JP3157022B2 - Surface acoustic wave device and communication system using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of transmitting a plurality of surface acoustic waves on a piezoelectric substrate and extracting a signal generated by the interaction of the surface acoustic waves by utilizing a physical nonlinear effect of the substrate. The present invention relates to a surface acoustic wave device and a communication system using the same.

[0002]

2. Description of the Related Art In recent years, the importance of a surface acoustic wave element has been increasing as a key device for performing spread spectrum communication. In addition, many applications as a real-time signal processing device are conceivable and are being actively studied.

FIG. 19 is a schematic plan view showing an example of such a conventional surface acoustic wave device.

In FIG. 1, a pair of input interdigital transducers 2 are provided on a piezoelectric substrate 1 and a center electrode 3 is provided therebetween. The transducer 2 is an electrode for exciting a surface acoustic wave signal, and the center electrode 3 is an electrode for transmitting the surface acoustic wave signals in opposite directions and extracting an output signal.

A signal F is applied to one of the transducers 2.
(T) exp (jωt) and the other signal G (t) exp
When (jωt) is respectively applied, two surface acoustic waves F (t−x / v) exp [jω (t−x / v)]... (1a) and G ( t− (L−x) / v) exp [jω (t− (L−x) / v)] (1b) is propagated. Here, v is the surface acoustic wave velocity, and L is the length of the center electrode 3.

On this propagation path, a product component of the surface acoustic wave is generated due to the non-linear effect, and this component is integrated and extracted in the range of the center electrode 3. The output signal H (t) is
It is expressed by the following equation.

[0007]

(Equation 2) Here, α is a proportionality constant.

Thus, the two signals F from the center electrode 3
A convolution signal of (t) and G (t) can be obtained.

However, such a configuration is generally not efficient enough.
6/2, vol. j69-C, No. 2, pp190-
198 ", a surface acoustic wave device as shown in FIG. 20 is proposed. The coordinate axes shown in FIG. 20 are added for convenience, and do not mean the crystal axes of the substrate.

In FIG. 20, reference numeral 11 denotes a piezoelectric substrate;
Reference numerals 12 and 13 denote two surface acoustic wave excitation input interdigital transducers which are formed on the surface of the substrate 1 so as to face each other at an appropriate distance in the x direction. 1
, 14-n are waveguides extending in the x direction between the transducers 12 and 13 and formed on the surface of the substrate 11 in parallel with each other. Also, 1
Reference numeral 5 denotes an output interdigital transducer which is formed on the surface of the substrate 11 at an appropriate distance from the waveguide in the y direction.

In this surface acoustic wave element, when an electric signal having an angular frequency ω is input to the surface acoustic wave excitation transducers 12 and 13, the surface acoustic wave having the frequency is excited, and the surface acoustic wave is transmitted through the waveguide 14-13. 1, 14-2, ..., 1
4-n propagates in the opposite direction in the x-axis direction, and a surface acoustic wave having an angular frequency of 2ω propagated in the y-axis direction is generated in the waveguide by a parametric mixing phenomenon. The surface acoustic wave reaches the output transducer 15, and the output transducer 15 can obtain a convolution electric signal of the two input signals.

[0012]

However, FIG.
In the surface acoustic wave convolver of (1), when trying to increase the interaction length (integration time) of signals, the waveguides 14-1 to 14-1
It is necessary to increase the length of 14-n. Since the length of the output transducer is equal to the length of the waveguide, the length of the output transducer naturally increases as the interaction length increases.

Since the width of the electrode finger of the output transducer is determined by the frequency of the convolution signal and the propagation speed of the surface acoustic wave of the substrate, the line width becomes narrower and the resistance increases as the input center frequency increases.

For example, when an output transducer is formed on a lithium niobate substrate by a comb-shaped electrode made of aluminum and having six counter electrodes having a cross width of 20 mm, a line width of 4.4 μm, and a film thickness of 0.3 μm. Has a radiation resistance of about 2.4Ω, while about 41
There is an electrode finger resistance of 0Ω, and the comb-shaped electrode as a whole is about 68
Ω.

When the conversion loss in the output transducer having this configuration was measured, as shown in FIG.
It was confirmed that there was a very large loss of about 2 dB.

As described above, if the surface acoustic wave waveguide is made long and the intersecting width of the comb-shaped electrode is widened in order to simultaneously process many signals, the resistance of the electrode fingers constituting the comb-shaped electrode increases, and this comb-shaped electrode becomes large. However, there is a disadvantage that the loss due to the electrode finger resistance increases, the efficiency of the device decreases, and the characteristics of the device deteriorate.

On the other hand, "Nakagawa et al., Jpn. J. Appl.
Phys. , Vol. 28, supplement 2
8-2, pp. 221-223 (1989) "has proposed a surface acoustic wave device as shown in FIG. 22, the same members as those in FIG. 20 are denoted by the same reference numerals, and detailed description will be omitted.

In the element shown in FIG. 22, the output transducer has a plurality of portions 25-1, 25-2, 25-3 each formed of a comb-shaped electrode in order to prevent interference due to electrical delay.
It is composed of These parts 25-1 to 25-3
Receives one-third of the surface acoustic wave generated from each of the waveguides 14-1 to 14-n and converts it into an electric signal. Output signals of these portions 25-1 to 25-3 are electrically combined and output via output lines 26 to output terminals 9a and 9b.
Taken out of

However, in the configuration of FIG. 22, the output transducer portions 25-1, 25-2 and 25-3 are used.
The electric fields of the signals output from E1 are arrows E1 'and E1, respectively.
The directions are alternately opposite as shown at 2 'and E3'. Therefore, the outputs of the parts 25-1 and 25-3 and the part 25-1
The output of -2 cancels each other out, and there is a problem that the convolution signal is not efficiently extracted from the terminals 9a and 9b.

(Object of the Invention) An object of the present invention is to solve the above-mentioned problems of the prior art, reduce the electric resistance, and efficiently extract a signal, and a communication device using the same. It is to provide a system.

