JPH0846467A - Adjusting method for frequency of resonator surface acoustic wave filter - Google Patents

Abstract

PURPOSE:To adjust the frequency characteristic of a resonator surface acoustic wave filter. CONSTITUTION:An insulating film 39A is adhered to cover the whole of an IDT 32, a grating reflector 33, an IDT 34 and a grating reflector 35, the both propagation speed of an SAW generated in a serial arm SAW resonator and a parallel arm SAW resonator lower by the same speed, and the both reactance characteristics of the serial arm SAW resonator and the parallel arm SAW resonator are moved to a low frequency side. Because this moving amount can be adjusted by the film thickness of the insulating film 39A, the insulating film 39A is adhered till a frequency characteristic becomes a desired one. By this procedure, the frequency adjustment of a resonator surface acoustic wave filter can be performed.

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 (surf) used in a high frequency signal processing section of a mobile phone device or the like.
ACE Acoustic Wave (hereinafter referred to as SAW) filter frequency adjustment method.

[0002]

2. Description of the Related Art A surface acoustic wave device is an interdigital transducer or a transducer (interdigital transducer) arranged on a piezoelectric substrate.
cer, hereinafter referred to as IDT), is a device for converting an electric signal into a surface acoustic wave. Among them, the surface acoustic wave filter has features of small size, light weight, and no adjustment, and the photolithography technology used for manufacturing a semiconductor device can be used in the manufacturing process thereof, and thus the mass productivity is excellent. SAW filters are generally classified into a transversal type and a resonator type. FIG. 2 is a structural diagram showing the configuration of a conventional general transversal SAW filter.
This transversal SAW filter includes a plurality of input IDTs 3 connected to the input terminals 2 on the piezoelectric substrate 1.
And a plurality of output IDTs 4 connected to the output terminal 5. The transversal SAW filter has a structure in which a large number of input IDTs 3 and output IDTs 4 are alternately arranged. FIG. 3 is a conceptual diagram of a SAW resonator. This SAW resonator includes an IDT 6 and a grating reflector 7. The resonator type SAW filter is an SA composed of an IDT and a grating reflector.
It is configured using a W resonator. Resonator type SA
W filters are classified into a ladder type and a dual mode type.
FIG. 4 is a block diagram of a ladder circuit using two SAW resonators shown in FIG. 3, and FIG. 5 is a block diagram of a dual mode SAW resonator. Generally, the resonator type SAW filter is
Compared with a transversal SAW filter, it has the characteristics of low loss, high attenuation, narrow band, and no matching circuit required.

FIG. 6 is a plan view of a reflector type SAW resonator. This SAW resonator has a piezoelectric substrate 11, and an input terminal 12 to which an electric signal is input is provided on the piezoelectric substrate 11.
Are formed. A comb-shaped electrode finger 14 a is connected to the input terminal 12. On the opposite side of the input terminal 12 on the piezoelectric substrate 11, the output terminal 13 is provided similarly to the input terminal 12.
Are formed. A comb-shaped electrode finger 14b is connected to the output terminal 13 so as to face the electrode finger 14a. The electrode finger 14a and the electrode finger 14b constitute the transducer 14. The transducer 14 has an input terminal 12
After converting the electric signal input from the SAW 16 into the SAW 16, the SAW 16 is converted into the electric signal. Propagation directions A, A'of the SAW 16 on both sides of the transducer 14.
Are provided with reflectors 15R and 15L. The reflectors 15R and 15L have a plurality of electrodes whose ends are connected to each other, and these electrodes are formed in parallel at equal intervals.
6 is reflected to generate a reflected wave. Next, FIG.
Will be described. High frequency signal (several hundred K
(Hz or more), a high frequency voltage is applied to the electrode finger 14a connected to the input terminal 12, and a high frequency voltage is inductively generated in the electrode finger 14b connected to the output terminal 13, but the phase is delayed. Therefore, there is a potential difference between both terminals.
As a result, the piezoelectric substrate 1 under the electrode fingers 14a and 14b is
The surface of 1 is distorted, and the SAW 16 having the same frequency as the input signal is excited. The SAW 16 propagates in the propagation directions A and A ′ of the SAW 16 on both sides of the transducer 14, and the reflector 1
The reflected wave is generated by being reflected by 5R and 15L. These reflected waves resonate with the newly generated SAW to generate a standing wave. An electric signal having the same frequency as this standing wave is output from the output terminal 13. Note that the impedance of the entire system viewed from the input terminal 12 is different when the output terminal 13 is released, terminated with a load, and grounded. In any case, the SAW excites and the resonator Behave. FIG. 7 is a circuit diagram of an electrically equivalent circuit of the SAW resonator. Like the crystal unit, the coil L,
It is represented by a parallel circuit of a series circuit of a capacitor C and a resistor R and a capacitance C0 of the IDT.

