JPH11195957A - Surface acoustic wave resonating complex filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain quick rise and fall characteristics with a small loss by permitting the length of surface acoustic wave in a propagating direction to be the specified times the wave length of surface acoustic wave which is propagated by means of the pass-band frequency of a resonator complex filter, providing plural transducers which are partitioned by means of respective propagating paths and electrically connecting the adjacent transducers serially and every other one in parallel. SOLUTION: The length of the surface acoustic wave in the propagating direction is made the (2n-1)/2 times the wave length of the surface acoustic wave which is propagated by the pass band frequency of the filter. The multiple surface acoustic wave transducers which consist of multiple pairs of mutually inserted electrode fingers and which are arranged along a surface acoustic wave propagating direction are connected serially or in serial/parallel combining relation. Since the phases of the surface acoustic wave excited by the serially connected transducers are made to be the mutually inverted phases, the propagating paths having electric length being a half of the wave length of surface acoustic wave are introduced between the transducers so as to reduce the piezoelectric effect of the substrate.

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 resonator composite filter, and more particularly, to a surface acoustic wave 1 having an interdigital electrode finger disposed on a piezoelectric substrate.
Combination of multiple aperture resonators, no loss associated with conversion and inversion, can be handled with high power, elastic surface for band pass or band rejection with sharp rise and fall characteristics with frequency The present invention relates to a wave resonator composite filter.

[0002]

2. Description of the Related Art A conventional so-called transversal surface acoustic wave filter is composed of an input interdigital transducer for converting an electric signal into a surface acoustic wave and an output interdigital transducer for converting an surface acoustic wave back into an electric signal again. It consisted of being arranged on a substrate. For example, Proceedings of IEE, Vol. 67 (1979), pp. 129-148 (Pr.
oc. IEEE Vol 67 (1979) pp. 129-146) and the like.

[0003]

However, in the above-mentioned prior art filter, the electric signal is once converted into a surface acoustic wave by the input transducer, and the surface acoustic wave is again converted into the electric signal by the output transducer. Is converted. Therefore, there is a disadvantage that the loss involved in the process of conversion and inverse conversion is very large.

Further, when a large electric power is input to the filter, a surface acoustic wave having a large amplitude is excited. Therefore, an interdigital electrode finger constituting a transducer of the filter (for example, an aluminum electrode for an 800 MHz band automobile telephone). (The finger width is 1.1 to 1.2 μm and the film thickness is 0.1 μm). Migration occurs in a very short time, and as migration progresses, it leads to disconnection or short circuit of the electrode finger. It was necessary to suppress the input power to about 10 dBm or less.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, to eliminate loss accompanying conversion and inverse conversion in principle, and to greatly improve the power range that can be handled. Another object of the present invention is to provide a filter capable of realizing a steep rising / falling characteristic with respect to a frequency that cannot be realized by a conventional filter.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a surface acoustic wave resonator having a piezoelectric substrate and a plurality of single-opening surface acoustic wave resonators formed on the piezoelectric substrate and cascaded from an input side to an output side. In the composite filter, at least one of the plurality of single-opening surface acoustic wave resonators has a length in the surface acoustic wave propagation direction that is equal to the pass band of the surface acoustic wave resonator composite filter. (2n-1) / 2 times (n is an integer of 1 or more) the wavelength of a surface acoustic wave that can propagate at a frequency, and is divided by a plurality of propagation paths that do not excite the surface acoustic wave from each other. This is achieved by having a plurality of transducers, among the plurality of transducers, adjacent transducers are electrically connected in series, and every other transducer is electrically connected in parallel. Door can be.

[0007]

As described above, a surface acoustic wave composite filter comprising a plurality of one-opening surface acoustic wave resonators, or a surface acoustic wave composite filter obtained by combining a one-opening surface acoustic wave resonator and a capacitor. By this, a conventional transversal surface acoustic wave filter, that is, an input interdigital transducer for converting an electric signal into a surface acoustic wave and an output interdigital transducer for converting the surface acoustic wave back into an electric signal again is formed. A filter whose operating principle is fundamentally different from a surface acoustic wave filter, that is, a filter that converts only a part of the power input to the filter into a surface acoustic wave, so that even if high power is input, migration of electrodes is extremely small. A filter can be realized.

Further, the steep rise / fall frequency characteristics are obtained by providing a resonator having a steep characteristic to a propagation path having a specified length of at least half or more of the wavelength of the surface acoustic wave inside the resonator. Can be realized by making the resonance frequency and the anti-resonance frequency of the resonator close to each other.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the contents of the present invention will be described with reference to specific embodiments.

