JP3394362B2 - Surface acoustic wave device - Google Patents

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 using a multistrip coupler.

[0002]

2. Description of the Related Art A surface acoustic wave device is a circuit element that performs signal processing by converting an electric signal into a surface wave, and is used for a filter, a resonator, a delay line and the like. Usually, a metal electrode called an interdigital transducer (IDT, comb-shaped electrode, interdigital transducer) is provided on an elastic substrate (piezoelectric substrate) having piezoelectricity to convert an electric signal into a surface wave and back conversion. There is.

As a surface acoustic wave device which is a first conventional example, a surface acoustic wave device in which a multistrip coupler is provided between the input and output IDTs is known. FIG. 11 shows a surface acoustic wave device which is a first conventional example using a multistrip coupler.
Shown in. Two input / output IDTs 10 on the piezoelectric substrate 100
2, 104 are provided. First input / output IDT 10
2 and the second input / output IDT 104 are arranged with their surface acoustic wave tracks 108 and 110 displaced from each other. First input / output IDT 102 and second input / output IDT
Between 104, two surface acoustic wave tracks 108, 1
The multi-strip coupler 106 is arranged so as to extend over 10.

The surface acoustic wave input from the first input / output IDT 102 propagates through the first surface acoustic wave track 108. The surface acoustic wave propagating through the first surface acoustic wave track 108 propagates through the multi-strip coupler 106 to the second surface acoustic wave track 110, and the second input / output ID
It is output from T104. Japanese Examined Patent Publication (Kokoku) No. 58-34048 discloses an elastic surface in which the direct contact is suppressed and the out-of-band attenuation is improved by grounding the electrode fingers of the same or different phases of the first conventional multi-strip coupler. A wave device is disclosed.

FIG. 12 shows an energy confinement type surface acoustic wave device (hereinafter abbreviated as a second example) using the first conventional multistrip coupler. As shown in FIG.
Two input / output IDTs 112, 11 on the piezoelectric substrate 110
4, multi-strip coupler 116, reflector 118, 1
20 are formed. The input / output IDT 112 is provided on the first surface acoustic wave track 122 of the piezoelectric substrate 110. One electrode finger of the input / output IDT 112 is connected to the input / output terminal, and the other electrode finger is grounded. The input / output IDT 114 is provided on the second surface acoustic wave track 124 of the piezoelectric substrate 110. Input / output IDT11
One electrode finger of 4 is connected to the input / output terminal, and the other electrode finger is grounded.

The multi-strip coupler 116 is on the right side of the input / output IDTs 112 and 114, and is the piezoelectric substrate 110.
Is formed over the first surface acoustic wave track 122 and the second surface acoustic wave track 124. The multi-strip coupler 116 connects the first surface acoustic wave track 122 and the second surface acoustic wave track 124.

Thus, the surface acoustic wave device using the multi-strip coupler is used as a connector between two surface acoustic wave tracks.

[0008]

However, in the case of the surface acoustic wave device of the first conventional example using the multi-strip coupler, as the surface acoustic wave characteristic, the out-of-band attenuation amount is deteriorated by the direct wave component. was there. Further, in the surface acoustic wave device described in Japanese Patent Publication No. 58-34048, since the electrode fingers are only grounded, the low-frequency side spurious cannot be suppressed sufficiently, and the grounded electrode finger If the phases are different, there is a problem that the surface wave propagation is hindered and the insertion loss becomes large.

Further, in the surface acoustic wave device of the second example using the multi-strip coupler, there is a problem that a plurality of spurs are generated outside the band, particularly on the low frequency side, and the out-of-band attenuation amount is deteriorated. . An object of the present invention is to suppress spurious out of band and improve out-of-band attenuation.
An object is to provide a surface acoustic wave device using a multistrip coupler.