FIG. 8 is a characteristic diagram of reactance characteristics of the SAW resonator shown in FIG. As shown in FIG. 8, the SAW resonator has a double resonance characteristic having a resonance frequency fr and an antiresonance frequency fa. Therefore, a band pass filter can be configured by configuring the SAW resonator in the same manner as a conventional LC filter. FIG. 9 is a circuit diagram of a bandpass filter in which two SAW resonators are connected to a one-stage ladder circuit. The bandpass filter includes a series arm SAW resonator 21, a parallel arm SAW resonator 22, an input terminal 23, and an output terminal 24. Figure 10
It is a figure which shows the characteristic of FIG. 9, Especially the figure (a) is a figure which shows the reactance characteristic of the series arm SAW resonator 21 and the parallel arm SAW resonator 22 in FIG. 9, and the figure (b) is a figure. It is a figure which shows the transmission characteristic S21 of 9. The meaning of each symbol in FIG. 10 is as follows. f0: Center frequency of ladder type circuit f1; Resonance frequency of parallel arm SAW resonator 22 f2; Anti-resonance frequency of parallel arm SAW resonator 22 f3; Resonance frequency of series arm SAW resonator 21 f4; Series arm SAW resonator 21 Anti-resonance frequency P; pass band D; attenuation range anti-resonance frequency f2 of parallel arm SAW resonator 22 and series arm S
When the resonance frequency f3 of the AW resonator 21 is matched, a bandpass filter having a transmission characteristic as shown in FIG. 10 can be constructed. In general, a large amount of attenuation cannot be obtained with a one-stage ladder circuit, so ladder circuits should be connected in cascade, for example, with three or five stages.
It is used as a multi-stage ladder circuit such as stages. FIG. 11 is a circuit diagram of a three-stage ladder type circuit, and FIG. 12 is a circuit diagram of a five-stage ladder type circuit.

FIG. 13 is a plan view of a resonator type SAW filter in which the SAW resonator is a one-stage ladder type circuit. In this resonator type SAW filter, the IDT 32 of the series arm SAW resonator, the grating reflector 33 of the series arm SAW resonator, and the ID of the parallel arm SAW resonator are provided on the piezoelectric substrate 31.
T34, parallel arm SAW resonator grating reflector 3
5, input extraction electrode 36, output extraction electrode 3
7, and a lead electrode 38 for grounding are provided.
FIG. 14 is a cross-sectional view taken along the line AA of FIG. In addition, IDT
32 and 34 and the grating reflectors 33 and 35,
An aluminum alloy containing a few% of copper or silicon in aluminum is used, and the extraction electrodes 36, 37, 38 are
Gold is used.

[0006]

However, when the series arm SAW resonator and the parallel arm SAW resonator are integrally formed on a single piezoelectric substrate, variations in film thickness of electrodes and widths of electrode fingers, etc. As a result, the resonance frequency of the series arm SAW resonator may not exactly match the anti-resonance frequency of the parallel arm SAW resonator, or the center frequency may shift even if they match. Therefore, the desired center frequency and the pass band width cannot be obtained, and there are problems such as an increase in insertion loss and generation of ripples in the pass band. It is an object of the present invention to eliminate the above problems and provide a SAW resonator whose characteristics can be easily adjusted.

[0007]

In order to solve the above-mentioned problems, the present invention is provided on a piezoelectric substrate and outputs an electric signal as an SA signal.
SA that converts the SAW into an electric signal after conversion to W
In a resonator type SAW filter configured in a ladder type circuit including a series arm SAW resonator using a plurality of W resonators and a parallel arm SAW resonator, the frequency is adjusted by the following method. That is, the resonance frequency or anti-resonance frequency of the series arm SAW resonator is measured, and the measurement result and the resonator type SA are measured.
The resonance frequency or anti-resonance frequency of the series arm SAW resonator is adjusted by depositing an insulating film on the series arm SAW resonator or performing an etching process by comparison with the center frequency of the W filter. Further, the anti-resonance frequency or the resonance frequency of the parallel arm SAW resonator is measured, and the measurement result and the resonator type SAW resonator are measured.
The anti-resonance frequency or the resonance frequency of the parallel arm SAW resonator is adjusted by applying an insulating film on the parallel arm SAW resonator or performing an etching process by comparison with the center frequency of the filter.

