JP3307284B2 - 2-port SAW resonator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-port type surface acoustic wave resonator using a surface acoustic wave (hereinafter referred to as a two-port SAW).
(Abbreviated as Surface Acoustic Wave) resonator, a two-port SA in which spurious (unnecessary resonance) caused by a higher-order longitudinal inharmonic mode is suppressed.
It relates to a W resonator.

[0002]

2. Description of the Related Art The basic electrode structure of a conventional two-port SAW resonator is disclosed in, for example, US Pat. No. 3,886,504. JP-A-61-251223 and JP-A-61-251223.
No. 230419 discloses an example of three interdigital electrodes. Two-port SA with three interdigital electrodes
In the W resonator, the center interdigital electrode serves as an input terminal, and the interdigital electrodes serving as output terminals are arranged on both sides thereof. Therefore, the frequency is stable with respect to the load fluctuation of the output side load circuit. If a type is used, a so-called ST-cut two-port SAW resonator formed on an ST-cut X propagation plate made of quartz single crystal has a zero temperature coefficient and is as excellent as a one-port type in terms of frequency stability. Things are obtained.

[0003]

However, in the above-mentioned prior art, when an electrode film thickness of 1000 mm or more is used to reduce the size of an element, an ST-cut 2-port SAW resonator having the three interdigital electrodes is required. In, below the main resonance frequency, there exist resonances due to a plurality of higher-order longitudinal inharmonic modes. Among these modes, the mode closest to the main resonance frequency is such that when the two-port SAW resonator is incorporated in the oscillation circuit, the frequencies are closely and simultaneously excited by the extension coil used for adjusting the oscillation frequency. As a result, there is a problem that a frequency jump is generated to cause a communication failure.

Furthermore, it has been discovered that, depending on the setting of the width of the cross bus bar conductor width, two spurious signals having substantially the same amplitude are generated even though the above-mentioned high-order longitudinal inharmonic mode group is completely suppressed. .

Accordingly, the present invention is to solve such a problem, and an object of the present invention is to provide a two-port SAW resonator having excellent frequency stability and no spurious to the communication market.

[0006]

Means for Solving the Problems] (1) 2-port SAW resonator of the present invention, on the piezoelectric element plate and a first interdigital electrode for exciting a surface acoustic wave, of the first interdigital electrode A pair of second and third interdigital electrodes for receiving surface acoustic waves on both sides, and a pair of reflectors on both sides of the first, second and third interdigital electrodes; in the two-port SAW resonator made, the reflector and the first, the <br/> second and third interdigital electrodes, the parallel conductors of the metal on the piezoelectric a flat plate with periodically arranged The distance between the closest parallel conductor between the reflector and the second and third IDTs is a space between the lines and spaces of the IDTs, and The period of the parallel conductor of the electrode is smaller than the period of the parallel conductor of the reflector. To raised frequency, and an energy trapped type in which the total reflection coefficient gamma and 10>gamma> 0.8, the period of the parallel conductors of the second and third interdigital electrodes, wherein the first The frequency is reduced by increasing the period of the parallel conductors of the interdigital transducer.

(2) In (1), the logarithm of the second and third IDTs is 1 / 2.times. The sum of the logarithms of the first, second and third IDTs. 75 to 1 / 3.75.

(3) In (1), the logarithm of the second and third IDTs is 1 / (4) of the sum of the logarithms of the first, second, and third IDTs. ± 2
%).

(4) In (1), the frequency increase of the first IDT is from 2000 to 12000 ppm.
It is characterized by being in the range.

(5) In (1), the frequency increase of the first interdigital transducer is in the range of 2500 to 7500 ppm.

(6) In (1), the number of pairs of the first IDTs is in the range of 80 to 110.

(7) In (1), the period of the parallel conductors of the second and third IDTs is substantially equal to that of the reflector.

[0013] In (8) (1), characterized in that the electrode film thickness of said first interdigital electrode is thinner than the thickness of the second and third interdigital electrodes.

[0014] (9) (1), wherein the ratio H / lambda of the wavelength lambda of the thickness H and the SAW of the third IDT of the first is, of 0.013 or al 0.03 It is characterized by being a range.

(10) In (1), the sum of the logarithms of the first, second and third IDTs is 18
Characterized in that 0 to 300 is below.

[0016] In (11) (1) to (10), the sum of the first and the second, and between the first and the third interdigital electrode, the cross busbar conductor width and space width on both sides length, as the wavelength of the surface acoustic wave lambda, n [lambda
+ (1/4) λ or nλ + (3/4) λ (where n is a natural number of 0, 1, 2,...).

