JPS63228814A - Piezoelectric ceramic oscillator and filter - Google Patents

Abstract

PURPOSE:To improve the temperature characteristics of a filter by securing a non-polarization state for the areas at both ends of a piezoelectric ceramic plate in its longitudinal direction together with a stepped processing part formed at the center area and keeping the vibration energy only in said processing part. CONSTITUTION:The AC voltage is applied between electrodes 11a and 11f with a grounded electrode 11d. No vibration is produced in an area I because this area is not polarized and therefore the area I serves as a mere capacitor. While the width W' of a center area III is smaller than width W of both areas II and IV and therefore the vibrating waves are transmitted only to the area III owing to an energy shut-up function. Then the temperature characteristics of the phase rotary value can be compensated at the center frequency of a filter by securing the desired temperature characteristics for both piezoelectric ceramic vibrators V1 and V2, i.e., the areas II, III and IV as well as a capacitor C1, i.e., the area I respectively.

Description

[Detailed Description of the Invention] [Summary] The present invention provides a timing extraction filter using a piezoelectric ceramic resonator, which has a large coupling coefficient but a large frequency temperature coefficient, and therefore does not have good temperature characteristics. In order to compensate for the drawbacks of the vibrator, the temperature coefficient of the timing extraction filter is improved by utilizing the capacitance of the piezoelectric ceramic itself and its temperature characteristics.

[Industrial application field]

The present invention relates to a piezoelectric ceramic vibrator and a timing extraction filter using the same, and more particularly to a method for improving the temperature characteristics of a timing extraction filter.

[Conventional technology]

For example, a conventional piezoelectric ceramic vibrator as disclosed in JP-A-58-24216 is shown in FIG. 8 (perspective view) and FIG. 9 (plan view). The timing extraction filter used is shown in FIG. This piezoelectric ceramic vibrator has a length l,
It consists of a piezoelectric ceramic plate 20 having a width W and a thickness t, and a concave portion is formed in the central portion of the piezoelectric ceramic plate 20 so that the width W is narrower than the widths on both sides. Metal thin films are formed on both sides of the piezoelectric ceramic plate 20 by vapor deposition or the like, and widthwise slits 23a and 23b from which these metal thin films are removed are formed on one side of the step of the recess (so that they do not overlap each other on both sides). Ru. As a result, two electrodes 21'a and 21b are formed by the metal thin film on one side, and two electrodes 21e and 21d are similarly formed from the metal thin film on the other side.

The arrow 24 indicates the polarization direction of the piezoelectric ceramic plate 20, and the thickness t is
They are polarized in the same direction, forming a width line oscillator.

When the AC voltage 22 is applied between the electrodes 21b and 21c, as shown in FIG.
An electric field is applied to I) to generate longitudinal vibration in the width direction, and vibration energy is concentrated in this central region (II), resulting in a so-called energy-trapped vibrator. Then, the areas at both ends (
I) can be used as a part that supports this vibrator.

In FIG. 10, vl and v2 are piezoelectric ceramic vibrators as shown in FIGS. 8 and 9, and C is a coupling capacitor. This coupling capacitor C is composed of discrete components and determines the bandwidth of the timing extraction filter.

[Problem that the invention seeks to solve]

In the conventional timing extraction filter as described above, the temperature characteristic of the phase amount of the filter is determined by the temperature characteristic of the piezoelectric ceramic vibrator, that is, the piezoelectric ceramic plate 20 itself, resulting in a problem of poor temperature characteristics.

[Means for solving problems]

In order to solve such problems, according to the present invention,
The regions at both ends of the piezoelectric ceramic plate in the length direction are made non-polarized,
A region near the center is polarized in the thickness direction, and a stepped portion whose width is further reduced in the center region of the central region is formed, so that vibration energy is confined only in this stepped portion. A piezoelectric ceramic vibrator is provided.

Furthermore, a timing extraction filter is provided in which the piezoelectric ceramic vibrator is used, a non-polarized region at at least one end thereof is used as a capacitor, a polarized region is used as an exciting portion, and the temperature coefficients thereof are configured to have the same sign.

[For production]

According to the present invention, the non-polarized region is configured as a capacitance (capacitor), the polarized region is configured as an excitation section (piezoelectric ceramic resonator), and by making these temperature coefficients have the same sign, the center of the timing extraction filter The temperature characteristics of the amount of phase rotation in the frequency are compensated, and the temperature characteristics of the filter are improved.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a piezoelectric ceramic vibrator of the present invention.
(a) is a plan view seen from above, (b) is a back view seen from below (back), and (c) is a sectional view.

