JP2001358556A - Surface acoustic wave device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface acoustic wave device having a superior passband characteristic in a high frequency band including a GHz band. SOLUTION: In an unbalanced SAW filter 11, a ground electrode (11A)1 is connected to an unbalanced side ground electrode 203 by a wire 207 and a ground electrode (11C)1 to a balanced side ground electrode 206 by a wire 208. An input electrode (11B)1 is connected to an unbalanced side signal electrode 202 by the wire 208 and a comb-shaped electrode (11B)2 is connected to a balanced side ground electrode 205 by a wire 209. In a balanced SAW filter 21, a ground electrode (21A)2 is connected to an unbalanced side ground 201 by a wire 210 and a ground electrode (21C)2 to a balanced side ground electrode 205 by a wire 211. One signal electrode (21B) 1 in a comb-shaped electrode 21B is connected to a balanced side signal electrode 206 by a wire 222, and the other signal electrode (21B)2 of the comb-shaped electrode 21B is connected to the balanced side signal electrode 204 by a wire 223. The secondary side electrodes (11A)2 and (11C)2 of the comb-shaped electrodes 11A and 11C are connected to the primary side electrodes (21A)1 and (21C)1 of the comb-shaped electrodes 21A and 21C. Consequently, the SAW filters 11 and 21 are constituted so that they ire cascade-connected. Then, they are connected to a power electrode 105 by a wire 114.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave device, and more particularly to a surface acoustic wave device having excellent pass band characteristics in a high frequency band including a GHz band.

[0002]

2. Description of the Related Art A surface acoustic wave device is a small-sized and
It is widely used as a filter or a resonator in a high-frequency circuit of a wireless communication device that is lightweight and operates in a very high frequency band.

[0003] Such a surface acoustic wave device is generally formed on a piezoelectric single crystal or polycrystalline substrate, but has a large electromechanical coupling coefficient k2, and therefore has a high surface wave excitation efficiency. As a substrate material having a small surface roughness, especially in a 64 ° rotation Y-cut plate made of a single crystal of LiNbO ₃ , 64 °
LiNbO ₃ substrate (K. Yamanouti and K. Shibayama,
J. Appl. Phys. Vol.43, no.3, March 1972, pp.856)
Alternatively, the propagation direction of the surface wave in the 36 ° rotated Y-cut plate of LiTaO ₃ single crystal is set to 36 ° YX Li
TaO ₃ substrates are widely used.

However, these cut angles are optimal when the additional mass effect of the electrodes formed on the piezoelectric crystal substrate can be neglected, and the elastic surface excited in a low frequency band of several hundred MHz or less. Although effective because of the long wavelength of the wave, in operation near the GHz band required by recent mobile phones and the like, the electrode thickness cannot be ignored with respect to the elastic wave wavelength to be excited, Not always optimal. In the operation in such a high frequency band, the effect of the additional mass of the electrode is remarkably exhibited.

In such an operation in a very short wavelength range, the thickness of the electrode on the piezoelectric substrate is increased, and the apparent electromechanical coupling coefficient is increased, so that the pass band width or the pass band of the surface acoustic wave filter is increased. Although it is possible to reduce the capacitance ratio γ of the surface acoustic wave resonator, the bulk wave radiated from the electrode toward the inside of the substrate increases in such a configuration, and the propagation loss of the surface wave increases. Problems arise. Such a bulk wave is converted to SSBW (surface skimming bul
k wave), and the surface wave is L
It is called SAW (Leaky surface acoustic wave). Regarding the propagation loss of LSAW in a surface acoustic wave filter using a thick electrode film, 36 ° YX LiTaO ₃ and 6 °
Analysis of 4 ° YX LiNbO ₃ substrate by Plessky et al. Or Edmonson et al. (VS Pl
essky and CS Hartmann, Proc. 1993 IEEE Ultrasoni
cs Symp., pp. 1239-1242; PJ Edmonson and CK
Campbell, Proc. 1994 IEEE Ultrosonic Symp., Pp75
-79).

Incidentally, such a conventional 36 ° YXL
LS such as iTaO ₃ or 64 ° YX LiNbO ₃
In the conventional surface acoustic wave filter using AW, when the electrode film thickness is small, the sound velocity value of the surface wave and the sound velocity value of the bulk wave approach, and as a result, a spurious peak due to the bulk wave appears in the pass band of the filter. (M. Ueda et al., Pro
c. 1994 IEEE Ultrasonic Symp., pp. 143-146).

FIG. 20 shows spurious peaks A and B due to a bulk wave appearing in the vicinity of the filter pass band in the surface wave filter according to Ueda et al. The filter is formed on a 36 ° YX LiTaO ₃ substrate and has a comb-shaped electrode made of an Al—Cu alloy having a thickness of 0.49 μm corresponding to 3% of the excitation wavelength.

Referring to FIG. 20, spurious peak B
Is generated outside the pass band formed near 330 MHz, while the spurious peak A is generated within the pass band.
As a result, it can be seen that ripple occurs in the pass band characteristic.

In the surface acoustic wave filter, the sound velocity of the surface wave depends on the additional mass of the electrode, that is, the film thickness.
Since the sound speed of the SBW does not depend on the thickness of the electrode, in operation in a high frequency band such as the GHz band, the thickness of the electrode increases with respect to the excitation surface wave wavelength, and the sound speed of the surface wave with respect to the bulk wave. Decrease relatively. As a result, the pass band of the filter shifts with respect to the spurious peak, and the pass band characteristics are flattened.

However, as described above, when the thickness of the electrode is increased with respect to the surface wave wavelength, the loss of the LSAW due to the SSBW is increased, and the squareness ratio of the pass band is deteriorated. As will be described later, the squareness ratio indicates the steepness of the filter characteristic. If the squareness ratio of the pass band is deteriorated, the filter characteristic becomes broad.

In particular, in a surface acoustic wave filter operating in a very high frequency band such as the GHz band, it is necessary to secure a certain thickness of the electrode in order to reduce the resistance of the comb-shaped electrode. The problems of increased loss and degraded squareness described above are unavoidable.

[0012]

Therefore, the present inventor has previously proposed Japanese Patent Application No. 7-265466 as a surface acoustic wave device which has solved the above-mentioned problems. In the surface acoustic wave device according to the application, in the short wavelength region such as the GHz band, the inventor cannot ignore the thickness of the electrode with respect to the wavelength of the surface acoustic wave to be excited. Remarkably appear,
This is because it has been found that the rotation angle θ of the single crystal substrate which gives the minimum propagation loss by the effect of the additional mass is shifted to the higher angle side.