[0010]

The above object is to provide a piezoelectric substrate having at least a surface layer formed of a piezoelectric material, and to excite surface acoustic waves of a first surface acoustic wave track formed on the surface of the piezoelectric substrate. A first surface acoustic wave transducer that receives, reflects, and propagates, and a second surface acoustic wave that is formed on the surface of the piezoelectric substrate and that excites, receives, reflects, and propagates the surface acoustic wave of a second surface acoustic wave track. A transducer and a plurality of strips formed over the first surface acoustic wave track and the second surface acoustic wave track on the surface of the piezoelectric substrate, the surface being propagated at a frequency at which a signal is desired to be transmitted. A surface acoustic wave characterized in that it has a multi-strip coupler in which strips having substantially the same wave phase are commonly connected in an electrically floating state. It is achieved by location.

Further, the above object is to provide a piezoelectric substrate having at least a surface layer formed of a piezoelectric material, and a surface acoustic wave of a first surface acoustic wave track that is formed on the surface of the piezoelectric substrate to excite, receive, reflect, A first surface acoustic wave transducer that propagates and a surface acoustic wave of a second surface acoustic wave track that is formed on the surface of the piezoelectric substrate is excited, received, reflected,
A second surface acoustic wave transducer that propagates, the first surface acoustic wave track on the surface of the piezoelectric substrate, and the second surface acoustic wave transducer.
A plurality of strips formed over the surface acoustic wave track of the first group, and the phase of the surface acoustic wave propagating at the frequency at which the signal is desired to be transmitted is the first phase. The strips of the second group are commonly connected to each other in a floating state and have a second phase in which the phase of the surface acoustic wave propagating at the frequency at which the signal is to be transmitted is different by about 180 degrees from the first phase. And a multistrip coupler commonly connected in a floating state.

Further, the above object is to provide a surface acoustic wave device having the above-mentioned first surface acoustic wave transducer and second surface acoustic wave transducer, which are provided at both ends of the first surface acoustic wave track. A first reflector for reflecting surface acoustic waves propagating in the surface acoustic wave track;
In the surface acoustic wave device, further comprising second reflectors provided at both ends of the surface acoustic wave track for reflecting surface acoustic waves propagating in the second surface acoustic wave track, and the above-mentioned multi-strip coupler is provided. It is achieved by

[0013]

According to the present invention, a plurality of strips are spread over the first surface acoustic wave track of the first surface acoustic wave transducer and the second surface acoustic wave track of the second surface acoustic wave transducer. By forming a multi-strip coupler having the same and connecting the strips in which the propagating surface acoustic waves have almost the same phase at the frequency at which the signal is to be transmitted, in an electrically floating state, the out-of-band attenuation is improved. be able to.

According to the present invention, the first surface acoustic wave track of the first surface acoustic wave transducer and the second surface acoustic wave track are provided.
Forming a multi-strip coupler having a plurality of strips across the second surface acoustic wave track of the surface acoustic wave transducer of FIG. The strips of the first group are connected together in an electrically floating state, and at the frequency at which the signal is to be transmitted,
Since the phase of the propagating surface acoustic wave is the second phase, which is different from the first phase by about 180 degrees, the strips of the second group are commonly connected in an electrically floating state, so that the out-of-band attenuation is improved. can do.

Further, in the surface acoustic wave device having the above-mentioned first surface acoustic wave transducer and second surface acoustic wave transducer, the first surface acoustic wave track is provided at both ends of the first surface acoustic wave track. And a second reflector provided at both ends of the second surface acoustic wave track for reflecting the surface acoustic wave propagating in the second surface acoustic wave and reflecting the surface acoustic wave propagating in the second surface acoustic wave track. Since the above-described multi-strip coupler is provided in the surface acoustic wave device further provided with, it is possible to suppress spurious generated on the low frequency side outside the band and improve the out-of-band attenuation amount.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A surface acoustic wave device according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a surface acoustic wave device according to this embodiment, and FIG. 2 is an explanatory diagram of an operation of the surface acoustic wave device shown in FIG. As shown in Figure 1,
Two input / output IDTs 12 and 1 are formed on the piezoelectric substrate 10 of ST quartz by an aluminum film having a thickness of about 1,200 nm.
4, a multistrip coupler 16 and reflectors 18 and 20 are formed.