(Embodiment 1) FIG. 1 is a block diagram of an embodiment of a filter according to the present invention, in which electrodes 4-1 4-2, and 4-3 are placed on a piezoelectric substrate capable of transmitting surface acoustic waves. , 4-4, 4-5, 4-6, etc., and a single-opening surface acoustic resonator, and a gap capacitor consisting of electrode patterns 5-1 and 5-2 are provided to form a resonator composite filter. It shows that it was formed. Here, each resonator is composed of an interdigital transducer consisting of a large number of pairs of mutually interleaved electrode fingers, and these transducers are internally formed by the electrode fingers of the transducer itself even if there are no reflectors on both sides. Vibration energy is confined in the transducer by reflection, forming a one-opening resonator.

A one-opening surface acoustic wave resonator (FIG. 3)
The electrical equivalent circuit of (a)) is given in FIG. 2B, and using this expression, the filter of FIG.
That is, a series arm resonator composed of an equivalent inductance 11-1, an equivalent capacitance 12-1, and a capacitance 13-1, and an equivalent inductance 11-2, an equivalent capacitance 12-2, an A shunt arm resonator consisting of a capacitor 13-2 is also cascaded when viewed from the output side, and a series arm resonator consisting of an equivalent inductance 11-4, an equivalent capacitance 12-4, and a capacitance 13-4, and an equivalent inductance. 11-3,
This is given by an equivalent circuit having a configuration in which the shunt arm resonator including the equivalent capacitance 12-3 and the capacitance 13-3 is connected to the shunt arm resonator via the gap capacitance 14. In the filter of the present invention shown in FIG. Both the series arm resonator and the shunt arm resonator on the input side have a length within the resonator in the propagation direction of the surface acoustic wave that is equal to or greater than the wavelength of the surface acoustic wave that can propagate at the passband frequency of the filter. The configuration includes a plurality of propagation paths. (In FIG. 4, the inductances 3-1, 3-2, 3-3, and 3-4 indicate external matching circuits.)

FIG. 5 shows the configuration of a conventional resonator composite filter. In this configuration, the input-side series arm resonator and the shunt arm resonator, like the output-side resonator, are both constituted by interdigital transducers composed of simple multiple counter electrode fingers. That is,
1 and 5, the output side resonator is the same, but the electrode configuration of the input side series arm resonator and the shunt arm resonator is different. In terms of an equivalent circuit, the filter having the configuration shown in FIG. 5 is also represented by the equivalent circuit shown in FIG. 4 as in the case of the configuration shown in FIG. 1. However, in FIG. 1 and FIG. The values of the components (inductance and capacitance) of the arm resonator and the shunt arm resonator are different.

FIG. 6 shows the results of simulating the frequency characteristics of the filter having the structure of FIG. 1 and the filter having the structure of FIG. 5 by a computer. Here, as an example, a case is assumed in which a frequency arrangement (800 MHz band) of a mobile phone used in a part of Europe is assumed. (A) is the frequency characteristic of the filter according to the configuration of the present invention in FIG. 1, (b)
Is the frequency characteristic of the conventional filter of FIG.
From these results, it can be seen that the filter having the configuration of the present invention can realize a filter having extremely steep rising and falling frequency characteristics and low loss.
With the conventional filter configuration, steep rise / fall frequency characteristics that can satisfy the specifications cannot be obtained, and the loss is small at the center of the required passband, but only results of breaking the specifications on both sides are obtained. Not been.

[0014] FIG. 6 (a), when comparing the (b), also in the pole f _1, f ₂ of the low-frequency side of (a), corresponding to the poles f _3, f ₄ of the high-frequency side (b) There are f ₁ ′ and f ₂ ′ on the low frequency side and f ₃ ′ and f ₄ ′ on the high frequency side, but the major difference is that f ₂ >
f ₂ ′, f ₃ <f ₃ ′. Generally, realization of steep rise / fall frequency characteristics affects the widths (f ₂ , f ₃ in (a), f ₂ ′, f ₃ ′ in (b)) closest to the pass band to the pass band characteristics. Is determined by how close it can be to the passband without giving Compared to (a), in (b), f ₂ >
'despite being, f _2' f ₂ due to the influence of the loss of low-frequency side of the pass band is increasing, also in the high frequency side, f _3>, regardless of the f ₃ ', similar Furthermore, the loss increases due to the influence of f ₂ ′.