In this application, the rotation angle θ of the LiTaO ₃ single crystal substrate is set to be higher than the conventional angle of 36 °, so that the rotation angle θ of the LiTaO ₃ single crystal substrate is centered on the X axis. In addition, a surface acoustic wave device having a high Q with a low attenuation of the surface wave in the GHz band by rotating at an angle in the range of 38 to 46 ° from the Y axis to the X axis direction is provided.

In addition, due to the additional mass effect of the electrode at such a high frequency, the position of the pass band of the filter shifts to the low frequency side with respect to the spurious peak, and therefore, on a LiTaO ₃ substrate having such a large rotation angle. In the surface acoustic wave device formed as described above, the spurious peak can be removed from the pass band of the filter.

When the rotation angle θ of the LiTaO ₃ single crystal substrate is changed as described above, various coefficients such as a coupling coefficient and a reflection coefficient also change. Along with this, the values of various parameters (for example, the logarithm of the comb-teeth electrode fingers, the electrode period of the reflector, etc.) for realizing the most appropriate characteristics as the surface acoustic wave device also vary with the rotation angle θ of the LiTaO ₃ single crystal substrate.
Changes from the conventional parameter value of 36 °. Therefore, in order to optimize the characteristics of the surface acoustic wave device, it is necessary to optimize the above various parameters when the rotation angle θ of the LiTaO ₃ single crystal substrate is made larger than before.

An object of the present invention is to provide a surface acoustic wave device that solves the above problems.

[0017]

According to the present invention, there is provided a LiTaO3 single crystal having a Y-axis centered on an X-axis.
Comb-shaped first and second electrode fingers are combined on a piezoelectric substrate having an azimuth rotated in the range of 40 ° to 42 ° in the Z-axis direction from the axis. And at least three comb electrodes arranged in a row in the propagation direction of the surface acoustic wave on the piezoelectric substrate, and a pair of reflection electrodes disposed so as to sandwich the plurality of comb electrodes. A balanced surface acoustic wave device element and an unbalanced surface acoustic wave device element to be connected in cascade, and a balanced terminal and an unbalanced terminal arranged opposite to each other. The terminal is constituted by a ground pad and a pair of signal pads formed so as to sandwich the ground pad, and the unbalanced terminal is constituted by a signal pad and a pair of ground pads formed so as to sandwich the signal pad. Has a structure And a wire for connecting the surface acoustic wave chip to the balanced terminal and the unbalanced terminal. On the element side of the unbalanced surface acoustic wave device, a comb-shaped electrode disposed in the center thereof. The signal side is wire-connected to the signal pad of the unbalanced terminal, and
The ground side of the comb-shaped electrode provided at the center of the unbalanced surface acoustic wave device element is wire-connected to the ground pad of the balanced terminal, and on both sides of the comb-shaped electrode provided at the center. One of the arranged comb-shaped electrodes is wire-connected to the ground pad of the unbalanced terminal, and the other is wire-connected to the ground pad of the balanced terminal. On the element side, a pair of signal sides provided on a comb-shaped electrode disposed at the center thereof are wire-connected to signal pads of the balanced terminals, respectively, and both side portions of the comb-shaped electrode disposed at the center are provided. Of the comb-shaped electrodes arranged at one end is connected to the ground pad of the unbalanced terminal by wire, and the other is connected to the ground pad of the balanced terminal by wire. It is an.

[0018]

Embodiments of the present invention will now be described with reference to the drawings.

FIGS. 1A and 1B show a surface acoustic wave device according to a first embodiment. Referring to FIG. 1A, the surface acoustic wave device according to the present embodiment is a so-called dual mode SAW filter, and includes a piezoelectric substrate (not shown).
Three comb-shaped electrodes 11A, 11B, 11C are provided between a pair of reflectors 10A, 10B formed above.

In this embodiment, a piezoelectric substrate having a direction in which a LiTaO ₃ single crystal is rotated from the Y axis to the Z axis in the range of 40 ° to 42 ° about the X axis as the substrate is used. As a result, as described above, a surface acoustic wave device having low Q in the GHz band and high Q can be realized.

The reflectors 10A and 10B are arranged in the X-axis direction of the substrate, and define the path of the surface acoustic wave propagating in the X-axis direction. On the other hand, each of the electrodes 11A, 11B, 11C
Is a primary electrode (11) formed with a plurality of primary electrode fingers.
A) Secondary electrodes (11A) 2, (11B) 2, (11C) formed with (1), (11B) 1, (11C) 1 and secondary electrode fingers opposed to the primary electrode fingers. 2, the primary electrode fingers and the secondary electrode fingers are alternately arranged in the X-axis direction and intersect with the path of the surface acoustic wave, similarly to a normal comb-shaped electrode.

In the configuration shown in FIG. 1A, the primary electrodes (11A) 1 and (11C) 1 of the electrodes 11A and 11C are connected to the input terminals, and the secondary electrodes (11A) 2 and (11C) are connected to the input terminals.
C) 2 is grounded. On the other hand, the primary electrode (11B) 1 of the electrode 11B is grounded, and the secondary electrode (11B) 2 is connected to the output terminal. That is, the SAW filter in FIG. 1A constitutes a so-called two-input one-output SAW filter.

In such a dual mode SAW filter,
As shown in FIG. 1B, a first mode having a frequency of f1 and a third mode having a frequency of f3 formed between the reflectors 10A and 10B are used. To realize a pass band characteristic having a pass band. However,
FIG. 1B shows the energy distribution of the surface acoustic wave in the structure of FIG.

FIG. 2 shows an impedance-log ratio characteristic of the surface acoustic wave device shown in FIG. here,
The logarithmic ratio is the ratio (N2 / N1) between the number of electrode pairs (N1) of the comb-shaped electrode 11B located at the center of the comb-shaped electrodes 11A to 11C and the number of electrode pairs (N2) of the comb-shaped electrodes adjacent to the comb-shaped electrode 11B. Say. FIG. 3 shows a bandwidth-log ratio characteristic of the surface acoustic wave device shown in FIG.

Referring first to FIG. 2, the solid line in FIG. 2 shows the change in the input impedance when the logarithmic ratio is changed, and the broken line shows the output when the logarithmic ratio is changed. This is a change in the side impedance. In a surface acoustic wave device that is a high-frequency device, both the input impedance and the output impedance are 5
It is desirable to be 0 Ω, and it is necessary to be at least 59 Ω or less.