The input / output IDT 12 is the first of the piezoelectric substrate 10.
Is provided on the surface acoustic wave track 22. The number of pairs of input / output IDTs 12 is 90.5, and the cross length is 10λ. One electrode finger of the input / output IDT 12 is connected to the input / output terminal, and the other electrode finger is grounded. Input / output IDT
14 is a second surface acoustic wave track 24 of the piezoelectric substrate 10.
It is provided above. The logarithm of the input / output IDT 14 is 90.
In 5 pairs, the intersection length is 10λ. One electrode finger of the input / output IDT 14 is connected to the input / output terminal, and the other electrode finger is grounded.

The multi-strip coupler 16 has an input / output I
It is formed on the right side of the DTs 12 and 14 and across the first surface acoustic wave track 22 and the second surface acoustic wave track 24 of the piezoelectric substrate 10. The multi-strip coupler 16 connects the first surface acoustic wave track 22 and the second surface acoustic wave track 24. The multi-strip coupler 16 is formed by strip electrodes 16a, 16b, ..., 16n parallel to the input / output IDTs 12 and 14, and the number of pairs is 70.5. The strip electrodes 16a, 16b, ..., 16n are connected so that the propagating surface acoustic waves have substantially the same phase. For example, as shown in FIG. 1, strip electrodes 16a, 16
.., 16n are commonly connected by electrode bars 16x, 16y. As a result, the groups of strip electrodes in which the phases of surface acoustic waves differ from each other by 180 degrees are commonly connected, and the phases of surface acoustic waves are fixed by the strip electrodes.

The strip electrodes 16a, 16b,
, 16n are commonly connected to every other line, but as a whole, they are not connected to anywhere and are in an electrically floating state. The pair of reflectors 18 are provided outside the input / output IDT 12 and the multi-strip coupler 16 and at both ends of the first surface acoustic wave track 22. The reflectors 18 each have 80 electrodes, and the period λ is 23.
It is 8 μm.

A pair of reflectors 20 are provided outside the input / output IDT 14 and the multistrip coupler 16 and at both ends of the second surface acoustic wave track 24. The reflectors 20 each have 80 electrodes, and the period λ is 2
It is 3.8 μm. The periods of the input / output IDTs 12 and 14 and the multistrip coupler 16 are set so that the center of the radiation conductance of the IDTs 12 and 14 is the center of the stop band of the reflectors 18 and 20.

FIG. 2 is an explanatory diagram of the operation of the multi-strip coupler 16. Ports 1 to 4 in FIG. 2 represent acoustic ports of the multistrip coupler 16. The acoustic energy incident from port 1 is the multistrip coupler 1
It is shown that the light is radiated to the ports 2 to 4 by 6.
When the surface acoustic wave is incident from the port 1, a part of the acoustic energy of the surface acoustic wave is converted into electric energy and is converted into acoustic energy again in the second surface acoustic wave track, so that the ports 2 and 4 are connected. Is radiated as a surface acoustic wave from. Part of the surface acoustic wave incident from port 1 leaks to port 3.

In this way, the surface acoustic wave incident on the first surface acoustic wave track from the port 1 is propagated to the second surface acoustic wave track by the multistrip coupler 16. In this way, the surface acoustic wave device of this embodiment is used as a connector between surface acoustic wave tracks operating at a desired frequency. The characteristics of the surface acoustic wave device according to this example are shown in FIGS.

FIG. 3 shows the calculated values of the radiant energy emitted from the ports 2 and 4 by the energy of the surface acoustic wave incident from the port 1. In this embodiment, since the strip electrodes in which the transmitted and received surface acoustic waves have substantially the same phase are electrically connected, the phase of the surface acoustic waves is fixed by each strip electrode. Therefore, the operating frequency f of the multi-strip coupler is fixed by the strip electrode repetition period λ. When the propagation velocity of the surface acoustic wave is v, the operating frequency f of the multistrip coupler is v
It is fixed at / λ.

Therefore, the multi-strip coupler does not transmit surface acoustic wave energy other than the fixed frequency f. Therefore, the transfer of energy between the surface acoustic wave tracks 22 and 24 at frequencies outside the pass band is suppressed. FIG. 4 shows the filter characteristics of the surface acoustic wave device of this embodiment. As described above, since the multi-strip coupler suppresses the transmission of energy outside the pass band, it can be seen that spurious outside the pass band, particularly spurious near the low frequency band, is also suppressed in the filter characteristic of FIG. .

