JP2002152004A - Resonator type surface acoustic wave device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resonator type surface acoustic wave device that enhances the frequency characteristic at lower frequencies in the pass band so as to have high steepness of the frequency characteristic in the vicinity of the pass band. SOLUTION: In the resonator type surface acoustic wave device configured by connecting series arm surface acoustic wave resonators 6A and parallel arm surface acoustic wave resonators 5, 7 placed on a piezoelectric substrate 1 in multi-stage in a ladder form, the parallel arm surface acoustic wave resonators 5, 7 are configured to be a regular type surface acoustic wave resonator 2 and applying weighting by the interleaving method to at least one of the series arm surface acoustic wave resonators 6A configures a surface acoustic wave resonator 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resonator type surface acoustic wave device, for example, a resonator type surface acoustic wave device used for a high frequency circuit of a mobile communication device.

[0002]

2. Description of the Related Art FIG. 7 shows a conventional resonator-type surface acoustic wave (Surface Acoustic Wave: hereinafter referred to as S) shown in, for example, pages 91 to 100 of the 26th EM Symposium Proceedings.
FIG. 1 is a schematic diagram illustrating a configuration of an apparatus (abbreviated as AW). In this figure, 1 is a piezoelectric substrate, 2 is a regular interdigital transducer (hereinafter referred to as IDT) provided on the piezoelectric substrate, 4 is a reflector also provided on the piezoelectric substrate, and 5 is Two sets of one parallel arm SAW resonator having a configuration in which two reflectors 4 and a regular IDT 2 are combined are provided. One set is located near the input terminal 9, and the other set is It is connected between the input terminal 9 or the output terminal 10 and the ground at a position near the output terminal 10, respectively.

[0003] Reference numeral 6 denotes a series arm SAW resonator in which two sets of a combination of two reflectors 4 and a normal type IDT 2 are provided. One set is located near the input terminal 9 and the other set. One set is connected in series between the input terminal 9 and the output terminal 10 at a position near the output terminal 10. 7 is the second
Of the first parallel arm SAW resonator 5
It is configured similarly to. Reference numeral 8 denotes the width of the intersection of the electrodes in the normal type IDT2. Also, the first and second parallel arms SAW
The resonators 5 and 7 and the series arm SAW resonator 6 are connected in a multi-stage ladder configuration to form a resonator type SAW device.

Next, the operation of the conventional resonator type SAW device will be described. FIG. 8A shows the connection relationship of the series arm SAW resonator 6 to the input / output terminals 9 and 10.
With such a two-terminal pair circuit, the input terminal 9
8B, all pass through the output terminal 10 at the resonance frequency fr, and do not pass at all at the anti-resonance frequency fa, and the attenuation pole 60 is generated, as shown in the pass characteristic in FIG. FIG. 9A shows first and second input / output terminals 9 and 10.
FIG. 9B shows the connection relationship between the second parallel arm SAW resonators 5 and 7. By using such a two-port pair circuit, the electric signal input to the input terminal 9 has the passing characteristic shown in FIG. As shown, at the anti-resonance frequency fa, all passes through the output terminal 10, and at the resonance frequency fr, it does not pass at all, and an attenuation pole 50 is generated. Therefore, the resonance frequency fr of the serial arm SAW resonator 6 shown in FIG. 8B and the anti-resonance frequency fa of the first and second parallel arm SAW resonators 5 and 7 shown in FIG. By connecting them in a multi-stage ladder type so as to match, a resonator type SAW device having band pass characteristics as shown in FIG. 10 can be obtained.

FIG. 11 shows that the number of regular IDTs 2 in the series arm SAW resonator 6 is 161 and the number of reflectors 4 is 1
00, the cross width 8 is 25 μm, and the first parallel arm SAW
The number of normal type IDTs 2 of the resonator 5 is 101, and the reflector 4
Are 100, the intersection width 8 is 45 μm, and the number of regular IDTs 2 of the second parallel arm SAW resonator 7 is 1.
81, the number of reflectors 4 is 100, and the intersection width 8 is 70 μ
FIG. 9 is a frequency characteristic diagram showing a calculation result of a pass characteristic of the resonator type SAW device when m is set. As shown in this figure,
In the conventional resonator type SAW device, there is a problem that the shoulder on the low band side in the pass band 11 is dropped and the steepness of the attenuation amount on the low band side of the pass band 11 is deteriorated. In addition, it is conceivable to increase the number of ladder-type steps in order to eliminate the shoulder on the low frequency side in the pass band 11 and improve the steepness, but in this case, the insertion loss also increases. become.

[0006]

SUMMARY OF THE INVENTION Conventional resonator type SAW
Since the device is configured as described above, there is a problem that the shoulder of the pass characteristic is distorted on the lower side of the pass band and the steepness of the attenuation on the lower side of the pass band is deteriorated. . Further, when the number of ladder-type steps is increased to improve steepness, there is a problem that insertion loss increases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has a small loss in a pass band.
Moreover, it is an object of the present invention to improve a shoulder SAW device of a pass characteristic on a low band side in a pass band and to obtain a resonator type SAW device having a large steepness near the pass band.