[0008]

According to the present invention, since the method for adjusting the frequency of the SAW resonator is configured as described above, the load applied to the piezoelectric substrate below the insulating film by depositing the insulating film on the series arm SAW resonator. Becomes larger and the resonance frequency or anti-resonance frequency of the series arm SAW resonator moves to the lower frequency side. Further, by etching the series arm SAW resonator, the load applied to the piezoelectric substrate in the etched portion is reduced, and the resonance frequency or antiresonance frequency of the series arm SAW resonator moves to the high frequency side. On the other hand, by depositing an insulating film on the parallel arm SAW resonator, the anti-resonance frequency or resonance frequency of the parallel arm SAW resonator moves to the low frequency side. Further, the anti-resonance frequency or the resonance frequency of the parallel arm SAW resonator is moved to the high frequency side by etching the parallel arm SAW resonator. Therefore, the above problem can be solved.

[0009]

EXAMPLE FIG. 15 is a characteristic diagram of reactance when f0 <f2 = f3. FIG. 16 is a characteristic diagram of the reactance when f2 = f3 <f0. FIG. 17 shows that f0 <
It is a characteristic diagram of reactance in the case of f2 <f3. FIG.
8 is a characteristic diagram of the reactance when f0 = f2 <f3. FIG. 19 is a characteristic diagram of the reactance when f2 <f0 <f3. FIG. 20 is a characteristic diagram of reactance when f2 <f3 = f0. In FIG. 21, f2 <f
It is a characteristic diagram of reactance in case of 3 <f0. FIG.
[Fig. 4] is a characteristic diagram of reactance when f2>f3> f0. FIG. 23 is a characteristic diagram of reactance when f2> f3 = f0. FIG. 24 is a characteristic diagram of reactance in the case of f2>f0> f3. In FIG. 25, f2 = f0
It is a reactance characteristic diagram in case of> f3. FIG. 26
[Fig. 3] is a characteristic diagram of reactance in the case of f0>f2> f3. However, f0 is the center frequency, f2 is the anti-resonance frequency of the parallel arm SAW resonator, and f3 is the resonance frequency of the series arm SAW resonator. As described above, there are 12 types of characteristics for which the frequency needs to be adjusted in the resonator type SAW filter configured in the ladder type circuit. First Example In the first example, the frequency adjustment method in the case of f0 <f2 = f3 shown in FIG. 15 and in the case of f2 = f3 <f0 shown in FIG. 16 will be described in (1) and (2) below. To do.

(1) Case of f0 <f2 = f3 FIG. 1 is a resonator type SAW for explaining a frequency adjusting method 1 of the resonator type SAW filter according to the first embodiment of the present invention.
FIG. 14 is a plan view of the filter, in which elements common to those in the conventional FIG. 13 are denoted by common reference numerals. In this Figure 1,
IDT 32, grating reflector 33, I in FIG.
An insulating film 39I is formed on the entire surface of each of the DT 34 and the grating reflector 35, and a part of each of the input extraction electrode 36, the output extraction electrode 37, and the ground extraction electrode 38. FIG. 27 shows A of FIG.
FIG. Next, the operation of FIG. 1 will be described. In the case of f0 <f2 = f3 shown in FIG. 15, if the insulating film 39I is deposited so as to cover the entire IDT 32, the grating reflector 33, the IDT 34, and the grating reflector 35, the load applied to the piezoelectric substrate 31 increases and the series connection is increased. Arm S
The SAW propagation speeds generated in the AW resonator and the parallel arm SAW resonator both decrease by the same speed, and the reactance characteristics of the series arm SAW resonator and the parallel arm SAW resonator both move to the low frequency side. The moving amount of this frequency is the insulating film 39I.
The insulating film 39I is deposited until f2 = f3 = f0. F0 <f by the above procedure
The frequency can be adjusted when 2 = f3.

