JPH09153765A - Saw(surface acoustic wave) filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively attain miniaturization without lowering performance by rationally reducing idle space on a substrate. SOLUTION: Four electrodes 51 , 52 , 53 and 54 forming a multistrip coupler 5 are respectively bent in the shape of crank and mutually cross at the intermediate section through insulating films 9, and an input transducer 3 and an output transducer 4 are respectively arranged above and under the crossing sections of four electrodes 51 , 52 , 53 and 54 on the left or right side of multistrip coupler 5.

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 filter utilizing surface waves propagating on the surface of an elastic body, and more particularly to an input transducer, an output transducer and a multi-strip coupler arranged on a substrate. shape,
The present invention relates to a miniaturized device by devising the position and the like.

[0002]

2. Description of the Related Art A typical example of a conventional surface acoustic wave filter is shown in FIG. The surface acoustic wave filter 10 of the illustrated example is a multi-strip composed of a predetermined number (four in this case) of linear electrodes arranged in the central portion of the piezoelectric substrate 2 and arranged in the left-right direction at regular intervals and extending in the vertical direction. A coupler 8 is arranged, an input transducer 3 is arranged at the upper left of the multi-strip coupler 8 and an output transducer 4 is arranged at the lower right thereof, and dampers 7, 7 are arranged at both ends. It is set up.

Each of the input transducer 3 and the output transducer 4 is composed of a pair of comb-shaped electrodes 3A, 3B and 4A, 4B which are vertically opposed to each other so that their electrode elements are partially alternated with each other. There is.

Here, the multi-strip coupler 8
Has been conventionally used to improve spurious caused by a bulk wave, and has been used for a filter in which both input and output electrodes are weighted in the width direction, and is input to a channel on the input transducer 3 side. The electric field of each electrode generated by the surface acoustic wave excites the surface acoustic wave on the output transducer 4 side, but a part of the surface acoustic wave input to the channel on the input transducer 3 side is excited by the multi-strip coupler 8. Since it propagates directly on the piezoelectric substrate 2 without being disposed, when the output transducer 4 is arranged at a position facing the input transducer 3 with the multistrip coupler 8 interposed therebetween, the surface acoustic wave excited by the multistrip coupler 8 and the excitation There is a problem in characteristics because the surface acoustic wave that is not transmitted is transmitted twice. Therefore, as shown in FIG. 3, the output transducer 4 is arranged diagonally to the input transducer 3 with the multi-strip coupler 8 interposed therebetween, and
Dampers 7, 7 are provided to absorb surface acoustic waves that are not excited by the multi-strip coupler 8.

Further, in the surface acoustic wave filter 10 of this example, since the electrodes of the multi-strip coupler 8 are linear, the traveling direction of the surface acoustic wave excited on the output transducer 4 side (lower half). Is the same as the traveling direction of the surface acoustic wave input to the channel (upper half) on the input transducer 3 side (white arrow in the figure).

[0006]

However, in the multi-strip coupler 8 used in the surface acoustic wave filter 10 described above, the electrodes which are its constituent elements are linear, and therefore, inevitably, as shown in FIG. As is clear from the above, the unused spaces Sa and Sb are formed above and below the input transducer 3 and the output transducer 4, which are positioned diagonally, respectively, and as a result, the board 2 That is, the chip area of the surface acoustic wave filter 10 becomes large, and there is a problem that it is not possible to meet the demand for miniaturization and high-density mounting.

The present invention has been made to solve the above-mentioned problems, and the purpose thereof is to reduce the play space on the substrate rationally and to reduce the size without deteriorating the performance. An object is to provide an effective surface acoustic wave filter.

[0008]

In order to achieve the above-mentioned object, the surface acoustic wave filter according to the present invention basically comprises:
An input transducer, an output transducer, and a multistrip coupler are arranged on a substrate, and a plurality of electrodes forming the multistrip coupler are respectively bent, and a traveling direction of a surface acoustic wave generated from the input transducer and The input transducer and the output transducer are arranged vertically in a vertical direction, and a part or all of the input transducer and the output transducer overlap each other in the traveling direction of the surface acoustic wave.