As a comparative example of this embodiment, a surface acoustic wave device of the second conventional example shown in FIG. 12 was prepared. As shown in FIG. 12, this surface acoustic wave device is the same as the surface acoustic wave device of FIG. 1 except that the strip electrodes in the multi-strip coupler are not commonly connected by the electrode bar. is there. The characteristics of the surface acoustic wave device of the comparative example are shown in FIGS.

FIG. 5 shows calculated values of the radiant energy of the surface acoustic wave incident from the port 1 and radiated from the port 2 and the port 4. In the comparative example, the energy of the surface acoustic wave is transmitted from the first surface acoustic wave track 22 to the second surface acoustic wave track 24 even at a frequency outside the pass band. It can be seen that this difference is remarkable when compared with FIG. 3 showing the radiant energy of this example.

FIG. 6 shows the filter characteristics of the surface acoustic wave device of the comparative example. Spurs outside the passband, especially
Spurs are generated on the low frequency side, which deteriorates the out-of-band attenuation. It can be seen that this difference is remarkable when compared with FIG. 4 showing the filter characteristic of the present embodiment.
The period of the strip electrodes of the reflectors 18 and 20 may be the same as that of the input / output IDTs 12 and 14, or may be slightly shifted. When the electrodes are formed of an aluminum film, if the period of the strip electrodes of the reflectors 18 and 20 is made slightly wider than that of the input / output IDTs 12 and 14, the confinement efficiency of surface acoustic wave energy is improved, and the efficiency of the surface acoustic wave device is improved. Is improved.

The present invention is not limited to the above embodiment, but various modifications can be made. For example, the present invention can be applied not only to the surface acoustic wave device having the structure shown in FIG. 1 but also to surface acoustic wave devices having other structures. Specific examples of other structures are shown in FIGS.
Shown in. The first modification shown in FIG. 7 is a surface acoustic wave device having a structure in which a pair of input / output IDTs are provided.

In the first modified example, as shown in FIG. 7, two pairs of input / output IDTs 12A and 12B are provided on the piezoelectric substrate 10.
14A, 14B, a multi-strip coupler 16, and reflectors 18, 20 are formed. Input / output IDT 12A, 1
2B is the first surface acoustic wave track 22 of the piezoelectric substrate 10.
It is provided above. The input / output IDTs 14A and 14B are
It is provided on the second surface acoustic wave track 24 of the piezoelectric substrate 10.

The multi-strip coupler 16 has an input / output I
It is formed between the DTs 12A and 14A and the input / output IDTs 12B and 14B, and is formed over the first surface acoustic wave track 22 and the second surface acoustic wave track 24 of the piezoelectric substrate 10. The multi-strip coupler 16 connects the first surface acoustic wave track 22 and the second surface acoustic wave track 24.

The multi-strip coupler 16 has an input / output I
Strip electrodes 16a, 16 parallel to the DTs 12, 14
, 16n. , 16n are commonly connected to every other strip electrodes 16a, 16b, ..., 16n by electrode bars 16x, 16y so that the propagating surface acoustic waves have substantially the same phase. The strip electrodes 16a, 16b, ..., 16n are commonly connected to every other line, but as a whole, they are not connected to anywhere and are in an electrically floating state.

The pair of reflectors 18 are connected to the input / output IDT 12
It is provided outside A and 12B and the multi-strip coupler 16 and at both ends of the first surface acoustic wave track 22. The pair of reflectors 20 are the input / output IDTs 14A, 1
4B and outside the multistrip coupler 16,
It is provided at both ends of the second surface acoustic wave track 24.

Input / output IDTs 12A, 12B, 14A, 1
The period of 4B and the multi-strip coupler 16 is IDT1.
The centers of the radiation conductances of 2A, 12B, 14A, and 14B are set to be the centers of the stop bands of the reflectors 18 and 20. The second modification shown in FIG. 8 is a surface acoustic wave device having a pair of multistrip couplers.