(2) Case of f2 = f3 <f0 FIG. 28 is a plan view of a resonator type SAW filter for explaining the frequency adjusting method 2 of the first embodiment of the present invention. Elements that are common to the elements are given common reference numerals. In FIG. 28, etching 39E is applied to the region where the insulating film 39A in FIG. 1 is formed. 29 is a cross-sectional view taken along the line AA of FIG. 28. Next, FIG.
Will be described. When f2 = f3 <f0 shown in FIG. 16, the IDT 32, the grating reflector 33, the IDT 3
4 and etching 3 on the entire grating reflector 35
When 9E is applied, the load applied to the piezoelectric substrate 31 is reduced, the propagation speeds of the SAWs generated in the series arm SAW resonator and the parallel arm SAW resonator both increase by the same speed, and the series arm SAW resonator and the parallel arm SAW resonator are increased. The reactance characteristics of the resonator both move to the high frequency side. Since the moving amount of this frequency can be adjusted by the etching amount of the etching 39E, the etching region is etched until f2 = f3 = f0. The frequency adjustment in the case of f2 = f3 <f0 can be performed by the above procedure. As mentioned above, this first
In the embodiment, the IDT 32 and the grating reflector 3
3, the insulating film 39I is applied to the entire IDT 34 and the grating reflector 35 or etching 39E is performed to adjust the reactance characteristics of the series-arm SAW resonator and the parallel-arm SAW resonator. And the anti-resonance frequency of the parallel arm SAW resonator can be matched with a predetermined center frequency. A desired frequency and filter characteristics can be obtained by this frequency adjusting method, and the yield is also improved. Second Example In a second example, a method of adjusting the frequency of the resonator type SAW filter in the case of f2 <f3 shown in FIGS. 17 to 21 will be described.

FIG. 30 is a plan view of a resonator type SAW filter for explaining the frequency adjusting method 1 according to the second embodiment of the present invention. Elements common to those in FIG. 13 are designated by common reference numerals. Is attached. In FIG. 30, an insulating film 39si is formed on the IDT 32 and the grating reflector 33 that form the series arm SAW resonator in FIG. 31 is a cross-sectional view taken along the line AA of FIG. Next, the operation of FIG. 30 will be described. When the insulating film 39si is applied so as to cover the IDT 32 and the grating reflector 33, the propagation speed of SAW generated in the series arm SAW resonator is reduced, and the reactance characteristic of the series arm SAW resonator moves to the low frequency side. Since the moving amount of this frequency can be adjusted by the film thickness of the insulating film 39si, when f2 <f3, the insulating film 39si is deposited until f2 = f3. FIG. 32 is a plan view of a resonator type SAW filter for explaining a frequency adjusting method 2 according to a second embodiment of the present invention, and elements common to those in FIG. 13 are designated by common reference numerals. ing. This figure 3
2, IDs forming the parallel arm SAW resonator in FIG.
Etching 39pe is applied to the regions of T34 and the grating reflector 35. FIG. 33 shows A-A of FIG.
It is a line sectional view. Next, the operation of FIG. 32 will be described. ID
When T34 and the grating reflector 35 are etched, the SAW propagation velocity generated in the parallel arm SAW resonator increases, and the reactance characteristic of the parallel arm SAW resonator moves to the high frequency side. Since this movement amount can be adjusted by the etching amount of 39 pe, if f2 <f3,
The etching region is etched until f2 = f3.

The adjustment method for matching the resonance frequency f3 of the series arm SAW resonator and the anti-resonance frequency f2 of the parallel arm SAW resonator in the case of f2 <f3 has been described above.
When f2 <f3, there are five types shown in FIGS. 17 to 21 in consideration of the relative magnitude relation with the center frequency f0. The frequency adjusting method in the case of these five types can be adjusted by combining the adjusting method shown in the second embodiment and the adjusting method shown in the first embodiment. As mentioned above,
In the second embodiment, the insulating film 39 is formed on the IDT 32 and the grating reflector 33 which form the series arm SAW resonator.
I to attach si or to form a parallel arm SAW resonator I
Etching 3 on DT 34 and grating reflector 35
By applying 9 pe, the resonance frequency f3 of the series arm SAW resonator and the anti-resonance frequency f2 of the parallel arm SAW resonator can be matched. Further, by combining with the adjusting method shown in the first embodiment, the resonance frequency f3 of the series arm SAW resonator and the anti-resonance frequency f2 of the parallel arm SAW resonator can be made equal to the center frequency f0.
By this frequency adjusting method, problems such as increase in insertion loss and generation of ripples in the pass band can be solved, desired frequency and filter characteristics can be obtained, and yield can be improved. Third Example In the third example, a frequency adjusting method of the resonator type SAW filter in the case of f2> f3 shown in FIGS. 22 to 26 will be described. FIG. 34 is a plan view of a resonator type SAW filter for explaining a frequency adjusting method 1 according to a third embodiment of the present invention. Elements common to those in FIG. 13 are designated by common reference numerals. ing. In FIG. 34, the parallel arm SA in FIG.
An insulating film 39pi is formed on the IDT 34 and the grating reflector 35 that form the W resonator. FIG.
FIG. 35 is a sectional view taken along the line AA of FIG. 34.