(12) In any one of the constitutions (1) to (11), the piezoelectric flat plate is ST cut or K cut of quartz.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a Rayleigh wave, a leaky wave,
STW (surface transversal w
ave) Two-port S of the present invention using surface acoustic waves such as waves
Details of the AW resonator will be described step by step.

An aluminum wire or a gold wire may be used as a conductor for electrically connecting the second and third interdigital electrodes. However, when the interdigital electrode is formed, it is more convenient to form the conductor on the piezoelectric flat plate in terms of cost and reliability. In the following description, a conductor crossing a portion where a surface acoustic wave propagates will be described as a cross bus bar conductor, and the others will be described as connection conductors.

FIG. 1 is a plan view showing an electrode pattern of a two-port SAW resonator according to the present invention. Each part in FIG.
Reference numeral 00 denotes a piezoelectric flat plate (hereinafter, simply referred to as a flat plate), which is an ST-X propagation cut, LST cut out from quartz.
-X propagation cut, K cut (rotation Y of 6.5 degrees around X axis)
In the plane of the cut, there is a phase propagation direction about 32.4 degrees from the X axis. ) Are element pieces obtained by shredding a specific wafer, 101 is a first reflector, and 105 is a second reflector.
103, a first interdigital electrode (IDT1),
102 is a second interdigital electrode (IDT2), 104 is a third interdigital electrode (IDT3), 108 is a first cross bus bar conductor, 109 is a second cross bus bar conductor, 1
10 is a third cross bus bar conductor, 111 is a fourth cross bus bar conductor, 107 is an AC signal source connected to the input terminal side of the element, 106 is an electrical load impedance connected to the output terminal side of the element, 120 Is the phase propagation direction of the surface acoustic wave such as the Rayleigh wave.

The IDT (Int)
and a conductor pattern such as a reflector, a cross bus bar conductor, and a connection conductor (112, 113) is formed by depositing a conductive metal film of Al, Au, Cu, or the like on the piezoelectric flat plate and performing sputtering or the like. And then forming a pattern by photolithography. From a viewpoint of an electric circuit, the IDT 1 (103) is an input side of the element, is connected to an electric AC signal source 107 by a conductor such as an aluminum wire, and a pair of IDTs 2 arranged on both sides thereof. (102), IDT3 (104) are mutually connected by connecting conductors (112, 113) to constitute an output-side IDT of the device as a whole, and furthermore, a pair of reflectors ( 101, 105).

More specifically, the IDT and reflector conductor strips (114, 115, etc.)
A large number of elongated rectangular conductor strips are arranged at regular intervals in parallel to the phase propagation direction X (120) of the surface acoustic wave in parallel. As shown in the figure, the periodic interval of the first reflector is PR1, the IDT2 is PT2, and the IDT1 is IDT1.
Is PT1, IDT3 is PT3, and the second reflector is PR2. Usually, the width in the X-axis direction of the portion where the conductor strip exists is called a line (L), and the width in the X-axis direction of the portion where no conductor exists exists is called a space (S). The inventions described in claims 1 to 10 and claim 12 hold regardless of the presence or absence of the cross bus bar conductor. However, when the cross bus bar conductor is provided, its width is B, and the space width on both sides thereof is SP1, SP
As 2, B + SP1 + SP2 is set to nλ + (1/4) λ or nλ + (3/4) λ. (However, n =
0, 1, 2, ... See FIG. 12 for details. ) Also IDT1
The fact that the sum of the space widths of the cross bus bar conductor between the IDT 1 and the IDT 2 and both sides thereof is equal to the sum of the space width of the cross bus bar conductor between the IDTs 1 and 3 and the space widths on both sides thereof is effective in suppressing spurious (oblique symmetric mode) described later. There is.

The operation of the two-port SAW resonator of FIG. 1 of the present invention is performed as follows. An AC signal applied from the electrical input signal source 107 is applied to an alternating electric field between electrode fingers connected to the positive electrode terminal (117) and the negative electrode terminal (116) of the IDT 1 (103), and a flat piezoelectric member is formed. , Which generates alternating vibratory stress. Due to the alternating stress,
Surface acoustic waves are radiated in the positive and negative directions of the X axis, and
In the reflectors 1 and 105, a large number of conductor strips are reflected to the center of the base plate to form a standing wave corresponding to the pitch of the reflector, thereby exhibiting a vibration phenomenon. IDT2 (10
3) and the IDT 3 (104) detect the oscillating charge generated by the elastic vibration, and the load impedance ZL of the
(106). As described above, a two-port SAW resonator that resonates in series at a frequency at which the vibration phenomenon has the maximum amplitude is realized.