The piezoelectric ceramic vibrator 1 is long! , width W, thickness P
It consists of a piezoelectric ceramic plate 10 made of ZT (Delcon lead titanate), and a concave portion is formed in the central part of the piezoelectric ceramic plate 10 so that the width W' is narrower than the width on both sides, and the piezoelectric ceramic plate lO Aluminum (A
A thin metal film such as I) or gold (Au) is formed. The above is basically the same as the conventional piezoelectric ceramic vibrator, but in the present invention, two slits in the width direction from which the metal thin film is removed are provided on each surface. That is, a slit 13a is formed on one side of the step of the recess (so that both sides do not overlap each other),
13d, and another slit 13b113C is provided at a position toward the end from these slits.

This allows the three electrodes 11 to be connected by the metal thin film on one side.
a, 11b, and 11C are formed, and three electrodes 11d, 11e, and Iff are similarly formed by the metal thin film on the other side, and regions (1) to (V) sandwiched between these electrodes.
is formed.

The regions (1) and (V) at both ends are non-polarized regions, and (I
The regions f), (III) and (IV) are polarized areas and are indicated by arrow 1.
As shown by 4, they are polarized in the same direction and in the direction of the thickness t. Further, in the region (1) or (V) at both ends, the electrode 11a or 11f on one side is adjacent to (II) or (IV).
) and is electrically connected to the central region (III), and on the other side, the electrode 11c or 11d is cut off from the electrode in the adjacent region by a slit.

Furthermore, in the region (II) or (IV), the electrode 11e or 11b on one side is cut from the electrode in the central region (III) by a slit in the same manner as described above.

In the piezoelectric ceramic vibrator 1 having such a structure, an AC voltage is applied between the electrode 11a and Iff, and the electrode 11d is grounded. Note that the electrode 11c is not grounded, at this time,
A voltage is applied vertically to region (1), but since it is a non-polarized region, vibrations are not excited and it acts as a mere capacitor. On the other hand, (II), (III)
The regions (IV) and (IV) are the polarization part and the vibration excitation part, but since the width W' of the region (III) is smaller than the width W of the regions (■) and (IV), due to the energy trapping effect, Vibration waves propagate only in the central region (III).

That is, in these (If), (III), and (Tl/) regions, the piezoelectric ceramic vibrator operates in the same way as the conventional piezoelectric ceramic vibrator shown in FIGS. 8 and 9. Note that the concave portion, that is, the central region ([[
The width dimension W+ in [), the length β' of the recess, etc. are set to optimal values so that the vibration trapping effect is effectively performed.

FIG. 2 is an equivalent circuit of one piezoelectric ceramic vibrator of the present invention shown in FIG. In Figure 2, this circuit is
It is composed of a resonant part shown by and a parallel-connected capacitor shown by C, but the resonant part V is in the area shown in Fig. 1 (
II), (III) and (rV), and the capacitance C corresponds to the capacitor region (I) in FIG. Figure 3 is an equivalent circuit of a general piezoelectric ceramic resonator, that is, the equivalent circuit of the parts corresponding to regions (II), (III), and (rV), which corresponds to one resonance part V in Figure 2. do.

FIG. 4 shows the basic circuit configuration of an electrically coupled timing extraction filter that combines two piezoelectric ceramic vibrators 1 of the present invention explained in FIG. 1 and one coupling capacitor CK. In FIG. 4, C1 and C2 are capacitors, CK is a coupling capacitor, and Vl and V2 are general piezoelectric ceramic vibrators. The piezoelectric ceramic vibrator 1 of the present invention is a combination of C1 or C2 and vl or v2.

The inventors of this application discovered that in a timing extraction filter circuit as shown in FIG. We have found a scale that compensates for the temperature characteristics of the amount of phase rotation at the center frequency of .

Figure 5 shows a piezoelectric ceramic vibrator V as shown in Figure 4.
Figure 6 shows the temperature characteristics of V2 and capacitor CI.

It shows the temperature characteristics of C2. In the present invention, the signs of the temperature characteristics of the capacitors C1 and C2 match the signs of the temperature characteristics with respect to the frequency of the piezoelectric ceramic vibrators Vl and V2 (both have negative slopes), and the ceramic itself is ferroelectric. Considering that it is a body, this is an application of the principle shown in Figure 4.