As shown in FIG. 8, the input / output IDTs 12 and 14 and the multi-strip coupler 16 are provided on the piezoelectric substrate 10.
A, 16B and reflectors 18, 20 are formed. The input / output IDT 12 is provided on the first surface acoustic wave track 22 of the piezoelectric substrate 10. The input / output IDT 14 is provided on the second surface acoustic wave track 24 of the piezoelectric substrate 10. One electrode finger of the input / output IDT 14 is connected to the input / output terminal, and the other electrode finger is grounded.

Multi-strip coupler 16A, 16B
Are formed on both sides of the input / output IDT 12 and the input / output IDT 14 and across the first surface acoustic wave track 22 and the second surface acoustic wave track 24 of the piezoelectric substrate 10. The multi-strip couplers 16A and 16B connect the first surface acoustic wave track 22 and the second surface acoustic wave track 24.

Multi-strip coupler 16A, 16B
Are strip electrodes 16Aa, 16Ab, ..., 16An; 16Ba, which are parallel to the input / output IDTs 12, 14, respectively.
16Bb, ..., 16Bn. These strip electrodes 16Aa, 16Ab, ..., 16An; 1
.., 16Bn are connected so that the propagating surface acoustic waves have substantially the same phase. For example, as shown in FIG. 8, strip electrodes 16Aa, 16A
16An; 16Ba, 16Bb, ..., 16B
Every other n electrode bar 16Ax, 16Ay; 16B
Commonly connected by x and 16By. Strip electrodes 16Aa, 16Ab, ..., 16An; 16Ba, 16
.., 16Bn are commonly connected to every other line, but as a whole, they are not connected to anywhere and are in an electrically floating state.

The pair of reflectors 18 are provided outside the input / output IDT 12 and the multi-strip couplers 16A and 16B and at both ends of the first surface acoustic wave track 22. The periods of the input / output IDTs 12 and 14 and the multistrip couplers 16A and 16B are set so that the center of the radiation conductance of the IDTs 12 and 14 is the center of the stop band of the reflectors 18 and 20.

The third modification shown in FIG. 9 is a surface acoustic wave device in which three surface acoustic wave tracks are provided and are connected by a pair of multistrip couplers. As shown in FIG. 9, input / output IDTs 12, 1 are provided on the piezoelectric substrate 10.
4, multi-strip couplers 16, 17, reflectors 18,
19 and 20 are formed. The input / output IDT 12 is provided on the first surface acoustic wave track 22 of the piezoelectric substrate 10.

The multi-strip coupler 16 has an input / output I
It is formed on the right side of the DT 12 and across the first surface acoustic wave track 22 and the third surface acoustic wave track 23 of the piezoelectric substrate 10. The multi-strip coupler 16 connects the first surface acoustic wave track 22 and the third surface acoustic wave track 23. The multi-strip coupler 16 is formed of strip electrodes 16a, 16b, ..., 16n parallel to the input / output IDT 12. These strip electrodes 16a, 16b, ..., 16n
Are connected so that the propagating surface acoustic waves have almost the same phase. For example, as shown in FIG. 10, every other strip electrodes 16a, 16b, ..., 16n are commonly connected by electrode bars 16x, 16y. The strip electrodes 16a, 16b, ..., 16n are commonly connected to every other line, but as a whole, they are not connected to anywhere and are in an electrically floating state.

The input / output IDT 14 is the second input / output of the piezoelectric substrate 10.
Of the surface acoustic wave track 24. The multi-strip coupler 17 is formed on the left side of the input / output IDT 14 and across the third surface acoustic wave track 23 and the second surface acoustic wave track 24 of the piezoelectric substrate 10. With this multi-strip coupler 17, the third
The surface acoustic wave track 23 and the second surface acoustic wave track 24 are connected.

The multi-strip coupler 17 has an input / output I
Strip electrodes 17a, 17b, ...
It is formed of 17n. These strip electrodes 1
.., 17n are connected so that the propagating surface acoustic waves have substantially the same phase. For example, as shown in FIG. 9, strip electrodes 17a, 17b, ...
Every other 17n is commonly connected by the electrode bars 17x and 17y. The strip electrodes 17a, 17b, ...
Every other 17n is commonly connected, but as a whole, it is electrically connected to nowhere and is in an electrically floating state.