FIG. 2 shows the attributes of FIG. 1 described above. The vertical axis in the figure indicates the reflector and ID, which are each element of the 2-port SAW resonator, in the X-axis direction in FIG.
This is the angular frequency ω (= 2πf) of T. The frequency is
The sound velocity V is obtained by dividing the sound velocity V of the surface acoustic wave to be used in a corresponding region by a period (also referred to as a pitch) P of a conductor strip constituting an element. That is, ω = 2
πV / 2P. Each period of the reflector and the IDT is
These are indicated by PR1, PR2, PT1, PT2, and PT3 in FIG. In the figure, ωR is the first and second reflectors, ωR
2 is the angular frequency of IDT2, ω1 is the angular frequency of IDT1, and ω3 is the angular frequency of IDT3. A feature of the present invention is that ω1 of IDT1 is the largest, and ω2 and ω3 of IDT2 and IDT3 are set smaller than ω1. The configuration of this angular frequency is appropriate when a crystal ST-X cut, a K cut, or the like is made of aluminum and has a so-called energy rising type wave number dispersion characteristic. If the cut-off flat plate has a gold electrode, such as a case where the cut-off plate has a frequency drop type wave number dispersion characteristic, it is necessary to reverse the magnitude relationship of the angular frequencies in FIG. For a description of the frequency-increase type and the drop type in the SAW resonator, see Suzuki, Shimizu, Yamauchi, et al.
IEICE Technical Report, US87-36, pp. 9-16 (198
0).

Next, how the suppression of the longitudinal inharmonic mode, which is the object of the present invention, is achieved by the configuration of FIGS. 1 and 2 of the present invention will be described by taking, as an example, the case where a Rayleigh wave in a crystal ST cut is used. This will be described with reference to more detailed configuration conditions and characteristic diagrams.

FIG. 3 shows the embodiment of FIG.
The positive and negative electrode fingers of DT2 and IDT3 (118 and 119 in FIG. 1)
, Etc.) for optimally setting the logarithm when one pair is used, and the sum M of logarithms of the three IDTs (= M1 +
M2 + M3) divided by the division number DIV to obtain IDT2 and IDT
FIG. 11 is a characteristic diagram showing a relationship between a logarithm M2 and M3 of 3 (M2 = M3) and a series equivalent resistance R1 of a 2-port SAW resonator. M1 is the logarithm of IDT1. The curve 300 in the figure is M = 300, 301 is M = 220, 302
Is the case where M = 180. In particular, it can be seen that the range of the number of divisions DIV in which R1 has the lowest value is DIV = 2.75 to 3.75 assuming that the fluctuation of R1 is 10% or less.

FIG. 4 shows the ID of a two-port SAW resonator.
Assuming that the logarithm of T2 and IDT3 is M2 = M3 = 0, the central I
Logarithm M1 of DT1 = M and frequency increase Δ of angular frequency ω1
This is a diagram illustrating a state of occurrence of a higher-order vertical inharmonic mode for a combination of f / f (unit is ppm). The black portions indicate the condition range in which the higher-order vertical inharmonic mode occurs. Therefore, if the device is manufactured in the condition range below the curve 400, the higher-order longitudinal inharmonic mode can be suppressed. The amount of frequency increase was defined as Δf / f = (ω1−ωR) / ωR with reference to the angular frequency ωR of the reflector. According to the figure, as the logarithm M1 of the IDT 1 increases, the frequency increase range in which the higher-order vertical inharmonic mode does not occur becomes narrower. A practical range is a curve 400 or less and the frequency increase Δf / f = 2
The combination range of 000 to 12000 ppm and logarithm M1 = 80 to 110 is good in that it has spurious suppression and a small value of R1. As a general tendency, as M1 is smaller and the amount of frequency rise and Δf / f are smaller, the higher-order longitudinal inharmonic mode tends not to occur. A curve 400 in the figure shows a condition for providing a cutoff frequency of occurrence.

