JP2959147B2 - Surface acoustic wave filter - Google Patents

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 for use in video equipment, communication equipment, etc., which suppresses generation of bulk waves.

[0002]

2. Description of the Related Art A conventional surface acoustic wave filter will be described below.

As shown in FIG. 3, a comb-shaped input electrode 2 and an output electrode 3 are arranged on a piezoelectric substrate 1, and the piezoelectric substrate 1 is mounted on a stem 6, and a method such as wire bonding is used. And is electrically connected to the terminal 7. When a surface acoustic wave passes through an electrically or acoustically discontinuous point in the course of propagation, a part of it is converted into a bulk wave, so that a ground electrode 9 is provided between the input side electrode 2 and the output side electrode 3. Arranged and connected to earth 10.

[0004]

However, in the above-described conventional configuration, a bulk wave is easily generated at the end of an electrically or acoustically discontinuous ground electrode during the propagation of a surface acoustic wave, so that the influence of the bulk acoustic wave is generated. Although measures are taken to make the back surface of the piezoelectric substrate as uneven as possible, such as to reduce as much as possible, there is a problem that it is insufficient and a problem that the cost is increased.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a surface acoustic wave filter which suppresses generation of a bulk wave on an electrode pattern and has good frequency characteristics.

[0006]

[MEANS FOR SOLVING THE PROBLEMS] To achieve this object
The surface acoustic wave device according to the present invention includes a piezoelectric substrate and a piezoelectric substrate.
Comb-shaped input / output electrodes provided on a flexible substrate
Continuous with the tooth row of the input and output electrodes provided between the force side electrodes
And a grid-like electrode disposed in the grid.
Hot electrode for the input and output electrodes
A floating electrode whose adjacent part is not connected to the ground
It is what it was.

[0007]

According to this configuration, generation of bulk waves and input-side power
By sufficiently suppressing the jump between the pole and the output side electrode,
In the process of surface acoustic wave propagation, electrical or acoustic
Continuous parts can be eliminated. In addition, the input and output power
Since the part adjacent to the hot electrode of the pole was a floating electrode,
Elastic surface between input or output electrode and grid electrode
It is possible to prevent a wave from being generated and changing the frequency characteristics. Obedience
Thus, the above object can be achieved.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. 1 and 2 showing the embodiment of the present invention, the same parts as those of the conventional example are denoted by the same reference numerals, and description thereof will be omitted. As shown in FIG. 1, a grid electrode 4 is provided between the input electrode 2 and the output electrode 3.

With this configuration, even if the surface acoustic wave generated from the input side electrode 2 reaches the end of the input side electrode 2, the grid electrode 4 is substantially continuously arranged with the input side electrode 2. The light passes through the grid electrode 4 without being converted into a bulk wave and reaches the output electrode 3. In addition, since the grid electrode 4 and the output side electrode 3 are also substantially continuously arranged, almost no bulk wave is generated here. In addition, by connecting the grid electrode 4 to the ground 8, the jump between the input electrode 2 and the output electrode 3 can be suppressed.

Further, by adjusting the period of the grid electrode 4 to a wavelength of a predetermined trap frequency, a surface acoustic wave is confined in the grid electrode 4, and the trap can be further deepened and improved.

Also, the input and output electrodes of the grid-shaped electrode 4 are used.
Float the part adjacent to the reset electrode without connecting it to earth.
The electrode 5 on the input side or the electrode on the output side
The generation of surface acoustic waves between the pole 3 and the grid electrode 4 is prevented.
Can be stopped.

[0012]

According to the present invention, the generation of bulk waves and
Sufficiently prevent jump between input and output electrodes
Can generate electric or sound in the process of surface acoustic wave
It is possible to eliminate acoustically discontinuous points. In addition,
The part of the output side electrode adjacent to the hot electrode is not connected to ground.
Since the floating electrode is in the connected state, the input side electrode or output
A surface acoustic wave is generated between the side electrode and the grid electrode,
A change in sex can be prevented.

[Brief description of the drawings]

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

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

FIG. 3 is a schematic plan view of a main part showing a configuration of a conventional surface acoustic wave filter.

[Explanation of symbols]

 2 Input electrode 3 Output electrode 4 Grid electrode

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H03H 9/145, 9/25, 9/64

Claims (2)

(57) [Claims] A piezoelectric substrate provided on the piezoelectric substrate;
Provided between the comb-shaped input and output electrodes and the input and output electrodes
The input and output electrodes are arranged in a grid pattern
Electrodes, which are connected to ground.
And the part of the input and output electrodes adjacent to the hot electrode
A surface acoustic wave filter which is a floating electrode not connected to the ground . 2. The method according to claim 1, wherein the grid electrode has a predetermined trap frequency.
The surface acoustic wave filter according to claim 1, wherein the frequency is adjusted to the length .