JPS603245B2 - piezoelectric vibrator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric vibrator, and particularly to a Shoelectric vibrator that utilizes spreading vibration.

FIGS. 1 to 3 are illustrative views showing different examples of conventional square plate type vibrators using spreading vibration, which are the background of the present invention.

Such a pressure eagle vibrator 1 has an electrode 12 formed on one main surface of a fin plate 11 such as PZT, and an electrode 13 formed on the other main surface. The vibrator 1 shown in FIG. 2 shows an example in which the electrode 14 formed on the other main surface of the piezoelectric plate 11 is a partial electrode. What is shown in Fig. 3 is the pressure fin plate 1.
A so-called three-terminal type vibrator is shown in which electrode 15 formed on the other main surface of 1 is a dot electrode, and 16 is a ring electrode. The principles of operation of these piezoelectric vibrators are already well known, and their explanation will be omitted here. FIG. 4 is a graph showing the frequency characteristics of the vibrator shown in FIG. 3, which is used in an intermediate frequency circuit of an AM band radio receiver, for example, as an example of a conventional square plate type pressure-turtle vibrator that utilizes spreading vibration. .

As can be seen from this graph, in the secondary model, the spurious waves such as the 3rd harmonic or 5th harmonic of the fundamental vibration frequency were extremely large, which caused a problem for me. For example, third harmonics are generated as shown in FIG.
That is, it is generated by a standing wave having a frequency three times that of the fundamental vibration in the direction in which the pressure fin plate 11 spreads.
Therefore, as a method of suppressing such spurious, the electrodes are, for example, as shown in FIG.
13', it is known to take measures to prevent such standing waves from appearing. In other words, if partial electrodes 12' and 13' are used as shown in Fig. 6, the surface charge in the shaded area in the surface charge distribution in Fig. 6 is canceled out, and the oscillation of the third harmonic is suppressed. It is. By appropriately changing the dimensions and shape of the partial electrodes,
It is also possible to suppress fifth-order harmonics, seventh-order harmonics, contour vibration spurious, etc. However, with this method, only a single target spurious (for example, only the third harmonic) is suppressed, and many spurious cannot be suppressed at the same time. Furthermore, due to other characteristics requirements, it may not be possible to arrange the electrodes in consideration only of spurious suppression. Therefore, a primary objective of the present invention is to provide an improved spreading vibration piezoelectric vibrator that is effective against all spurs.

To summarize, this invention has a piezoelectric plate of a piezoelectric vibrator having a rectangular shape, and the ratio of the longest side to the shortest side of the rectangle is 0.7 to 1. This is a piezoelectric vibrator that was selected to be useful. FIG. 7, FIG. 8, and FIG. 9 are plan views showing different embodiments of the present invention, and simply show the shape of the piezoelectric plate.

7 corresponds to FIG. 1, FIG. 8 corresponds to FIG. 2, and FIG. 9 corresponds to FIG. 3. In this invention, the shape of the main surface of the piezoelectric plate is not square as in the prior art, but rectangular. And the length of the long side of the rectangle is a
and short side length b: b/a: 0.7, 0.9
Choose 8. FIG. 10 is a graph in which the axis is this side ratio b/a and the vertical axis is the ratio dB between the anti-resonant resistance and the resonant resistance.

Line A in FIG. 10 indicates the frequency of the fundamental vibration, for example 45 z. And line B is its third harmonic, for example 1
．． 2M ratio, and line C represents its fifth harmonic, for example 2. ■
The line D shows the contour vibration, for example, a 650k ratio, and the line E shows the bending vibration, for example, a 300k ratio. This first
As can be seen from Figure 0, almost all spurious vibrations can be effectively suppressed by setting the side ratio b/a from approximately 1.7 to 0.98. FIG. 11 shows the frequency characteristics when the present invention is applied to the three-terminal piezoelectric vibrator shown in FIG. 9, for example, and the side ratio b/a
is set to 0.96, for example.

If you look at this Figure 1, compared to the conventional one (Figure 4),
It can be seen that the invention can effectively suppress all harmonics. The same is true for contour vibration (Figure 10), and no matter what electrode structure (for example, Figure 7, Figure 8, or Figure 9), it has the same effect of suppressing spurious vibration. It is something. As can be seen in Fig. 10, spurious vibrations can be suppressed even when the side ratio b'a is 0.7 or less, but if this side ratio b/a is too small, the workability becomes poor and the case The structure to be incorporated into the system becomes complicated.

At the same time, a resonance splitting phenomenon occurs, which is not preferable. Therefore, in this invention, the side ratio b/a is set from 0.7 to 0.
I chose it as 98. Note that the present invention can be used in a resonator, a three-terminal filter, a ladder type filter, and the like.

As described above, according to the present invention, the shape of the main surface of the piezoelectric plate is rectangular,
By selecting the ratio of the shortest side to 0.7 to 0.98, all harmonics can be effectively suppressed.

Note that it goes without saying that the electrode structure formed on the piezoelectric slope may have any other shape other than the shapes shown in FIGS. 7 to 9 of the embodiment, and the point is that The main surface of the plate is selected to have the shape described above. Conventionally, such a piezoelectric vibrator has a square shape because it is symmetrical when viewed from the vibration mode point and vibration is more likely to occur when the material is uniform. Therefore, if the external shape and dimensions of the pressure plate are changed as in this invention, it will also affect the fundamental vibration and spurious, but in any case, for the fundamental vibration, there is a minimum dimension on which the wavelength can ride. Therefore, changing the external shape and dimensions has little effect on the fundamental vibration. On the other hand, spurious vibrations such as third-order harmonics and fifth-order harmonics naturally have shorter wavelengths than fundamental vibrations, and the effects of changing the shape and dimensions appear more strongly than on fundamental vibrations. A feature of the present invention is that the optimum external dimensions are selected based on the balance between the basic vibration and the spurious vibration.

[Brief explanation of drawings]

1 to 3 are illustrative views showing different examples of conventional square piezoelectric vibrators using spreading vibration, which are the background of the present invention. FIG. 4 is a graph showing an example of frequency characteristics when the three-terminal piezoelectric vibrator shown in FIG. 3 is used in an AM band intermediate frequency circuit, for example. FIG. 5 is a diagram showing an example of third harmonics. FIG. 6 is a diagram showing an example of suppressing the third harmonic. 7 to 9 are planar illustrative views showing different embodiments of the present invention, respectively. FIG. 10 is a graph showing the characteristics of the anti-resonant resistance and the resonant resistance with respect to the side ratio b/a. FIG. 11 shows, for example, the embodiment of FIG.
It is a graph showing frequency characteristics when used in an M-band intermediate frequency circuit. In the figure, 1 is a piezoelectric vibrator, 11
Hasho electric board, 12 and 13 are full electrodes, 14 are partial electrodes, 1
5 is a dot electrode, and 16 is a ring electrode. Hook drawing, Z drawing, 3 drawings, bowl drawing, Atsushi drawing, 7 drawings, 8 drawings, 9 drawings, Atsushi. Illustration

Claims (1)

[Claims] 1 A piezoelectric vibrator that utilizes the spreading vibration of a piezoelectric plate whose main surface has a rectangular shape, the ratio of the length of the long side of the rectangle to the length of the short side of the rectangle being 0.7 to 0.98. A piezoelectric vibrator that is characterized by: