JPH03143111A - Surface acoustic wave device - Google Patents

Abstract

PURPOSE:To prevent a defective characteristic due to a broken electrode finger by interconnecting all adjacent electrode fingers of equipotential with a connection pattern and placing the connection pattern in a manner that the pattern is not overlapped in the propagation direction of a surface acoustic wave. CONSTITUTION:A connection pattern 35 except for bus electrodes is provided to connect the vicinity of adjacent electrode finger tips of the same length in weight electrode fingers 33 and dummy electrode fingers 34. Moreover, a connection pattern 36 except for bus electrodes is provided to connect the vicinity of adjacent electrode finger tips of the different length. The connection patterns 35, 36 connect the electrode fingers of equipotential along the envelope of the weight coefficient. Moreover, the connection patterns 35, 36 adjacent to each other are connected at positions not over lapped in the propagation direction of the surface acoustic wave. Thus, even when a broken electrode (d) takes place or two electrode fingers are broken simultaneously, since a characteristic defect is caused, no characteristic defect is generated.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a surface acoustic wave device that is applied as a surface acoustic wave filter using an apodized electrode, and is particularly aimed at improving the poor characteristics and deterioration of the characteristics of the apodized electrode. It relates to a surface acoustic wave device.

[Conventional technology]

Generally, in order to realize the filter characteristics of a surface acoustic wave filter, it is known to use an apodized electrode on a piezoelectric substrate as a weighting electrode that weights the size of the intersection width depending on the location. FIG. 2 shows an example of a conventional surface acoustic wave device, in which bus electrodes 1.
I have 2. Between these bus electrodes L2, weighted electrode fingers 3 and dummy electrode fingers 4, which intersect the earth potential electrode fingers, are connected.

By the way, in the conventional surface acoustic wave device described above, the weighting electrode fingers 3 and the dummy electrode fingers 4 are not connected to adjacent electrode fingers in a DC manner. For this reason, when a cut a occurs in the electrode finger during the manufacturing process, no potential is applied to the tip portion 5 of the cut electrode finger, resulting in poor characteristics.

Incidentally, a surface acoustic wave device shown in FIG. 3 has also been considered as an improvement plan that eliminates such drawbacks.

That is, in this proposal, bus electrodes 11 and 12 are provided to bring all the electrode fingers to the same potential. Connected between these bus electrodes 11, 12 are weighted electrode fingers 13 and dummy electrode fingers 14 that intersect with electrode fingers at other potentials. These weighted electrode fingers 13 and dummy electrode fingers 1
The vicinity of the tips of four adjacent electrode fingers of the same length are connected by a connection pattern 15.

In this case, for the cut b of the electrode finger, connection pattern 1
Since adjacent electrode fingers are connected by 5, a potential is applied to the tip portion 16, thereby preventing characteristic defects.

[Problem to be solved by the invention]

However, in the example shown in FIG. 3, when two electrode fingers break at the same time, as in case C of the electrode finger breaks, no potential is applied to the tip portion 17, resulting in poor characteristics.

Furthermore, in either case, characteristic deterioration due to the sheet resistance of the electrode fingers was unavoidable.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a surface acoustic wave device that prevents characteristic defects due to breakage of electrode fingers and prevents characteristic deterioration due to sheet resistance of electrode fingers. .

[Means to solve the problem]

The present invention provides a surface acoustic wave device in which at least one apodized electrode is used on a piezoelectric substrate, and the apodized electrodes are connected to the same potential by a bus electrode. In addition, as a pattern other than the bus electrode for connecting all dummy electrode fingers to the same potential, there is a connection pattern that connects adjacent electrode fingers along the envelope of the weighting coefficient, and the positions of the adjacent connection patterns are Non-polymerization occurs in the propagation direction of surface acoustic waves, thereby preventing poor characteristics due to breakage of electrode fingers.
This aims to prevent characteristic deterioration due to the sheet resistance of the electrode fingers, thereby achieving the above-mentioned purpose.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a pattern diagram showing an embodiment of a surface acoustic wave device according to the present invention.

In this embodiment, bus electrodes 31 and 32 are provided to bring all the electrode fingers to the same potential. These bus electrodes 31.
A weighted electrode finger 33 and a dummy electrode finger 34 that intersect with electrode fingers of other potentials are connected between the electrode fingers 32 and 32 . Among these weighted electrode fingers 33 and dummy electrode fingers 34, a connection pattern 35 other than the bus electrode is provided in order to connect adjacent tips of electrode fingers having the same length. Furthermore, among the weighted electrode fingers 33 and the dummy electrode fingers 34,
In order to connect adjacent electrode fingers of different lengths, a connection pattern 36 other than the bus electrode is provided. This connection pattern 35, 36 connects electrode fingers of the same potential along the envelope of the weighting coefficient.

Furthermore, the adjacent connection patterns 35 and 36 are connected at positions that do not overlap in the propagation direction of the surface acoustic waves.

In the above configuration, since all adjacent electrode fingers of the same potential are connected by the connection patterns 35 and 36,
Even if a break d occurs in the electrode finger as shown in FIG. 1, or if two electrode fingers break at the same time as in the case e shown in FIG. 1, a potential is applied to the tip portions 37 and 38.
No characteristic defects occur.

For the same reason, the conventional characteristic deterioration caused by the sheet resistance of the electrode fingers can also be improved.

Note that since the connection positions of the connection patterns 35 and 36 do not overlap with the propagation direction of the surface acoustic waves, acoustic reflection of the surface acoustic waves can also be suppressed to a minimum.

According to the embodiment described above, all adjacent electrode fingers having the same potential are connected by the connection patterns 35 and 36, and the connection patterns 35 and 36 are connected in a non-overlapping state in the propagation direction of the surface acoustic wave. , it is possible to prevent characteristic defects due to cuts d, e, etc. of the electrode fingers, and it is also possible to prevent characteristic deterioration due to sheet resistance of the electrode fingers.

〔Effect of the invention〕

As explained above, according to the present invention, all adjacent electrode fingers of the same potential are connected by a connection pattern, and the connection patterns are installed so as not to overlap in the propagation direction of surface acoustic waves, so that the electrode fingers can be disconnected. Excellent effects such as being able to prevent characteristic defects caused by the electrode fingers and preventing characteristic deterioration caused by the sheet resistance of the electrode fingers are achieved.

[Brief explanation of the drawing]

FIG. 1 is a pattern diagram showing an embodiment of the surface acoustic wave device according to the present invention, FIG. 2 is a pattern diagram showing a conventional surface acoustic wave device, and FIG. 3 is a pattern diagram showing another conventional surface acoustic wave device. It is a pattern diagram. 31.32...Bath electrode, 33...Weighting electrode finger (apodized electrode)
, 34...Dummy electrode finger (apodized electrode)
35.36...Connection pattern.

Claims (1)

[Claims] In a surface acoustic wave device configured by using at least one apodized electrode on a piezoelectric substrate that weights the size of the intersection width depending on the location, and connecting the apodized electrode to the same potential by a bus electrode, the weighting electrode finger and the dummy electrode are used. As a pattern other than the bus electrode for connecting all the fingers to the same potential, there is a connection pattern that connects adjacent electrode fingers along the envelope of the weighting coefficient, and the positions of the adjacent connection patterns are elastically arranged. A surface acoustic wave device characterized by non-polymerization in the propagation direction of surface waves.