Therefore, focusing on the input side impedance, the input side impedance tends to increase substantially as the logarithmic ratio increases. When the logarithmic ratio is approximately 80% or less, the impedance becomes 59Ω or less. Focusing on the output-side impedance, the output-side impedance shows a tendency to decrease substantially as the logarithmic ratio increases.
When it is 5% or more, the impedance becomes 59Ω or less.

On the other hand, paying attention to the relationship between the bandwidth and the logarithmic ratio shown in FIG. 3, when the logarithmic ratio is approximately 70%, the maximum bandwidth is set. This also has a characteristic that the bandwidth decreases. The bandwidth required for the surface acoustic wave device is at least 33 MHz or more. Therefore, in order to satisfy the bandwidth required for the surface acoustic wave device, the logarithmic ratio should be 55% or more and 80% or more.
It is necessary to set below.

Therefore, in the surface acoustic wave device according to the present embodiment, the logarithmic ratio is 55 to 55 based on the results shown in FIGS.
It is characterized by being set to 80%. in this way,
Number of electrode pairs (N1) of comb-shaped electrode 11B located at the center
And the logarithmic ratio (N2 / N1), which is the ratio of the number of electrode pairs (N2) of the comb-shaped electrodes adjacent to the comb-shaped electrode 11B, to 55
By setting it to 80%, the bandwidth can be widened, and the terminal resistance of the surface acoustic wave device, which is a high-frequency device, can be brought close to 50Ω, which has the best characteristics.

In particular, according to the characteristics shown in FIG. 3, by setting the logarithmic ratio (N2 / N1) to 65 to 75%,
The bandwidth can be set in a wide range of about 34 MHz or more, and a SAW filter with particularly good bandwidth characteristics can be realized.

Next, attention is directed to FIGS. FIG. 4 shows a result obtained by simulating a bandwidth-electrode distance (HD) characteristic in the surface acoustic wave device shown in FIG. Here, the inter-electrode distance (HD) refers to, from the center of the electrode fingers at both ends of the comb electrode 11B located at the center of the comb electrodes 11A to 11C, adjacent to the comb electrode 11B located at the center. Other comb electrodes 11A, 1
The distance to the center of the 1C electrode finger.

Even when the width of each electrode finger is different, the measurement start point of the distance between electrodes (HD) is the center position of each electrode finger in the X direction. In each figure, the distance between electrodes (HD) on the horizontal axis is a multiple of the wavelength (λ) of the surface acoustic wave propagating on the substrate surface.

Referring to FIG. 4, as described above, the surface acoustic wave device needs to have a bandwidth of at least 33 MHz. Therefore, the inter-electrode distance (H
D) is 0.75λ to 0.990λ or more from FIG.
Therefore, the distance (HD) between the electrodes is 0.75λ to 0.90λ.
By setting to, the bandwidth of the surface acoustic wave element can be increased to a practically usable bandwidth. Therefore, in the surface acoustic wave device according to this embodiment, the distance (HD) between the electrodes is set to 0.75λ to 0.75λ from the viewpoint of improving the band characteristics of the filter.
0,90λ.

FIG. 4 shows the result of the simulation. Therefore, there is a range where the bandwidth is 33 MHz or more even in the region where the inter-electrode distance (HD) is 0.5λ or less. Is smaller than or equal to 0.5λ, the adjacent electrode fingers actually interfere with each other, and the distance (HD) between the electrodes cannot be actually set to be smaller than or equal to 0.5λ. On the other hand, FIG. 5 shows the in-band ripple-electrode distance characteristics in the surface acoustic wave device shown in FIG. Here, the in-band ripple refers to a pulsating component included in the filter band, and it is desirable that this in-band ripple does not occur (that is, it is desirable that it be 0 dB).

However, it is difficult to completely remove the in-band ripple, and a practical surface acoustic wave device needs to have at least an in-band ripple of 2.0 dB or less. Note that, also in this figure, the inter-electrode distance (HD) on the horizontal axis is a multiple of the wavelength (λ) of the surface acoustic wave propagating on the substrate surface.

Therefore, referring to FIG. 5, the in-band ripple has a minimum value when the inter-electrode distance is around 0.8λ, and is shorter or shorter than the minimum inter-electrode distance. Even so, the value of the in-band ripple shows a characteristic of increasing. In addition, the in-band ripple is sufficient for practical use.
In order to make it equal to or less than dB, the distance between the electrodes must be 0.78λ to
It must be set between 0.85λ. For this reason, in the surface acoustic wave device according to the present embodiment, the distance between the electrodes is set to 0.7 from the surface that prevents the in-band ripple from affecting the filter characteristics.
It is set to 8λ to 0.85λ.

FIG. 6 shows the bandwidth-electrode period ratio characteristics of the surface acoustic wave device shown in FIG. Here, the term “electrode period ratio” means that the surface elasticity is a comb-shaped electrode 11 constituting the device.
The electrode period of A to 11C is λ _IDT and the reflectors 10A, 1
When the electrode period of 0B is λ _ref , this comb-shaped electrode 11
It means the ratio (λ _IDT / λ _ref ) between the electrode period λ _{IDT of A} to 11C and the electrode period λ _ref of the reflectors 10A and 10B.

Thus, referring to FIG. 6, the bandwidth becomes maximum when the electrode period ratio (λ _IDT / λ _ref ) is 0.982, and decreases even if the electrode period ratio increases from this maximum electrode period ratio. However, the bandwidth shows a characteristic of decreasing. As described above, the bandwidth of the surface acoustic wave device is at least 33 MHz.
It is desirable that this is the case.

Therefore, in order to set the bandwidth to 33 MHz or more, the value of the electrode period ratio (λ _IDT / λ _ref ) is set to 0.977.
０．９0.992. Therefore, in the surface acoustic wave device according to the present embodiment, the electrode period ratio (λ _IDT / λ
_ref ) is set between 0.977 and 0.992,
Thus, the bandwidth can be set to a desired value.

Next, attention is directed to FIGS. FIG.
Shows the impedance-electrode cross width characteristic of the surface acoustic wave device shown in FIG. 1, and FIG. 8 shows the bandwidth-electrode cross width characteristic of the surface acoustic wave device shown in FIG.

