JPH03185909A - Piezoelectric resonator - Google Patents

Abstract

PURPOSE:To realize a piezoelectric resonator capable of obtaining a broad band eliminate characteristic by forming the shape of a vibration electrode to be a square whose sides are in parallel with the side ridge of a piezoelectric substrate. CONSTITUTION:Vibration electrodes 2a, 3a and 4a, 4b are formed to be a square in parallel with the side ridge of a piezoelectric substrate 1. Polarization processing is applied to the substrate 1 in parallel with the long side (direction of arrow A), and the thickness-shear vibration mode is caused in the part placed between the vibration electrodes 2a, 3a and 4a, 4b. Moreover, since the vibration electrodes 2a, 3a and 4a, 4b are formed square, the thickness-torsion vibration is stimulated and when the piezoelectric resonator is used for a tap, a band eliminating characteristic is obtained. That is, the high frequency response with respect to the center frequency is increased to attain a bread band and when the resonator is applied to the trap, a broad band trap is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a three-terminal piezoelectric resonator using an energy-trapped thickness-shear vibration mode, and particularly to a piezoelectric resonator suitable for a trap.

[Conventional technology]

Conventionally, a three-terminal piezoelectric resonator that utilizes a thickness-shear vibration mode has been used for audio traps in television receivers, etc. This piezoelectric resonator, as shown in FIG.
Vibrating electrode portions 11a and 12a are provided on one main surface of the piezoelectric substrate 1o, respectively.
Two individual electrodes 11° 12 are provided, and
Two vibrating electrode parts 1 facing the above vibrating electrode part on the other main surface
A common electrode 13 having electrodes 3a and 13b is provided. The vibrating electrode portions 11a, 12a, 13a, 13b
has a circular shape, and when applied to a trap, a band-eliminate characteristic having a large attenuation only at the center frequency f0 can be obtained as shown in FIG.

[Problem to be solved by the invention]

By the way, in order to remove interference signals etc., the center frequency fo
There are cases where it is desired to attenuate a frequency range with a wide range between high and low frequencies to a certain level, but conventional traps with circular vibrating electrodes can only attenuate extremely narrow bands, so they cannot meet such requests. . Furthermore, although it is possible to meet the above requirements by cascading a plurality of traps with different characteristics, this has the drawback of increasing the size of the device and increasing cost.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a piezoelectric resonator that can obtain broadband band 1 elinate characteristics with a single piezoelectric resonator.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a vibrating electrode section having a rectangular shape with each side parallel to the side edges of the piezoelectric substrate.

[Effect]

Generally, the vibrating electrode part has thickness shear vibration (TS mode).
In addition to this, thickness shear vibration (TT mode) is also excited. Thickness shear vibration is excited depending on the distance from the vibrating electrode section to the side edge of the piezoelectric substrate, but with conventional circular vibrating electrode sections, the distance from the electrode end to the side edge of the piezoelectric substrate varies, so the thickness Almost no torsional vibration is excited, and the center frequency is f as shown in FIG. It only produces a small Lusbons on the high frequency side. In contrast, in the present invention, the vibrating electrode part has a rectangular shape with each side parallel to the side edge of the piezoelectric substrate, so the distance from the electrode end to the side edge of the piezoelectric substrate is constant, and the thickness shear vibration is strong. Excited.

As a result, the center frequency f0 caused by thickness shear vibration
It is possible to increase the high-frequency response and achieve a wide band.

In addition, by making the vibrating electrode part square, the center frequency f
The magnitude of the response higher than o and its frequency can be freely set.

〔Example〕

FIG. 1 shows an example of a piezoelectric resonator according to the present invention.

In the figure, a piezoelectric substrate 1 is made of a horizontally long rectangular piezoelectric ceramic substrate, and an output electrode 2.3 is formed on its main surface by sputtering, thin coating, etc., and a common electrode 2.3 is formed on the other main surface. 4 is similarly formed. The output electrodes 2 and 3 include vibrating electrode sections 2a and 3a, and terminal electrode sections 2b and 3b that are electrically connected to the vibrating electrode sections 2a and 3a and extended to the lower end of the piezoelectric substrate l. Further, the common electrode 4 includes two vibrating electrode parts 4a facing the vibrating electrode parts 2a and 3a,
4b, and one terminal electrode portion 4c that is electrically connected to this and drawn out to the lower end of the piezoelectric substrate l. The vibrating electrode parts 2a, 3a and 4a, 4b have a rectangular shape parallel to the side edges of the piezoelectric substrate 1. The piezoelectric substrate l is polarized in a direction parallel to its long side (in the direction of the arrow), thereby forming vibrating electrode parts 2a, 3a, and 4a.
, 4b, a thickness shear vibration mode is generated. In addition, the vibrating electrode portions 2a, 3a and 4a, 4
Since b is square, thickness torsional vibration is also excited,
When this piezoelectric resonator is used as a trap, band elimination characteristics as shown in FIG. 2 or 3 can be obtained.

Fig. 2 shows the shapes of the vibrating electrode parts 2a, 3a and 4a, 4b being elongated, in other words, in the direction of the polarization axis (direction A) of the vibrating electrode parts.
The ratio of the length of the parallel side X to the length of the perpendicular side y is approximately 17
3, and FIG. 3 shows the case where the shapes of the vibrating electrode parts 2a, 3a and 4a, 4b are square, in other words, the ratio of X and y is about 1. As is clear from the figure, x
In the case of /yξ1/3, the high-frequency response of the center frequency f0 due to thickness shear vibration is slightly smaller than the response of the center frequency f0, but in the case of x/yξ1, the high-frequency response of the center frequency f0 is and the response at the center frequency 10 are approximately equal. Further, the frequency f1 that produces a high-frequency response of X/y#1/3 is slightly higher than the frequency f2 that produces a high-frequency response of x/yξ1. In either case, the high-frequency response of the center frequency f0 is larger than that of the circular vibrating electrode section (see Figure 5), and the band
Erigonate characteristics are made broadband.

The polarization axis direction of the piezoelectric substrate 1 is parallel to the long side (direction A)
The direction is not limited to , but may be parallel to the short side, and as long as the ratio of the length of the side parallel to the polarization axis direction of the vibrating electrode part X and the length of the perpendicular side y is the same, similar bands Eliminating characteristics can be obtained. In this case, since the direction of the polarization axis is perpendicular to the direction in which the vibrating electrode sections are arranged, there is a feature that interference between the left and right vibrating electrode sections is reduced, and spurious noise is reduced.

Further, in the above embodiment, an example was shown in which the left and right vibrating electrode portions had the same shape, but they may have mutually different shapes. For example, if one vibrating electrode part is rectangular and the other vibrating electrode part is square, the center frequency f will be as shown by the broken line in FIG. Although the response on the high frequency side is slightly degraded, it has the characteristic that the amount of attenuation in the middle region can be increased.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the vibrating electrode part has a rectangular shape with each side parallel to the side edges of the piezoelectric substrate, so that the vibrating electrode part receives not only thickness-shear vibration but also thickness-shear vibration. Wearing vibrations are also excited, increasing the response in the high frequency range of the center frequency, making it possible to achieve a wide band. Therefore, when the present invention is applied to a trap, a broadband trap can be realized.

[Brief explanation of drawings]

Fig. 1 is a front view of an example of a piezoelectric resonator according to the present invention, Fig. 2 is a band elimination characteristic diagram of a Ti unit with a dimensional ratio x/yξ1/3 of the vibrating electrode part, and Fig. 3 is a diagram of the band elimination characteristic of the vibrating electrode part. FIG. 4 is a front view of the conventional example, and FIG. 5 is a band elimination characteristic diagram of the conventional example. 1... Piezoelectric substrate, 2.3... Input/output electrode, 4...
Common electrode, 2a, 3a, 4a, 4b --- vibrating electrode section.

Claims (1)

[Claims] (1) providing two individual electrodes each having a vibrating electrode portion on one main surface of the piezoelectric substrate, and providing a common electrode having two vibrating electrode portions facing the vibrating electrode portion on the other main surface;
A three-terminal piezoelectric resonator using an energy-trapped thickness-shear vibration mode, characterized in that the vibrating electrode portion has a rectangular shape with each side parallel to a side edge of a piezoelectric substrate.