[0008]

According to the present invention, there is provided a resonator type SAW device in which a plurality of series arm SAW resonators and a plurality of parallel arm SAW resonators provided on a piezoelectric substrate are connected in a multi-stage ladder form. In the resonator type SAW device configured as described above, the parallel arm SAW resonator is a normal type SAW resonator, and at least one of the series arm SAW resonators is a SAW resonator weighted by a thinning method. Things.

A resonator type SAW device according to the present invention is constructed by connecting a plurality of series arm SAW resonators and parallel arm SAW resonators provided on a piezoelectric substrate in a multi-stage ladder form. In a resonator type SAW device, a serial arm SAW
The resonator is a regular SAW resonator, and the parallel arm S
At least one of the AW resonators is a SAW resonator weighted by a thinning method.

A resonator type SAW device according to the present invention is constructed by connecting a plurality of series arm SAW resonators and parallel arm SAW resonators provided on a piezoelectric substrate in a multi-stage ladder form. In a resonator type SAW device, a serial arm SAW
At least one of the resonator and the parallel arm SAW resonator is a SAW resonator weighted by a thinning method.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of the first embodiment. In this figure,
1 is a piezoelectric substrate, 2 is a regular type IDT provided on the piezoelectric substrate, and 3 is a thinned type ID constituting a main part of the present invention.
At T, an electrode obtained by a predetermined electrode design method is formed by thinning out, for example, as shown in the figure. 4 is a reflector also provided on the piezoelectric substrate, 5 is a first parallel arm SAW resonator, and two reflectors 4 and a regular IDT 2
Are provided, one set is located near the input terminal 9, and the other set is provided at the output terminal 10.
Are connected between the input terminal 9 or the output terminal 10 and the ground, respectively.

Reference numeral 6A denotes a series arm SAW resonator in which two sets each having a configuration in which two reflectors 4 and a thinned-out IDT 3 are combined are provided. One set is located at a position near the input terminal 9 and the other set. Are connected in series between the input terminal 9 and the output terminal 10 at a position near the output terminal 10.
Reference numeral 7 denotes a second parallel arm SAW resonator, and the first parallel arm SAW resonator
The configuration is the same as that of the resonator 5. 8 is a regular type IDT2
Alternatively, it is the crossing width of the electrodes in the thinning type IDT3.
The first and second parallel arm SAW resonators 5 and 7 and the series arm SAW resonator 6A are connected in a multi-stage ladder configuration to form a resonator SAW device.

FIG. 2 shows that the number of thinned IDTs 3 of series arm SAW resonator 6A in the first embodiment is 161.
The number of the reflectors 4 is 100, the intersection width 8 is 30 μm, the number of the normal type IDTs 2 of the first parallel arm SAW resonator 5 is 101, the number of the reflectors 4 is 100, and the intersection width 8 is 45 μm, the number of regular type IDTs 2 of the second parallel arm SAW resonator 7 is 181 and the number of reflectors 4 is 10
FIG. 9 is a frequency characteristic diagram showing calculation results of the pass characteristics of the resonator type SAW device when there are no zeros and the intersection width 8 is 70 μm. 2 is a frequency characteristic diagram showing a pass characteristic of the conventional resonator type SAW device shown in FIG. 7, and 13 is a first embodiment.
FIG. 5 is a frequency characteristic diagram showing a pass characteristic of the resonator type SAW device of FIG. As is clear from this characteristic diagram, the first embodiment
In the resonator type SAW device described above, the shoulder of the lower band in the pass band 11 is improved and the steepness of the higher band of the pass band 11 is particularly increased.

Embodiment 2 FIG. Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 3 shows the second embodiment.
FIG. 3 is a schematic diagram showing the configuration of FIG. In this figure, the same or corresponding parts as those in FIG. The difference from FIG. 1 is that the series arm SAW resonator 6 is configured as a combination of two reflectors 4 and a normal type IDT 2 similarly to the conventional device, and the second parallel arm SAW resonator is The point is that the reflectors 4 and the thinned-out IDTs 3 are combined. That is, in FIG. 3, 7A is a second parallel arm SAW resonator. The configuration of the thinning type IDT 3 is the same as that shown in FIG.

4 indicates that the number of regular type IDTs 2 of the serial arm SAW resonator 6 in the second embodiment is 16
One, the number of reflectors 4 is 100, and the intersection width 8 is 25 μm.
The number of regular type IDTs 2 of the first parallel arm SAW resonator 5 is 101, the number of reflectors 4 is 100, and the intersection width is 8
Is 45 μm, the number of thinned-out IDTs 3 of the second parallel arm SAW resonator 7A is 181 and the number of reflectors 4 is 10
FIG. 13 is a frequency characteristic diagram showing calculation results of the pass characteristics of the resonator type SAW device when there are no zeros and the intersection width 8 is 65 μm. As shown in this figure, in the resonator type SAW device according to the second embodiment, the shoulder on the low frequency side in the pass band 11 is improved as compared with the characteristic 12 of the conventional device, and the pass band 11 The steepness on the low frequency side is large.