Here, the electrode cross width (W) is defined as the primary electrodes (11A) 1 to (11A) of the comb electrodes 11A to 11C.
C) 1 electrode finger and secondary electrodes (11A) 2 to (11C)
2 refers to a width dimension in which the electrode fingers overlap in the X direction (see FIG. 1A). In each of the figures, the electrode cross width (W) on the horizontal axis is a multiple of the wavelength (λ) of the surface acoustic wave propagating on the substrate surface.

Referring first to FIG. 7, the impedance tends to decrease gradually as the electrode cross width (W) increases. As described above, the surface acoustic wave device, which is a high-frequency device, exhibits the best filter characteristics when the input / output impedance of the filter matches the terminating resistance. The allowable impedance is ± 1 with respect to the optimum value.
0%, specifically, when the terminating resistance is 50Ω, good characteristics can be realized if the input / output impedance value of the filter is in the range of 40Ω to 60Ω. Accordingly, a desired impedance characteristic can be obtained by setting the electrode cross width (W) from 40λ to 80λ according to FIG. On the other hand, referring to FIG. 8, the bandwidth becomes the maximum bandwidth when the electrode cross width (W) is 60λ,
If the electrode crossing width increases or decreases from the maximum electrode crossing width, the bandwidth decreases. As described above, a practically usable bandwidth of a surface acoustic wave device is at least 33 MHz or more. Therefore, the electrode cross width is set to 4
When set to 0λ to 70λ, a good bandwidth can be obtained.

That is, according to the characteristics shown in FIGS. 7 and 8, by setting the electrode cross width (W) to 40λ to 70λ, the impedance characteristics and the bandwidth can be set to appropriate values for a surface acoustic wave device. Therefore, in the surface acoustic wave device according to the present embodiment, the electrode cross width (W) is set to 40λ to 70λ.

Next, a second embodiment will be described with reference to FIG. However, in FIG. 9, parts corresponding to the parts described above are denoted by the same reference numerals, and description thereof will be omitted.

Referring to FIG. 9, the surface acoustic wave device (SAW filter) according to the present embodiment is composed of the same LiTaO ₃ single crystal as that of the first embodiment, which is forty-four from the Y axis to the Z axis around the X axis. It is configured on a piezoelectric substrate (not shown) having an azimuth rotated at an angle in the range of ° to 42 °.

On the piezoelectric substrate, reflectors 10A, 10A, which are aligned in the X-axis direction as shown in FIG.
A first surface acoustic wave element element (hereinafter, referred to as a SAW filter 11) composed of a comb-shaped electrode 11A, 11B, and 11C sequentially arranged between the reflector 10B and the reflectors 10A and 10B.
And a second surface acoustic wave device composed of reflectors 20A, 20B arranged on the same piezoelectric substrate and arranged in the X-axis direction, and comb-shaped electrodes 21A, 21B, 21C sequentially arranged between the reflectors 20A, 20B. Element (hereinafter, SAW filter 2)
1), the SAW filter 11 and the SAW filter 21 connect the secondary electrode (11B) 2 forming the comb electrode 11B to the primary electrode (21B) 1 forming the comb electrode 21B. Cascade-connected.

In the embodiment shown in FIG. 9, the comb electrodes 11A, 11A
The primary electrodes (11A) 1 and (11C) 1 of C are grounded in common, and the secondary electrodes (1
1A) 2 and (11C) 2 correspond to one of the comb electrodes 21A and 21C.
It is connected to the secondary electrodes (11A) 1 and (11C) 1. Further, the secondary electrodes of the comb electrodes 21A and 21C (11
A) 2 and (11C) 2 are configured to be commonly grounded. Further, the primary electrode (11B) 1 of the comb-shaped electrode 11B
Is connected to the input electrode pad and the comb-shaped electrode 21B
Of the secondary electrode (21B) 2 is connected to the output electrode pad.

In the embodiment shown in FIG. 9, the SAW filter 11 has an electrode intersection width of W1, whereas the SAW filter 21 has
Is set to W2 (≠ W1), and as a result, the input impedance and the output impedance of the entire surface acoustic wave device (SAW filter) are set to different values. That is, the input impedance of the entire surface acoustic wave device is determined by the input impedance of the SAW filter 11 having an electrode cross width of W1, while the overall output impedance is determined by the output impedance of the SAW filter 21 having an electrode cross width of W2. Is determined.

It is known that the input / output impedance of a SAW filter is inversely proportional to the number of electrode pairs and the electrode cross width, but the number of electrode pairs cannot be freely selected because it determines the pass band characteristics of the filter. In contrast,
Since the electrode cross width can be set relatively independently of the pass band characteristics of the filter, the electrode cross width W in the embodiment of FIG.
By setting 1 and the electrode cross width W2 independently, S
The input impedance of the AW filter 1 and the output impedance of the SAW filter 2 can be independently and freely changed to match the terminal impedance. This method is effective when the terminal impedance on the input side is different from the terminal impedance on the output side.

More specifically, in this embodiment, the input side S
The electrode cross width (W1) of the AW filter 11 is set to 40λ to 60λ with respect to the wavelength λ of the surface acoustic wave, and the electrode cross width (W2) of the output side SAW filter 21 is set to the wavelength λ of the surface acoustic wave. 20λ to 60λ (W1, W
2 is set to 60λ). Other parameters that determine the characteristics of the surface acoustic wave device shown in FIG. 9 are the SAW filter 11 and the SAW filter 2.
1 are set to the same values as those of the surface acoustic wave device shown in FIG. That is, the electrode ratio (N2 / N1) of both the SAW filter 11 and the SAW filter 21 is 55 to 80%.
The distance between the electrodes (HD) is set to 0.75λ to 0.90λ with respect to the wavelength λ of the surface acoustic wave, and the electrode period ratio (λ _IDT / λ _ref ) is set to 0.1. 97
It is set to 7 to 0.992. In particular, of the above parameters, the electrode ratio (N2 / N1) is 65 to 75%.
By setting to, a surface acoustic wave device having a wider bandwidth can be realized.

FIG. 19 shows an embodiment of the relationship between the output terminal impedance and the bandwidth of the surface acoustic wave device (SAW filter) shown in FIG. In the figure,
The input side means impedance of the SAW filter is fixed at 50Ω, and shows the change of the bandwidth when the output side termination impedance (RL) is changed. Referring to FIG. 19, when W2 / W1 = 1,
It has a characteristic that the bandwidth is reduced when the output side termination impedance (RL) is 100Ω or more. In contrast, W2
In the case where /W1=0.6 and W2 / W1 = 0.4 (that is, when the electrode cross widths W1 and W2 are different), the output-side termination impedance (RL) is 75Ω to 20Ω.
Good results can be obtained in the range of 0Ω.

