JPH0548373A - Surface acoustic wave circuit - Google Patents

Abstract

PURPOSE:To attain the circuit of little error and high performance by providing an interdigital electrode interleaving between electrodes and earth electrodes, varying a crossing width by a prescribed value each while taking the interleaved part as a border so as to implement weighting. CONSTITUTION:The weighting is implemented by varying the crossing width of interdigital electrodes 1a, 2a by a prescribed value each as widths W4-W1 from one end of electrodes 1, 2 in the lengthwise direction toward the other end while a missing part of the interdigital electrode in the electrode 1 and the earth electrode 2 in the lengthwise direction as a border. The quantity of conversion from a radio wave into a sound wave is reduced according to the weighting and number of pairs of the electrodes 1a, 2a is increased. When the number of the electrodes 1a, 2a is increased to decrease the crossing width, the degree of freedom of the weighting is increased and the sound waves at the electrodes 1a, 2a are synthesized, then the reflection in the electrodes 1, 2 hardly takes place. Since the crossing width of the electrodes 1a, 2a is changed by a prescribed value each by thaking its thinned-out part as a border to attain analog weighting, the error is reduced and high performance is realized.

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 circuit such as a narrow band filter.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional surface acoustic wave circuit described in, for example, Surface Acoustic Wave Engineering, page 67, FIGS. G
ND) electrodes 1a and 2a are comb-teeth electrodes each having one end attached to the electrode 1 and the ground electrode 2, and their free ends are provided so as to partially intersect each other. Reference numeral 3 is a piezoelectric substrate on which the above electrodes are arranged.

Next, the operation will be described. The radio wave input to the electrode 1 is converted into a sound wave by the pattern of the comb-teeth electrodes 1a and 2a. The amount of electric wave to be converted into a sound wave at each pattern position changes substantially in proportion to the cross width w of the comb-teeth electrodes 1a and 2a. In the configuration of FIG.
Are the same, the energy density is constant. Figure 4
In, in the longitudinal direction of the electrode 1 and the ground electrode 2, there is a portion where the comb-teeth electrodes 1a and 2a are not thinned out. Weighting is performed according to the position and the number of parts without the comb-teeth electrode,
The desired performance is achieved, and this method is named thinning-out weighting.

[0004]

Since the conventional surface acoustic wave circuit is constructed as described above, in the conventional weighting of the thinning method, it is only necessary to set whether or not there is no electrode. Therefore, this is a weighting method in which the number is changed digitally instead of being changed in an analog manner and the number thereof is very small. Therefore,
An analog method cannot be realized. Therefore, there is a problem that unnecessary electric field components are generated and frequent setting cannot be performed.

The present invention has been made to solve the above problems, and an object thereof is to obtain a high-performance surface acoustic wave circuit with few errors.

[0006]

A surface acoustic wave circuit according to a first aspect of the present invention is provided by thinning out each of an electrode and a ground electrode that are arranged in parallel on a piezoelectric substrate, and the thinning point is a boundary. In addition, the comb-teeth electrodes are weighted by changing the crossing width by a constant value.

The surface acoustic wave circuit according to the second aspect of the present invention is provided by thinning out each of the electrode and the ground electrode arranged in parallel on the piezoelectric substrate, and the crossing width is a constant value with the thinning point as a boundary. Each of them is provided with comb-teeth electrodes which are weighted by varying the crossing position in the crossing width direction.

The surface acoustic wave circuit according to the third aspect of the present invention is provided by thinning out each of the electrode and the ground electrode arranged in parallel on the piezoelectric substrate, and the energy density becomes uniform in the direction of the cross width. As described above, the comb-teeth electrode in which the intersecting width is randomly varied and weighted is provided.

[0009]

According to the first aspect of the present invention, the crossing width is changed by a constant value with respect to the thinned-out portion of the comb-teeth electrode as a boundary, and the weighting is performed in an analog manner to achieve high performance.

According to a second aspect of the present invention, the crossing width is changed at a constant value with the thinned-out portion of the comb-teeth electrode as a boundary, and the crossing positions are varied in the crossing direction for weighting. Weighting is possible, the energy density is almost constant, and spurious generation can be suppressed.

According to a third aspect of the present invention, the intersection width of the comb-teeth electrodes is randomly weighted by randomly varying the intersection width so that the energy density becomes uniform in the direction of the intersection width. The same effect as the invention described in 2 is obtained.

[0012]

EXAMPLES Example 1. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the invention according to claim 1. In FIG. 1, 1 is an electrode, 2 is a ground electrode, 1a and 2a are comb-teeth electrodes, and 3 is a piezoelectric substrate.
In the present embodiment, the crossing width of the comb-teeth electrodes 1a and 2a from one end side to the other end side of the electrodes 1 and 2 in the longitudinal direction is bordered by a portion where there is no comb-teeth electrode in the longitudinal direction of the electrode 1 and the ground electrode 2. Cross width w
4, w3, w2, w1, w2 ... W4 are changed by a constant value and weighted. Therefore, the amount of conversion from radio waves to sound waves is reduced according to this weighting, and the logarithm of the comb-teeth electrodes 1a, 2a can be increased. it can. In other words, if the logarithm is increased and the cross width is decreased, the degree of freedom in weighting increases. Therefore, by finally synthesizing the sound waves of the respective comb-teeth electrodes, reflection from the electrodes can be made less likely to occur. However, in this embodiment, the intermediate portion between the electrodes 1 and 2 has the largest mountain-shaped energy density.

Embodiment 2. FIG. 2 shows an embodiment of the invention described in claim 2. In the present embodiment, the electrode 1 and the ground electrode 2 are separated from each other by the portions where the comb-teeth electrodes 1a and 2a in the longitudinal direction are not provided
The cross widths of the comb-teeth electrodes 1a and 2a from one end side to the other end side in the longitudinal direction of both electrodes 1 and 2 are set to cross widths w4, w3, w2, w1,
w2 ... w4 are changed by a constant value, and the intersecting positions are varied in the direction of the intersecting width w, and weighted so that the energy density becomes substantially constant.
The reflections at a and 2a become uniform and can cancel each other out, and spurious can be suppressed.

Example 3. FIG. 3 shows an embodiment of the invention described in claim 3. In this embodiment, the cross width w of the comb-teeth electrodes 1a and 2a is randomly varied from one end side to the other end side in the longitudinal direction of the electrode 1 and the ground electrode 2 so that the energy density becomes constant in the direction of the cross width. By weighting the weights, it is possible to finely weight them and suppress the generation of spurious.

[0015]

As described above, according to the first aspect of the present invention, the intersecting width of the comb-teeth electrodes is changed by a constant value with the thinning-out point of the comb-teeth electrodes as a boundary and weighted in an analog manner. Can achieve high performance.

According to the second aspect of the present invention, the intersection width of the comb-teeth electrodes is changed by a constant value with the thinning-out portion of the comb-teeth electrodes as a boundary, and the intersection positions are varied in the direction of the intersection width. Since the energy density in the cross width direction can be set to be substantially constant, high performance can be realized.

According to the third aspect of the present invention, since the cross width of the comb-teeth electrodes is randomly changed and weighted so that the energy density is constant in the direction of the cross width, the energy density is finely and uniformly made. It can be set and high performance can be realized.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a surface acoustic wave circuit according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a surface acoustic wave circuit according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram showing a surface acoustic wave circuit according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram showing a conventional surface acoustic wave circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 electrode 2 ground electrode 1a, 2a comb tooth electrode 3 piezoelectric substrate

Claims (3)

[Claims] 1. A comb-teeth electrode, which is provided by thinning out each of an electrode and a ground electrode arranged in parallel on a piezoelectric substrate, and weighted by changing a crossing width by a constant value with the thinning-out point as a boundary. Surface acoustic wave circuit. 2. An electrode and a ground electrode, which are arranged in parallel on a piezoelectric substrate, are thinned out, and the crossing width is changed by a constant value at the thinning point as a boundary, and the crossing position is set in the crossing width direction. A surface acoustic wave circuit having comb-teeth electrodes which are dispersed and weighted. 3. An electrode and a ground electrode, which are arranged in parallel on a piezoelectric substrate, are thinned out, and the intersection width is randomly varied so that the energy density becomes uniform in the direction of the intersection width. Surface acoustic wave circuit with weighted comb-teeth electrodes.