JPH04129314A - Piezoelectric resonator - Google Patents

Abstract

PURPOSE:To allow the piezoelectric resonator of one kind of material component to be used as a broad band type and a high output type and to attain miniaturization through the integration of a capacitor to the resonator by providing the piezoelectric resonator and the capacitor to a piezoelectric ceramic board. CONSTITUTION:A piezoelectric resonator 12 and a capacitive component 13 are provided in parallel with a piezoelectric ceramic board 11. The resonator 12 is made up of a couple of resonance electrodes 14, 15 on both sides in the middle of the board 11 opposite to each other, terminal electrodes 16, 17 provided to opposite ends at both sides of the board 11, resonance electrodes 14, 15 on the same side and connecting electrodes 18, 19 connecting the electrodes 16, 17. The capacitive component 13 is so structured that the capacitor electrodes 20, 21 leading to the electrodes 16, 17 along one side ridge on both sides of the board 11 are provided with their tips opposite to each other in the middle of the board 11 and a capacitor part 22 is formed between opposite faces of both the capacitor electrodes 20, 21, and an equivalent circuit is shown in figure.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a piezoelectric resonator, and more particularly to a piezoelectric resonator used as a ceramic discriminator in an FM@=J4 circuit.

<Prior art> Fig. 13 shows an FM demodulation circuit, in which a discriminator 3 is incorporated between a limiter amplifier 1 and a low frequency amplifier 2, and a receiver receives FM radio waves and converts them into sound. Then, the discriminator 3 converts FM (frequency modulation) to AM (amplitude modulation).

By the way, in a ceramic discriminator, if the demodulation pressure voltage is set high (the bandwidth becomes narrow), but as a user's request, one with a wide demodulation bandwidth and one with a high demodulation output voltage is required.

In order to meet this demand, as a single discriminator, (I) the composition of the ceramic material is different, and dF=l F
Line up two systems with narrow and wide r-Fal (bandwidth), or ■ Change the polarization voltage to control the degree of polarization of the ceramic piezoelectric body, and line up two systems with narrow and wide dF.
There are two types available.

In addition, as a discriminator stage, (1) by adding a parallel capacitor to the discriminator,
It can be narrow or wide depending on the circuit constant.

<Problem to be solved by the invention> However, in the case of (I), the above conventional countermeasures:
In addition to using two types of materials, the capacitance of the electrodes does not match the IC, and since the capacitance is controlled by arranging the electrodes in series or parallel, there is a problem that the electrodes become two elements and become larger.

Further, in the above-mentioned method 0, since the ceramic piezoelectric body is not saturated polarized, there is a problem that the variation in dF is very large (and the yield is also deteriorated).

Furthermore, the above means (to) adds a capacitor capacity on the circuit, which increases the number of parts and increases costs.

Therefore, in order to solve the above-mentioned problems, this invention can support a wide band and high output with a single type of piezoelectric ceramic material composition, and can also use a saturated polarization state, which can reduce dF variation, and can also be miniaturized. The purpose is to provide a piezoelectric resonator that can save space.

<Means for Solving the Problems> In order to solve the above problems, the present invention provides a piezoelectric resonator in which a piezoelectric ceramic substrate is provided with at least one resonator portion and at least one capacitor portion. , the resonator portion is formed by providing resonant electrodes facing each other on both surfaces of the piezoelectric ceramic substrate, and terminal electrodes connected from each resonant electrode to opposite ends of the piezoelectric ceramic substrate, and the capacitor portion The device is connected to the terminal electrodes on both sides of the piezoelectric ceramic substrate, and adopts a configuration in which capacitance electrodes are opposed or adjacent to each other on both sides of the piezoelectric ceramic substrate. Since it is provided on a piezoelectric ceramic substrate, the circuit can be simplified and the number of parts can be reduced, and since a saturated polarization state can be used for the piezoelectric ceramic substrate, variations in dF can be reduced.

Furthermore, capacitor electrodes can be easily constructed by soldering them facing each other or simply placing their tips close to each other, without removing polarization.

<Examples> Examples of the present invention will be described below with reference to FIGS. 1 to 12 of the accompanying drawings.
This will be explained based on the diagram.

FIG. 1 shows a first embodiment of the present invention, in which a piezoelectric resonator 12 and a capacitor portion 13 are provided in parallel on a piezoelectric ceramic substrate 11.

The piezoelectric resonator 12 includes a pair of resonant electrodes 14 provided on both sides of the piezoelectric ceramic substrate 11 so as to face each other in the center thereof.
．． 15, terminal electrodes 16.17 provided at opposite ends of both sides of the piezoelectric ceramic substrate 11, and a connection electrode f8.19 connecting the resonant electrode 14.15 and the terminal electrode 16.17 located on the same surface. It is formed.