On the other hand, when the terminal impedance is 50Ω, the electrode crossing width of the SAW filter is from 40λ to 60λ.
, Good characteristics can be obtained, but the termination impedance (R
When L) is from 75Ω to 200Ω, the electrode cross width is 20λ to
Good characteristics are obtained at 60λ. Therefore, a surface acoustic wave device (SAW
In the case of (filter), the above combination is required.

Next, a description will be given of a surface acoustic wave device according to a third embodiment. FIG. 12 shows a surface acoustic wave device according to a third embodiment, and FIGS. 10 and 11 show surface acoustic wave devices as a comparative example of the third embodiment. First, FIG.
A surface acoustic wave device which is a comparative example of the third embodiment will be described with reference to FIGS. 10 to 12 show a configuration including a package of the surface acoustic wave device according to the second embodiment. However, the same reference numerals are given to the parts described above, and the description will be omitted.

First, the surface acoustic wave device shown in FIG. 10 will be described. In the surface acoustic wave device shown in the figure, a piezoelectric substrate 1 carrying the surface acoustic wave device having the configuration shown in FIG. 9 is carried on a ceramic package substrate 100, and input terminals and output terminals are provided on the package substrate 100. They are arranged to face each other.

The input terminal is a pair of ground electrodes 101 and 103
Are formed so as to sandwich the input electrode 102 from both sides. The output terminals are ground electrodes 104 and 106.
Are formed so as to sandwich the output electrode 105 from both sides.

In the configuration of FIG. 10, the SAW on the piezoelectric substrate 1
In the filter 11, the ground electrode of the comb-shaped electrode 11A (FIG. 9)
The electrode (11A) 1) is connected to the input-side ground electrode 103 on the package 100 by an Al wire 107, and the ground electrode of the comb-shaped electrode 11C (electrode (11C) 1 in FIG. 9) is connected to the output-side ground on the package 100. Al wire 1 for electrode 106
08.

An input electrode (electrode (11B) 1 in FIG. 9) of the comb electrode 11B is connected to the input electrode 102 by an Al wire 109, and a ground electrode (electrode (11B) 2 in FIG. 9) of the comb electrode 11B. ) Is the input-side ground electrode 101
Are connected by an Al wire 110.

On the other hand, among the SAW filters 21 on the piezoelectric substrate 1, the ground electrode (the electrode (21A) 2 in FIG. 9) of the comb-shaped electrode 21A is connected to the input-side ground electrode 101 on the package 100 by the Al wire 111. And the comb-shaped electrode 21C
The ground electrode (electrode (21C) 2 in FIG. 9) is connected to the output-side ground electrode 104 on the package 100 by an Al wire 112.

The ground electrode (electrode (21B) 1 in FIG. 9) of the comb-shaped electrode 21B is connected to the output-side ground electrode 106 by an Al wire 113. Further, the output electrode of the comb-shaped electrode 21B (the electrode (21B) 2 in FIG. 9) is connected to the output electrode 10B.
5 is connected by an Al wire 114. Also, S
The AW filter 11 and the SAW filter 21 are composed of secondary electrodes (11A) 2, (11C) of the comb electrodes 11A, 11C.
2 is the primary electrode (21A) of the comb electrodes 21A and 21C.
, (21C) 1 to form a cascade connection.

Next, the surface acoustic wave device shown in FIG. 11 will be described. The same components as those shown in FIG. 10 are denoted by the same reference numerals, and description thereof will be omitted.

The surface acoustic wave device shown in FIG. 11 has a configuration in which Al wires 114 and 115 are added to the configuration of the surface acoustic wave device shown in FIG. Specifically, the ground electrode of the comb electrode 11C (the electrode (11C) in FIG. 9)
1) is also connected to the input-side ground electrode 101 on the package 100 by the Al wire 114, and furthermore, the comb-shaped electrode 2
The 1A ground electrode (electrode (21A) 2 in FIG. 9) is also connected to the output side ground electrode 106 on the package 100 by the Al wire 1.
15.

Next, a surface acoustic wave device according to a third embodiment will be described with reference to FIG. In FIG. 12, the same components as those shown in FIGS. 10 and 11 are denoted by the same reference numerals, and description thereof will be omitted.

In the configuration of FIG. 12, the SAW on the piezoelectric substrate 1
In the filter 11, the ground electrode of the comb-shaped electrode 11A (FIG. 9)
The electrode (11A) 1) is connected to the input-side ground electrode 103 on the package 100 by an Al wire 107, and the ground electrode of the comb-shaped electrode 11C (the electrode (11C) 1 in FIG. 9) is connected to the input-side ground on the package 100. The electrode 101 (ground pad) is connected by an Al wire 114 (input side ground wire).

The input electrode (electrode (11B) 1 in FIG. 9) of the comb electrode 11B is connected to the input electrode 102 (signal pad) by an Al wire 109 (input side signal wire), and the ground of the comb electrode 11B is grounded. Electrode (electrode (11 in FIG. 9)
B) 2) is the input-side ground electrode 101 (ground pad)
Are connected by an Al wire 110 (input side ground wire).

On the other hand, among the SAW filters 21 on the piezoelectric substrate 1, the ground electrode (electrode (21A) 2 in FIG. 9) of the comb electrode 21A is connected to the output side ground electrode 106 (ground pad) on the package 100 by Al. The ground electrode (electrode (21C) 2 in FIG. 9) of the comb electrode 21C is connected to the output-side ground electrode 104 (ground pad) on the package 100 by the Al wire 112 (output side). Ground wire).

The ground electrode (electrode (21B) 1 in FIG. 9) of the comb electrode 21B is connected to the output-side ground electrode 106 (ground pad) by an Al wire 113 (output-side ground wire). Further, the output electrode (the electrode (21B) 2 in FIG. 9) of the comb electrode 21B is connected to the output electrode 105 (signal pad) by an Al wire 114 (output side signal wire).

That is, the surface acoustic wave device having the configuration shown in FIG. 12 is different from the configuration shown in FIG. 11 in that the ground electrode (electrode (11C) 1 in FIG. 9) of the comb-shaped electrode 11C and the output-side ground electrode 1
06 and the comb-shaped electrode 21A
The grounding electrode (electrode (21A) 2 in FIG. 9) and the Al wire 111 connecting the input-side grounding electrode 101 are removed.