Next, FIG. 5 shows that, when the frequency rise of IDT1 is fixed in the above range, the frequency rise of IDT1 DF1 = (Δf / f) 1, and that of IDT2 and IDT3 is DF. Frequency rise rate DF / DF
The horizontal axis of 1 indicates the relationship between the series equivalent resistance of the two-port SAW resonator R1 (curve 500) and the equivalent capacitance C1 (curve 501). As can be seen from the figure, the lowest R1 is realized when the frequency increase rate DF / DF1 is near 1.0, and C1 decreases as the frequency increase rate departs from 1.0. In particular, as the frequency rise rate becomes 1.0 or less, it can be estimated from the decrease in C1 that the vibration amplitude of the two-port SAW resonator tends to concentrate at the center of the element. Next, FIG.
Shows the relationship of the equivalent series resistance R1 to the ratio H / λ of the surface acoustic wave wavelength λ to the film thickness H of the aluminum electrode. In this case, the frequency increase amount of the IDT1 is 5000p
pm and the sum M from IDT1 to IDT3 is 300
As a pair, 4 was selected as the IDT division number DIV, and 0.0 was selected as the frequency increase rate. As can be seen from the figure, the characteristic curve 600 realizes an R1 value of 40Ω or less that can be used without any problem in the oscillation circuit in the range of H / λ = 1.3% to 3%. In the range where H / λ is 1.3% or less, the total reflection coefficient 全体 of the entire electrode of the IDT decreases, so that the resonance condition cannot be configured, thereby causing a rapid increase in R1. The above Γ is defined as the following equation (1), and preferably satisfies the range of 10>Г> 0.8, thereby realizing a so-called energy trap type SAW resonator.

The upper limit 10 of Г is a boundary value at which the equivalent series resistance R1 tends to increase due to a conversion loss from a surface acoustic wave to a bulk wave or a friction loss of an electrode material with an increase in the number of electrode fingers of the IDT. Corresponding to

[0030]

(Equation 1)

Here, M is the logarithm of the IDT, a is the reflection coefficient of the surface acoustic wave per electrode, H is the film thickness of the conductor, and λ is the wavelength of the surface acoustic wave. The flat plate 200
Is an IDT made of Al conductor on a conventional quartz crystal plate of ST cut X propagation, a = 0.255, H / λ
If 0.03 and M = 80 pairs, a one-port SAW resonator having sufficient performance and similar to that of FIG. 2 can be constructed. At this time, Γ = about 2.448.

Next, the transmission characteristics of the two-port SAW resonator obtained under the above-described conditions will be described with reference to FIGS.

The above transmission characteristic is a logarithmic value of a ratio of an input voltage VIN to the element generated by the signal source 107 in FIG. 1 to an output voltage VOUT from the element. That is, 20LOG
₁₀ (V _OUT / V _IN ). The output voltage is equal to the voltage across the load impedance ZL (106). This time, a resistance value of 50Ω was used as ZL. Further, as the configuration conditions of the two-port SAW resonator, M = 270 pairs, 174 reflector conductor strips, H / λ = 2.0%, I
DT division number 2.75, cross busbar width B is 25.08
μm, space width SP1 1.79 μm, SP2 5.
It was 37 μm. FIG. 7 shows the frequency increase rate DF / DF1 =
1.5. Curve 700 is the transmission characteristic,
In addition to the main resonance mode S0, which is a fundamental longitudinal mode, there are a large number of symmetric first-order (S1) to third-order (S3) and spurious modes composed of obliquely symmetric high-order longitudinal inharmonic modes existing between the symmetric modes. You can see that it is doing.
In the oblique symmetric mode, the amplitude of the vibration displacement has a rotationally symmetric displacement of 180 degrees with respect to the center origin in the X-axis direction (120 in FIG. 1) of the two-port SAW resonator. Is better, the resonance amplitude is smaller. FIG. 8 shows a case where the frequency rise rate is 1.0. FIG. 9 shows a case where the frequency increase rate is 0.0. FIG.
, A curve 900 represents the forward transmission characteristic (S21) in the state of FIG. 1, and a curve 901 represents a reverse transmission characteristic (S12) when the signal source 107 and the load 106 of FIG. 1 are exchanged.
It is. It can be seen that a slight shift has occurred between the two. However, this shift causes a slight change in the resonance frequency, which is inconvenient especially when a frequency accuracy of several ppm is required. The cause is that the input and output I
Since it was presumed that the values of the parallel capacitances created by the DT electrode fingers were not equal, as a result of studying the countermeasures, when the number of divisions of the IDT was set to DIV = 4.0, completely identical transmission characteristics were obtained. At this time, the logarithm of IDT1 and (IDT
2 + the sum of the logarithms of IDT3) are exactly the same, but 4
Even if there was a difference of about ± 2%, there was no problem in practical use. FIG.
In the case of, the spurious components S1 and S2 move away from the main resonance S0 and are attenuated. Further, the frequency rise rate of the IDT is reduced, and DF / DF1 = −0.5.
In the case of 0, the above-mentioned high-order longitudinal mode spurious has completely disappeared. Only the main resonance S0 exists.