In the first embodiment of the piezoelectric resonator 12 shown in FIG.
The capacitor portion 13 is provided with capacitor electrodes 20 and 21 connected to the terminal electrodes 16 and 17 along one edge of both sides of the piezoelectric ceramic substrate 11 so that their tips face each other at the center of the piezoelectric ceramic substrate 11. It has a structure in which a capacitive portion 22 is formed between opposing surfaces of capacitive electrodes 20 and 21, and FIG. 2 shows an equivalent circuit similar to the above.

The second embodiment shown in FIG.
The capacitor portions 22 and 22 of the first embodiment are provided on both sides of the capacitor to increase the capacitance value, and FIG. 4 shows an equivalent circuit thereof.

In the third embodiment shown in FIG. 5, the piezoelectric ceramic substrate 11 of the second embodiment is shortened, thereby making it possible to reduce the overall size.

In the first to third embodiments described above, the capacitance value of the capacitor section 22 can be controlled by the opposing areas of both capacitor electrodes 20 and 21.

Further, due to the piezoelectric characteristics of the piezoelectric ceramic substrate 11, the capacitive part 22 also has vibrations, so in order to suppress this vibration, a mass load is applied to the capacitive part 22 with a material such as solder, or Alternatively, vibrations may be suppressed by a partial polarization method in which polarization is applied.

Next, in the fourth embodiment shown in FIGS. 6 to 9, the capacitor portion can be formed without using solder mounding or partial polarization, and the number of man-hours and material costs can be reduced. .

As shown in FIGS. 6 and 9, piezoelectric ceramic substrate 1
Capacitive electrodes 20 and 21 provided on both sides of the piezoelectric ceramic substrate 11 are arranged close to each other with an interval in the center of the piezoelectric ceramic substrate 11, so that a capacitive portion 22 is obtained as a stray capacitance as shown in FIG.

When the material is constant, the stray capacitance value is controlled by controlling the lines of electric force by changing the width a of the capacitive electrodes 21 and 22 and the distance d between the electrodes, as shown in Figure 1O. .

FIG. 11 shows an example of the electrical characteristics (impedance waveform) of the piezoelectric resonator of the present invention, in which the capacitance value of the capacitive part is 2.0.
pF, 4.0pF, 6. As OpF increases, the band (lFr-Fat) becomes 13%, 24%, 31
%is decreasing.

FIG. 12 shows demodulation characteristics, in which the demodulation output increases as the capacitance value of the capacitor section increases.

In this example, C=4. The output is increased by 2.0dB at OpF.

Although the demodulation characteristic data was evaluated using an IC using bridge-balance type detection, the piezoelectric resonator of the present invention can also be used with other types of four-way detection.

<Effects of the Invention> As described above, according to the present invention, piezoelectric resonators and capacitors are provided on two piezoelectric ceramic substrates, so it is possible to support broadband types and high output types with one material composition. Moreover, by integrating the capacitor, it becomes possible to downsize the device and save space for mounting.

Additionally, piezoceramic substrates can use saturation polarization, dF
= l Fr - Fa The variation in Fal can be reduced.

Incidentally, the variation in dF was conventionally σ = 81 KHz, but this invention can reduce it to 115 a = 16 KHz.

[Brief explanation of drawings]

Fig. 1 is a plan view showing the first embodiment of the piezoelectric resonator, Fig. 2 is an equivalent circuit diagram of the above, Fig. 3 is a plan view showing the second embodiment of the same, and Fig. 4 is an equivalent circuit of the above. 5 is a plan view showing the third embodiment, FIG. 6 is a plan view showing the fourth embodiment, FIG. 7 is a front view of the above, and FIG. 8 is an equivalent circuit diagram of the same. , FIG. 9 is a plan view showing an example of the same miniaturized state, and FIG.
11 is a waveform diagram showing an example of electrical characteristics, FIG. 12 is a measurement diagram showing demodulation characteristics, and FIG. 13 is a circuit diagram of the FM demodulation circuit. 11... Piezoelectric ceramic substrate 12... Piezoelectric resonator 13... Capacitor portion 14, 15... Resonant electrode 16.17... Terminal electrode 20, 21... Capacitive electrode 8 patent attorney 1) Figure 13 Figure 3 Figure 4 Figure 5 Figure 15 10 ZZ lj 11 1/ Figure 11 REQ (MHz) Figure 6 tL7 Figure 8 Figure 9 Figure 12 Figure 10.5 10. 6 10.7 10,8 10.9 FREQLIENCY (MHz) 11.0 11.1

Claims (1)

[Claims] A piezoelectric resonator in which at least one resonator part and at least one capacitor part are provided on a piezoelectric ceramic substrate, the resonator part being connected from each resonant electrode to resonant electrodes facing each other on both sides of the piezoelectric ceramic substrate. and terminal electrodes drawn out to opposite ends of the piezoelectric ceramic substrate, and the capacitor portion is connected to the terminal electrodes on both sides of the piezoelectric ceramic substrate, and is opposed to or adjacent to the piezoelectric ceramic substrate on both sides. A piezoelectric resonator characterized by being formed by capacitive electrodes.