JPS603247B2 - piezoelectric vibrator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric vibrator, and particularly to a piezoelectric 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 vibrator 1 has an electrode 12 formed on one main surface of a pressure plate 11 such as PZr, 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. The one shown in FIG. 3 is a so-called three-terminal type vibrator in which the electrode 15 formed on the other main surface of the compression box plate 11 is a dot electrode, and the electrode 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 oscillator shown in FIG. 3, which is used in an intermediate frequency circuit of an AM band radio receiver, as an example of a conventional square plate type pressure fin oscillator using spreading vibration. .

As can be seen from this graph, in the conventional device, spurious waves such as the third harmonic or the fifth harmonic of the fundamental vibration frequency are extremely large, which has been a problem. For example, third harmonics are generated as shown in FIG.
That is, it is generated when a standing wave with a frequency three times the fundamental vibration is placed in the spreading direction of the electric plate 11. Therefore, as a method to suppress such spurious signals,
For example, as shown in FIG.
As 3a, it is known to take measures to prevent such standing waves from appearing. In other words, if the partial electrodes 12a and 13a 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. . By appropriately changing the dimensions and shape of the partial electrodes in this way, 5
Third harmonics, seventh harmonics, contour vibration spurious, etc. can also be suppressed. 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. Also, for other characteristic requirements,
In some cases, it may not be possible to arrange electrodes that take only spurious suppression into consideration. 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 uses a piezoelectric plate of a Shoden vibrator as a parallelogram, and the ratio of the long side to the short side of the parallelogram is 0.7 to 0. This is a piezoelectric vibrator that is uneven and one of the angles formed by the two sides is selected to be from 75o to 8y.
FIGS. 7 to 10 are plan views showing different embodiments of the present invention, and simply show the shape of the pressure crab plate.

7 corresponds to FIG. 1, FIG. 8 corresponds to FIG. 2, and FIGS. 9 and 10 correspond to FIG. 3. In this invention, the shape of the main surface of the piezoelectric plate is not a square as in the conventional case, but a parallelogram. Then, the ratio of the length a of the longest side of the parallelogram to the length b of the short side is b/a
=0.7 None, and 0. Select speckled. At the same time, one of the angles formed by the two sides of the parallelogram is 0 = 75o to 8
Choose 90. FIG. 11 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. 11 indicates the frequency of fundamental vibration, for example, 45 Hz. And line B is its third harmonic, for example 1
．． 2M, and line C indicates its fifth harmonic, for example 2. Line D shows contour vibration, for example, 650 kHb, and line E shows bending vibration, for example, 300 kHz. Also,
FIG. 12 is a graph in which the rectangular axis represents such an angle of 0, and the ratio dB between the anti-resonant resistance and the resonant resistance is represented on the vertical axis.

The line A' in FIG. 12 is the frequency of the fundamental vibration, for example, 45
Indicates water Hz. Line B' indicates the third harmonic, for example 1.2M, and line C' indicates the fifth harmonic, for example 2.2M. MHz, and the line D' represents the contour vibration, for example, 650 MHz.
k& and line E indicates bending vibration, for example, a 300k ratio.
As can be seen from these FIGS. 11 and 12, the shape of the main surface of the piezoelectric plate is a parallelogram, and the ratio b/a of the length a of the long side to the length b of the short side is 0.7. 0. Choose a spot, and one angle o between the long side and the short side is 75o to 89
It can be seen that by selecting 0, almost all spurious vibrations can be effectively suppressed.

FIG. 13 shows the frequency characteristics when the present invention is applied to the three-terminal piezoelectric vibrator shown in FIG. 9 or 10, for example.
The side ratio b/a is, for example, 0.96, and the angle 8 is, for example, 87. I'm taking it to y.

Looking at FIG. 13, it can be seen that the present invention can suppress all harmonics more effectively than the subordinate one (FIG. 4). The same applies to contour vibrations (Figures 11 and 12), and no matter what electrode structure (for example, Figures 7, 8, 9, or 10), the same This has the effect of suppressing spurious vibrations. Furthermore, Figures 11 and 12
As can be seen in the figure, there is an effect of suppressing spurious vibration even when the side ratio b/a is 0.7 or less and the angle is 750 or less, but if the 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.
For me, I chose the angle 0 from 750 to 8 degrees. 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 a parallelogram,
The ratio of the longest side to the shortest side is 0.7 or 0.98, and the angle between the two sides is between 750 and 89.
By selecting 0, all harmonics can be effectively suppressed.

Note that it goes without saying that the electrode structure formed on such a piezoelectric plate may have any shape other than the shapes shown in FIGS. 7 to 10 of the embodiment, and the main point is that The main surface of the piezoelectric 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 is made of a uniform material because it is easier for vibration to occur. Therefore, if the outer shape and dimensions of the piezoelectric plate are changed as in this invention, it will also affect the fundamental vibration and the spurious, but in any case, the fundamental vibration is limited to the maximum 4 dimensions that the wavelength can ride on. It is sufficient if there is
Changing the external shape or dimensions has little effect on the fundamental vibration. On the other hand, spurious vibrations such as 3rd harmonics and 5th harmonics naturally have shorter wavelengths than fundamental vibrations, and the effects of changes in 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]

FIGS. 1 to 3 are illustrative diagrams showing different examples of square piezoelectric vibrators that utilize spreading vibration of a slave, which is 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. FIG. 5 is a diagram showing an example of third harmonics. FIG. 6 is a diagram showing an example for suppressing the third harmonic. 7 to 10 are planar illustrative views showing different embodiments of the present invention, respectively. 11th
The figure is a graph showing the characteristics of antiresonance resistance/resonance resistance with respect to the side ratio b/a. FIG. I2 is a graph showing the characteristics of anti-resonance resistance/resonance resistance for an angle of 0. FIG. 13 is a graph showing frequency characteristics when, for example, the embodiment of FIG. 9 or 10 is used in an AM band intermediate frequency circuit. In the figure, 1 is a piezoelectric vibrator, 11' is an indentation plate, 13' is a full-surface electrode, 14' is a partial electrode, 15', 15
r indicates a dot electrode, and 16' and 16'' indicate a ring electrode. Tuko'3 figure

Claims (1)

[Claims] 1 A piezoelectric vibrator that utilizes the spreading vibration of a piezoelectric plate whose main surface has a parallelogram shape, and the ratio of the length of the long side to the length of the short side of the parallelogram is 0.7 to 0. .9
8, and one of the angles formed between the long side and the short side of the parallelogram is 75° to 89°.