As a more specific example, a plurality of electrodes forming the multi-strip coupler are each bent in a crank shape so that they intersect each other through an insulating film at an intermediate portion, and An example is one in which the input transducer and the output transducer are respectively arranged above and below the intersection of the plurality of electrodes on either the right or left side of the multistrip coupler.

As still another example, a plurality of electrodes forming the multi-strip coupler are respectively bent in a crank shape, and the input transducer and the input transducer are provided above and below the intermediate portion of the multi-strip coupler, respectively. The output transducer may be provided.

As described above, by forming the plurality of electrodes forming the multi-strip coupler into a crank shape or the like, the degree of freedom in arrangement of the input transducer and the output transducer is increased, and they are arranged on both sides of the multi-strip coupler. Since it is not necessary to do so, the play space on the substrate is rationally reduced, and the surface acoustic wave filter can be effectively downsized without deteriorating the performance.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of a surface acoustic wave filter according to the present invention. In the surface acoustic wave filter 1 shown in FIG. 1 and the surface acoustic wave filter 1'shown in FIG. 2 described later, the portions corresponding to the respective portions of the conventional surface acoustic wave filter 10 shown in FIG. 3 described above are the same. The symbols are attached to omit or simplify their explanation. The surface acoustic wave filter 1 shown in the drawing has a piezoelectric substrate 2 made of ceramic, an input transducer 3,
The output transducer 4 and the multi-strip coupler 5 are arranged, and the dampers 7, 7, 7, 7 are arranged above and below the left and right ends, respectively. The positions of the input transducer 3 and the output transducer 4 are arranged. ,
Also, the shapes and lengths of the plurality of electrodes forming the multi-strip coupler 5 are different from those of the conventional one shown in FIG.

That is, in the present embodiment, a plurality of wires (4 in this case) forming the multi-strip coupler 5 are formed.
The electrodes 5 ₁ , 5 ₂ , 5 ₃ , 5 _{4 of the present invention} are bent in a crank shape so as to intersect each other in the middle portion with insulating films 9, 9 ,. The four electrodes 5 ₁ , on the left side of the multi-strip coupler 5,
The input transducer 3 and the output transducer 4 are arranged above and below the intersection of 5 ₂ , 5 ₃ , and 5 ₄ , respectively, and the right side of the input transducer 3 and the output transducer 4 that is closer to the multi-strip coupler 5 The four electrodes 5 ₁ , seen from the edge,
The order of arrangement of 5 ₂ , 5 ₃ and 5 ₄ is the input transducer 3
Whereas the 5 ₁ -5 ₂ -5 ₃ -5 ₄ is a side, it becomes 5 ₄ -5 ₃ -5 ₂ -5 ₁ opposite the output transducer 4 side.

The input transducer 3 and the output transducer 4 have a pair of comb-shaped electrodes 3A, which are vertically opposed to each other so that their respective electrode elements are partially alternated, as in the conventional one. 3B and 4
It consists of A and 4B.

The input transducer 3, the output transducer 4 and the multi-strip coupler 5 are formed by vapor-depositing aluminum on the substrate 2 and then chemically etching the same, and the damper 7 is formed by applying a silicone resin and drying it. It is formed.

Here, the multi-strip coupler 5
Is the channel on the input transducer 3 side (upper half)
The surface acoustic waves are excited on the output transducer 4 side (lower half) by the electric field of each electrode generated by the surface acoustic waves input to. In the surface acoustic wave filter 1 of this embodiment, the electrodes 5 ₁ , 5 ₂ ,
Because 5 ₃ and 5 ₄ are in the shape of a crank, the traveling direction of the surface acoustic wave excited on the output transducer 4 side (lower half) is the elastic surface input to the channel (upper half) on the input transducer 3 side. It is opposite to the direction of wave travel (white arrow in the figure).

As described above, in the surface acoustic wave filter 1 of the present embodiment, the multi-strip coupler 5 has a crank shape, so that the degree of freedom in arrangement of the input transducer 3 and the output transducer 4 is increased, and the multi-strip coupler 5 is provided. Since it is not necessary to dispose the couplers on both sides of the coupler 5, the play space on the substrate 2 is rationally reduced, and the surface acoustic wave filter can be effectively downsized without deteriorating the performance.