[0021]

According to the present invention, as a means for solving the above-mentioned problems, a piezoelectric substrate and a first substrate provided on the substrate and exciting first and second surface acoustic waves, respectively, are provided. And a second input transducer, a surface acoustic wave waveguide that propagates the first and second surface acoustic waves in opposite directions, and an emission from the waveguide due to the interaction of the first and second surface acoustic waves. A surface acoustic wave element comprising: an output transducer that converts a third surface acoustic wave into an electric signal and extracts the electric signal; wherein the output transducers are arranged in a width direction of the third surface acoustic wave;
Each of the plurality of portions includes a comb-shaped electrode having a plurality of portions for receiving a part of the third surface acoustic wave and outputting a signal, and the plurality of portions are combined in the same direction with electric fields of electric signals output from the plurality of portions. And the comb-shaped electrode
Is 3/3 of the electrode finger resistance of this comb-shaped electrode.
It is intended to provide a surface acoustic wave device characterized by being larger than 1 .

Further , the present invention provides a piezoelectric substrate and
To excite the first and second surface acoustic waves, respectively.
First and second input transducers,
For propagating the second surface acoustic wave and the second surface acoustic wave in opposite directions
Phase of the surface acoustic wave waveguide and the first and second surface acoustic waves
Third surface acoustic wave emanating from the waveguide by interaction
And an output transducer that converts
In the surface acoustic wave device having:
A transducer is arranged in the width direction of the third surface acoustic wave.
Each of which receives a part of the third surface acoustic wave and outputs a signal.
A comb-shaped electrode having a plurality of portions for
Indicates that the electric fields of the electrical signals output from
Connected to each other to form
Several parts of the electrodes are electrically connected to each other in series
A surface acoustic wave element characterized by
is there. Further, the present invention provides a piezoelectric substrate,
And the first and second surface acoustic waves are excited, respectively.
First and second input transducers and the first and second input transducers
Elastic surface that propagates two surface acoustic waves in opposite directions
Interaction between Waveguide and First and Second Surface Acoustic Waves
Generates a third surface acoustic wave generated from the waveguide
And an output transducer that converts the signal into a signal and takes it out.
A surface acoustic wave device comprising:
Are arranged in the width direction of the third surface acoustic wave.
Each receive a part of the third surface acoustic wave and output a signal
A comb-shaped electrode having a plurality of portions;
However, the electric fields of the electric signals output from each other are synthesized in the same direction.
Connected to each other, and
Some of the parts are electrically connected to each other in series
And some of the other parts are electrically
Surface acoustic wave element characterized by being connected in parallel to
It is to provide a child.

Further , the present invention provides a piezoelectric substrate,
To excite the first and second surface acoustic waves, respectively.
First and second input transducers,
For propagating the second surface acoustic wave and the second surface acoustic wave in opposite directions
Phase of the surface acoustic wave waveguide and the first and second surface acoustic waves
Third surface acoustic wave emanating from the waveguide by interaction
And an output transducer that converts
In the surface acoustic wave device having:
A transducer is arranged in the width direction of the third surface acoustic wave.
Each of which receives a part of the third surface acoustic wave and outputs a signal.
A comb-shaped electrode having a plurality of portions for
Indicates that the electric fields of the electrical signals output from
Connected to each other to form
Dog leg type with two or more sections
Providing a surface acoustic wave device comprising a comb-shaped electrode
To offer.

Further, the present invention provides a transmitter for transmitting a signal modulated in accordance with information, a receiving circuit for receiving a modulated signal transmitted from the transmitter, a circuit for generating a reference signal, The surface acoustic wave device of the present invention for outputting a convolution signal of a signal received by a circuit and a reference signal, and a circuit for demodulating information using the convolution signal output from the surface acoustic wave device. Consist of
A communication system is provided.

[0025]

According to the means of the present invention, among the output terminals of a plurality of acoustoelectric transducers, the output terminals having different polarities of the electric signals converted from the surface acoustic waves are electrically connected in series. The electric fields of the electric signals converted by the electric converter are combined in the same direction and can be extracted without canceling the output.

According to the means of the present invention, in which a plurality of acoustoelectric transducers are electrically connected in parallel, a time lag until an electric signal converted by each acoustoelectric transducer reaches an output terminal is obtained. And the characteristics of the element can be improved.

Further, according to the means of the present invention in which a plurality of acoustoelectric transducers are electrically connected in series and in parallel, the impedance of the acoustoelectric transducer as a whole can be changed, and an external circuit and an external circuit can be connected. Can be easily matched.

According to the means of the present invention in which the acoustoelectric transducer is constituted by a dog-leg type comb-shaped electrode, the radiation resistance of the comb-shaped electrode can be increased and the electrode finger resistance can be relatively reduced. The loss due to the electrode finger resistance can be reduced, and the characteristics of the element can be improved.

Also, the acoustoelectric transducer is a comb-shaped electrode,
According to the means of the present invention, the width of the intersecting electrode and the like are set so that the radiation resistance of the comb electrode is substantially larger than one third of the electrode finger resistance of the comb electrode. The electrode finger resistance of the comb-shaped electrode constituting the electric converter can be reduced, thereby reducing the loss due to the electrode finger resistance and improving the characteristics of the element.

[0030]

(Embodiment 1) FIG. 1 is a schematic plan view showing a first embodiment of a surface acoustic wave device according to the present invention.

In FIG. 1, reference numeral 31 denotes a piezoelectric substrate. As such a piezoelectric substrate, for example, a substrate made of lithium niobate or the like can be used.

Symbols 32 and 33 indicate x on the surface of the substrate 31.
FIG. 3 shows an input interdigital transducer formed so as to be opposed to and arranged at an appropriate distance in a direction. The transducers 32 and 33 are composed of comb electrodes. Such a comb-shaped electrode is formed using a conductor such as aluminum, silver, or gold as a material by using a photolithography technique.
These transducers 32 and 33 are provided so as to excite surface acoustic waves that propagate in the positive and negative directions of the x-axis, respectively.

Reference numerals 34-1, 34-2 to 34-3,.
34-n are the transducers 32 on the surface of the substrate 31.
33 shows a surface acoustic wave waveguide provided between the surface acoustic wave waveguides 33 and 33. These waveguides extend in the x direction and are arranged at a constant pitch in parallel with each other.

Regarding the above-mentioned waveguides, “Surface Acoustic Wave Engineering” No. 82-
This is described in detail on page 102, and a thin film waveguide and a topographic waveguide are known. In the present invention, the surface of the substrate is coated with a conductor such as aluminum, silver, or gold.
Preferably, a v / v waveguide is used.