Next, the operation of FIG. 34 will be described. f2> f
In the case of 3, when the insulating film 39pi is applied so as to cover the IDT 34 and the grating reflector 35, the parallel arm SAW
The propagation speed of the SAW generated in the resonator decreases and the parallel arm S
The reactance characteristic of the AW resonator moves to the low frequency side.
Since this movement amount can be adjusted by the film thickness of the insulating film 39pi, the insulating film 39pi is deposited until f2 = f3. FIG. 36 shows a resonator type SAW according to a third embodiment of the present invention.
FIG. 14 is a plan view of a resonator type SAW filter for explaining a frequency adjusting method 2 of the filter, in which elements common to those in FIG. 13 are designated by common reference numerals. In FIG. 36, the IDT3 that constitutes the series arm SAW resonator in FIG.
2 and etching 3 in the area of the grating reflector 33
9se is given. 37 is a cross-sectional view taken along the line AA of FIG. 36. Next, the operation of FIG. 36 will be described. f2> f
In the case of 3, when the IDT 32 and the grating reflector 33 are etched, the load applied to the piezoelectric substrate 31 is reduced, the propagation speed of the SAW generated in the series arm SAW resonator is increased, and the reactance characteristic of the series arm SAW resonator is high. Move to the side. Since this moving amount can be adjusted by the etching amount of the etching 39se, the etching region is etched until f2 = f3. With the above procedure, f
The frequency can be adjusted when 2> f3. As described above, when f2> f3, the anti-resonance frequency f2 of the parallel arm SAW resonator and the resonance frequency f3 of the series arm SAW resonator are set.
The adjustment method for matching and has been explained. When f2> f3, there are five types shown in FIGS. 22 to 26 in consideration of the relative magnitude relationship with the center frequency f0. The frequency adjustment method for these five cases can be adjusted by combining the adjustment method shown in the third embodiment and the adjustment method shown in the first embodiment.

As described above, in the third embodiment, the insulating film 39pi is attached to the IDT 34 and the grating reflector 35 which form the parallel arm SAW resonator, or the IDT 32 which forms the series arm SAW resonator. By performing etching 39se on the grating reflector 33,
Anti-resonance frequency f2 of parallel arm SAW resonator and series arm SAW
The resonance frequency f3 of the resonator can be matched.
Further, by combining with the adjusting method shown in the first embodiment, the resonance frequency f3 of the series arm SAW resonator and the anti-resonance frequency f2 of the parallel arm SAW resonator are set to the center frequency f0.
Can be matched. By this frequency adjusting method, problems such as increase in insertion loss and generation of ripples in the pass band can be solved, desired frequency and filter characteristics can be obtained, and yield can be improved. The present invention is not limited to the above embodiment, and various modifications can be made. Examples of the transformation order include the following. (1) Although the embodiment has been described using the one-stage ladder-type resonator SAW filter, it can be applied to a multi-stage resonator-type SAW filter and the same effect can be obtained. (2) The frequency adjusting method of the present invention can be applied to the case of adjusting the reactance characteristic of the SAW resonator. (3) The reactance characteristics of the SAW resonator can also be adjusted by making the region where the insulating film is formed and the region where etching is performed on the SAW resonator have various contours.

[0016]

As described in detail above, according to the present invention, the resonance frequency or anti-resonance of the series arm SAW resonator is obtained by depositing an insulating film on the series arm SAW resonator or by performing an etching process. The frequency is adjusted, and the anti-resonance frequency or the resonance frequency of the parallel arm SAW resonator is adjusted by applying an insulating film on the parallel arm SAW resonator or performing an etching process. The resonance frequency or anti-resonance frequency of the resonator and the anti-resonance frequency or resonance frequency of the parallel arm SAW resonator can be made to match, and further, can be made to match the center frequency. Therefore, a desired center frequency and pass band width can be obtained, ripples in the pass band can be prevented, and insertion loss can be reduced.

[Brief description of drawings]

FIG. 1 is a plan view of a resonator type SAW filter for carrying out a frequency adjusting method 1 according to a first embodiment of the present invention.

FIG. 2 is a plan view of a transversal type SAW filter.