Next, the difference between the characteristics shown in FIGS.
This will be described in comparison with the difference between the filter configurations shown in FIGS. The value f ₃ close to the lower pass band in FIG.
Input-side shunt arm resonator (see 11-2,
12-2 and 13-2). That is,
Resonant frequency of the shunt arm resonator coincides with f _2.
Further, formed by pole f closer to the pass band of the high band side (a) ₃ is a series arm resonator 1 (corresponding to 11-1,12-1,13-1 in Figure 4). In other words, the anti-resonance frequency of the series arm matches the f _3. Similarly, the other poles f ₂ and f ₄ on the low frequency side and the high frequency side match the resonance frequency and the anti-resonance frequency of the shunt arm resonator and the series arm resonator on the output side in FIG. 1, respectively. Exactly the same relationship holds between FIG. 6B and the filter configuration of FIG. 5, and poles f ₂ ′ and f ₃ ′ close to the pass band are respectively shown in FIG.
Match the resonance frequency and anti-resonance frequency of the input side shunt arm resonator and series arm resonator, and
The other poles f ₁ ′ and f ₄ ′ coincide with the resonance frequency and anti-resonance frequency of the shunt arm resonator on the output side.

As can be seen from the above description, the difference between the filter having the configuration shown in FIG. 1 and the filter having the configuration shown in FIG. 5 lies in the configuration of the series arm resonator and the shunt arm resonator on the input side. That is, FIG. 1 is a characteristic of the filter according to the present invention. By using the one-opening surface acoustic wave resonator having such a configuration, even if the corresponding poles f ₂ and f ₃ of FIG. Can be sufficiently reduced, and a filter having extremely steep rising and falling frequency characteristics can be obtained. On the other hand, when a single-opening surface acoustic wave resonator having a normal structure is used on the input side as shown in FIG.
As shown in (b), even if the corresponding poles f ₂ ′ and f ₃ ′ are sufficiently separated from the filter pass band, the pass band characteristics of the filter are affected, and steep rise / fall frequency characteristics cannot be realized.

Next, the configuration of each resonator, which is the difference between the configuration of FIG. 1 and the configuration of FIG. 5, will be described. FIG. 3A is a diagram showing a schematic structure of a normal one-opening surface acoustic wave resonator composed of an interdigital transducer composed of simple multiple counter electrode fingers, and an equivalent circuit of this resonator is shown in FIG. As shown in FIG. 2), this is represented by a parallel connection of a capacitance 13 between electrode fingers and a series inductance 11 and a capacitance 12 generated by elastic vibration. The frequency characteristic of the impedance (Z) of this circuit is Z = 0 at the resonance frequency (fr) and Z = ∞ at the anti-resonance frequency (fa), as shown in FIG.

Here, in order to explain the relationship between the resonator configuration and the pass characteristic of the filter, the resonator shown in FIG. 3A is replaced with a shunt between a power supply and a load as shown in FIG. Considering the circuit introduced into the arm, the pass characteristic of such a circuit is a pole because Z = 0 at the resonance frequency (fr) of the resonator, and Z = で は at the antiresonance frequency (fa), so There is no effect on the characteristics. FIG. 10A shows this pass characteristic. As can be seen from FIG.
Will determine the rise of the pass characteristic of the filter. For example, as shown in FIGS.
By making r and fa close to each other, the rising characteristic can be made steeper.

In the single-aperture surface acoustic wave resonator having the structure shown in FIG. 3A, fr and fa are determined by the piezoelectric effect of the piezoelectric substrate used. For example, LiNbO ₃ , LiTa
In the case of a substrate having a large piezoelectric effect such as an O ₃ substrate, the interval between fr and fa is large. Therefore, the rise of the pass characteristic is gentle and the characteristic is as shown in FIG. In a small substrate, the fr-fa interval is extremely close, and therefore, the rise of the pass characteristic becomes steep,
The characteristic as shown in FIG. 10B or 10C is obtained.

From the above, in order to realize a filter having the characteristics shown in FIG. 6A, the pole f ₂ corresponding to the steep rising characteristic has a resonator having the characteristics shown in FIG. in the formed, pole f ₁ corresponding to the wide-band frequency characteristic will be may be formed by a resonator having the characteristics shown in Figure 10 (a). For example, it is possible in principle to obtain the above configuration by combining a plurality of single-port surface acoustic wave resonators formed on substrates having different piezoelectric effects, such as LiNbO ₃ and quartz, by wire bonding or the like. is there. However, combining a plurality of resonators formed on different substrates is impractical considering the manufacturing process, assembly, packaging, and the like.

