JPH01231511A - Piezoelectric resonator - Google Patents

Abstract

PURPOSE:To omit a damping resistance which is used as an individual parts by setting the distance between a vibrating electrode part and an external connecting part at the value less than four times as much as the thickness of a piezoelectric substrate. CONSTITUTION:A vibrating electrode part A is formed at the center part of a strip-shaped piezoelectric substrate 1 with the short side part defined as an external connecting part B. The distance between both parts A and B is set at the comparatively small value less than four times as much as the thickness of the substrate 1. That is, the distance between the parts A and B is set at L together with the thickness of the substrate 1 set at (t) respectively. Thus in case of L<4t, the part B functions as a damping resistance with reduction of L and the effect of the dimpling resistance increases in terms of an exponential function. As a result, the part B, i.e., an end part of the substrate 1 functions as an equivalent damping resistance. Then the control of the phase characteristics, etc., is possible to the frequency of a piezoelectric resonator. Thus it is not required to add a special individual parts to the outside.

Description

DETAILED DESCRIPTION OF THE INVENTION (Al Industrial Field of Application) This invention relates to an energy-trapped thickness-shear vibration mode piezoelectric resonator.

(bl Conventional technology) So-called energy-trapped thickness-shear vibration in which electrodes are attached to both main surfaces of a strip-shaped piezoelectric substrate from the short sides to the center, and some of the electrodes are opposed to each other at the center of the piezoelectric substrate. Mode piezoelectric resonators are used as piezoelectric filters, ceramic discriminators, etc.

An example of its application as a ceramic discriminator is shown below. Figure 2 shows the conventional general Ordrecher type F.
It is a block diagram of an M detection circuit.

In the figure, 1 is a limiter circuit that amplifies the FM signal SIF and outputs a signal with a constant amplitude, 3 is a capacitor that together with 4 constitutes a phase shift circuit, and 4 is a resonant circuit including a piezoelectric resonator. The output signal of the limiter circuit 1, in which the capacitor 3 and the resonant circuit 4 constitute a phase shift circuit, is shifted by 90 degrees at the FM carrier frequency. The frequency-shifted FM signal undergoes a phase change by this phase shift circuit. A multiplication circuit 5 calculates the product of the output signal e1 of the limiter circuit 1 and the output signal e2 of the phase shift circuit, and outputs a signal with a pulse width corresponding to the phase difference between el and e2. 6 is a low-pass filter, which filters only the low frequency of the output signal of the multiplication circuit 5. This signal is amplified by the amplifier circuit 7 to obtain an FM detected signal. FIG. 3 shows a general configuration of the resonant circuit 4. As shown in FIG. Here, X is a piezoelectric resonator, L is an extension coil, and R is a damping resistor.

te1 Problems to be Solved by the Invention When using the phase characteristics of a piezoelectric resonator with respect to frequency as in the above example, a damping resistor was required to correct its linearity.

An object of the present invention is to provide a piezoelectric resonator that does not require a damping resistor as an individual component used together with the piezoelectric resonator.

(Means for Solving Problem d1) The piezoelectric resonator of the present invention has electrodes attached to both main surfaces of a strip-shaped piezoelectric substrate from the short sides to the center, and one of the electrodes is attached at the center of the piezoelectric substrate. In a piezoelectric resonator in which the electrodes located on the short sides of the piezoelectric substrate form a vibrating electrode portion facing each other and the external connection portion is an electrode located on the short side of the piezoelectric substrate, the distance between the vibrating electrode portion and the external connection portion is determined by the thickness of the piezoelectric substrate. 4
It is characterized by being less than twice that.

te1 action In the piezoelectric resonator of the present invention, a vibrating electrode part is formed in the center of a strip-shaped piezoelectric substrate, and the short side part is used as an external connection part. Since the distance between the vibrating electrode part and the external connection part is relatively short, less than four times the thickness of the piezoelectric substrate, the thickness shear vibration of the vibrating electrode part is subjected to a damping effect by the external connection part. That is, since the external connection portion is connected to the outside by a method such as soldering, mass is added. This additional mass equivalently acts as a damping resistance.

(G) Embodiment FIG. 1 is an external perspective view of a piezoelectric resonator which is an embodiment of the present invention. In the figure, 1 is a strip-shaped piezoelectric substrate, which is polarized in the long side direction. 2a and 2b are piezoelectric substrates 1
The electrodes are attached to both main surfaces of the piezoelectric substrate from the short sides to the center, and part of the picture electrodes are opposed to each other in the center of the piezoelectric substrate. This opposing portion A becomes a vibrating electrode portion. 4a and 4b are solder resists printed on the electrodes 2a and 2b, and the ends of the shorter sides of the solder resists serve as external connection parts B. 3a and 3b are solders for external connection, and their positions are regulated by solder resists 4a and 4b.

In the piezoelectric resonator shown in FIG. 1, if the distance between the vibrating electrode part A and the external connection part 8 is L, and the thickness of the piezoelectric substrate is used, then there is a vibrating free part that satisfies L>4t. If it exists, the thickness shear vibration near the vibrating electrode portion A is not damped. Conversely, when the condition L<4t is satisfied, the external connection portion acts as a damping resistance as L decreases, and its effect increases exponentially. Therefore, when the piezoelectric resonator is used as a ceramic discriminator as shown in FIG. 2, the dimension of L is set so that the phase characteristic with respect to the frequency of the piezoelectric resonator becomes linear. This eliminates the need for a damping resistor as an external component.

In addition, the dimensions of the facing width of the electrodes constituting the vibrating electrode part A are as follows:
The value is set to such a value that sufficient thickness shear vibration is excited in the vibrating electrode portion A and that high-order vibration modes are unlikely to occur.

+g1 Effects of the Invention As described above, according to the present invention, the external connection portion, which is the end of the piezoelectric substrate, acts as an equivalent damping resistance, so it is possible to adjust the phase characteristics with respect to the frequency of the piezoelectric resonator, etc. There is no need to add special individual parts externally for this purpose.

This makes it possible to reduce costs and save space.

[Brief explanation of the drawing]

FIG. 1 is an external perspective view of a piezoelectric resonator according to an embodiment of the present invention, FIG. 2 is a block diagram of an FM detection circuit using a piezoelectric resonator as a ceramic discriminator, and FIG. A circuit diagram of the block is shown. 1-Strip-shaped piezoelectric substrate, 2a, 2b-electrodes, A-vibration electrode section, B-external connection section. Applicant: Zaiyo Seisakusho Co., Ltd.

Claims (1)

[Claims] (1) Electrodes are applied from the short sides to the center of both main surfaces of the strip-shaped piezoelectric substrate to form a vibrating electrode section in which some of the electrodes face each other at the center of the piezoelectric substrate, and In a piezoelectric resonator whose external connection is an electrode located on the short side of the substrate, the distance between the vibrating electrode and the external connection is 4 times the thickness of the piezoelectric substrate.
A piezoelectric resonator characterized in that the piezoelectric resonator is less than twice as large.