JPS6314510A - Surface acoustic wave device - Google Patents

Abstract

PURPOSE:To suppress the occurrence of a retarded ripple while preventing electromagnetic, electrostatic induction and direct induction by providing a cut-off part or a recessed part to a part of a shield electrode and interposing an exciting electrode to the cut-off part or the recessed part. CONSTITUTION:The cut-off part 14a formed by removing the electrode pattern near an exciting electrode 12, that is, nearly at the middle of the shield electrode 14 is formed to the shield electrode 14. The exciting electrode 12 is interposed in the cut-off part 14a so as to approach the shield electrode 14. Thus, the distance between the exciting electrode 12 and a reception electrode 13 is minimized. Thus, the occurrence of a retarded ripple due to a tripple transit echo is suppressed while providing a shield electrode preventing the electromagnetic, electrostatic induction and direct induction. Moreover, a recessed part is provided to the shield electrode in place of the cut-off part and the exciting electrode is interpolsed to the recessed part so as to obtain the similar effect.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a surface acoustic wave device used for an oscillator, a delay line, etc.

(Prior Art) A surface acoustic wave device generally used for an oscillator, a delay line, etc. has a grooved light beam as shown in FIG. 4, for example.

In the figure, reference numeral 1 denotes a piezoelectric substrate, and on one main surface of this piezoelectric substrate 1, an electric pattern consisting of β is formed. to 2
a and 2a, and weighted by changing the length of each electrode finger. A receiving electrode 3 is formed by crossing a pair of comb-shaped electrodes 3a, 3a at a predetermined interval on one side in the wave propagation direction.

A shield electrode 4 is formed between the excitation electrode 2 and the reception electrode 3, and dummy electrodes 5 are formed at roughly predetermined positions.

According to the surface acoustic wave device configured in this way,
The surface acoustic waves excited from the excitation frost enclosure 2 propagate through the piezoelectric substrate 1 and are received by the receiving mold 1 . At that time, as described above, the shield electrode 4 formed between the excitation electrode 2 and the reception electrode 3 conducts electrostatic and direct induction from the excitation electrode 2 to the reception electrode 3. (Refer to Japanese Patent Application Laid-Open No. 103938/1983.) Furthermore, the dummy electric current (5) prevents the occurrence of a difference in phase velocity.

(Problems to be solved by the invention) By the way, in such surface acoustic wave devices, the excitation type (
The delay ripple caused by the electrical reflection so-called triple transit echo that occurs between He 2 and the receiving type (He 3) is: ΔT=4Jα・Ta/(1-α)...Pay) where ΔT: Delay ripple Ta : Delay time α is expressed by the magnitude of the triple transit echo relative to the main signal.

On the other hand, when forming the shield electrode 4 between the excitation electrode 2 and the reception electrode 3 as in the surface acoustic wave device described above, a predetermined space is required for forming the shield electrode 4. Due to such a space, the distance between the excitation electrode 2 and the receiving type water 3 increases, and the delay time T
a becomes longer.

Therefore, as is clear from the above equation (a), there is a problem in that the delay ripple Δd generated by the triple transit echo becomes large.

The present invention was devised in view of the above-mentioned circumstances, and an object of the present invention is to provide a surface acoustic wave device that prevents electromagnetic, electrostatic, and direct induction while suppressing the occurrence of delay ripples.

[Structure of the Invention] (Means for Solving the Problems) That is, the surface acoustic wave device of the present invention includes a substrate that propagates surface acoustic waves, and a pair of comb-shaped electric conductors formed on one main surface of the substrate. (A receiving electrode consisting of an excitation electrode that intersects and is weighted, and a pair of comb-shaped electrodes that are formed at a predetermined interval in the propagation direction of the surface acoustic waves excited from this excitation electrode.) and a shield electrode formed between the excitation electrode and the reception electrode. It has a concave portion facing the excitation electrode, and the excitation type (water is interposed in these divided portions or concave portions).

(Function) In the surface acoustic wave device of the present invention, the shield electric cable has a divided part or four parts facing the excitation type one in the vicinity of the excitation type one car, and these divided parts or four parts By interposing the excitation electrode in the excitation electrode and the reception type (
You can minimize the distance between you and the fish. For this reason, it is possible to use a shield electrode that can prevent electromagnetic, electrostatic, and direct induction (although it is possible to suppress the occurrence of delay ripples).

(Example) Below, details of an example of the present invention will be described. IIl will be explained based on the drawings.

The first embodiment of a surface acoustic wave device according to an embodiment of the present invention is described below.
As shown in the figure.

In the figure, reference numeral 11 denotes a piezoelectric substrate 11 made of, for example, 1-iTao3, which propagates surface acoustic waves, and an electrode pattern made of, for example, 8° C. is formed on one main surface of this piezoelectric substrate 11. In other words, the reference numeral 12 is an apodized excitation type (apodized type excitation type) consisting of a pair of interdigitated electrodes 12a, 12a, which are connected by changing the length of one finger of each electrode, and whose characteristics within the passband are determined. It is Amami.