With this configuration, the input side SA
Each Al wire 107, 10 connected to the W filter 11
Reference numerals 9, 110 and 114 denote input-side electrodes 101 to 103, respectively.
, And all the Al wires 112 to 115 connected to the output-side SAW filter 21 are connected to the output-side electrodes 104 to 106.
The SAW filter 11 and the SAW filter 21 are composed of the secondary electrodes (11A) 2, (1) of the comb-shaped electrodes 11A, 11C.
1C) 2 is used as the primary electrode (21) of the comb electrodes 21A and 21C.
A) 1 and (21C) 1 are connected in a cascade connection, as shown in FIGS.
This is the same as the surface acoustic wave device shown in FIG. FIG.
13 shows attenuation-frequency characteristics of the surface acoustic wave device shown in FIGS. In the same figure, an arrow A indicates the characteristics of the surface acoustic wave device of the comparative example shown in FIG. 10, and an arrow B indicates the characteristics of the surface acoustic wave device of the comparative example shown in FIG. FIG. 12 is indicated by arrow C.
9 shows the characteristics of the surface acoustic wave device according to the third embodiment shown in FIG.

Referring to FIG. 13, the surface acoustic wave device according to the comparative example shown by arrows A and B has a characteristic of relatively low attenuation, whereas the surface acoustic wave device shown by arrow C according to the present embodiment. It can be seen that the amount of attenuation has a large attenuation and good characteristics. Therefore, by using the connection method shown in FIG. 12 for the wire connection, good characteristics can be obtained as a SAW filter.

Although the reason for exhibiting such characteristics is not clear, interference occurs because the input and output sides are balanced and the input and output sides are completely separated by wiring. It is considered that the fact that they are not performed is one of the reasons for exhibiting the above characteristics.

Next, a surface acoustic wave device according to a fourth embodiment will be described. FIG. 14 shows a surface acoustic wave device according to a fourth embodiment. However, in the figure, the same reference numerals are given to the previously described portions, and description thereof will be omitted.

The surface acoustic wave device shown in FIG. 14 has a structure in which the piezoelectric substrate 1 carrying the surface acoustic wave device having the structure shown in FIG. 9 is carried on a ceramic package substrate 100. SAW filter 11 and balanced SA
The configuration includes a W filter 21. An unbalanced terminal and a balanced terminal are arranged on the package substrate 100 so as to face each other.

The unbalanced terminals are a pair of ground electrodes 201 and
03 is formed so as to sandwich the signal electrode 202 from both sides. The balanced terminal is a pair of signal electrodes 20.
4 and 206 are formed so as to sandwich the ground electrode 205 from both sides.

In the configuration shown in FIG. 14, among the unbalanced SAW filters 11 on the piezoelectric substrate 1, the ground electrode of the comb electrode 11A (the electrode (11A) 1 in FIG. 9) is the unbalanced ground electrode 203 on the package 100. (Ground pad) by an Al wire 207, and a ground electrode (FIG. 9) of the comb electrode 11C.
Electrode (11C) 1) is connected to the balanced side ground electrode 206 (ground pad) on the package 100 by an Al wire 208.
Connected by

The input electrode (electrode (11B) 1 in FIG. 9) of the comb-shaped electrode 11B is connected to the unbalanced signal electrode 202 (signal pad) by an Al wire 208, and the ground electrode of the comb-shaped electrode 11B (FIG. 9). Electrode (11B) 2) is connected to the balanced side ground electrode 205 (ground pad) by the Al wire 20.
9.

On the other hand, the balanced SAW on the piezoelectric substrate 1
In the filter 21, the ground electrode of the comb electrode 21A (FIG. 9)
Electrode (21A) 2) is connected to the unbalanced-side ground electrode 201 (ground pad) on the package 100 by an Al wire 210.
The ground electrode (electrode (21C) 2 in FIG. 9) of the comb-shaped electrode 21C is connected to the balanced side ground electrode 205 (ground pad) on the package 100 by an Al wire 211.

One signal electrode (the electrode (21B) 1 in FIG. 9) of the comb-shaped electrode 21B is connected to the balanced-side signal electrode 206.
(Signal pad) by an Al wire 222, and the other signal electrode of the comb-shaped electrode 21B (the electrode (21
B) 2) A is applied to the balanced side signal electrode 204 (signal pad).
They are connected by the l-wire 223.

The unbalanced SAW filter 11 and the balanced SAW filter 21 are different from each other in that the secondary electrodes (11A) 2 and (11C) 2 of the comb electrodes 11A and 11C are connected to the comb electrode 21.
A and 21C are connected in cascade by connecting to the primary electrodes (21A) 1 and (21C) 1.

This embodiment is characterized in that an Al wire 211 is provided between the ground electrode (electrode (21C) 2 in FIG. 9) of the comb-shaped electrode 21C and the balanced side ground electrode 205. Here, FIG. 15 shows an attenuation-frequency characteristic (shown by an arrow D in the figure) of a surface acoustic wave device having a configuration in which an Al wire 211 is disposed between the ground electrode of the comb-shaped electrode 21C and the balanced-side ground electrode 205. And the attenuation-frequency characteristics of the surface acoustic wave device having a configuration in which the Al wire 211 is not provided between the ground electrode of the comb-shaped electrode 21C and the balanced-side ground electrode 205 (in the figure,
Arrow E).

As shown in the figure, in the configuration in which the Al wire 211 is not provided between the ground electrode of the comb-shaped electrode 21C and the balanced-side ground electrode 205 indicated by the arrow E, the attenuation becomes a relatively low value. Therefore, the characteristics as a SAW filter are not good. On the other hand, between the ground electrode of the comb-shaped electrode 21C indicated by the arrow D in FIG.
In the configuration in which the l-wire 211 is provided, it can be seen that the degree of attenuation is large, and the SAW filter has good characteristics. Therefore, by disposing the Al wire 211 between the ground electrode of the comb-shaped electrode 21C and the balanced-side ground electrode 205, it is possible to obtain good characteristics as a SAW filter.

Next, a fifth embodiment will be described. FIG. 16 shows a surface acoustic wave device according to a fifth embodiment.
The surface acoustic wave device according to the present embodiment uses LiTa as a substrate.
O ₃ single crystal is 40 ° ~ from Y axis to Z axis centering on X axis
A so-called dual type surface acoustic wave device (hereinafter referred to as dual surface acoustic wave device) in which two surface acoustic wave device elements having different band frequency characteristics are formed on a piezoelectric substrate having an orientation rotated at an angle in a range of 42 °. Device).