The pair of reflectors 18 are provided outside the input / output IDT 12 and the multi-strip coupler 16 and at both ends of the first surface acoustic wave track 22. The pair of reflectors 19 are provided outside the multi-strip couplers 16 and 17 and at both ends of the third surface acoustic wave track 23. The pair of reflectors 20 has an input / output IDT1.
4 and the outer side of the multi-strip coupler 17, and are provided at both ends of the second surface acoustic wave track 24.

The periods of the input / output IDTs 12 and 14 and the multistrip couplers 16 and 17 are set so that the center of the radiation conductance of the IDTs 12 and 14 is the center of the stop band of the reflectors 18 and 20. Further, in the above embodiment, the strip electrodes of the multi-strip coupler are commonly connected to each other, but it suffices to connect the strip electrodes having substantially the same phase of the propagating surface acoustic wave, and the period and the elastic surface of the multi-strip coupler are connected. It may be every two or every three depending on the frequency of the wave.

For example, as shown in FIG. 10, the pitch of the multi-strip coupler 16 is set to the input / output IDTs 12, 1
4, when the reflectors 18 and 20 are arranged at a half of the pitch, the strip electrodes 16a, 16b, ..., 16n of the multi-strip coupler 16 may be commonly connected two by two. That is, the strip electrodes 16a and 16b of the multi-strip coupler 16 are commonly connected, the strip electrodes 16c and 16d are commonly connected, and similarly, two strip electrodes are commonly connected.

Further, as the surface acoustic wave device of the present invention,
Not limited to the structure of the surface acoustic wave device of the above-described embodiment, a large number of I
The present invention can be applied to a surface acoustic wave device having a structure in which DTs are connected in parallel (IIDT structure) and a surface acoustic wave device having another structure. Further, although ST quartz is used as the piezoelectric substrate in the above-described embodiments, other piezoelectric material substrates may be used. Even if the entire substrate is not a piezoelectric material, at least the surface layer is a substrate formed of a piezoelectric material. I wish I had it.

[0046]

As described above, a plurality of strips are spread over the first surface acoustic wave track of the first surface acoustic wave transducer and the second surface acoustic wave track of the second surface acoustic wave transducer. Forming a multi-strip coupler having and at the frequency at which the signal is desired to be transmitted,
Since the strips in which the propagating surface acoustic waves have substantially the same phase are commonly connected in an electrically floating state, the amount of out-of-band attenuation can be improved.

Further, according to the present invention, the first surface acoustic wave track of the first surface acoustic wave transducer and the second surface acoustic wave track are provided.
Forming a multi-strip coupler having a plurality of strips across the second surface acoustic wave track of the surface acoustic wave transducer of FIG. The strips of the first group are connected together in an electrically floating state, and at the frequency at which the signal is to be transmitted,
Since the phase of the propagating surface acoustic wave is the second phase, which is different from the first phase by about 180 degrees, the strips of the second group are commonly connected in an electrically floating state, so that the out-of-band attenuation is improved. can do.

Further, in the surface acoustic wave device having the above-mentioned first surface acoustic wave transducer and second surface acoustic wave transducer, the first surface acoustic wave track is provided at both ends of the first surface acoustic wave track. And a second reflector provided at both ends of the second surface acoustic wave track for reflecting the surface acoustic wave propagating in the second surface acoustic wave and reflecting the surface acoustic wave propagating in the second surface acoustic wave track. Since the above-described multi-strip coupler is provided in the surface acoustic wave device further provided with, it is possible to suppress spurious generated on the low frequency side outside the band and improve the out-of-band attenuation amount.

[Brief description of drawings]

FIG. 1 is a diagram showing a surface acoustic wave device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an operation of the surface acoustic wave device according to the embodiment of the present invention.

FIG. 3 is a graph showing frequency characteristics of radiant energy in a surface acoustic wave device according to an embodiment of the present invention.

FIG. 4 is a graph showing filter characteristics of a surface acoustic wave device according to an embodiment of the present invention.

FIG. 5 is a graph showing frequency characteristics of radiant energy in a surface acoustic wave device of a comparative example.

FIG. 6 is a graph showing filter characteristics of a surface acoustic wave device of a comparative example.

