JPH04216208A - Piezoelectric resonator - Google Patents

Abstract

PURPOSE:To reduce the unnecessary resonance response of a nonconfined mode and to present the compact and low-priced piezoelectric resonator concerning the piezoelectric resonator using a longitudinal thickness higher harmonic energy confining resonator used for a filter or an oscillator. CONSTITUTION:Oscillating electrodes 2 facing the front and back sides are formed on both the main plane central parts of a piezoelectric substrate 1 while being overlapped, and a pair of independent partial electrodes 5 are formed on the counter sides close to these oscillating electrodes 2. Therefore, since oscillation energy is attenuated at the above-mentioned partial electrode parts 5 because of mechanical load as the electrode and the effect of piezoelectric short-circuiting, the piezoelectric resonator can be obtained to reduce the unnecessary resonance response close to thickness longitudinal fundamental resonance.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric resonator using a thick longitudinal harmonic energy confinement type resonator used in filters, oscillators, etc.

0002

[Prior Art] Typical conventional examples are shown in Figs. 3(a) and (
This will be explained below using b). FIG. 6(d) is a plan view showing a piezoelectric resonator using a thickness-longitudinal harmonic energy confinement type vibration mode. This figure shows a state in which the extraction electrode 8 led out from the electrode 7 is connected to the extraction electrode 9 provided at the end.
The entire surface portion was molded with a mold, and a free vibration space 11 was formed on and in the vicinity of the vibration electrode 7.

The thickness vertical harmonic energy confinement mode of the piezoelectric resonator configured as described above is achieved by the free vibration space 11 formed on and near the vibrating electrode 7, which allows the vibration of the vibrating electrode 7 to be unhindered and to be controlled by the electrode. At the same time as the resonance response is performed efficiently, the unconfined mode propagating from the vibrating electrode 7 toward the contour of the piezoelectric substrate 6 is caused by the outer resin 1.
Since the viscosity of zero is turned into thermal energy and attenuated, the reflected wave from the contour is effectively reduced, and unnecessary electrical resonance responses near the resonance frequency other than the fundamental wave and the predetermined thickness vertical harmonic mode are attenuated. It was composed.

0004

[Problem to be Solved by the Invention] However, the conventional voltage resonator described above utilizes only a specific energy trapping mode of the thickness longitudinal harmonic, and in particular, a piezoelectric resonator that utilizes this specific energy trapping mode is When used as an oscillation element, low-order unconfined modes (propagation modes) cannot be sufficiently attenuated, and unnecessary resonance responses occur near the low-order modes at low frequencies.

The present invention disperses this unconfined mode (propagation mode) with a simple structure without adopting an additional method such as molding with the exterior resin 10 explained in the conventional example, thereby reducing the low-order mode. The object of the present invention is to provide a small piezoelectric resonator that can reduce unnecessary resonance responses that occur nearby.

[0006]

[Means for Solving the Problems] In order to solve the above problems, a piezoelectric resonator according to the present invention includes a vibrating electrode that overlaps the central portion of both principal planes of a piezoelectric substrate and faces each other, and an end portion that is led out from the vibrating electrode. Each of the vibration electrodes is provided with an extraction electrode cross-connected to the extraction electrode provided on one side of the vibrating electrode, and a pair of independent partial electrodes are formed on opposing sides close to the vibrating electrode.

[0007]

[Operation] With this configuration, the unconfined mode that propagates from the vibrating electrode part through the main plane and reaches the contour part of the piezoelectric substrate can be transmitted to the mechanical Because the vibration energy is attenuated by the mechanical load and the piezoelectric short circuit effect, it is possible to reduce unnecessary resonance responses near the thickness longitudinal fundamental resonance, and especially when this resonator is used as an initial resonance element, it is possible to reduce the unnecessary resonance response in the low-order mode. oscillation can be controlled.

[0008]

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a perspective view showing a piezoelectric resonator according to the present invention, in which a piezoelectric substrate 1 is polarized in the thickness direction, the fundamental thickness longitudinal mode determined by the thickness t is an unconfined (propagating) mode, and the triple thickness longitudinal mode is an energy confined mode. The piezoelectric substrate 1 is configured to have a constant (Poisson's ratio) that becomes a mode, and although a polarized piezoelectric substrate 1 is used in this embodiment, the scope of application of the present invention is not limited to this. It is also possible to use a piezoelectric single crystal with spontaneous polarization, an oriented film, etc.