FIG. 2 shows a second embodiment of the surface acoustic wave filter according to the present invention. The surface acoustic wave filter 1 ′ shown in FIG. 2 has the same configuration as in the first embodiment described above.
The input transducer 3, the output transducer 4, and the multi-strip coupler 6 are arranged on the piezoelectric substrate 2 made of ceramic, and the dampers 7, 7 are arranged at both left and right ends. The arrangement position of the output transducer 4 and the shapes and lengths of the plurality of electrodes forming the multi-strip coupler 6 are different from those of the first embodiment.

That is, in the present embodiment, a plurality of wires (4 in this case) forming the multi-strip coupler 6 are formed.
Electrodes 6 ₁ , 6 ₂ , 6 ₃ , 6 ₄ are bent in a crank shape, and the multi-strip coupler 6
The input transducer 3 and the output transducer 3 are respectively arranged above and below the intermediate portion of the input electrode 3 and the four electrodes 6 viewed from the right end of the input transducer 3 near the multi-strip coupler 6.
_1, 6 _2, 6 _3, 6 ₄ sequence order is to become a 6 ₁ -6 ₂ -6 ₃ -6 _4, viewed from the left end closer to the multi-strip coupler 6 at the output transducer 4 4 The arrangement order of the book electrodes 6 ₁ , 6 ₂ , 6 ₃ , 6 ₄ is 6 _{4 −} 6 ₃ − 6 ₂ −
It is the opposite of 6 ₁ .

In the surface acoustic wave filter 1'of this embodiment, the electrodes 6 ₁ ,
Although 6 ₂ , 6 ₃ , and 6 ₄ have a crank shape, unlike the first embodiment, the traveling direction of the surface acoustic wave excited on the output transducer 4 side (lower half) is the channel on the input transducer 3 side. It becomes the same as the traveling direction of the surface acoustic wave input to (upper half) (white arrow in the figure).

Also in the surface acoustic wave filter 1'of the second embodiment, since the multi-strip coupler 6 has a crank shape, the degree of freedom of arrangement of the input transducer 3 and the output transducer 4 is increased, and the multi-strip is performed. Since it is not necessary to dispose the couplers on both sides of the coupler 6, the play space on the substrate 2 is rationally reduced, and the surface acoustic wave filter can be effectively downsized without deteriorating the performance.

[0022]

As can be understood from the above description, in the surface acoustic wave filter according to the present invention, the degree of freedom in arrangement of the input transducer and the output transducer is increased, and it is necessary to arrange them on both sides of the multi-strip coupler. Since it is eliminated, the play space on the substrate can be rationally reduced, and the size can be effectively reduced without deteriorating the performance.

[Brief description of the drawings]

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

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

FIG. 3 is a plan view showing an example of a conventional surface acoustic wave filter.

[Explanation of symbols]

 1 surface acoustic wave filter (first embodiment) 1'surface acoustic wave filter (second embodiment) 2 piezoelectric substrate 3 input transducer 4 output transducer 5 multi-strip coupler (first embodiment) 6 multi-strip coupler (second embodiment) Form) 7 Damper 9 Insulating film

Claims (3)

[Claims] 1. A surface acoustic wave filter comprising an input transducer, an output transducer, and a multistrip coupler arranged on a substrate, wherein a plurality of electrodes forming the multistrip coupler are respectively bent to form the input transducer. The input transducer and the output transducer are arranged above and below in a direction perpendicular to the traveling direction of the surface acoustic wave generated from, and a part or all of the input transducer and the output transducer are mutually relative to the traveling direction of the surface acoustic wave. A surface acoustic wave filter characterized by overlapping. 2. A plurality of electrodes forming the multi-strip coupler are respectively bent in a crank shape so as to intersect each other at an intermediate portion with an insulating film interposed therebetween. The surface acoustic wave filter according to claim 1, wherein the input transducer and the output transducer are provided above and below an intersecting portion of the plurality of electrodes on one side, respectively. 3. A plurality of electrodes forming the multi-strip coupler are respectively bent in a crank shape, and the input transducer and the output transducer are arranged above and below the intermediate portion of the multi-strip coupler, respectively. The surface acoustic wave filter according to claim 1, wherein the surface acoustic wave filter is provided.