Embodiment 3 Next, a third embodiment of the present invention will be described with reference to the drawings. FIG. 5 shows the third embodiment.
FIG. 3 is a schematic diagram showing the configuration of FIG. In this figure, the same or corresponding parts as those in FIG. The difference from FIG. 3 is that the second parallel arm SAW resonator 7A
In addition to the above, two sets of series arm SAW resonators are also configured as a combination of two reflectors 4 and a thinned-out IDT 3. That is, in FIG. 5, 6A is a series arm SAW resonator. The configuration of the thinning type IDT 3 is the same as that shown in FIG.

In FIG. 6, reference numeral 15 denotes 161 thinned-out IDTs 3, 100 reflectors 4, and an intersection width 8 of 30 in the series arm SAW resonator 6A in the third embodiment.
μm and the normal type IDT of the first parallel arm SAW resonator 5.
2, the number of reflectors 4 is 100, the intersection width 8 is 45 μm, the number of thinned-out IDTs 3 of the second parallel arm SAW resonator 7A is 181 and the number of reflectors 4 is 100 Resonator type SA when the intersection width 8 is 65 μm
FIG. 9 is a frequency characteristic diagram showing a calculation result of a pass characteristic of the W device. As shown in this figure, the resonator type SA of the third embodiment
The W device has a pass band 11 compared to the characteristic 12 of the conventional device.
The lower shoulder in the inside is improved and the pass band 1 is improved.
The sharpness on both the low frequency side and the high frequency side of No. 1 is large.

[0018]

The resonator type SAW device according to the present invention has the following features.
Since the parallel arm SAW resonator is a normal type SAW resonator and at least one of the series arm SAW resonators is a SAW resonator weighted by a thinning method, a loss in a pass band is small, and The shoulder of the lower band in the pass band is improved, and the steepness of the higher band in the pass band is increased.

In the resonator type SAW device according to the present invention, the series arm SAW resonator is a normal type SAW resonator, and at least one of the parallel arm SAW resonators is weighted by a thinning method. Since the resonator is a resonator, the loss in the pass band is small, the shoulder of the lower band in the pass band is improved, and the steepness in the lower band of the pass band is increased.

In the resonator type SAW device according to the present invention, since at least one of the series arm SAW resonator and the parallel arm SAW resonator is a SAW resonator weighted by a thinning method, a pass band is provided. In this case, the shoulder loss on the low band side in the pass band is improved, and the steepness on the low band side and the high band side of the pass band is increased.

[Brief description of the drawings]

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

FIG. 2 is a frequency characteristic diagram showing a pass characteristic according to the first embodiment.

FIG. 3 is a schematic diagram showing a configuration of a second embodiment of the present invention.

FIG. 4 is a frequency characteristic diagram showing a pass characteristic according to the second embodiment.

FIG. 5 is a schematic diagram showing a configuration of a third embodiment of the present invention.

FIG. 6 is a frequency characteristic diagram showing a pass characteristic according to the third embodiment.

FIG. 7 is a schematic diagram showing a configuration of a conventional resonator type SAW device.

FIG. 8 is an explanatory diagram for explaining an operation of a conventional resonator type SAW device.

FIG. 9 is an explanatory diagram for explaining an operation of a conventional resonator type SAW device.

FIG. 10 is a frequency characteristic diagram showing pass characteristics in a conventional resonator type SAW device.

FIG. 11 is a frequency characteristic diagram showing pass characteristics in a conventional resonator type SAW device.

[Explanation of symbols]

Reference Signs List 1 piezoelectric substrate, 2 regular type IDT, 3 thinning type IDT, 4 reflector, 5 first parallel arm SA
W resonator, 6,6A series arm SAW resonator,
7, 7A second parallel arm SAW resonator, 8 cross width, 9 input terminal, 10 output terminal, 11
Pass band.

Claims (3)

[Claims] 1. A resonator type surface acoustic wave configured by connecting a plurality of series arm surface acoustic wave resonators and a parallel arm surface acoustic wave resonator provided on a piezoelectric substrate in a multi-stage ladder form. In the apparatus, the parallel arm surface acoustic wave resonator is a normal surface acoustic wave resonator, and at least one of the series arm surface acoustic wave resonators is weighted by a thinning method. A resonator-type surface acoustic wave device. 2. A resonator type surface acoustic wave configured by connecting a plurality of series arm surface acoustic wave resonators and a parallel arm surface acoustic wave resonator provided on a piezoelectric substrate in a multi-stage ladder form. In the apparatus, the serial arm surface acoustic wave resonator is a normal surface acoustic wave resonator, and at least one of the parallel arm surface acoustic wave resonators is weighted by a thinning method. A resonator-type surface acoustic wave device. 3. A resonator type surface acoustic wave configured by connecting a plurality of series arm surface acoustic wave resonators and a parallel arm surface acoustic wave resonator provided on a piezoelectric substrate in a multi-stage ladder form. In the apparatus, at least one of the series arm surface acoustic wave resonator and the parallel arm surface acoustic wave resonator is a surface acoustic wave resonator weighted by a thinning method. Surface wave device.