That is, as described above, PZT (Delcon lead titanate) is used as the piezoelectric ceramic plate 10 constituting the piezoelectric ceramic resonator, but the absolute value of its temperature coefficient depends on the component ratio of PZT and other externally added materials. It can be changed by adding additives. Further, the temperature coefficient value of the capacitor CL C2 can be similarly changed by changing the component ratio and additives. Therefore,
It is possible to make the temperature characteristics of the piezoelectric ceramic vibrators Vl and V2 and the temperature characteristics of the capacitors C1 and C2 as shown in FIGS. 5 and 6.

As described above, piezoelectric ceramic vibrator V1. The temperature characteristics of V2, that is, regions (II), (III), and (IV) are as shown in FIG. 5, and the capacitor CI.

By setting the temperature characteristics of C2, that is, region (I) as shown in FIG. 6, the temperature characteristics of the phase rotation amount at the center frequency of the filter are compensated, and as shown in FIG. Compared to the conventional timing filter circuit configuration shown in the figure, the temperature characteristics of the filter are improved, and stable characteristics against temperature changes can be obtained.

〔Effect of the invention〕

According to the present invention, the temperature characteristics of a timing extraction filter using a piezoelectric ceramic vibrator are improved, thereby contributing to high stability of the filter. It also leads to an improvement in yield.

[Brief explanation of the drawing]

FIG. 1 shows a piezoelectric ceramic vibrator of the present invention.
(a) is a plan view seen from above, (b) is a back view seen from below (s), (e) is a sectional view, Fig. 2 is an equivalent circuit of the piezoelectric ceramic vibrator in Fig. 1, and Fig. 3 The figure shows an equivalent circuit of a general piezoelectric ceramic vibrator, and FIG. 4 shows two piezoelectric ceramic vibrators 1 of the present invention explained in FIG. 1 and a coupling capacitor CK.
A basic circuit diagram of an electrically coupled timing extraction filter combining one piezoelectric ceramic resonator V1 is shown in Figure 5.
．． Figure 6 is a diagram showing the temperature characteristics of capacitors C1 and C2, Figure 7 is a diagram comparing the filter phase temperature characteristics of the conventional filter and the filter of the present invention, and Figure 8 is a diagram showing the temperature characteristics of V2.
Figure 9 is a perspective view showing a conventional piezoelectric ceramic vibrator, Figure 9 is a schematic plan view showing the conventional piezoelectric ceramic vibrator, and Figure 10 is a circuit of a timing extraction filter using a conventional piezoelectric ceramic vibrator. It is a diagram. ■... Piezoelectric ceramic vibrator 10 of the present invention... Piezoelectric ceramic plates 11a to 11f... Electrodes 133 to 13d... Slits Vl, V2 (V)... Piezoelectric ceramic vibrator CI, C2 (C )...Capacitor CK...
・Coupling capacitor 1, W, t...Length, width, thickness Fig. 1 13a to +3d...Slit Equivalent circuit of the piezoelectric ceramic vibrator of the present invention Part 2 O Equivalent circuit of the piezoelectric ceramic vibrator Part 2 Figure 3: Electrical coupling type timing filter Figure 4: Temperature characteristics of coupling capacitor 5: C, C2 Figure 6:

Claims (1)

[Claims] 1. Regions at both longitudinal ends of the piezoelectric ceramic plate (10) (I
), (V) is in a non-polarized state, and the region (II) near the center,
(III) and (IV) in the thickness direction, and also forms a stepped part with a reduced width in the central region (III), and vibration energy is applied only to this stepped part. A piezoelectric ceramic vibrator configured to confine 2. Electrode layers are formed on both sides of the piezoelectric ceramic plate (10) in the thickness direction, and the electrode layer on one side forms the boundary between the non-polarized region (I) at one end and the polarized region (II) adjacent thereto, A slit (13c, 13d) extending in the width direction is formed at the boundary between this polarized region (II) and the central stepped part (III) to divide it into three parts, and the electrode layer on the other side is connected to the other end. A slit (13b, 13a) and is divided into three parts, and the electrode (11a) on one surface at the one end and the electrode (11f) on the other surface at the other end constitute input/output terminals, and any of these input terminals The piezoelectric ceramic vibrator according to claim 1, wherein the electrode (11d) on one opposite surface is grounded. 3. Regions at both ends of the piezoelectric ceramic plate (10) in the length direction ( I
), (V) is in a non-polarized state, and the region (II) near the center,
(III) and (IV) in the thickness direction, and also forms a stepped part with a reduced width in the central region (III), and vibration energy is applied only to this stepped part. A timing extraction method in which a piezoelectric ceramic vibrator is configured such that the oscillator is confined, a non-polarized region at at least one end of the piezoelectric ceramic vibrator is used as a capacitor, a polarized region is used as an excitation portion, and these temperature coefficients are configured to have the same sign. filter.