A pair of comb-shaped electrodes 13a, 13a are intersected on one side in the propagation direction of the surface acoustic waves excited from the excitation electrode 12, and the reception type 4 13 is spaced at a predetermined interval from the excitation type 1 12. It is formed with. Further, a shield electrode 14 which is set to a ground potential is formed between the excitation type (Φ12 and the reception electrode 13).
4, there is a divided part 14 from which the electrode pattern has been removed.
a is formed. The excitation electrode 12 is interposed in the divided portion 14a so as to be close to the shield electrode 14. Roughly excitation electrode 12 shield electric 1 car 1
The comb@electrode 12a on the side adjacent to the shield electrode 4 is at the ground potential, which is the same potential as the shield electrode (the comb 14).

Further, a dummy electrode 15 is formed at a predetermined position.

That is, the dummy electrodes 15 ensure that the lengths of the electrode patterns on each surface acoustic wave propagation path are approximately the same, eliminating differences in the phase velocity lx of the surface acoustic waves propagating on the voltage substrate 11.

In the surface acoustic wave device of this embodiment configured as described above, the surface acoustic wave excited from the excitation electrode 12 propagates on the piezoelectric substrate 11 and is received by the reception electrode 13. At that time, the shield electrode 14 formed between the excitation electrode 12 and the reception electrode 13 and the reception type (electrode finger 12b near the side of the comb 13) of the comb-shaped electrode 12a which is set to the ground potential of the excitation type (to 12) It becomes possible to prevent electromagnetic, electrostatic, and direct induction from the electric potential 12 to the receiving type () 13. Also, the excitation type (12) is interposed within the dividing portion 14a, and this excitation electrode 12 The distance between the receiver electrode 13 and the receiver electrode 13 is considered to be very small.For this reason, the delay time Ta can be shortened, and the delay ripple Δd generated by the triple transit echo can be suppressed as much as possible (conventional example formula ( b) see).

In this case, the overall length of the surface acoustic wave device can be shortened, and costs can be reduced by making it smaller and lighter.

Next, this embodiment device was actually manufactured, and a conventional surface acoustic wave device was also manufactured, and the group delay characteristics and frequency characteristics of these devices were measured. The results are shown in FIG.

In the figure, (a) shows the frequency characteristics of this example device, (b) shows a part of it enlarged ten times, and (c) shows its group delay characteristics. In addition, (2) shows the frequency characteristics of the conventional device, and (e) shows a part of it at 10
The image is shown enlarged twice, and () shows its group delay characteristics.

As is clear from the above, the group delay characteristics and frequency characteristics of the device of this example were very good compared to the conventional example, and it was confirmed that the occurrence of delay ripples was suppressed. In addition, the area of this device is approximately 7% compared to conventional ones.
I was able to reduce it.

Incidentally, in the above-mentioned embodiment, the shield electrode 14 was provided with the divided portion 14a, but the present invention is not limited to this, and the present invention has a recessed portion toward either the shield electrode or the excitation electrode. Almost the same effect can be obtained even if an excitation voltage is interposed in the recess.

Further, although the shield electrode 14 and the excitation electrode 12 are rarely separated, the electrode finger 1 of the excitation electrode 12a set to the ground potential as shown in FIG. 3 is not limited to this.
The same effect can be obtained even if the shield electrode 2b and the shield electrode 14 are joined together, that is, they are not integrated.

[Effects of the Invention] As explained above, according to the surface acoustic wave device of the present invention,
It is important to prevent electromagnetic, electrostatic, and direct induction, and to sufficiently suppress the occurrence of triple ripple.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing a surface acoustic wave device according to an embodiment of the present invention, Fig. 2 is a graph showing measurement results conducted to confirm the effect of this embodiment device, and Fig. 3 is a perspective view showing a surface acoustic wave device according to an embodiment of the present invention. A plan view showing a modified example of the surface acoustic wave device, and FIG. 4 is an oblique view showing a conventional surface acoustic wave device. 5-Fig. 12...... Excitation type (Φ 13...... Receiving type (to) 14...... Seal 1-Electric (car 14a...
... Separation Department Applicant: Toshiba Corporation (Deposit: Toshiba Electronic Device Engineering Co., Ltd. Agent: Patent Attorney: Suyama 1!L-

Claims (3)

[Claims] (1) A substrate that propagates surface acoustic waves, an excitation electrode formed by intersecting a pair of comb-shaped electrodes formed on one main surface of this substrate and weighted, and an excitation electrode that is excited from this excitation electrode. A receiving electrode formed by intersecting a pair of comb-shaped electrodes formed at a predetermined interval in the propagation direction of surface acoustic waves, and a shield electrode formed between the excitation electrode and the receiving electrode. In the surface acoustic wave device, the shield electrode has a divided portion or a recess toward the excitation electrode at a position adjacent to the excitation electrode, and the excitation electrode is interposed in the divided portion or the recess. Features of surface acoustic wave device. (2) The surface acoustic wave device according to claim 1, wherein a comb-shaped electrode on the side of the excitation electrode adjacent to the shield electrode is set at the same potential as the shield electrode. (3) The surface acoustic wave device according to claim 1, wherein a comb-shaped electrode of the excitation electrode adjacent to the shield electrode is integrated with the shield electrode.