finger. In FIG. 9, the broken line indicates the shoulder characteristics before the integrated reflector is provided, and the solid line indicates the shoulder characteristics after the integrated reflector is provided. Thus, in the surface acoustic wave filter, shoulder characteristics on both sides of the band can be improved by providing an integrated reflector in which two types of reflectors having different center frequencies are electrically connected to each other in the propagation path portion of the oblique electrode finger. .

JP 2002-057551 A Japanese Patent No. 5363812

  However, the surface acoustic wave filter described in Patent Document 2 has improved shoulder characteristics by using an integrated reflector in which two reflectors having different center frequencies are connected and integrated, but within the surface acoustic wave band. There was a problem that ripples were likely to occur.

  The present invention has been made in view of such circumstances, and an object thereof is to generate ripples in a surface acoustic wave band in a surface acoustic wave filter in which a reflector is provided in a propagation path portion of an oblique electrode finger. It is an object of the present invention to provide a surface acoustic wave filter that prevents the above.

One aspect of the present invention is a surface acoustic wave filter that passes an electric signal in a frequency range from a first frequency to a second frequency higher than the first frequency, and is formed on the piezoelectric substrate and the piezoelectric substrate. The surface acoustic wave generating means for generating the surface acoustic wave corresponding to the frequency from the first frequency to the second frequency by inputting an electric signal, and the surface acoustic wave generating means formed on the piezoelectric substrate are generated. Surface acoustic wave receiving means for receiving the surface acoustic wave and converting it into an electrical signal, and the surface acoustic wave generated by the surface acoustic wave generating means between the surface acoustic wave generating means and the surface acoustic wave receiving means A surface acoustic wave reflecting means for reflecting a part of the surface acoustic wave, and the surface acoustic wave generating means comprises a pair of generation side oblique electrodes having a plurality of generation electrode fingers for generating the surface acoustic waves, and the generation side oblique The pole is such that the electrode finger interval between adjacent generation electrode fingers gradually spreads along one direction orthogonal to the propagation direction of the surface acoustic wave, and is the maximum and minimum electrode finger interval. A surface acoustic wave having first and second wavelengths is generated at each position, and the surface acoustic wave receiving means has a pair of reception-side oblique electrodes having a plurality of reception electrode fingers for receiving the surface acoustic wave. The reception-side oblique electrodes are such that the electrode finger intervals of the reception electrode fingers adjacent to each other gradually spread along the one direction, and at each position where the maximum and minimum electrode finger intervals are obtained, The surface acoustic wave having the first and second wavelengths generated by the generation-side oblique electrode is received, and the surface acoustic wave reflecting means is a low frequency lower than the first frequency by a predetermined frequency. Frequency and the second Be one that reflects the surface acoustic wave having a center frequency higher by the high-frequency frequencies predetermined than wave number, comprising a plurality of reflectors arranged along the propagation direction of the surface acoustic wave, wherein Each reflector is divided into a plurality of channels through a plurality of boundary portions for each predetermined frequency between the low frequency and the high frequency in a direction perpendicular to the propagation direction. The surface acoustic wave filter is characterized in that a vertical position is different from each other of the reflectors .

  According to the present invention, in a surface acoustic wave filter in which a reflector is provided in a propagation path portion of an oblique electrode finger, ripples in a band are distributed to other bands by dispersing boundary portions of reflectors having different periods into a plurality of channels. Therefore, ripples can be prevented from occurring in the surface acoustic wave band.

It is a figure which shows notionally the structure of the surface acoustic wave filter 100 in 1st Embodiment. It is a figure which shows the frequency characteristic of the insertion loss of the surface acoustic wave filter 100 in 1st Embodiment. It is a figure which shows notionally the structure of the conventional elastic filter 200. FIG. It is a figure which shows the frequency characteristic of the insertion loss of the conventional surface acoustic wave filter 200. FIG. It is a figure which shows notionally an example of a structure of the surface acoustic wave filter in 2nd Embodiment. It is a figure which shows notionally an example of a structure of the surface acoustic wave filter in 3rd Embodiment. It is a figure which shows notionally an example of a structure of the surface acoustic wave filter in 4th Embodiment. It is a modification in embodiment of this invention. It is a figure explaining the difference in the shoulder characteristic of the surface acoustic wave filter before providing a reflector in the propagation path part of an oblique electrode finger, and after providing.