The present invention overcomes these problems, and equivalently corresponds to FIGS. 10 (a), 10 (b) and 10 (c) by using a single piezoelectric substrate and by using a resonator electrode configuration. And a filter having a steep rising / falling characteristic as shown in FIG. 6A and a plurality of one-opening surface acoustic wave resonators formed on the same substrate. Can be realized by combining the above with an electrode pattern or the like.

FIGS. 8A and 8B show an example of a series arm resonator and a shunt arm resonator on the input side. FIG. 8A shows a normal one-port aperture constituted by an interdigital transducer consisting only of simple multiple counter electrode fingers. An example of a surface acoustic wave resonator, (b) is a one-opening surface acoustic wave resonator including a plurality of propagation paths having an electric length longer than the wavelength of the surface acoustic wave therein, one for every four pairs of electrode fingers. Examples of those that include the propagation path of
(C) is an example of a single aperture surface acoustic wave resonator including a plurality of propagation paths as in (b), but having one propagation path for every two pairs of electrode fingers. The frequency characteristic of the impedance of each of these resonators is as shown in FIG.
(a), (b) and (c) correspond to (a), (b) and (b) in FIG. 8, respectively.
This corresponds to (c). From the results of FIG. 9, the interval between the resonance frequency (fr) and the anti-resonance frequency (fa) is (a),
(b), (c) are narrowed in the order, and when these resonators are used as filter elements, (a), (b),
It can be expected that a filter having steeper rising / falling characteristics can be obtained in the order of (c). Specifically, an example of the pass characteristic when these resonators are used in the resonator portion of FIG. 7A is as shown in FIG.
(b) and (c) correspond to (a), (b) and (c) in FIG. 9, respectively.
Corresponding to From this result, it is known that the rising characteristics are steep in the order of (a), (b), and (c).

As described above, by introducing a plurality of propagation paths having an electric length longer than the wavelength of the surface acoustic wave into the resonator, compared with a normal one-opening surface acoustic wave resonator, The fr and fa of the resonator can be made closer,
When these resonators are used, a steep rising characteristic can be obtained as a pass characteristic. However, the reason why the interval between fr and fa is reduced in a resonator including a plurality of the above-described propagation paths is as follows. That is, in general, the surface acoustic wave is excited by applying a positive / negative high-frequency voltage between mutually interposed electrode fingers formed on the piezoelectric substrate. Although it is due to propagation on the surface of the substrate as a surface acoustic wave, in the resonator having the configuration shown in FIG.
Spacing ~fa, as described above, it is determined by the piezoelectric effect of the piezoelectric substrate, for example, widely fr~fa interval is large substrates of piezoelectric effect such as LiNbO _3, LiTaO _3, a small substrate of the piezoelectric effect of quartz or the like Then, the fr-fa interval is narrow. Therefore, in order to narrow the fr~fa intervals large substrates of a piezoelectric effect such as LiNbO _3, LiTaO ₃ is not it is necessary to reduce the equivalently piezoelectric effect in the electrode structure of the resonator, FIG. 8 (b (C) and (c) show that the piezoelectric effect is equivalently reduced by introducing a plurality of propagation paths having a wavelength equal to or longer than the wavelength of the surface acoustic wave into the resonator.

The reason why the piezoelectric effect is equivalently reduced by introducing a propagation path into the resonator can be explained as follows. The electrode fingers inserted in the resonator serve as excitation electrode fingers for exciting the surface acoustic wave, but the portion of the propagation path does not excite the surface acoustic wave. The greater the number of propagation paths, the lower the density of the excitation electrode fingers in the resonator, and a decrease in the density of the excitation electrode fingers is equivalent to a reduction in the piezoelectric effect of the substrate. Therefore, the piezoelectric effect of the substrate can be reduced by introducing a propagation path into the resonance path, and an arbitrary value smaller than the original piezoelectric effect of the substrate can be equivalently obtained by appropriately selecting the number of propagation paths. Can be. From the above, by changing the configuration of the resonator using a single piezoelectric substrate, it is possible to realize a resonator having a wide fr-fa interval and a narrow resonator.