Further, the optimum value of the frequency increase of the IDT 1 will be described with reference to FIG. ID for ITD1
The frequency increase rate DF / DF1 of T2 and IDT3 is -0.5
(Curve 1101) and 0.0 (Curve 1102). IDT for both properties
1 has a minimum value of R1 at about 5000 ppm, and the frequency rise DF1 of IDT1 is approximately 20 ppm.
It can be seen that a good R1 around 20Ω can be realized from 00 to 12000 ppm. However, at this time, M = 300, H / λ = 2.5%, IDT division number DIV =
4.0.

As can be seen from the above results, in the case of the crystal ST-X cut, the goals of a two-port SAW resonator, that is, R1 is small and no spurious mode exists at all, cannot be satisfied at the same time. If a compromise is found which substantially satisfies the condition (1), it can be summarized as the following preferable conditions. Frequency rise amount DF1 = 4000 to 100
00 ppm, frequency rise rate DF / DF1 is near 0, ID
The number of divisions of T is around 4, and H / λ is around 2 to 2.5%.
DF / DF1 is near 0 when DF = 0 and IDT2 and I
The period of the parallel conductor of DT3 is substantially equal to that of the reflector.

Finally, in the two-port SAW resonator of the present invention in which cross busbar conductors are formed between the IDT1 to IDT3, the IDT1 and IDT2, and the IDT2 and IDT3, the cross busbar conductor width B and both sides thereof are set. The total length of the space widths SP1 and SP2 and the transmission characteristics will be described with reference to FIGS.

FIG. 12 is a plan view of an electrode pattern of a two-port SAW resonator according to the present invention, which constitutes the cross bus bar conductor described above. In FIG. 12, 1201 is an IDT.
1, 1202 is IDT2, 1203 is IDT3, 120
4, 1205 are cross bus bar conductors, 1206, 120
7 is a reflector. The width of the cross bus bar conductors 1204 and 1205 is B, the width of the space between the IDT 1 (1201) and the cross bus bar conductor is SP1, and the width of the IDT 2
The width of the space between (1202) or IDT3 (1203) and the cross busbar conductor (1204) is SP2. When the dimension B + SP1 + SP2 is (n + 1) λ or nλ + (１ ／) λ (n = 0, 1, 2,...), The transmission characteristic is a waveform having two resonance frequencies as shown by 1302 in FIG. Becomes This resonance phenomenon occurs as two substantially equal amplitudes even though the above-described high-order longitudinal inharmonic mode group is completely suppressed. In order to avoid the phenomenon that these two modes are excited, it is necessary to design B + SP1 + SP2 under appropriate conditions, and B + SP1 + SP2 is nλ + (1/4) λ
Alternatively, in the case of nλ + (3/4) λ, the transmission characteristics are as shown in FIG.
, A waveform having only one resonance mode as shown by 1301 can be avoided, and the phenomenon in which the two resonance modes are excited can be avoided.

[0038]

As described above, according to the present invention, in a two-port SAW resonator having a pair of reflectors and three IDTs, the second ID and the third ID are set with respect to the first IDT.
The frequency rise rate of T is set small, the first frequency rise amount is set to 2000 to 12000 ppm, and IDT2 and IDT2 are increased.
By setting the number of electrode finger pairs of T3 to a logarithm of 2.75 to 3.75 or a quarter of the total number of electrode finger pairs of the entire IDT, it is possible to suppress spurious due to higher-order longitudinal inharmonic mode. Becomes Furthermore, by appropriately setting the cross bus bar conductor and the space width on both sides thereof, other separate spurious modes can be suppressed, so that the series resonance resistance value R1 can be as small as about 20Ω, and the high frequency band of 500 MHz or more can be realized. In the above, a two-port SAW resonator having excellent frequency stability can be provided to the market.

The basic structure of the present invention also applies to the case of a flat plate using another cut angle in quartz, the case of using another piezoelectric material, and the case of using a surface acoustic wave other than a Rayleigh wave. It is added that a good two-port SAW resonator can be configured by optimizing the detailed setting values.

[Brief description of the drawings]

FIG. 1 is a plan view of a two-port SAW resonator according to one embodiment of the present invention.