Among the above two surface acoustic wave device elements, the surface acoustic wave device element having a low band frequency has a configuration in which a plurality of comb-shaped electrodes are arranged along the propagation direction of the surface acoustic wave. More specifically, it has the same configuration as the surface acoustic wave device having the multi-mode filter structure shown in FIG. 1 or FIG. Note that the example shown in FIG. 16 shows an example in which the surface acoustic wave device having the multi-mode filter structure shown in FIG. 9 (hereinafter, referred to as a multi-mode surface acoustic wave device element) is applied.

On the other hand, a surface acoustic wave device element having a high band frequency is a ladder type surface acoustic wave device element in which a surface acoustic wave resonator is ladder-connected. In FIG. 16, the same components as those in the above-described embodiments are denoted by the same reference numerals, and description thereof will be omitted.

The ladder-type surface acoustic wave device element includes comb electrodes 31A to 31E and a reflector 32
A to 36A and 32B to 36B.
The input terminal is a primary electrode (31) of the comb electrodes 31A and 31B.
A) 1, (31B) 1. The secondary electrode (31A) 2 of the comb-shaped electrode 31A is grounded,
The secondary electrode (31B) 2 of the comb electrode 31B is the comb electrode 3
Primary electrodes (31C) 1, (31D) 1 of 1C and 31D
It is connected to the.

The secondary electrode (31) of the comb-shaped electrode 31C
C) 2 is grounded, and the secondary electrode (31D) 2 of the comb electrode 31D is the primary electrode (31D) of the comb electrode 31E.
E) It is connected to 1 and the output terminal. Further, the secondary electrode (31E) 2 of the comb-shaped electrode 31E is grounded.

On the other hand, the reflectors 32A and 32B are
1A, and the reflector 33
Reference numerals A and 33B denote the comb-shaped electrodes 31B and the reflectors 34A and 34B.
Denotes a comb-shaped electrode 31C, reflectors 35A and 35B are disposed so as to interpose a comb-shaped electrode 31D, and reflectors 36A and 36B are disposed so as to interpose a comb-shaped electrode 31E.

Here, in the dual surface acoustic wave device having the above configuration, the film thickness of the electrode constituting the multi-mode surface acoustic wave device element and the film thickness of the electrode constituting the ladder type surface acoustic wave device element are different. Let's focus on the explanation. In the case of a multi-mode surface acoustic wave device element, the ripple does not enter the pass band, so that the thickness of the electrode can be reduced. On the other hand, in the case of a ladder-type surface acoustic wave device element, if the thickness of the electrode is reduced, ripples enter the pass band and filter characteristics deteriorate, so that it is difficult to reduce the thickness of the electrode.

On the other hand, in an electronic device such as a mobile phone in which a surface acoustic wave device is provided, a high frequency band (for example, 1.7 to 1.7) is used.
In some cases, a filter in the 1.9 GHz band and a filter in a low frequency band (for example, 800 to 900 MHz) are required. If this is realized by independent surface acoustic wave devices, the number of components will increase and the result will be contrary to the miniaturization required for electronic devices. Therefore, in order to satisfy the above requirements, it is conceivable to form both a high frequency band filter and a low frequency band filter in the same device.

Therefore, it is assumed that two multimode surface acoustic wave device elements are formed on the same substrate.
As described above, in the case of the multi-mode surface acoustic wave device element, since the ripple does not enter the pass band, it is possible to make the electrode film thinner than the rattan type filter. However, in general, the film thickness of the electrodes of the surface acoustic wave device is
It is known that it is inversely proportional to the set band frequency value. Therefore, when an attempt is made to realize a high-frequency band filter using a multi-mode surface acoustic wave device element, the thickness of the electrode becomes thin, and conversely, the electrode thickness becomes low. When the frequency band filter is to be realized by the multi-mode surface acoustic wave device element, the thickness of the electrode becomes large.

That is, when it is attempted to form a high-frequency band filter and a low-frequency band filter both composed of multimode surface acoustic wave device elements on the same substrate, the thicknesses of the respective filters are different. Therefore, in order to manufacture a dual surface acoustic wave device in which both the high-frequency band filter and the low-frequency band filter are composed of the multi-mode surface acoustic wave device elements, it is necessary to form the high-frequency band filter with the electrodes having a low thickness due to the difference in the electrode film thickness. It becomes necessary to form the electrodes of the frequency band filter by a different process, and the manufacturing efficiency of the dual surface acoustic wave device becomes extremely poor.

On the other hand, assuming that two ladder type surface acoustic wave device elements are formed on the same substrate, in the case of the ladder type surface acoustic wave device element, ripples enter the pass band as described above. Due to the possibility, the thickness of the electrode cannot be reduced. Specifically, a film thickness of about 10% of the surface acoustic wave λ is required.

Therefore, when an attempt is made to realize a high-frequency band filter using a ladder-type surface acoustic wave device element,
The surface acoustic wave λ becomes shorter and the film thickness becomes thinner accordingly. Further, as described above, in the case of the ladder-type surface acoustic wave device element, if the film thickness is set to 0.1λ or less, ripples may be introduced. Conversely, when the low-frequency band filter is to be realized by a ladder-type surface acoustic wave device element, the surface acoustic wave λ becomes longer and the film thickness accordingly increases.

Therefore, even when manufacturing a dual surface acoustic wave device in which both the high frequency band filter and the low frequency band filter are composed of the ladder type surface acoustic wave device elements, the difference in the electrode film thickness causes the high frequency band filter to operate. It is necessary to form the electrodes and the electrodes of the low-frequency band filter by different processes, and the production efficiency of the dual surface acoustic wave device becomes extremely poor.

However, by forming the multi-mode surface acoustic wave device element and the ladder type surface acoustic wave device element on the same substrate as in the present embodiment, the dual surface acoustic wave which solves the above-mentioned problem is solved. The device can be realized. Hereinafter, this will be described.

FIG. 18 shows a loss-frequency characteristic when a high frequency SAW filter having a center frequency of 1.9 GHZ is realized by a ladder type surface acoustic wave device. As shown in the figure, the ladder-type surface acoustic wave device shows good frequency characteristics, and no ripple is observed. At this time, the thickness of the electrode (Al electrode) of the ladder type surface acoustic wave device was 200 nm.