Next, consider a circuit as shown in FIG. 7B in which a resonator is introduced into a series arm between a power supply and a load. The pass characteristic of such a circuit has no effect on the pass characteristic because Z = 0 near the resonance frequency (fr) of the resonator, and has a pole at the antiresonance frequency (fa) because Z = ∞. . FIG. 11 shows the transmission characteristics.
(b) and (c) show the pass characteristics when the resonators of FIGS. (a), (b) and (c) are used, respectively. From this result, also in this case, exactly as in the case of FIG.
It can be seen that a sharp fall characteristic can be obtained by using a resonator having a plurality of propagation paths inside.

As described above, it is known that there is a clear difference in characteristics between the surface acoustic wave resonator composite filter having the configuration shown in FIG. 1 and the surface acoustic wave composite filter having the configuration shown in FIG. That is, in the case of the configuration of FIG. 1, by using a resonator having a plurality of surface acoustic wave propagation paths inside,
The frequency characteristic is as shown in FIG. 6 (a), and is promising as a filter that requires extremely steep rising and falling characteristics, such as for a car phone. On the other hand, in the case of the configuration of FIG. 5, the frequency characteristic is as shown in FIG. 6B, and it cannot be expected that the filter is used as a filter having a steep frequency characteristic.

(Embodiment 2) This embodiment relates to another configuration example of the one-opening surface acoustic wave resonator of the filter of the present invention.

FIG. 2 shows an interdigital transducer composed of a large number of pairs of electrode fingers interposed between a plurality of surface acoustic wave transducers arranged along the surface acoustic wave propagation direction. FIG. 1 shows a circuit connected in series or in a series / parallel combination.

For example, in the case of the transducer shown in FIG. 3A, if the number of the excitation electrode fingers is sufficiently large, the single-aperture resonance will be performed as in the case of FIG. Form a bowl. The characteristic of this resonator is that the impedance is about four times as large as that of the conventional resonator having the same electrode index as shown in FIG. Therefore, a resonator configuration promising as a high impedance filter is obtained. Another feature of the resonator is that the surface acoustic waves excited by the transducers arranged in the propagation direction of the surface acoustic wave and electrically connected in series have opposite phases to each other. Therefore, in order for the surface acoustic waves excited from each transducer to be added in phase in the propagation direction of the surface acoustic waves, a length of half the wavelength of the surface acoustic waves is required between the transducers connected in series. It is necessary to introduce a propagation path having an electrical length.

Considering FIG. 2A as a specific example in which a propagation path of a half of the wavelength of the surface acoustic wave is introduced between the series-connected transducers, this resonator has In order to make the frequency (fr) close to the anti-resonance frequency (fa), a plurality of propagation paths having a length equal to or longer than the surface acoustic wave wavelength as shown in FIGS. 8B and 8C are particularly introduced. No need. This is because the propagation path of half the surface acoustic wave wavelength introduced between the serially connected transducers performs the same function. In order to make fr and fa close to each other, the number of unit transducers connected in series may be reduced, and the number of transducers in the resonator, that is, the number of propagation paths may be increased. Therefore, FIG.
As in (b) and (c), an effect equivalent to reducing the piezoelectric effect of the substrate can be obtained.

2 (b) and 2 (c) have the same basic structure as FIG. 2 (a), but FIG. 2 (b) shows a propagation path introduced between the serially connected transducers, and FIG. 3 / (c) shows a structure in which a propagation path having a length of 5/2 is also introduced. By increasing the length of the introduction propagation path, the same effect as increasing the number of propagation paths can be obtained. As in the case of (a), the piezoelectric effect of the substrate is reduced, and the interval between fr and fa is reduced. It becomes possible.

In the above description, the example in which the single-aperture resonator shown in FIGS. 2 and 8 is used as the resonator has been described. Alternatively, it is obvious that a similar effect can be obtained in a resonator in which a surface acoustic wave reflector formed by ion implantation or the like is introduced. Also, the substrate is
Not only a piezoelectric substrate, but also a piezoelectric thin film formed on a non-piezoelectric substrate such as Si may be used. Conversely, the same applies when a non-piezoelectric thin film is formed on a piezoelectric substrate. Needless to say, the effect was obtained.

[0033]

As described above, according to the present invention, when the resonator having the conventional configuration is used, the rising and falling frequency characteristics of the filter are uniquely determined by the piezoelectric effect of the substrate. Without being affected by the characteristics of the substrate.
A filter having steep rising / falling frequency characteristics was realized.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of one embodiment of a surface acoustic wave resonator composite filter of the present invention (hereinafter abbreviated as “filter of the present invention”).