FIG. 2 is a characteristic diagram showing the configuration conditions of FIG. 1;

FIG. 3 is a characteristic diagram showing a relationship between the number of divisions of the IDT of FIG. 1 and R1.

FIG. 4 is a characteristic diagram showing a frequency rise amount of the IDT 1 of FIG. 1;

FIG. 5 is a characteristic diagram showing a relationship between a frequency increase rate and R1 indicated by IDT2 and IDT3 in FIG. 1;

FIG. 6 is a characteristic diagram showing a relationship between an electrode film thickness H and R1 in FIG.

FIG. 7 is a characteristic diagram showing the transmission characteristics of FIG. 1;

FIG. 8 is a characteristic diagram showing the transmission characteristics of FIG.

FIG. 9 is a characteristic diagram showing the transmission characteristics of FIG. 1;

FIG. 10 is a characteristic diagram showing the transmission characteristics of FIG. 1;

FIG. 11 is a characteristic diagram showing the relationship between the amount of increase in the frequency of IDT1 and R1 in FIG. 1;

FIG. 12 is a plan view of an electrode pattern of a two-port SAW resonator according to one embodiment of the present invention.

FIG. 13 is a characteristic diagram showing the transmission characteristics of FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 piezoelectric flat plate 101 first reflector 102 second IDT (IDT2) 103 first IDT (IDT1) 104 third IDT (IDT3) 105 second reflector

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H03H 9/25 H03H 9/145

Claims (12)

(57) [Claims] To 1. A piezoelectric on a flat plate, the first for exciting surface acoustic waves and the IDTs, the first interdigital sides to receive the surface acoustic wave one-second and third of the electrodes and interdigital electrodes, in yet said first, second port SAW resonator formed by arranging a reflector pair on opposite sides of said second and said third interdigital electrode, said reflector and said first, said the second and third interdigital electrodes, wherein the metal of the parallel conductors to the piezoelectric on a flat plate configured by periodically arranged, most between the second and the third interdigital electrode and the reflectors The distance between adjacent parallel conductors is defined by the space among the lines and spaces of the interdigital transducer, and the period of the parallel conductor of the first interdigital transducer is made smaller than the period of the parallel conductor of the reflector. raised frequency, and the total reflection coefficient gamma 1 >Γ> 0.8
Wherein the period of the parallel conductors of the second and third interdigital electrodes is larger than the period of the parallel conductors of the first interdigital electrode to reduce the frequency. 2 port SA
W resonator. 2. The method according to claim 1, wherein the logarithm of said second and third interdigital electrodes is from 1 / 2.75 to 1/3 of the sum of the logarithms of said first, second and third interdigital electrodes. 2. A two-port SAW according to claim 1, wherein said two-port SAW is in the range of 75.
Resonator. 3. The logarithm of the second and third IDTs is 1 / (4 ± 2%) of the sum of the logarithms of the first, second and third IDTs. The two-port SAW resonator according to claim 1, wherein: 4. The two-port SAW resonator according to claim 1, wherein the amount of increase in the frequency of the first IDT is in the range of 2,000 to 12,000 ppm. 5. The two-port SAW resonator according to claim 1, wherein the amount of increase in the frequency of the first IDT is in the range of 2500 to 7500 ppm. 6. The two-port SAW resonator according to claim 1, wherein the number of pairs of the first interdigital electrodes ranges from 80 to 110. 7. The two-port SAW resonator according to claim 1, wherein the period of the parallel conductor of the second and third IDTs is substantially equal to that of the reflector. 8. A 2 according to claim 1, characterized in that thinner than the thickness of the first interdigital transducer electrode film thickness before <br/> Symbol second and third interdigital electrodes Port SAW resonator. 9. The ratio H / λ between the film thickness H of the first to third IDTs and the wavelength λ of the surface acoustic wave is 0.01.
2. The method according to claim 1, wherein the range is from 3 to 0.03.
A two-port SAW resonator as described . Wherein said first, said second and the logarithm of the sum of the third IDT, two-port SAW resonator according to claim 1, characterized in that the 300 hereinafter more than 180. Wherein said first and said second, and between the first and the third interdigital electrode, the total length of the space width on both sides of the cross-bus bar conductor width, the wavelength of the surface acoustic wave As λ, nλ + (1/4) λ or nλ + (3
11. The two-port SAW resonator according to claim 1, wherein the two-port SAW resonator is configured to be λ (where n is a natural number of 0, 1, 2,...). 12. The two-port SAW resonator according to claim 1, wherein the piezoelectric plate is ST cut or K cut of quartz.