Reference numeral 5 denotes an output interdigital transducer formed on the surface of the substrate 31 at an appropriate distance in the y direction from the waveguides 34-1 to 34-n. The transducer 5 includes a plurality of portions 5-1 5-2, and 5-3 divided in the x direction. These portions 5-1 to 5-3 are each formed of a comb-shaped electrode.
Such a comb-shaped electrode is made of a material such as aluminum, silver, or gold by using a photolithography technique.

Output transducer parts 5-1 to 5-
3 converts a part of the surface acoustic waves emitted from the waveguides 34-1 to 34-n into electric signals. These three portions are provided so that the entire width of the surface acoustic wave can be received.

The output transducer portion 5-1 is composed of electrode fingers 5-1a and 5-1b. Similarly, the portion 5-2 includes the electrode fingers 5-2a and 5-2b, and the portion 5-3 includes the electrode fingers 5-3a and 5-3b. The electrode fingers 5-1b and 5-2a and the electrode fingers 5-2b and 5-3a are electrically connected by wires (conductive wires) 30, respectively. Also, the electrode finger 5-1
A lead line 40 is connected to the terminals a and 5-3b so that an output signal is taken out between the output terminals 39a and 39b.

In the surface acoustic wave device of this embodiment, when an electric signal having the central angular frequency ω is inputted to one of the input terminals 37a and 37b, the first transducer is excited by the input transducer 32. The first surface acoustic wave propagates in the positive x direction and enters the waveguides 34-1 to 34-n. Similarly, when an electric signal having the central angular frequency ω is input to the other input terminals 38a and 38b, the input transducer 33 excites the second surface acoustic wave. This second surface acoustic wave propagates in the negative direction of x and
-1 to 34-n.

As described above, the first and second surface acoustic waves propagate in the waveguides 34-1 to 34-n in directions opposite to each other. From the waveguides 34-1 to 34-n, a third surface acoustic wave having a central angular frequency of 2 [omega] that propagates in the y-axis direction is generated by the parametric mixing phenomenon. This third surface acoustic wave corresponds to a convolution signal of the signals input to the input transducers 32 and 33, respectively. The third surface acoustic wave is divided and received by portions 5-1 to 5-3 of the output transducer, and is converted into an electric signal.

Here, the output transducer part 5-
The electric field of the electric signal output from 1,5-2,5-3 is
As shown in FIG. 1, they are E1, E2, and E3. Since the electrode fingers 5-1b and 5-2a and 5-2b and 5-3a having different polarities of electric signals are connected in series among the electrode fingers of each part, the output signals of each part are the same. Direction (in-phase)
And the combined signal is output to the output terminals 39a and 39b.
Taken out of

The surface acoustic wave waveguides 34-1 to 34-n
The array pitch (distance between the center lines of adjacent waveguides) is
It is formed so as to have the same wavelength as the third surface acoustic wave generated from these waveguides. With this configuration,
The signal waves generated in the respective waveguides 34-1 to 34-n overlap in phase, and the third surface acoustic wave can be efficiently excited.

(Embodiment 2) FIG. 2 is a schematic plan view showing a surface acoustic wave element according to a second embodiment of the present invention. 2, the same members as those in FIG. 1 are denoted by the same reference numerals, and detailed description will be omitted.

In this embodiment, part of the electrode fingers of the parts 35-1, 35-2, and 35-3 constituting the output transducer 35 are integrally formed by printed wiring on the substrate 31 and are directly connected. This is different from the first embodiment.

It is apparent that the present embodiment can provide the same operation and effect as the first embodiment.

Further, in this embodiment, each of the portions 35-1, 3-3
Since wires for connecting 5-2 and 35-3 are not required,
There is an effect that the device can be easily manufactured as compared with the first embodiment.

(Embodiment 3) FIG. 3 is a schematic plan view showing a third embodiment of the surface acoustic wave device according to the present invention. 3, the same members as those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted.

This embodiment differs from the second embodiment in that an output transducer 36 is provided on the substrate opposite to the output transducer 35 with the waveguides 34-1 to 34-n interposed therebetween. The output transducer 36 has the same configuration as the transducer 35. That is, the transducer 36 includes a plurality of parts 36- connected in series.
1, 36-2 and 36-3.

In this embodiment, the transducer 35
The surface acoustic wave propagating in the direction toward (i.e., the negative direction of the y-axis) is converted into an electric signal by the transducer 35 as in the first embodiment, and is extracted from the output terminals 39a and 39b. On the other hand, the waveguides 34-1 to 34-n propagate the surface acoustic wave also in the direction toward the transducer 36 (y-axis direction). This surface acoustic wave is converted into an electric signal by the portions 36-1 to 36-3 of the output transducer 36. The output signals of the portions 36-1 to 36-3 are combined so that the direction of the electric field is the same, and the output line 41
Through the output terminals 10a and 10b.
By adding the signals extracted from the respective output terminals, the output of the entire device can be obtained.

In this embodiment, the surface acoustic waves generated from the waveguide are received by the output transducer without leakage, and all are converted into electric signals.
Double output can be obtained.

In this embodiment, the transducer 35
And 36 are positioned approximately equidistant with respect to the waveguide, but if the distance from the waveguide to these transducers is different, two outputs with a time difference from each transducer can be obtained. Can also.

In the first embodiment, an output transducer having the same configuration as that of the transducer 5 may be provided on the substrate opposite to the transducer 5 with the waveguide therebetween.

In the above embodiment, each transducer is composed of three parts. However, the number of these parts is not limited to three,
The output transducer may be composed of one or four or more parts. As described above, the point that the number of parts constituting the output transducer can be appropriately set is the same in all the following embodiments.

(Embodiment 4) FIG. 4 is a schematic plan view showing a surface acoustic wave element according to a fourth embodiment of the present invention. 4, the same members as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

The surface acoustic wave element of the present embodiment differs from the first embodiment in that the output transducer 45 is constituted by a so-called dog-leg type comb electrode. A dog-leg electrode can be considered as a comb-shaped electrode in which a plurality of sections are connected in series, with a portion where electrode fingers intersect as one unit (section). Regarding such a dog leg type electrode, K.K. L. Lakin et a
l. , IEEE Trans. MTT. , Vol. MT
T-22, No. 8, pp. 763-768 (197
This is described in detail in 4).

