JPH03145320A - Surface acoustic wave device - Google Patents

Abstract

PURPOSE:To reduce an influence of mutual surface waves of filters provided on one substrate by providing a saw tooth-shaped groove or minute holes formed by dry etching. CONSTITUTION:A saw tooth-shaped groove 14 is formed between interdigital electrodes 12a and 12b for transmission/reception and interdigital electrodes 13a and 13b for transmission/reception constituting filters 12 and 13 with a high precision by dry etching. This groove has a prescribed inclination to the surface wave propagation direction of an arrow A and is extended in this direction of the arrow while alternately changing the direction of this inclination. Plural minute holes 16 may be formed by dry etching instead of the groove 14. Thus, unnecessary surface waves 15 are scattered, and an influence of mutual acoustic waves of filters 12 and 13 on one substrate 11 is surely prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to a multi-channel surface acoustic wave device used in a high frequency band (100-formerly 42 or higher) such as for satellite broadcasting.
(b) Conventional technology A SAW filter is a combination of a pair of comb-shaped interdigital filters mounted on a piezoelectric substrate. A device that forms poles and marks 90 an alternating current signal on one transmitting electrode to generate an elastic wave on the substrate surface, which is received by the other receiving electrode and converted into a tL signal again. This conversion process realizes a bandpass filter. Such SAW
The filter can have multiple transmitting and receiving interdigital TL poles formed on the same substrate, and filters having different arbitrary frequency characteristics can be constructed on the same substrate. For example, in regions such as Europe where several broadcasting satellites have been launched, one SAW filter is used to handle signals transmitted with different bandwidths, and the output side is switched to each channel. . As a result, it is possible to achieve a reduction in size compared to using multiple SA to V filters. However, in this case, since a plurality of funoltas having different inter-wave number characteristics are formed on the same substrate, there is a problem that selectivity between each channel is poor and noise due to mutual interference etc. deteriorates the characteristics.

In order to solve this problem, Japanese Patent Application Laid-open No. 102507/1983 (HO3H9/25) proposes forming a groove (3) between each filter (1) and (2) as shown in Fig. 4. ing.

In the figure, (1a) and (2a) are interdigital electrodes for transmission, (lb) and (2b) are interdigital electrodes for reception, and (lc) and (2c) are shield electrodes.

However, as shown in the figure, the surface wave propagation direction (, l
In the linear groove (3) parallel to the groove (3), all unnecessary surface waves incident from the same direction are reflected in the same direction. (lb) (2b), there is a possibility that it will be output as noise.

In addition, when a die/guts, scriber, etc. are used as a method of forming such a groove (3), cutting waste is generated, and this cutting waste is particularly
A W 7, Ruta is very inconvenient.

(c) Problems to be Solved by the Invention The present invention has been made in view of the above-mentioned problems, and is a surface acoustic wave filter in which a plurality of interdigital electrodes for transmitting and receiving are formed on the same substrate. It is an object of the present invention to reliably prevent the influence of elastic waves and to eliminate the above-mentioned inconveniences caused by cutting debris during groove formation.

(d) Means for Solving the Problems The surface acoustic wave device of the present invention is a surface acoustic wave device in which a plurality of sets of transmitting and receiving interdigital electrodes are provided on the same substrate, and in which a plurality of pairs of transmitting and receiving interdigital electrodes are provided on the same substrate. Provided with sawtooth-shaped grooves or the like formed by dry etching that extend in the direction of surface wave f propagation while alternately changing the inclination direction to the surface wave propagation direction in the opposite direction, or a plurality of micropores formed by dry etching. It is characterized by:

(Function) Since the surface acoustic wave device of the present invention is configured as described above,
Surface waves are reflected and absorbed by the sawtooth-shaped grooves or micropores.

(f) Example Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a perspective view of the surface acoustic wave device of the present invention.

(11) is a piezoelectric substrate such as L+TaO3, (12a) (1
3a) is the interdigital electrode for transmission, (12b) (
13b) is a reception interdigital electrode, which is formed on the piezoelectric substrate (11) by odolingraphy or the like. These interdigital electrodes for transmission and reception (12a
H13a) (12b) (13b) are electric t% (1
2a) (12b) and one-pole (13a) (13b) strings constitute filters (12) and (13) having different frequency characteristics. (12c) (13c) are shield electrodes, (
12d) (12d) (13d) (13d) is an absorbing material that prevents unnecessary surface waves reflected from the end face of the substrate.

(14) is a sawtooth-shaped groove, and each filter (12
)(13) Interdigital for transmitting and receiving? i
A precise shape is formed by dry etching between the S (12a) (12b) and the transmitting/receiving interdigital electrodes (13a) (13b). The groove (14) has a predetermined inclination with respect to the surface wave propagation direction (A), and is formed to extend in the surface wave propagation direction (A) while changing the #i oblique direction alternately.

Since the groove (14) is formed into a sawtooth shape, it scatters the unnecessary surface waves (15) as shown in Fig. 2.In addition, in order to absorb the unnecessary surface waves, this K(1
4) may be coated with an absorbent material.

In addition, by forming a plurality of fine holes (16) (16)... as shown in Fig. 3 instead of the grooves (14) by dry etching, the unnecessary surface waves (15) can be scattered. I can do it.

In addition, when processing grooves (holes) by dry etching, no cutting debris or the like is generated on the piezoelectric substrate, so it is suitable for SAW filters for high frequency bands.

Note that if you try to form deep grooves (holes) by dry etching, it will take time, but surface waves produce 9oo! of energy at a depth within one wavelength! For example, in the 400\IHz band, one wavelength is approximately 8 com, and Li
In the case of a Ta0+ substrate, the amount of processing is deep enough to be handled by dry etching.

(g) As explained in detail about the invention, the sawtooth-shaped grooves and the fineness formed by the dry etching of the present invention have a greater effect of scattering unnecessary surface waves than the conventional ones, and this makes it possible to The influence of surface waves between the valley filters provided above can be reduced. In addition, since it is formed by dry etching, no cutting debris or the like is generated, so that adverse effects on the electrode pattern are suppressed.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the surface acoustic wave device of the present invention, FIGS. 2 and 3 are enlarged views of the main parts, and FIG. 4 is a diagram showing a conventional example. (11)... Piezoelectric substrate, (12a) (13a)...
Interdigital electrodes for transmission, (12b) (13b)
...interdigital electrode for reception, (14) ... groove,
(16)...(padding hole. Figure 1)

Claims (1)

[Claims] (1) In a surface acoustic wave device in which multiple sets of transmitting and receiving interdigital electrodes constituting a filter each having a predetermined frequency characteristic are provided on the same substrate, surface wave propagation occurs between each set of transmitting and receiving interdigital electrodes. It is characterized by comprising a sawtooth-shaped groove formed by dry etching that extends in the surface wave propagation direction while alternately changing the inclination direction to the opposite direction, or a plurality of micropores formed by dry etching. surface acoustic wave device.