FIG. 2 is a schematic configuration diagram of a one-opening surface acoustic wave resonator used in another embodiment of the filter of the present invention.

FIG. 3 is a diagram showing (a) a schematic configuration, (b) an equivalent circuit, and (c) a frequency characteristic of impedance of a normal one-opening surface acoustic wave resonator.

FIG. 4 is an equivalent circuit of the filter of the present invention.

FIG. 5 is a configuration diagram of a conventional filter.

6 (a) is a diagram showing the pass characteristic of the filter of the present invention in FIG.
(B) shows the pass characteristics of the conventional filter of FIG.

FIG. 7 is a diagram showing a circuit included in a (a) shunt arm and (b) a circuit included in a series arm of a one-port surface acoustic wave resonator.

FIG. 8 is a diagram showing a configuration of a one-opening surface acoustic wave resonator;
(A) is a conventional resonator, and (b) and (c) are resonators used in the filter of the present invention.

9 (a), (b) and (c) are frequency characteristics of the impedance of the resonators (a), (b) and (c) in FIG. 8, respectively.

FIG. 10A shows the pass characteristics of the circuit.

FIG. 11B shows the pass characteristics of the circuit of FIG.

[Explanation of symbols]

1, 1 ', 2, 2' ... input / output electrical terminals, 3-1, 3-2, 3-3,
3-4… I / O matching inductance, 4-1, 4-2, 4-3, 4-
4, 4-5, 4-6, 9, 10 ... resonator electrodes, 5-1, 5-2 ... electrode patterns, 6-1, 6-2, 6-3, 6-4, 6-5, 6 -6: sound absorbing material, 7: piezoelectric substrate, 8, 8 ': electric terminals of resonator, 11, 11-1, 11-2,
11-3, 11-4… Equivalent inductance of resonator, 12, 12-1,
12-2, 12-3, 12-4 ... equivalent capacitance of the resonator, 13, 13-1, 13-
2, 13-3, 13-4: The capacitance of the resonator.

Continuing on the front page (72) Inventor Nobuhiko Shibaki 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory of Hitachi, Ltd.

Claims (5)

[Claims] 1. A piezoelectric substrate, comprising: a piezoelectric substrate;
A surface acoustic wave resonator composite filter having a plurality of one-opening surface acoustic wave resonators cascaded from an input side to an output side; In the surface acoustic wave resonator, the length of the surface acoustic wave in the propagation direction is (2n-1) of the wavelength of the surface acoustic wave that can be propagated at the passband frequency of the surface acoustic wave resonator composite filter.
/ 2 times (n is an integer of 1 or more), which has a plurality of propagation paths that do not excite surface acoustic waves, and a plurality of transducers partitioned by the respective propagation paths, and among the plurality of transducers, A surface acoustic wave resonator composite filter, wherein adjacent transducers are electrically connected in series, and every other transducer is electrically connected in parallel. 2. A surface acoustic wave composite filter according to claim 1, wherein a capacitance is cascaded in addition to said plurality of single-opening surface acoustic wave resonators. . 3. The surface acoustic wave composite type filter according to claim 2, wherein said capacitance is a capacitance formed by a gap between electrodes on said piezoelectric substrate. filter. 4. A surface acoustic wave resonator composite filter having a plurality of one-opening surface acoustic wave resonators formed on a piezoelectric substrate, wherein the one-opening surface acoustic wave resonator is formed on the piezoelectric substrate. Having first, second and third electrode patterns having a plurality of electrode fingers electrically connected to each other, wherein the plurality of electrode fingers of the second electrode pattern are the first and third electrodes The surface acoustic wave propagation path is formed by being interposed between the plurality of electrode fingers of the pattern and interposed between the electrode fingers of the pattern, and the transmitted surface acoustic wave is in phase with the propagation direction of the surface acoustic wave in the propagation direction. 1. A surface acoustic wave composite filter characterized by having a propagation portion for adding in (1). 5. The surface acoustic wave resonator composite filter according to claim 4, wherein said propagation portion has a length on said second electrode pattern in a propagation direction of said surface acoustic wave on said propagation path. The filter is formed by providing a portion that is (2n-1) / 2 times (n is an integer of 1 or more) the wavelength of the surface acoustic wave that can propagate at the pass band frequency of the wave resonator composite filter. Surface acoustic wave composite filter.