In this embodiment, the same operation and effect as those of the first embodiment can be obtained. The radiation resistance of the dog-leg type comb-shaped electrode is proportional to the square of the number of dog-leg sections. On the other hand, the electrode finger resistance is almost constant irrespective of the number of dog leg sections. Therefore, for example, when a dog-leg type comb electrode having three sections is used as the output transducer, the ratio between the radiation resistance and the electrode finger resistance becomes 9 times that in the case where a normal comb electrode is used, and the electrode finger resistance is increased. Can be relatively reduced, thereby improving the characteristics of the device.

(Embodiment 5) FIG. 5 is a schematic plan view showing a fifth embodiment of the surface acoustic wave device according to the present invention. In FIG. 5, the same members as those in FIG. 4 are denoted by the same reference numerals, and detailed description will be omitted.

This embodiment is different from the fourth embodiment in that an output transducer 46 is provided on the substrate opposite to the output transducer 45 with the waveguides 34-1 to 34-n therebetween. The output transducer 46 has the same configuration as the transducer 45. That is, the transducer 46 is formed of a dog leg type electrode.

In this embodiment, the transducer 45
The surface acoustic wave propagating in the direction toward (i.e., the negative direction of the y-axis) is converted into an electric signal by the transducer 45 as in the fourth embodiment, and is extracted from the output terminals 39a and 39b. On the other hand, the waveguides 34-1 to 34-n propagate the surface acoustic wave also in the direction toward the transducer 46 (the positive direction of the y-axis). This surface acoustic wave is converted into an electric signal by the output transducer 46, and is extracted from the output terminals 10 a and 10 b via the lead 41. By adding the signals extracted from the respective output terminals, the output of the entire device can be obtained.

In the present embodiment, the surface acoustic waves generated from the waveguide are received by the output transducer without leakage and all are converted into electric signals.
Double output can be obtained.

In this embodiment, the transducer 45
And 46 are positioned approximately equidistant with respect to the waveguide, but if the distance from the waveguide to these transducers is different, two outputs from each transducer with a time difference from each other can be obtained. Can also.

In the above embodiment, a plurality of portions of the output transducer are connected in series. However, these portions are connected in parallel so that electric fields of signals output from the respective portions are combined in the same direction. You may connect. This example will be described below.

(Embodiment 6) FIG. 6 is a schematic plan view showing a surface acoustic wave element according to a sixth embodiment of the present invention. 6, the same members as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, the output transducer 55 for converting the surface acoustic waves emitted from the waveguides 34-1 to 34-n into an electric signal includes four parts 55-1, 55-2, 55-.
3 and 55-4, which are different from the first embodiment in that these parts are electrically connected in parallel. Here, each of the portions 55-1 to 55-4 is formed of a comb-shaped electrode. One electrode finger of these comb-shaped electrodes is connected to the output terminal 39a by a lead wire (conductor) 50. The other electrode finger of each comb-shaped electrode is connected to the output terminal 39b by a lead 50.

In the present embodiment, the waveguides 34-1 to 34-34 are used.
-N is output from the output transducer 5
The signal is converted into an electric signal in each of the five parts 55-1 to 55-4. Then, the output signals of the respective parts are synthesized so that the electric fields thereof are directed in the same direction, and are extracted from the output terminals 39a and 39b.

In this embodiment, as in the first embodiment, the effect of reducing the electrode finger resistance of the output transducer can be obtained. In the present embodiment, the parts 55-1 to 55-5
5-4 are connected in parallel, so that the output signals of the respective portions can be output from the output terminals 39 with almost no time difference from each other.
a, 39b.

(Embodiment 7) FIG. 7 is a schematic plan view showing a surface acoustic wave device according to a seventh embodiment of the present invention. In FIG. 7, the same members as those in FIG. 6 are denoted by the same reference numerals, and detailed description will be omitted.

In this embodiment, the waveguides 34-1 to 34-34 are used.
-N, the output transducer 65 for converting the surface acoustic wave emitted from the n into an electric signal includes three portions 65-1, 65-2.
And 65-3. These parts consist of comb electrodes. One of the electrode fingers of these comb electrodes is formed integrally with the electrode fingers of the other comb electrodes. That is, each comb-shaped electrode is connected by a printed wiring. In addition, these parts 65-1 to 65-3
Are electrically connected in parallel by a lead wire 51. Then, the output signals of the respective parts are synthesized so that the electric fields thereof are directed in the same direction, and are extracted from the output terminals 39a and 39b.

In this embodiment, the same operation and effect as in the sixth embodiment can be obtained. Further, in the present embodiment, since the number of lead lines is reduced, an effect is obtained that makes it easier to fabricate the element than in the sixth embodiment.

(Embodiment 8) FIG. 8 is a schematic plan view showing an eighth embodiment of the surface acoustic wave device according to the present invention. 8, the same members as those in FIG. 7 are denoted by the same reference numerals, and detailed description thereof will be omitted.

This embodiment is different from the seventh embodiment in that an output transducer 66 is provided on the substrate opposite to the output transducer 65 with the waveguides 34-1 to 34-n therebetween. The output transducer 66 has the same configuration as the transducer 65. That is, the transducer 66 includes three parts 66-1 to 66-3.

In the present embodiment, the extraction of the signal from the output transducer 65 is performed by the printed wiring 52.
And the extraction wiring 54. Also, a signal is output from the output transducer 66 to the output terminals 58a and 58b via the printed wiring 53 and the lead wire 57. As described above, since the number of lead lines is reduced by using the printed wiring, there is an effect that the element can be more easily formed.

In this embodiment, the surface acoustic wave propagating in the negative direction of the y-axis is converted into an electric signal by the transducer 65 as in the seventh embodiment, and is extracted from the output terminals 39a and 39b. On the other hand, the surface acoustic waves propagating in the positive y-axis direction from the waveguides 34-1 to 34-n are converted into electric signals by the output transducer 66, and output terminals 58a, 58
8b. By adding the signals extracted from the output terminals, the output of the entire device can be obtained.

In this embodiment, the surface acoustic waves generated from the waveguide are received by the output transducer without leakage, and all are converted into electric signals.
Double output can be obtained.

