Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2000-03-28
2001-11-06
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S31300R
Reexamination Certificate
active
06313563
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a surface acoustic wave device for use as a resonator and a band filter, and more particularly, the present invention relates to an edge reflection type surface acoustic wave device which utilizes Shear Horizontal (SH) type surface acoustic wave.
2. Description of the Related Art
Edge reflection type surface acoustic wave devices which utilize SH type surface acoustic waves such as BGS (Bleustein-Gulyaev-Shimizu wave) waves, Love waves, leaky waves and other such surface acoustic waves are known. In an edge reflection type surface acoustic wave device, a surface acoustic wave is reflected between a pair of opposite edges of a surface acoustic wave substrate. Therefore, it is not necessary to provide reflectors at both ends of the surface acoustic wave substrate or on both sides in the surface acoustic wave propagation direction of the area in which interdigital transducers are located. Accordingly, a surface acoustic wave device having a reduced size can be provided.
In an edge surface acoustic wave device including a surface acoustic wave substrate made of a piezoelectric single crystal, an unnecessary wave, such as a bulk wave or other undesirable wave, propagating from the surface of the substrate to the inner portion thereof and excited simultaneously with an SH type surface acoustic wave is reflected between the edges of the surface acoustic wave substrate and causes a large ripple to be generated in an attenuation frequency characteristic. For example, a large ripple tends to occur in the top thereof, that is, in the pass band.
SUMMARY OF THE INVENTION
In order to solve the problems described above, preferred embodiments of the present invention provide an edge reflection type surface acoustic wave device in which an SH type surface acoustic wave is utilized, and a ripple appearing in the frequency characteristic is prevented from occurring.
An edge reflection type surface acoustic wave device according to a preferred embodiment of the present invention includes a surface acoustic wave substrate made of a piezoelectric single crystal and having first and second opposite edges, and at least one interdigital transducer located on the surface acoustic wave substrate and being arranged such that a Shear Horizontal type surface acoustic wave is reflected between the first and second opposite edges, wherein the surface acoustic wave substrate is made of an ion-implanted piezoelectric single crystal substrate.
Preferably, the piezoelectric single crystal substrate is made of at least one of a 36° to 41° rotation Y plate LiTaO
3
, a 41° rotation Y plate LiNbO
3
, and a 64° rotation Y plate LiNbO
3
.
As the ions to be implanted, at least one of Ar ions, N ions, Be ions, B ions, and P ions are preferably used, and more preferably, P ions are used.
A method of manufacturing an edge reflection type surface acoustic wave device according to a preferred embodiment of the present invention includes the steps of preparing a surface acoustic wave substrate made of a piezoelectric single crystal, implanting ions into the surface of the surface acoustic wave substrate, forming at least one interdigital transducer on the surface acoustic wave substrate, and cutting the surface acoustic wave substrate in the thickness direction to form first and second opposite edges.
In the method of manufacturing an edge reflection type surface acoustic wave device according to a preferred embodiment of the present invention, preferably, the piezoelectric single crystal substrate includes at least one of a 36° to 41° rotation Y plate LiTaO
3
, a 41° rotation Y plate LiNbO
3
, and a 64° rotation Y plate LiNbO
3
.
Further, in the method of manufacturing an edge reflection type surface acoustic wave device according to a preferred embodiment of the present invention, preferably, as ions to be implanted, at least one of Ar ions, N ions, Be ions, B ions, and P ions are preferably used when the ion implantation is carried out.
More preferably, the above-described ion implantation is carried out under the conditions of an acceleration voltage of about 50 keV to about 150 keV and an ion implantation quantity of about 1×10
4
ions/cm
2
to about 1×10
16
ions/cm
2
.
For the purpose of illustrating the invention, there is shown in the drawings several forms which are presently preferred, it being understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.
REFERENCES:
patent: 5389806 (1995-02-01), Hickernell et al.
patent: 5463901 (1995-11-01), Hachigo et al.
patent: 5952899 (1999-09-01), Kadota et al.
patent: 5977686 (1999-11-01), Kadota et al.
patent: 5986523 (1999-11-01), Morizumi et al.
patent: 6127769 (2000-10-01), Kadota et al.
patent: 63-169806 (1988-07-01), None
patent: 6-303073 (1994-10-01), None
patent: 10-229319 (1998-08-01), None
Ago Junya
Horiuchi Hideya
Kadota Michio
Kawai Hiroshi
Negoro Yasuhiro
Dougherty Thomas M.
Keating & Bennett LLP
Murata Manufacturing Co. Ltd.
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