FIG. 7 is a diagram showing a surface acoustic wave device according to a first modification of the present invention.

FIG. 8 is a diagram showing a surface acoustic wave device according to a second modification of the present invention.

FIG. 9 is a diagram showing a surface acoustic wave device according to a third modified example of the present invention.

FIG. 10 is a diagram showing a surface acoustic wave device according to another modification of the present invention.

FIG. 11 is a diagram showing a surface acoustic wave device of a first conventional example.

FIG. 12 is a diagram showing a surface acoustic wave device of a comparative example.

[Explanation of symbols]

10 ... Piezoelectric substrate 12, 14 ... Input / output IDT 12A, 12B, 14A, 14B ... Input / output IDT 16 ... Multi-strip coupler 16a, 16b, ..., 16n ... Strip electrodes 16x, 16y ... Electrode bar 16A, 16B ... Multi-strip coupler 16Aa, 16Ab, ..., 16An ... Strip electrodes 16Ax, 16Ay ... Electrode bar 16Ba, 16Bb, ..., 16Bn ... Strip electrodes 16Bx, 16By ... Electrode bar 18, 19, 20 ... Reflector 22 ... First surface acoustic wave track 23 ... Third surface acoustic wave track 24 ... Second surface acoustic wave track 100 ... Piezoelectric substrate 102, 104 ... Input / output IDT 108 ... First surface acoustic wave track 110 ... Second surface acoustic wave track 110 ... Piezoelectric substrate 112, 114 ... Input / output IDT 116 ... Multi-strip coupler 118, 120 ... Reflector 122 ... First surface acoustic wave track 124 ... Second surface acoustic wave track

Continuation of front page (56) Reference JP 59-4215 (JP, A) JP 59-41915 (JP, A) JP 55-18141 (JP, A) JP 56-46318 (JP , A) JP-A-55-82529 (JP, A) JP-A-3-162116 (JP, A) US Patent 4166987 (US, A) US Patent 3836876 (US, A) US Patent 3988703 (US, A) (US Pat. 58) Fields investigated (Int. Cl. ⁷ , DB name) H03H 9/25 H03H 9/145 H03H 9/64

Claims (3)

(57) [Claims] 1. A piezoelectric substrate having at least a surface layer formed of a piezoelectric material, and a first substrate formed on the surface of the piezoelectric substrate for exciting, receiving, reflecting and propagating a surface acoustic wave of a first surface acoustic wave track. And a second surface acoustic wave transducer that is formed on the surface of the piezoelectric substrate and that excites, receives, reflects, and propagates the surface acoustic wave of the second surface acoustic wave track. Having a plurality of strips formed over the first surface acoustic wave track and the second surface acoustic wave track, the propagating surface acoustic waves have substantially the same phase at the frequency at which the signal is desired to be transmitted. A surface acoustic wave device comprising: a multi-strip coupler in which strips are electrically connected to each other in a floating state. 2. A piezoelectric substrate having at least a surface layer made of a piezoelectric material, and a first substrate formed on the surface of the piezoelectric substrate for exciting, receiving, reflecting and propagating surface acoustic waves of a first surface acoustic wave track. And a second surface acoustic wave transducer that is formed on the surface of the piezoelectric substrate and that excites, receives, reflects, and propagates the surface acoustic wave of the second surface acoustic wave track. It has a plurality of strips formed over the first surface acoustic wave track and the second surface acoustic wave track, and the propagating surface acoustic wave has a first phase at a frequency at which a signal is desired to be transmitted. In the first group of strips, which are electrically connected together in a floating state, at a frequency at which a signal is desired to be transmitted,
The phase of the propagating surface acoustic wave is about 180 times that of the first phase.
A surface acoustic wave device, comprising: a multi-strip coupler in which strips of a second group having different second phases are commonly connected in an electrically floating state. 3. The surface acoustic wave device according to claim 1, wherein the surface acoustic wave device is provided at both ends of the first surface acoustic wave track and reflects surface acoustic waves propagating in the first surface acoustic wave track. 1 reflector and a second reflector that is provided at both ends of the second surface acoustic wave track and that reflects a surface acoustic wave propagating through the second surface acoustic wave track. Surface acoustic wave device.