In this embodiment, the transducer 65
And 66 are arranged at substantially the same distance from the waveguide, but if the distance from the waveguide to these transducers is different, two outputs with a time difference from each transducer can be obtained. Can also.

Further, in the present invention, a plurality of portions of the output transducer may be connected in series and partially in parallel.
This example will be described below.

(Embodiment 9) FIG. 9 is a schematic plan view showing a ninth embodiment of a surface acoustic wave device according to the present invention. 9, the same members as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, the output transducer 75 for converting the surface acoustic waves generated from the waveguides 34-1 to 34-n into electric signals is composed of four parts 75-1, 75-2, 75.
-3 and 75-4. And part 7
5-1 and 75-2 and 75-3 and 75-4 are wires 7
0 is electrically connected in series. Also, two pairs (75-1, 75-
2) and (75-3, 75-4) are electrically connected in parallel by a lead wire 71.

In this embodiment, the waveguides 34-1 to 34-34 are used.
-N is output from the output transducer 7
The signals are converted into electric signals by the five parts 75-1 to 75-4. Then, the output signals of the respective parts are synthesized so that the electric fields thereof are directed in the same direction, and are extracted from the output terminals 39a and 39b. In this embodiment, as in the first embodiment,
The effect of reducing the electrode finger resistance of the output transducer is obtained.

Further, the parts 75-1 to 75-4 of this embodiment
The impedance _{Z 1, Z 1 = R i} + jX i ( where the real part of R _i impedance, X _i is the imaginary part of the impedance, j is imaginary unit, i = 1, 2, 3,
Assuming 4), the overall impedance is expressed as 1 / Z = 1 / (Z ₁ + Z ₂ ) + 1 / (Z ₃ + Z ₄ ).

As in this embodiment, the impedance of the output transducer can be adjusted to a desired value by appropriately combining the series and parallel connections. Therefore, by adjusting the impedance of the output transducer so as to be close to the impedance of the external circuit, it becomes easy to achieve impedance matching with the external circuit.

(Embodiment 10) FIG. 10 is a schematic plan view showing a tenth embodiment of a surface acoustic wave device according to the present invention. FIG.
In FIG. 9, the same members as those in FIG.

In this embodiment, the waveguides 34-1 to 34-34 are used.
-N, the output transducer 85 for converting the surface acoustic wave generated from the n into an electric signal has four portions 85-1, 85-
2, 85-3 and 85-4. These parts consist of comb electrodes. One of the electrode fingers of these comb electrodes is formed integrally with the electrode fingers of the other comb electrodes. That is, each comb-shaped electrode is connected by a printed wiring. Also, two pairs (85-
1, 85-2) and (85-3, 85-4) are electrically connected in parallel by a lead wire 80. Then, the output signals of the respective parts are synthesized such that the electric fields are directed in the same direction, and are taken out from the output terminals 39a and 39b.

In this embodiment, the same operation and effect as in the ninth embodiment can be obtained. Further, in this embodiment, since the number of lead lines is reduced, an effect is obtained that makes it easier to fabricate the element than in the ninth embodiment.

(Embodiment 11) FIG. 11 is a schematic plan view showing an eleventh embodiment of a surface acoustic wave device according to the present invention. FIG.
In FIG. 1, the same members as those of FIG. 10 are denoted by the same reference numerals, and a detailed description thereof will be omitted.

This embodiment is different from the tenth embodiment in that an output transducer 86 is provided on the substrate opposite to the output transducer 85 with the waveguides 34-1 to 34-n therebetween. The output transducer 86 has the same configuration as the transducer 85. That is, the transducer 86 is composed of four portions 86-1 to 86-4.

In the present embodiment, the extraction of the signal from the output transducer 85 is performed by the printed wiring 8.
1 and the extraction wiring 82. Further, from the output transducer 86, a printed wiring 83,
Output terminals 90a, 90b
The signal is output to As described above, since the number of lead lines is reduced by using the printed wiring, there is an effect that the element can be more easily formed.

In this embodiment, the surface acoustic wave propagating in the negative y-axis direction is converted into an electric signal by the transducer 85 in the same manner as in the tenth embodiment, and the output terminals 39a, 39b
Taken out of On the other hand, the surface acoustic waves propagating in the positive y-axis direction from the waveguides 34-1 to 34-n are converted into electric signals by the output transducer 86, and output terminals 90a, 90a.
90b. By adding the signals extracted from the output terminals, the output of the entire device can be obtained.

In the present embodiment, since the surface acoustic waves generated from the waveguide are received by the output transducer without leakage and all are converted into electric signals, it is possible to obtain twice the output of the tenth embodiment. it can.

In this embodiment, the transducer 85
And 86 are arranged at substantially equal distances from the waveguide, but if the distance from the waveguide to these transducers is different, two outputs with a time difference from each transducer can be obtained. Can also.

Next, the electrical resistance of the surface acoustic wave device according to the present invention will be described. The following description is based on the first to first embodiments.
Although the present invention can be applied to any of the embodiments, the description will be made by taking the element of FIG. 6 as an example.

In the element shown in FIG. 6, the portions 55-1, 55-2, 55-3 and 55-4 of the output transducer are respectively regular comb electrodes. Radiation resistance R _a at the center frequency of such a comb-shaped electrodes is given by the following equation.

R _a = 2 · K ² / (π ² · f · ε · w) (3) where w is the maximum cross width of the comb-shaped electrode, K ² is the electromechanical coupling coefficient of the piezoelectric substrate, and f is The operating frequency, ε, is the dielectric constant of the piezoelectric substrate.

[0093] On the other hand, the electrode finger resistance R _e of the comb-shaped electrodes is given by the following equation.

R _e = (2 · r · w) / (d · h · N) (4) where r is the resistivity of the comb electrode, w is the maximum cross width of the comb electrode, and d is the line of the comb electrode. The width, h is the thickness of the comb electrode, and N is the number of electrode fingers constituting the comb electrode.

[0095] Figure 12 is a the radiation resistance R _a and the electrode finger resistance R _e, is a diagram showing the relationship between loss due to the electrode fingers resistor R _e, the maximum way, radiation resistance R _a is shown in FIG. inversely proportional to the cross width w, the electrode finger resistance R _e is proportional to the maximum cross width w.