A vibrating electrode 2 is formed approximately at the center of the main plane of the piezoelectric substrate 1 by means of vapor deposition, plating, etc. so that the front and back sides are overlapping each other, and an extraction electrode 3 led out from the vibrating electrode 2 is connected to the end portion of the piezoelectric substrate 1. electrode portions each having a cross-connected shape to the extraction electrode 4 provided on one side are formed on the front and back surfaces, and the vibrating electrodes 2 overlap to form a vibration confinement electrode portion;
The extraction electrodes 4 are arranged so as not to overlap.

Further, the shape of the vibrating electrode 2 is circular,
In order to avoid overtone resonance, the diameter D of the vibrating electrode 2 is set to a value whose upper limit is determined by the Beckmann constant determined by the thickness t of the piezoelectric substrate and the amount of frequency reduction Δ, so that the vibration of the third harmonic mode in the thickness longitudinal direction is It is configured to realize a single resonance confined in the vicinity.

A pair of independent partial electrodes 5 were formed on both main planes of the piezoelectric substrate 1 on opposite sides close to the vibrating electrode 2 in a rectangular shape so as to face each other from front to back. This partial electrode 5 may have any shape and size as long as it does not overlap with the area in the vicinity of the vibrating electrode 2 where the triple-thickness vertical harmonic mode is confined and does not come into contact with the extraction electrode 3 and the extraction electrode 4. good.

The function of the partial electrode 5 is that when a high frequency electric field having a frequency close to that which excites the thickness longitudinal fundamental vibration mode determined by the thickness t is applied to the vibrating electrode 2, a propagating wave that is not confined in the vibrating electrode 2 is generated. The vibration energy propagates around the piezoelectric substrate 1 in a cylindrical wave shape, but due to the mechanical load of the partial electrode 5 as an electrode and the piezoelectric short circuit, the vibration energy is absorbed by the partial electrode 5, causing an unnecessary resonance response. It is something that will be reduced.

FIGS. 2(a) and 2(b) are frequency characteristic diagrams showing the relationship between the resonance impedance Z in the vicinity of the thickness longitudinal fundamental vibration mode and the thickness longitudinal triple harmonic mode, and the broken line indicates the piezoelectric resonance according to this embodiment. The solid line indicates a conventional piezoelectric resonator in which the partial electrode 5 is not formed. As is clear from this frequency characteristic diagram, energy confinement is sufficient in the triple-thickness longitudinal mode shown in Figure (b), so there is no difference between the two, but in Figure (d), there is no difference between the two. In the vicinity of the resonant frequency of the thickness longitudinal fundamental mode of the unconfined mode shown in FIG.

[0014]

[Effects of the Invention] As described above, in the piezoelectric resonator according to the present invention, the unnecessary resonance response of the unconfined mode of the thickness vertical harmonic energy confined type vibrator can be suppressed by providing a pair of independent partial electrodes on the piezoelectric substrate. In particular, it is possible to create a small, high-performance piezoelectric resonator without the need to add a separate process to coat it with an exterior resin, or to secure space for this on the piezoelectric substrate. It is of great industrial value as it can be used to obtain

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a piezoelectric resonator according to an embodiment of the present invention.

[Figure 2] (a) Frequency characteristic diagram near the thickness longitudinal fundamental resonance frequency of the same example (b) Frequency characteristic diagram near the thickness longitudinal threefold resonance frequency of the same example

[Figure 3] (a) Plan view showing a conventional piezoelectric resonator (b) Cross-sectional view showing a conventional piezoelectric resonator

[Explanation of symbols]

1 Piezoelectric substrate 2 Vibrating electrode 3 Extraction electrode 4 Takeout electrode 5 Partial electrode

Claims (1)

[Claims] Claim 1: A vibrating electrode is arranged in a pair on both main planes of a plate-shaped piezoelectric substrate. A piezoelectric resonator comprising a pair of independent partial electrodes formed on opposing sides of a piezoelectric substrate close to the vibrating electrode, which are formed so as to overlap each other.