FIG. 3 is a conceptual diagram of a SAW resonator.

FIG. 4 is a configuration diagram of a ladder circuit.

FIG. 5 is a configuration diagram of a dual mode SAW resonator.

FIG. 6 is a plan view of a reflector type SAW resonator.

FIG. 7 is a circuit diagram of an equivalent circuit of a SAW resonator.

FIG. 8 is a characteristic diagram of reactance of a SAW resonator.

FIG. 9 is a circuit diagram of a one-stage ladder type circuit.

FIG. 10 is a characteristic diagram of FIG. 9.

FIG. 11 is a circuit diagram of a three-stage ladder type circuit.

FIG. 12 is a circuit diagram of a 5-stage ladder type circuit.

FIG. 13 is a plan view of a resonator type SAW filter.

14 is a cross-sectional view taken along the line AA of FIG.

FIG. 15 is a characteristic diagram of reactance when f0 <f2 = f3.

FIG. 16 is a characteristic diagram of reactance when f2 = f3 <f0.

FIG. 17 is a characteristic diagram of reactance when f0 <f2 <f3.

FIG. 18 is a characteristic diagram of reactance when f0 = f2 <f3.

FIG. 19 is a characteristic diagram of reactance when f2 <f0 <f3.

FIG. 20 is a characteristic diagram of reactance when f2 <f3 = f0.

FIG. 21 is a characteristic diagram of reactance when f2 <f3 <f0.

FIG. 22 is a characteristic diagram of reactance when f2>f3> f0.

FIG. 23 is a characteristic diagram of reactance when f2> f3 = f0.

FIG. 24 is a characteristic diagram of reactance when f2>f0> f3.

FIG. 25 is a characteristic diagram of reactance when f2 = f0> f3.

FIG. 26 is a characteristic diagram of reactance when f0>f2> f3.

27 is a cross-sectional view taken along the line AA of FIG.

FIG. 28 is a plan view of a resonator type SAW filter for implementing the frequency adjustment method 2 according to the first example of the present invention.

29 is a cross-sectional view taken along the line AA of FIG. 28.

FIG. 30 is a plan view of a resonator type SAW filter for carrying out a frequency adjusting method 1 according to a second embodiment of the present invention.

31 is a cross-sectional view taken along the line AA of FIG.

FIG. 32 is a plan view of a resonator type SAW filter for carrying out a frequency adjusting method 2 according to a second embodiment of the present invention.

33 is a cross-sectional view taken along the line AA of FIG. 32.

FIG. 34 is a plan view of a resonator type SAW filter for carrying out a frequency adjusting method 1 according to a third example of the present invention.

FIG. 35 is a cross-sectional view taken along the line AA of FIG. 34.

FIG. 36 is a plan view of a resonator type SAW filter for carrying out a frequency adjusting method 2 according to a third embodiment of the present invention.

37 is a cross-sectional view taken along the line AA of FIG.

[Explanation of symbols]

21 series arm SA
W resonator 22 Parallel arm SA
W resonator 31 Piezoelectric substrate 39I, 39i, 39pi Insulating film 39E, 39pe, 39se, Etching f0 Center frequency f2 Anti-resonance frequency f3 Resonance frequency

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuyoshi Sakamoto 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd.

Claims (1)

[Claims] 1. A serial arm surface acoustic wave resonator comprising a plurality of surface acoustic wave resonators provided on a piezoelectric substrate and converting an electric signal into a surface acoustic wave and then converting the surface acoustic wave into an electric signal. In a resonator type surface acoustic wave filter configured in a ladder type circuit composed of parallel arm surface acoustic wave resonators, the resonance frequency or anti-resonance frequency of the series arm surface acoustic wave resonator is measured, and the measurement result and the resonance Frequency or anti-resonance of the series arm surface acoustic wave resonator by depositing an insulating film on the series arm surface acoustic wave resonator or by performing etching treatment by comparison with the center frequency of the container type surface acoustic wave filter. The frequency is adjusted, the anti-resonance frequency or the resonance frequency of the parallel arm surface acoustic wave resonator is measured, and the parallel arm elastic surface is calculated by comparing the measurement result with the center frequency of the resonator type surface acoustic wave filter. A resonator type surface acoustic wave filter characterized by adjusting an anti-resonance frequency or a resonance frequency of the parallel arm surface acoustic wave resonator by depositing an insulating film on the wave resonator or performing an etching treatment on the wave resonator. Frequency adjustment method.