Then, as shown in FIG. 12, 3R _a = R _e
When crossing width w _o satisfying the loss due to the electrode fingers resistance is about 6 dB.

Therefore, 3R _a > R _e , that is, from the above equations (3) and (4), (r · w) / (d · h · N) <3 · K ² / (π ² · f · ε (W) By forming the output transducer so as to satisfy the relationship of (5), the loss due to the electrode finger resistance can be suppressed to within 6 dB.

[0098] Therefore, this embodiment, 3R _a> R _e, i.e. the radiation resistance R _a of the comb electrodes, output with large comb-shaped electrode than substantially 1/3 of the electrode fingers resistance R _e of the comb electrodes By configuring a transducer, the loss due to electrode finger resistance is reduced.

[0099] it was a substantially 3R _a> R _e here,
As shown in the graph of FIG. 12, the intersecting width w of the comb-shaped electrodes satisfying this condition is a value smaller than w _o , and the configuration and the manufacturing of the acoustic-electric transducer using the plurality of comb-shaped electrodes are reduced.
This is because it is most preferable from the viewpoint of efficiency.

In this embodiment, the output transducer portions 55-1, 55-2, 55-3, and 55-4 are made of aluminum, each having an intersection width of 5 mm and a line width of 4.4 μm.
m, to form a 6-to comb-shaped electrode having a film thickness of 0.3 [mu] m, the electrode finger resistance per part one R _e is about 17Omu, radiation resistance R _a
About 9.6Ω becomes which satisfies the condition of the 3R _a> R _e.

When the conversion loss of the output transducer composed of the portions 55-1, 55-2, and 55-3 was measured, it was about 11 dB as shown in FIG. 13, which was about 22 dB of the conventional example shown in FIG. Thus, the loss was reduced by about 11 dB, and the efficiency was improved.

FIG. 14 is a block diagram showing an example of a communication system using a surface acoustic wave device as described above as a convolver. In FIG. 14, reference numeral 125 indicates a transmitter. This transmitter spreads the spectrum of the signal to be transmitted and transmits the signal from antenna 126. The transmitted signal is received at antenna 120 of receiver 124,
The received signal 101 is input to the frequency conversion circuit 102.
The IF signal 103 converted by the frequency conversion circuit 120 into a frequency that matches the input frequency of the surface acoustic wave convolver is shown in FIG.
11 is input to a convolver 104 including a surface acoustic wave device of the present invention as shown in FIG. Here, IF signal 10
3 is input to one input transducer of the convolver, for example the transducer 32 of FIG.

On the other hand, the reference signal 106 output from the reference signal generation circuit 105 is input to the other input transducer of the surface acoustic wave convolver 104, for example, the transducer 33 shown in FIG. The convolver 104 generates the IF signal 103 and the reference signal 10 as described above.
6 and a convolution operation (correlation operation) is performed.
An output signal (convolution signal) 109 is output from an output transducer, for example, the transducer 5 of FIG.

The output signal 109 is input to the synchronization circuit 108. In the synchronization circuit 108, the synchronization signals 111 and 1 are output from the output signal 109 of the surface acoustic wave convolver 104.
12 are input to the reference signal generation circuit 105 and the despreading circuit 107, respectively. Reference signal generation circuit 10
In step 5, the timing of the reference signal 106 is adjusted using the synchronization signal 111 and output. The despreading circuit 107 returns the IF signal 103 to a signal before being subjected to spectrum spreading using the synchronization signal 112. This signal is applied to the demodulation circuit 110
Is converted into an information signal and output. FIG. 15 shows a configuration example of the despreading circuit 107. In FIG. 15, reference numeral 121 denotes a code generator, and 123 denotes a multiplier. Code generator 121
, A synchronization signal 112 output from the synchronization circuit 108 is input, and a code 122 whose timing is adjusted by the synchronization signal 112 is output. The multiplier 123 has I
F signal 103 and code 122 are input, and IF signal 103
And the result of multiplication by reference numeral 122 is output. At this time, IF
If the timing of the signal 103 matches the timing of the code 122, the IF signal 103 is converted into a signal before being spread spectrum and output.

When the frequency of the received signal 101 matches the input frequency of the surface acoustic wave convolver 104,
The frequency conversion circuit 102 is unnecessary, and the received signal 101 may be directly input to the surface acoustic wave convolver 104 through an amplifier and a filter. Although FIG. 14 omits amplifiers and filters for easy understanding, amplifiers and filters may be inserted before or after each block as necessary. Furthermore, in this embodiment, the transmission signal is received by the antenna 120, but the transmitter and the receiver may be directly connected by a wired system such as a cable without using the antenna 120.

FIG. 16 is a block diagram showing a first modification of the receiver 124 in the communication system of FIG.
In FIG. 16, the same members as those in FIG. 14 are denoted by the same reference numerals, and detailed description will be omitted.

In this example, a synchronization follow-up circuit 113 is provided,
The IF signal 103 is also input to the synchronization tracking circuit 113. Also, the synchronization signal 11 output from the synchronization circuit 108
2 is input to the synchronization tracking circuit 113 and the synchronization tracking circuit 11
3 is input to the despreading circuit 107. These points are different from the example of FIG. Examples of the synchronization tracking circuit include a tau dither loop circuit and a delay locked loop circuit, and any of them may be used.

In this embodiment, the same operation and effect as those in the example shown in FIG. 14 can be obtained.
After the rough synchronization is performed, synchronization is further accurately performed by the synchronization follow-up circuit 113, and the synchronization is followed, so that the loss of synchronization hardly occurs and the error rate can be reduced.

FIG. 17 is a block diagram showing a second modification of the receiver 124 in the communication system of FIG.
17, the same members as those in FIG. 14 are denoted by the same reference numerals, and detailed description will be omitted.

In this example, the output from the surface acoustic wave convolver 104 is input to the detection circuit 115, and demodulation is performed by the output of the detection circuit 115. As the detection circuit 115, there are a synchronous detection circuit, a delay detection circuit, and an envelope detection circuit, which can be selectively used depending on a signal modulation method or the like.