FIG. 17 shows the loss-frequency characteristics when the low-frequency SAW filter is realized by a multi-mode surface acoustic wave device. In particular, in FIG. 17, the electrodes (Al electrodes) constituting the multi-mode surface acoustic wave device
The characteristics in the case where the film thicknesses are set to 200 nm, 240 nm, and 280 nm are shown together in the same drawing. As shown in the figure, when the film thickness of the electrode is changed, the filter characteristics change, but the film thickness is 200 nm, which is equal to the film thickness of the ladder-type surface acoustic wave device previously shown in FIG.
Even when m, good filter characteristics are shown.

Therefore, as shown in FIGS. 17 and 18, the multi-mode surface acoustic wave device element and the ladder type surface acoustic wave device element are formed on the same substrate, and the multi-mode surface acoustic wave device element has a band frequency. The multi-mode type is configured by using as a low frequency band filter of about 800 to 900 MHz band and using a ladder type surface acoustic wave device element as a high frequency band filter of about 1.7 to 2.0 GHz band. The film thickness of each electrode of the surface acoustic wave device element and the ladder type surface acoustic wave device element can be made equal to about 200 nm, so that the film can be formed by the same manufacturing process.

Thus, a filter in a high frequency band (for example, 1.7 to 1.9 GHz band) required in the market and a low frequency band (for example, 800 to 900 MHz) are required.
Band) can be formed in the same device (substrate), and the manufacturing process becomes extremely efficient because the electrode thickness of each surface acoustic wave device element is equal,
It is possible to provide the dual surface acoustic wave device at a low cost.

[0098]

According to the present invention, since the degree of attenuation can be increased, a surface acoustic wave device having good characteristics can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a surface acoustic wave device according to a first embodiment.

FIG. 2 is a diagram illustrating impedance-log ratio characteristics of the surface acoustic wave device according to the first embodiment.

FIG. 3 is a diagram illustrating a bandwidth-log ratio characteristic of the surface acoustic wave device according to the first embodiment.

FIG. 4 is a diagram illustrating a bandwidth-drive electrode distance characteristic of the surface acoustic wave device according to the first embodiment.

FIG. 5 is a diagram illustrating a bandwidth-distance between driving electrodes of the surface acoustic wave device according to the first embodiment.

FIG. 6 is a view showing a bandwidth-electrode period characteristic of the surface acoustic wave device according to the first embodiment.

FIG. 7 is a diagram illustrating impedance-aperture length characteristics of the surface acoustic wave device according to the first embodiment.

FIG. 8 is a diagram illustrating a bandwidth-aperture length characteristic of the surface acoustic wave device according to the first embodiment.

FIG. 9 is a configuration diagram of a surface acoustic wave device according to a second embodiment.

FIG. 10 is a configuration diagram illustrating a comparative example of the surface acoustic wave device according to the third embodiment.

FIG. 11 is a configuration diagram illustrating a comparative example of the surface acoustic wave device according to the third embodiment.

FIG. 12 is a configuration diagram of a surface acoustic wave device according to a third embodiment.

FIG. 13 is a diagram showing loss-frequency characteristics of a surface acoustic wave device according to a third embodiment together with a comparative example.

FIG. 14 is a configuration diagram of a surface acoustic wave device according to a fourth embodiment.

FIG. 15 is a diagram showing a loss-frequency characteristic of the surface acoustic wave device according to the fourth embodiment together with a comparative example.

FIG. 16 is a configuration diagram of a dual surface acoustic wave device.

FIG. 17 is a diagram showing a loss-frequency characteristic of a multi-mode surface acoustic wave device element in one embodiment of the dual surface acoustic wave device together with a comparative example.

FIG. 18 is a diagram showing a loss-frequency characteristic of a ladder-type surface acoustic wave device element in a dual surface acoustic wave device together with a comparative example.

FIG. 19 is a diagram showing a bandwidth-impedance characteristic of the surface acoustic wave device shown in FIG.

FIG. 20 is a diagram showing pass band characteristics of a surface acoustic wave device which is an example of the related art.

[Explanation of symbols]

10A, 10B, 20A, 20B, 32A to 36A, 3
2B to 36B Reflectors 11A to 11C, 21A to 21C 31A to 31E Comb-shaped electrodes (11A) 1 to (11C) 1, (21A) 1 to (21C)
1 Primary electrode (11A) 2-(11C) 2, (21A) 2-(21C)
2 Secondary electrodes 101 to 104, 106 Ground electrode 102 Input electrode 105 Output electrode 107 to 115, 207 to 223 Al wire

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsuyoshi Endo 4-1-1 Uedanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Yoshiro Fujiwara 4-chome, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa No. 1 Fujitsu Limited F-term (reference) 5J097 AA12 AA15 BB03 BB14 CC02 DD07 DD13 DD28 GG03 HA04 KK04

Claims (1)

[Claims] 1. A single crystal of LiTaO3 is placed on a Y-axis around an X-axis.
Comb-shaped first electrode fingers and second electrode fingers are combined on a piezoelectric substrate having an orientation rotated at an angle in the range of 40 ° to 42 ° in the Z-axis direction from the axis. And at least three comb electrodes arranged in a row in the propagation direction of the surface acoustic wave on the piezoelectric substrate, and a pair of reflection electrodes disposed so as to sandwich the plurality of comb electrodes. A balanced surface acoustic wave device element and an unbalanced surface acoustic wave device element to be cascade-connected, and a balanced terminal and an unbalanced terminal that are arranged to face each other. The terminal is constituted by a ground pad and a pair of signal pads formed so as to sandwich the ground pad, and the unbalanced terminal is constituted by a signal pad and a pair of ground pads formed so as to sandwich the signal pad. With structure A ceramic package, and a wire connecting the surface acoustic wave chip to the balanced terminal and the unbalanced terminal. On the unbalanced type surface acoustic wave device element side, a comb-shaped electrode The signal side is wire-connected to the signal pad of the unbalanced terminal, and the ground side of the comb-shaped electrode provided at the center of the unbalanced surface acoustic wave device element is wire-connected to the ground pad of the balanced terminal. One of the comb-shaped electrodes disposed on both sides of the comb-shaped electrode disposed in the center is connected to the ground pad of the unbalanced terminal, and the other is connected to the ground pad of the balanced terminal. Further, on the element side of the balanced surface acoustic wave device, a pair of signal sides provided on a comb-shaped electrode disposed at the center thereof are respectively connected to the balanced end. One of the comb-shaped electrodes disposed on both sides of the comb-shaped electrode disposed in the center is connected to the ground pad of the unbalanced terminal, and the other is connected to the signal pad. Is connected to a ground pad of the balanced terminal by a wire.