(First embodiment)
Hereinafter, the surface acoustic wave filter according to the first embodiment will be described with reference to the drawings.
FIG. 1 is a diagram conceptually showing the structure of a surface acoustic wave filter 100 in this embodiment.

  As shown in FIG. 1, the surface acoustic wave filter 100 according to this embodiment includes a piezoelectric substrate 11, oblique electrode fingers 12 to 15 formed of a metal thin film having the same thickness on the piezoelectric substrate 11, an integrated reflector 20, and the like. It has. In FIG. 1, in order to make the configuration easy to understand, there are four electrode fingers for the oblique electrode fingers 12 and 14 and three electrode fingers for the oblique electrode fingers 13 and 15. Hereinafter, the propagation direction of the surface acoustic wave is referred to as the x-axis direction, and the direction perpendicular to the x-axis direction is referred to as the y-axis direction.

The piezoelectric substrate 11 is made of a ferroelectric piezoelectric material such as lithium niobate, potassium niobate, lithium tantalate, or langasite. In the present embodiment, the piezoelectric substrate 11 is formed of a 28 degree Y-cut LiNbO ₃ single crystal substrate and has a rectangular shape as shown in FIG.

  The oblique electrode fingers 12 and 13 are formed on the piezoelectric substrate 11 by a metal thin film made of, for example, an AlCu alloy, and are arranged so that the electrode fingers are alternately adjacent to each other. The oblique electrode fingers 12 and 13 are connected to an electric signal source (not shown) such that the oblique electrode finger 13 is on the ground side, for example, and an electric signal is input from the electric signal source. The oblique electrode fingers 12 and 13 constitute a surface acoustic wave generating means according to the present invention, and each electrode finger included in the oblique electrode fingers 12 and 13 constitutes a generated electrode finger according to the present invention.

  Further, in the oblique electrode fingers 12 and 13, the interval between the electrode fingers adjacent to each other is formed so as to increase toward the upper side in the y-axis direction. The oblique electrode fingers 12 and 13 have electrode finger end portions 12a and 13a, respectively. Here, as shown in the drawing, a surface acoustic wave having a wavelength of λ1 is generated on the electrode finger end portion 13a side, and the electrode finger intervals of the oblique electrode fingers 12 and 13 on the line segment A are respectively λ1. On the other hand, a surface acoustic wave having a wavelength of λ2 is generated on the electrode finger end portion 12a side, and the electrode finger interval between the oblique electrode fingers 12 and 13 on the line segment B is λ2. That is, in the diagonal electrode fingers 12 and 13, the electrode finger interval changes from the maximum interval λ1 to the minimum interval λ2. Note that λ1 corresponds to the first wavelength according to the present invention, and λ2 corresponds to the second wavelength according to the present invention.

  On the other hand, the oblique electrode fingers 14 and 15 are configured similarly to the oblique electrode fingers 12 and 13, respectively. That is, the oblique electrode fingers 14 and 15 are formed on the piezoelectric substrate 11 by a metal thin film of, for example, an AlCu alloy, and are arranged so that the respective electrode fingers are alternately adjacent. In addition, the oblique electrode fingers 14 and 15 are connected to the ground side, for example, so that the oblique electrode fingers 15 receive surface acoustic waves, convert them into electric signals, and output the converted electric signals. The oblique electrode fingers 14 and 15 constitute a surface acoustic wave receiving means according to the present invention, and each electrode finger included in the oblique electrode fingers 14 and 15 constitutes a reception electrode finger according to the present invention.

  Further, in the diagonal electrode fingers 14 and 15, the interval between the electrode fingers adjacent to each other is formed so as to increase toward the upper side in the y-axis direction. The oblique electrode fingers 14 and 15 have electrode finger end portions 14a and 15a, respectively. In addition, a surface acoustic wave having a wavelength of λ1 is received on the electrode finger end portion 15a side, and the electrode finger interval between the oblique electrode fingers 14 and 15 on the line segment A is λ1. On the other hand, a surface acoustic wave having a wavelength of λ2 is received on the electrode finger end portion 14a side, and the distance between the electrode fingers of the oblique electrode fingers 14 and 15 on the line segment B is λ2. That is, also in the oblique electrode fingers 14 and 15, the electrode finger interval changes between the maximum interval λ1 and the minimum interval λ2.

  In the above-described configuration, the oblique electrode fingers 12 and 13 receive an electric signal from an electric signal source (not shown), and out of the frequency components included in the electric signal, frequency components corresponding to the distance from the electrode finger interval λ1 to λ2 are obtained. The surface acoustic wave is generated based on the piezoelectric effect by the piezoelectric substrate 11. Specifically, assuming that the frequency of the surface acoustic wave generated at the electrode finger interval λ1 is the first frequency and the frequency of the surface acoustic wave generated at the electrode finger interval λ2 is the second frequency, the oblique electrode fingers 12 and 13 Generates a surface acoustic wave corresponding to the frequency components from the first frequency to the second frequency among the frequency components included in the input electrical signal.

  The surface acoustic waves generated by the oblique electrode fingers 12 and 13 propagate along the surface of the piezoelectric substrate 11 and travel in the x-axis direction, and are received by the oblique electrode fingers 14 and 15. The oblique electrode fingers 14 and 15 convert the received surface acoustic waves into electrical signals based on the piezoelectric effect by the piezoelectric substrate 11 and output electrical signals including frequency components from the first frequency to the second frequency. It has become.

  An integrated reflector 20 is provided on the piezoelectric substrate 11 between the oblique electrode fingers 12 and 13 and the oblique electrode fingers 14 and 15. Hereinafter, the integrated reflector 20 will be described in detail.

  A line segment A shown in FIG. 1 is a line segment that connects the electrode finger end portion 13a and the electrode finger end portion 15a, and a line segment B connects the electrode finger end portion 12a and the electrode finger end portion 14a. It is a line segment. For the sake of convenience, the line segment A and B are equally divided into six channels ch1 to ch6 (six frequency bands). The distance between the electrode fingers becomes narrower from ch1 to ch6, the surface acoustic wave having the lowest frequency propagates in ch1, and the surface acoustic wave having the highest frequency propagates in ch6.

  The integrated reflector 20 is formed on the piezoelectric substrate 11 by, for example, an AlCu alloy metal thin film, and reflects a surface acoustic wave having a predetermined frequency. The integrated reflector 20 is connected to ground. The integrated reflector 20 includes a low-frequency reflector 20a and a high-frequency reflector 20b. The integrated reflector 20 constitutes a surface acoustic wave reflecting means according to the present invention.

  The low-frequency reflector 20a includes the first reflectors 22a, 22b, 22c, 22d, 22e, and 22f having different lengths in the y-axis direction, and the first reflectors 22a, 22b, 22c, 22d, 22e, and 22f. And a connecting portion 21 electrically connected to each. Note that the length of each first reflector in the y-axis direction becomes shorter along the x-axis direction in the order of the first reflectors 22a, 22b, 22c, 22d, 22e, and 22f. The reflector interval of each of the first reflectors 22a, 22b, 22c, 22d, 22e, and 22f is 1/2 · (λ3) and has a relationship of λ1 <λ3.

  The high-frequency reflector 20b includes second reflectors 23a, 23b, 23c, 23d, 23e, and 23f having different lengths in the y-axis direction, and second reflectors 23a, 23b, 23c, 23d, 23e, and 23f. And a connection part 24 electrically connected to each. The length of the second reflector in the y-axis direction becomes longer along the x-axis direction in the order of the second reflectors 23a, 23b, 23c, 23d, 23e, and 23f. The reflector interval of each of the second reflectors 23a, 23b, 23c, 23d, 23e, and 23f is 1/2 · (λ4), and has a relationship of λ2> λ4.

The low band reflector 20a reflects a surface acoustic wave having a low frequency component in the pass band. The high frequency reflector 20b reflects a surface acoustic wave having a high frequency component in the pass band.
Further, as shown in FIG. 1, in the channel ch6, the first reflector 22a is electrically connected to the second reflector 23a. In the channel ch5, the first reflector 22b is electrically connected to the second reflector 23b. In the channel ch4, the first reflector 22c is electrically connected to the second reflector 23c. In the channel ch3, the first reflector 22d is electrically connected to the second reflector 23d. In the channel ch2, the first reflector 22e is electrically connected to the second reflector 23e. In the channel ch1, the first reflector 22f is electrically connected to the second reflector 23f. Thus, each of the first reflectors 22a, 22b, 22c, 22d, 22e, and 22f is electrically connected to each of the second reflectors 23a, 23b, 23c, 23d, 23e, and 23f, and Each connected boundary is distributed over a plurality of channels.

Next, the frequency characteristic of the insertion loss of the surface acoustic wave filter 100 in this embodiment will be described.
FIG. 2 is a diagram illustrating frequency characteristics of insertion loss of the surface acoustic wave filter 100 according to the present embodiment. In FIG. 2, the vertical axis represents insertion loss and the horizontal axis represents frequency.

  As shown in FIG. 2, the surface acoustic wave composite waveform 110 is obtained by combining the components of the surface acoustic waves generated in the regions ch1 to ch6 (see FIG. 1). And a waveform falling portion 112.

The rising part 111 of the waveform is a shoulder characteristic on the lower side of the pass band obtained by setting the electrode finger interval λ1 and the reflector interval 1/2 · (λ3) to desired values.
Since the low-frequency reflector 20a is a notch filter that reflects only the frequency f1 lower than the first frequency among the surface acoustic waves generated by the oblique electrode fingers 12 and 13, the rising portion of the waveform At 111, the shoulder characteristics on the low band side of the pass band are made steep.

The waveform falling portion 112 is a shoulder characteristic on the high band side of the pass band obtained by setting the electrode finger interval λ2 and the reflector interval 1/2 · (λ4) to desired values.
The high-frequency reflector 20b is a notch filter that reflects only the frequency f2 of the surface acoustic waves generated by the oblique electrode fingers 12 and 13 that is higher than the second frequency by a predetermined frequency. In the section 112, the shoulder characteristic on the high frequency side of the pass band is made steep.
Also, as shown in FIG. 2, the insertion loss of the surface acoustic wave composite waveform 110 changes substantially constant within the band from the first frequency to the second frequency.

Next, the effect of this embodiment will be described. FIG. 3 is a diagram conceptually showing the structure of a conventional surface acoustic wave filter 200. In addition, about the structure similar to 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.
As shown in FIG. 3, the conventional surface acoustic wave filter 200 includes a piezoelectric substrate 11, oblique electrode fingers 12 to 15 formed of a metal thin film having the same film thickness on the piezoelectric substrate 11, and an integrated reflector 31. I have. The integrated reflector 31 includes a low-frequency reflector 31a and a high-frequency reflector 31b.

The low-frequency reflector 31a includes a first reflector 32a and a connection portion 32b that electrically connects the first reflector 32a.
The low band reflector 31a reflects a surface acoustic wave having a low frequency component in the pass band.

The high-frequency reflector 31b includes a second reflector 32c and a connection portion 32d that electrically connects the second reflector 32c.
The high frequency reflector 31b reflects a surface acoustic wave having a high frequency component in the pass band. Further, the first reflector 32a and the second reflector 32c are electrically connected as shown in the vicinity of the center of the line segments A and B.

  FIG. 4 is a diagram showing the frequency characteristics of the insertion loss of the conventional surface acoustic wave filter 200. In FIG. 4, the vertical axis represents the insertion loss and the horizontal axis represents the frequency. The surface acoustic wave composite waveform 210 is a composite of the surface acoustic wave components generated in the regions ch1 to ch6 (see FIG. 1). The waveform rising portion 211 and the waveform falling portion 212 are combined. Including.

The rising portion 211 of the waveform is a shoulder characteristic on the lower side of the pass band obtained by setting the electrode finger interval λ1 and the reflector interval 1/2 · (λ3) to desired values.
The low-pass reflector 31a is a notch filter that reflects only the center frequency f1 of the surface acoustic waves generated by the oblique electrode fingers 12 and 13 that is lower than the first frequency by a predetermined frequency. In the portion 211, the shoulder characteristics on the low frequency side of the pass band are steep.

The waveform falling portion 212 is a shoulder characteristic on the high frequency side of the pass band obtained by setting the electrode finger interval λ2 and the reflector interval 1/2 · (λ4) to desired values.
The high-frequency reflector 31b is a notch filter that reflects only the center frequency f2 of the surface acoustic waves generated by the oblique electrode fingers 12 and 13 that is higher than the second frequency by a predetermined frequency. At the descending portion 212, the shoulder characteristics on the high frequency side of the pass band are steep.

  As shown by an arrow A in FIG. 4, ripple occurs at the frequency f3 within the band of the surface acoustic wave composite waveform 210. The reason why ripple occurs in the band is that the boundary portion between the low-frequency reflector 31a and the high-frequency reflector 31b, which are reflectors having different frequencies of the reflected surface acoustic wave, is provided on the same channel. This is because characteristic degradation has occurred in some channels. The frequency f3 is the frequency of the surface acoustic waves generated by the oblique electrode fingers 12 and 13 at the position corresponding to the boundary portion.

  However, as described above, according to the present embodiment, the surface acoustic wave filter 100 has a boundary portion between the low-frequency reflector 20a and the high-frequency reflector 20b, which are reflectors having different frequencies of the reflected surface acoustic waves. They are not collinear in the x-axis direction. Specifically, the boundary portion between the low-frequency reflector 20a and the high-frequency reflector 20b is dispersed in a plurality of channels. Therefore, the characteristic deterioration at the boundary between the low-frequency reflector 20a and the high-frequency reflector 20b is dispersed in a plurality of channels, so that ripples can be prevented from occurring in the surface acoustic wave band.

(Second Embodiment)
Next, a second embodiment of the surface acoustic wave filter according to the present invention will be described.
FIG. 5 is a diagram conceptually illustrating an example of the configuration of the surface acoustic wave filter 300 according to the second embodiment.
As shown in FIG. 5, the surface acoustic wave filter 300 includes a piezoelectric substrate 11, oblique electrode fingers 12 to 15 formed of a metal thin film having the same film thickness on the piezoelectric substrate 11, and an integrated reflector 40. . In addition, about the structure similar to 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The integrated reflector 40 includes a low-frequency reflector 40a and a high-frequency reflector 40b. The integrated reflector 40 constitutes a surface acoustic wave reflecting means according to the present invention.

  The low-pass reflector 40a is electrically connected to each of the first reflectors 22a, 22b, 22c, 22d, 22e, and 22f and each of the first reflectors 22a, 22b, 22c, 22d, 22e, and 22f. Part 21.

The high-frequency reflector 40b includes second reflectors 23a, 23b, 23c, 23d, 23e, and 23f having different lengths in the y-axis direction, and second reflectors 23a, 23b, 23c, 23d, 23e, and 23f. And a connection portion 24 electrically connected to each.
It has.

  In the first embodiment, the surface acoustic wave filter 100 includes channels ch6, ch5, ch4, ch3, ch2 as each boundary portion between the low-frequency reflector 20a and the high-frequency reflector 20b advances in the x-axis direction. In this embodiment, as shown in FIG. 5, the order in which each of the boundary portions is distributed and arranged in the channels ch1 to ch6 is random.

  As described above, according to the present embodiment, the surface acoustic wave filter 300 has a plurality of boundary portions between the low-frequency reflector 40a and the high-frequency reflector 40b, which are reflectors having different frequencies of reflected surface acoustic waves. Distributed across channels. Therefore, since the characteristic deterioration at the boundary between the low-frequency reflector 40a and the high-frequency reflector 40b is dispersed in a plurality of channels, it is possible to prevent ripples from occurring in the surface acoustic wave band.

(Third embodiment)
Next, a third embodiment of the surface acoustic wave filter according to the present invention will be described.
FIG. 6 is a diagram conceptually illustrating an example of the configuration of the surface acoustic wave filter 400 according to the third embodiment.
As shown in FIG. 6, the surface acoustic wave filter 400 includes a piezoelectric substrate 11, oblique electrode fingers 12 to 15 formed of a metal thin film having the same film thickness on the piezoelectric substrate 11, and an integrated reflector 50. . In addition, about the structure similar to 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

The integrated reflector 50 includes a low-frequency reflector 50a and a high-frequency reflector 50b. The integrated reflector 50 constitutes the surface acoustic wave reflecting means according to the present invention.
The low-frequency reflector 50a includes first reflectors 22a, 22d, 22e, and 22f, and a connection portion 21 that is electrically connected to each of the first reflectors 22a, 22d, 22e, and 22f.

  The high-frequency reflector 50b includes second reflectors 23a, 23d, 23e, and 23f and a connection portion 24 that is electrically connected to each of the second reflectors 23a, 23d, 23e, and 23f.

  In the first embodiment, the surface acoustic wave filter 100 includes channels ch6, ch5, ch4, ch3, ch2 as each boundary portion between the low-frequency reflector 20a and the high-frequency reflector 20b advances in the x-axis direction. , Ch1 are distributed and arranged in this order. However, in the present embodiment, as shown in FIG. 6, each of the boundary portions may be distributed to two or more channels in channels ch1 to ch6. A plurality of the boundary portions may be arranged in one channel.

  As described above, according to the present embodiment, the surface acoustic wave filter 400 is such that the boundary portion between the low-pass reflector 50a and the high-pass reflector 50b, which are reflectors having different frequencies of reflected surface acoustic waves, is the x-axis. Not collinear in direction. Specifically, the boundary between the low-frequency reflector 50a and the high-frequency reflector 50b is dispersed in a plurality of channels. Therefore, the characteristic deterioration at the boundary between the low-frequency reflector 50a and the high-frequency reflector 50b is dispersed in a plurality of channels, so that it is possible to prevent ripples from occurring in the surface acoustic wave band.

(Fourth embodiment)
Next, a fourth embodiment of the surface acoustic wave filter according to the present invention will be described.
FIG. 7 is a diagram conceptually illustrating an example of the configuration of the surface acoustic wave filter 500 according to the fourth embodiment.
As shown in FIG. 7, the surface acoustic wave filter 500 includes a piezoelectric substrate 11, oblique electrode fingers 12 to 15 formed of a metal thin film having the same film thickness on the piezoelectric substrate 11, and an integrated reflector 60. . In addition, about the structure similar to 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

The integrated reflector 60 includes a low-frequency reflector 60a and a high-frequency reflector 60b. The integral reflection 50 constitutes a surface acoustic wave reflecting means according to the present invention.
The low-frequency reflector 60a includes first reflectors 22a, 22b, 22c, 22d, 22e, and 22f.

  The high-frequency reflector 60b includes second reflectors 23a, 23b, 23c, 23d, 23e, and 23f.

  In the first embodiment, in the surface acoustic wave filter 100, the boundary portion between the low-frequency reflector 20a and the high-frequency reflector 20b is short-circuited. However, as shown in FIG. Each of the boundary portions between the reflector 60a and the high-frequency reflector 60b is disposed so as to be opened. The open boundary between the low-frequency reflector 60a and the high-frequency reflector 60b is distributed and arranged in the order of channels ch6, ch5, ch4, ch3, ch2, and ch1 as it proceeds in the x-axis direction. .

  As described above, according to the present embodiment, the surface acoustic wave filter 500 has a boundary portion between the low-frequency reflector 60a and the high-frequency reflector 60b, which are reflectors having different frequencies of reflected surface acoustic waves, in the x-axis. Not collinear in direction. Specifically, the boundary between the low-frequency reflector 60a and the high-frequency reflector 60b is dispersed in a plurality of channels. Therefore, the characteristic deterioration at the boundary portion between the low-frequency reflector 60a and the high-frequency reflector 60b is dispersed in a plurality of channels, so that ripples can be prevented from occurring in the surface acoustic wave band.

In the present embodiment, as in the second embodiment, the order in which the open boundary portions of the low-frequency reflector 60a and the high-frequency reflector 60b are dispersed and arranged in the channels ch1 to ch6 may be random. .
Further, in the present embodiment, as in the third embodiment, each of the open boundary portions of the low-frequency reflector 60a and the high-frequency reflector 60b is distributed to two or more channels in the channels ch1 to ch6. It is sufficient that a plurality of the boundary portions may be arranged in one channel.

The present invention is not limited to the above-described embodiment described with reference to the drawings, and various modifications can be considered within the technical scope thereof.
FIG. 8 is a modification of the embodiment of the present invention. FIG. 8A is a modification of the boundary portion between the low-frequency reflector and the high-frequency reflector according to the first embodiment, the second embodiment, and the third embodiment. FIG. 8B is a modification of the boundary portion between the low-frequency reflector and the high-frequency reflector according to the fourth embodiment.
In the first embodiment, the second embodiment, and the third embodiment, the boundary portion between the low-frequency reflector and the high-frequency reflector is parallel to the channel. For example, FIG. As shown in FIG. 4, the channel may be connected obliquely.
In the fourth embodiment, the open boundary between the low-frequency reflector and the high-frequency reflector is parallel to the channel. For example, as shown in FIG. It may be diagonal.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

  In the above-described embodiment, the case where the integrated reflector 31 is connected to the ground has been described. However, the embodiment of the present invention is not limited to this, and the integrated reflector 31 may not be connected to the ground. Good.

  In the above-described embodiment, the case where the oblique electrode fingers 12 to 15 are formed of a metal thin film having the same film thickness has been described. However, the embodiment of the present invention is not limited to this, and the same film thickness is used. It may not be formed of a metal thin film.

100, 200 Surface acoustic wave filter 11 Piezoelectric substrate 12-15 Diagonal electrode fingers 12a, 13a, 14a, 15a Electrode finger end portions 20, 31 Integrated reflector 20a, 31a Low-frequency reflectors 20b, 31b High-frequency reflectors 21, 24 , 32b, 32d connecting portions 22a, 22b, 22c, 22d, 22e, 22f First reflectors 23a, 23b, 23c, 23d, 23e, 23f Second reflectors

Claims (1)

A surface acoustic wave filter that passes an electrical signal in a frequency range from a first frequency to a second frequency higher than the first frequency,
A piezoelectric substrate, surface acoustic wave generating means for generating a surface acoustic wave according to a frequency from the first frequency to the second frequency by inputting an electric signal formed on the piezoelectric substrate, and on the piezoelectric substrate A surface acoustic wave receiving means that receives the surface acoustic wave generated by the surface acoustic wave generating means and converts the surface acoustic wave into an electrical signal; and the elasticity between the surface acoustic wave generating means and the surface acoustic wave receiving means. A surface acoustic wave reflecting means for reflecting a part of the surface acoustic wave generated by the surface wave generating means,
The surface acoustic wave generation means includes a pair of generation side oblique electrodes having a plurality of generation electrode fingers for generating the surface acoustic wave,
The generation-side oblique electrode is such that the electrode finger interval between adjacent generation electrode fingers gradually spreads along one direction perpendicular to the propagation direction of the surface acoustic wave, and the maximum and minimum electrodes Generating surface acoustic waves of the first and second wavelengths at respective positions to be a finger interval;
The surface acoustic wave receiving means includes a pair of reception-side oblique electrodes having a plurality of reception electrode fingers for receiving the surface acoustic wave,
The reception-side oblique electrodes are formed such that electrode finger intervals of adjacent reception electrode fingers gradually spread along the one direction, and are at the maximum and minimum electrode finger intervals at the generation side. Receiving the surface acoustic waves of the first and second wavelengths generated by the oblique electrodes;
The surface acoustic wave reflecting means for reflecting the surface acoustic wave having a center frequency higher by the high-frequency frequencies predetermined than a predetermined frequency by a lower low frequency and the second frequency than the first frequency And
A plurality of reflectors arranged along the propagation direction of the surface acoustic wave,
Each of the reflectors is divided into a plurality of channels through a plurality of boundary portions for each predetermined frequency between the low frequency and the high frequency in a direction perpendicular to the propagation direction,
The surface acoustic wave filter according to claim 1, wherein the boundary portion is formed in a position different from each other in the vertical direction .

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