Now, assuming that the received signal 101 is a signal that has been subjected to certain modulation such as phase modulation, frequency modulation, and amplitude modulation.
The output 109 from the surface acoustic wave convolver 104 reflects such modulation information. In particular, the length d of the waveguide of the surface acoustic wave convolver 104 is represented by T representing the time per data bit of the received signal 101 and v representing the surface acoustic wave velocity.
If d = vT is satisfied, the modulation information appears as it is at the output 109, for example, the phase-modulated signal f
(T) exp (jθ) is transmitted, and this signal is assumed to be received as the reception signal 101.

At this time, when the reference signal g (t) 106 is input to the surface acoustic wave element 104, the output 109 is f (t) exp (jθ) g (τ−t) dt = exp (jθ) f (t ) G (τ-t) dt (6), and information of phase modulation appears. Therefore, the output 109 of the surface acoustic wave element 104 is connected to an appropriate detection circuit 115.
Can be demodulated by passing through

FIG. 18 is a block diagram showing a third modification of the receiver 124 in the communication system of FIG.
18, the same members as those in FIG. 17 are denoted by the same reference numerals, and the detailed description will be omitted.

In this example, a synchronization circuit 108 is provided, and the output 109 of the surface acoustic wave convolver 104 is connected to the synchronization circuit 10.
8 is also entered. Further, a synchronization signal 111 is output from the synchronization circuit 108 and input to the reference signal generation circuit 105. These points are different from the example of FIG.

In this embodiment, the same operation and effect as in the example of FIG. 17 can be obtained. However, in this embodiment, a synchronization circuit 108 is provided, and the reference signal generation circuit 105 is controlled by a synchronization signal 111 output from the synchronization circuit 108. As a result, synchronization can be stably achieved.

The present invention can be variously applied in addition to the embodiments described above. For example, by using a double electrode (split electrode) for the comb-shaped electrode constituting the input transducer in the first to eleventh embodiments, it is possible to suppress the reflection of surface acoustic waves in the input transducer and to further improve the characteristics of the element. Can be

Similarly, by making the comb-shaped electrode constituting the output transducer a double electrode (split electrode), reflection of surface acoustic waves on the output transducer can be suppressed, and the characteristics of the element can be further improved. it can.

In the first to eleventh embodiments, a regular comb electrode having a constant cross width and pitch of electrode fingers is used as a transducer, but a weighted electrode such as an apodized electrode may be used.

Further, in the first to eleventh embodiments, the substrate is not limited to a single crystal substrate made of lithium niobate, but may be a parametric substrate such as a semiconductor or glass substrate having a piezoelectric film added thereto. Any material and structure having a mixing effect may be used.

In the first to eleventh embodiments, the surface acoustic wave excited by the input transducer is guided to the surface acoustic wave waveguide as it is. A beam width compressor such as a strip coupler may be provided.

The present invention covers all the above-mentioned application examples without departing from the scope of the claims.

The coordinate axes shown in FIGS. 1 to 11 are added for convenience, and do not mean the crystal of the substrate or the like.

[0123]

As described above, according to the present invention, among the output terminals of a plurality of acoustoelectric transducers, output terminals having different polarities of electric signals converted from surface acoustic waves are electrically connected in series. , The electric fields of the electric signals converted by the acoustoelectric converter are in the same direction, are combined in the same phase, and it is possible to prevent the output from being canceled out, thereby improving the efficiency of the element.

Further, according to the present invention, by connecting a plurality of acousto-electric transducers electrically in parallel, the time difference until the electric signal converted by the acousto-electric transducer reaches the output terminal is reduced. And the characteristics of the element can be improved.

Further, according to the present invention, the impedance of the entire acoustoelectric transducer can be changed by electrically connecting a plurality of acoustoelectric transducers in combination with the serial connection and the parallel connection. , Impedance matching with an external circuit can be easily achieved.

Also, according to the present invention, the acoustoelectric converter is constituted by a dog-leg type comb-shaped electrode,
The radiation resistance of the acoustoelectric converter can be increased, and the loss due to electrode finger resistance can be relatively reduced. Therefore, the effect that the characteristics of the element can be improved by this is obtained.

Further, according to the present invention, the acoustoelectric converter is a comb-shaped electrode, and the radiation resistance of the comb-shaped electrode is substantially larger than one third of the electrode finger resistance of the comb-shaped electrode. By setting the intersection width of the electrodes and the like, the overall resistance of the acoustoelectric converter can be reduced, the loss due to the resistance can be reduced, and the characteristics of the element can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing a first embodiment of a surface acoustic wave device according to the present invention.

FIG. 2 is a schematic plan view showing a second embodiment of the surface acoustic wave device according to the present invention.

FIG. 3 is a schematic plan view showing a third embodiment of the surface acoustic wave device according to the present invention.

FIG. 4 is a schematic plan view showing a fourth embodiment of the surface acoustic wave device according to the present invention.

FIG. 5 is a schematic plan view showing a fifth embodiment of the surface acoustic wave device according to the present invention.

FIG. 6 is a schematic plan view showing a surface acoustic wave device according to a sixth embodiment of the present invention.

FIG. 7 is a schematic plan view showing a seventh embodiment of the surface acoustic wave device according to the present invention.

FIG. 8 is a schematic plan view showing an eighth embodiment of the surface acoustic wave device according to the present invention.

FIG. 9 is a schematic plan view showing a ninth embodiment of a surface acoustic wave device according to the present invention.

FIG. 10 is a schematic plan view showing a tenth embodiment of the surface acoustic wave device according to the present invention.

FIG. 11 is a schematic plan view showing an eleventh embodiment of a surface acoustic wave device according to the present invention.

FIG. 12 is a diagram showing the relationship between the maximum intersection width of a comb-shaped electrode, radiation resistance, and electrode finger resistance.

FIG. 13 is a diagram showing conversion loss of an output transducer in a surface acoustic wave device according to the present invention.

FIG. 14 is a block diagram showing an example of a communication system used for the surface acoustic wave device of the present invention.

FIG. 15 is a block diagram showing a specific configuration example of the despreading circuit of FIG. 14;

FIG. 16 is a block diagram showing a modification of the receiver shown in FIG. 14;

FIG. 17 is a block diagram showing a modification of the receiver shown in FIG. 14;

FIG. 18 is a block diagram showing a modification of the receiver shown in FIG. 14;

FIG. 19 is a schematic plan view showing an example of a conventional surface acoustic wave element.

FIG. 20 is a schematic plan view showing an example of a conventional surface acoustic wave element.

FIG. 21 is a diagram illustrating conversion loss of an output transducer in the element of FIG. 20;

FIG. 22 is a schematic plan view showing another example of a conventional surface acoustic wave device.

[Description of sign]

1, 11, 31 Substrate 2, 12, 13, 32, 33 Excitation electrode (input transducer) 3 Central electrode 14-1 to 14-n, 34-1 to 34-n Surface acoustic wave waveguide element 5-1 to 5- 3,15,25-1 to 25-3,35,3
5-1 to 35-3, 36, 36-1 to 36-3, 65,
65-1 to 65-3, 66, 66-1 to 66-3, 75
-1 to 75-4,85,85-1 to 85-4,86,8
6-1 to 86-4 acousto-electric transducer (comb-shaped electrode) (output transducer) 45, 46, 5, 55-1 to 55-4 dog-leg-type comb-shaped acousto-electric transducer 37a, 37b, 38a, 38b Input terminal 9a , 9b, 10a, 10b, 39a, 39b, 58
a, 58b, 90a, 90b Output terminals 26, 40, 41, 50, 51, 54, 57, 71, 8
0, 81, 82, 84 Lead-out wiring 30, 70 Wire (conductor) 52, 53, 81, 83 Printed wiring

──────────────────────────────────────────────────続 き Continued on the front page (31) Priority claim number Japanese Patent Application No. 2-225089 (32) Priority date August 29, 1990 (1990. August 29) (33) Priority claim country Japan (JP) (31) Priority claim number Japanese Patent Application No. 2-225090 (32) Priority date August 29, 1990 (August 29, 1990) (33) Priority claim country Japan (JP) (56) References Electronic communications Journal Transaction C, Vol. J69-C, no. 9, issued September 25, 1986, p. 1215-1216 (58) Fields investigated (Int. Cl. ⁷ , DB name) H03H 9/72 H03H 9/145

Claims (6)

(57) [Claims] 1. A piezoelectric substrate, first and second input transducers provided on the substrate for exciting first and second surface acoustic waves, respectively, and the first and second surface acoustic waves A surface acoustic wave waveguide that propagates in a direction opposite to each other, and an output transducer that converts a third surface acoustic wave generated from the waveguide into an electrical signal by the interaction of the first and second surface acoustic waves and extracts the electric signal. In the surface acoustic wave element comprising, the output transducer is:
The third surface acoustic waves are arranged in the width direction, each of which comprises a comb-shaped electrode having a plurality of parts that receive a part of the third surface acoustic waves and output a signal, and the plurality of parts are each Are connected to each other so that the electric fields of the electric signals output from the comb electrodes are combined in the same direction , and the radiation resistance of the comb-shaped electrode
The value is greater than one third of the electrode finger resistance of this comb-shaped electrode
A surface acoustic wave device. 2. The maximum cross width of the comb-shaped electrode is w, the resistivity of the comb-shaped electrode is r, the line width of the comb-shaped electrode is d, the thickness of the comb-shaped electrode is h, the number of electrode fingers of the comb-shaped electrode is N, and The electromechanical coupling coefficient is K ² , the operating frequency of the element is f, and the dielectric constant of the substrate is ε
And the following conditional expression: A surface acoustic wave device according to claim 1, wherein satisfying the. 3. A piezoelectric substrate and a piezoelectric substrate provided on the substrate.
A first and a second to excite the first and second surface acoustic waves, respectively
2 input transducers and said first and second resilience
Surface acoustic wave waveguides that propagate surface waves in opposite directions
And the interaction of the first and second surface acoustic waves
The third surface acoustic wave generated from the waveguide is converted into an electric signal.
Ammunition comprising a transducing output transducer
In the surface acoustic wave device, the output transducer is:
The third surface acoustic waves are arranged in the width direction, and each is arranged in the third surface acoustic wave.
A plurality of units that receive a part of the surface acoustic wave and output a signal
Comprising a comb-shaped electrode having a plurality of
As but electric field of the electric signal output is synthesized in the same direction
Being connected to each other, and a plurality of portions of the comb-shaped electrode
Minutes are electrically connected to each other in series
Surface acoustic wave device. 4. A piezoelectric substrate and a piezoelectric substrate provided on the substrate.
A first and a second to excite the first and second surface acoustic waves, respectively
2 input transducers and said first and second resilience
Surface acoustic wave waveguides that propagate surface waves in opposite directions
And the interaction of the first and second surface acoustic waves
The third surface acoustic wave generated from the waveguide is converted into an electric signal.
Ammunition comprising a transducing output transducer
In the surface acoustic wave device, the output transducer is:
The third surface acoustic waves are arranged in the width direction, and each is arranged in the third surface acoustic wave.
A plurality of units that receive a part of the surface acoustic wave and output a signal
Comprising a comb-shaped electrode having a plurality of
So that the electric fields of the electrical signals output by
Being connected to each other, and a plurality of portions of the comb-shaped electrode
Some of them are electrically connected to each other in series.
Other parts of the parts are electrically parallel to each other
A surface acoustic wave device connected to the device. 5. A piezoelectric substrate and a piezoelectric substrate provided on the substrate.
A first and a second to excite the first and second surface acoustic waves, respectively
2 input transducers and said first and second resilience
Surface acoustic wave waveguides that propagate surface waves in opposite directions
And the interaction of the first and second surface acoustic waves
The third surface acoustic wave generated from the waveguide is converted into an electric signal.
Ammunition comprising a transducing output transducer
In the surface acoustic wave device, the output transducer is:
The third surface acoustic waves are arranged in the width direction, and each is arranged in the third surface acoustic wave.
A plurality of units that receive a part of the surface acoustic wave and output a signal
Comprising a comb-shaped electrode having a plurality of
So that the electric fields of the electrical signals output by
That they are connected to each other and that the
Consists of a dog-leg comb electrode with an upper section
A surface acoustic wave device. 6. A transmitter for transmitting a signal modulated according to information, a receiving circuit for receiving a modulated signal transmitted from the transmitter, a circuit for generating a reference signal, and a signal received by the receiving circuit. 6. A surface acoustic wave element according to claim 1, which outputs a convolution signal of the reference signal and a reference signal, and demodulation of information using the convolution signal output from the surface acoustic wave element. A communication system comprising: