JPS5859619A - Piezo-electric filter utilizing higher order width vibration - Google Patents

Abstract

PURPOSE:To minimize the size of the titled filter by utilizing higher order width vibrations. CONSTITUTION:Prescribed electrodes are installed to one face of a piezo-electric porcelain strip 10 which is polarized in the direction of width in the case of width-length vibration and in the direction of length in the case of side slipping vibration. When the second mode is to be utilized, to suppress the third and forth modes, the center of the gap (g1) between the electrodes 11 and 12 is brought to a location where the stress of the third mode becomes 0 (zero), as shown in (a). Moreover, when the gap between the electrodes 12 and 13 is represented as (g2) and that between the electrodes 13 and 14 is represented as (g3), centers of the gaps (g2) and (g3) are brought to locations where the stress of the forth mode is 0 (zero). In the same way, when the third mode is to be utilized, the second, forth and fifth modes are suppressed by arranging the electrodes as shown in (b). Moreover, when the forth mode is to be utilized, the third, fifth and sixth modes are suppressed, by arranging the electrodes as shown in (c).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric filter used in a short wave band of several MHz or more, and in particular, an object of the present invention is to provide an energy trap type piezoelectric filter that uses a high-order width vibration mode of a piezoelectric strip. shall be.

Conventionally, various vibration modes have been used in piezoelectric filters, so-called ceramic filters, depending on the application, such as the frequency and fractional bandwidth used. Frequency is several MH
In the case of z or less, a vibrating lard in which a sheet metal body vibrates, such as contour vibration of two circular plates or square plates, or length vibration of a rectangular wave, is used.

- When the wave number on the blade side is from several MHz to several tens of MHz, a so-called energy confinement vibration mode is used in which vibration energy is locally concentrated in the center of the piezoelectric magnetic plate.

In the former type of filter that uses contour vibration or length vibration, the element is supported and the electrical terminals are taken out by pressing a metal terminal plate with small protrusions on the vibration node, or by using a thin lead wire at the vibration node. However, with the pressure welding method, there are reliability problems such as peeling of the electrode at the pressure welding part and poor contact due to mechanical vibration, while the soldering method requires the soldering work. In addition to being difficult, it also had the disadvantage of having a large degree of dispersion and stiffness due to the support.

On the other hand, in the latter type of filter that uses energy trapping, the connection with the lead terminal is made by soldering at the edge of the board, which has little effect on vibration, so the characteristic A highly reliable filter with less interference can be obtained. but.

This is because conventional energy confinement resonators utilize a thickness vertical mode or a thickness shear mode.

The resonant frequency is determined by the thickness of the ceramic substrate. Therefore, if you try to lower the resonant frequency.

The thickness of the substrate increases, and the external dimensions increase in proportion to this. ◎For this reason, the applicable frequencies for energy confinement are limited to the HF and VHF bands of several MHz' or higher, and are limited to frequencies below several MHz' Jfi. It has been considered difficult to realize energy confinement filters for medium wave bands.

As a solution to such problems, the present inventors have
Patent Application No. 55-36960 and Patent Application No. 56-3'6
In No. 961, he proposed a filter that utilizes the width vibration of a thin piezoelectric strip, and showed that it was possible to realize a compact piezoelectric filter for medium wave bands.

This also utilizes low-order fundamental width vibrations, and therefore the upper limit of the applicable frequency was about 2 to 3 FvIHz.

The present invention c.' Utilizes higher-order width vibration to
The purpose of this invention is to provide a compact piezoelectric filter suitable for shortwave bands of Hz or higher.

There are an infinite number of high-order width vibrations in IJzo. In these less-order and high-ρ modes, the thickness vibration and resonance frequency approach or overlap, so the practically useful modes are low-order, second-order, third-order φ, and fourth-order modes. it is conceivable that. less than,
A single mode filter and a multimode filter will be described as energy confinement filters of the present invention that utilize modes of these orders.

First, the configuration of a single mote filter according to the present invention will be explained as follows.
As shown in FIG.

FIG. 1 shows the case where high-order width longitudinal vibration and high-order width vertical vibration using the piezoelectric longitudinal effect are used, and FIG. 2 shows the case where the high-order width longitudinal vibration using the piezoelectric transverse effect is used.

In each figure, (a), (b), and (e) are quadratic and cubic, respectively.

The configuration when using the 4th mode is shown. In the case of width-longitudinal vibration in Fig. 1, in the case of widthwise one-width shear vibration, a piezoelectric ceramic (piezoelectric ceramic) polarized in the length direction is used.
An electrode as shown in the figure is provided on one side. Symbols in the diagram, 1
1 and 13.15 and 17.19 and 21 are input/
This is the output side electrode.

Furthermore, 12, 14, 16, 18, 20, and 22 are drawn out and connected to the peripheral portion by a common electrode. Electrodes 11-22
A dash is attached to each peripheral extraction electrode corresponding to the . 1 and 2 are input/output lead terminals, and 3 is a grounding lead terminal.

In this filter, other width vibrations having a different order N from the mode of use become spurious, so in practical use it is necessary to use electrodes that suppress this. A specific example of such an electrode configuration will be described below.

First, in the case of using the second-order mode as shown in FIG. let Further, if the gap between electrodes 12 and 13 is g2, and the gap between electrodes 13 and 14 is g3, then
The centers of gaps g2 and g3 are aligned at the position where the stress of the fourth mode is O.

In the case of using the third-order mode in the same figure (b), in order to suppress the second-order, fourth-order, and fifth-order modes, as shown in the figure,
The center of the gap g1 is aligned with the center of the plate width where the stress in the second and fourth modes is zero, and the centers of the gaps g2 and g3 are aligned with the position where the stress in the fifth mode is zero. Furthermore, the first
In Figures (a) and (b).

The magnitudes of g2 and g3 are adjusted so that the driving forces for the primary (fundamental) mode cancel each other out.

Try to suppress the primary mode.

In addition, in the case of using the fourth mode as shown in Fig. 1(c), the third mode,
In order to suppress the 5th and 6th modes, the center of the gap g1 is made to coincide with the position where the stress of the 3rd and 6th modes is 0,
The electrodes are formed so that the centers of the gaps g2 and g3 are aligned with the position where the fifth-order mode stress is zero. Furthermore, +gz
and g3 are adjusted so that the driving forces for the secondary mode cancel each other out, thereby suppressing that mode.

By employing the electrode configuration as described above, it is possible to achieve good characteristics with less spurious.

In the case of width-longitudinal vibration using the piezoelectric transverse effect shown in Fig. 2, the excitation electric field is applied in the thickness direction, so
It is provided in a portion corresponding to the gap gt + g2 + ga in the figure, and its width is bleb2 rb3. In this configuration, the spurious of this width vibration is also suppressed and good filter characteristics are realized.

Next, as a specific example of a multi-mode filter using high-order width vertical vibration utilizing piezoelectric transverse effect, a configuration for a dual mode is shown in FIG. (a) and (b) in the figure.

(C) shows the case of using the secondary, tertiary, and quartic modes, respectively. In this multimode filter.

As shown in the figure, the central part of a piezoelectric ceramic strip having a width of 2H and polarized in the thickness direction is symmetrically adjacent to a length region of 21+21' in the length direction, and is elastically coupled in two energy length regions. Configure by letting That is, Fig. 2 (
, ), one resonator has an electrode 111 and a common electrode 113.
The other resonator is composed of an electrode 112 and a common electrode.

130 and 131 are back electrodes. In this case, the center of each strinozo electrode in the width direction is aligned with the position where the stress in the usage mode is maximum. Thus, only the utilization mode is most strongly excited. In Figures 2(b) and (c).

The electrodes constituting each resonator are divided so that the center Z° of the electrode strip is located at the point of maximum stress in the third and fourth modes, respectively.

In FIG. 2(b), 115 and 118 are common electrodes, and electrode 1
16 constitutes one resonator, and electrode 117 constitutes the other resonator. In FIG. 2C, electrodes 122 and 125 are common electrodes, and together with electrodes 120 and 123 constitute one resonator, and with electrodes 121 and 124 constitute the other resonator. Note that if the widths of all IJ electrodes are made equal, the third
In figures (,) and (C), it is 5th order or less.

In FIG. 4B, spurious vibrations of the fourth order or lower width are suppressed, and good filter characteristics with few spurious waves are realized over a wide frequency range.

As an example of the present invention, FIG. 1 (
b) and the prototype filters shown in FIG. 3(b) will be explained in detail.

Example 1 Third-order widthwise longitudinal vibration of a PbTiOs piezoelectric ceramic strip polarized in one width direction was utilized with an electrode configuration as shown in FIG. 1(b). I prototyped a 4.5 MHz single mode filter and connected two of them in cascade as shown in Figure 4 (,).

The characteristics in that case are shown in Figure (b). However, the dimensions of this filter element are length t6=10mmn width2H=
1.4 wm, thickness 2t = 0.1 wn, and electrode length 2L = 2. It is m. Figure 3 (
Looking at the characteristics of b).

Although spurious vibrations of the first, second, fourth, and fifth orders occur, it is clear that they are suppressed to about -20 dB by the electrode configuration described above.

Example-2 Pb (Z + , T s )Co 3 polarized in the thickness direction with an electrode configuration as shown in FIG. 3(b)
Using the third-order width longitudinal vibration of the piezoelectric ceramic string, 10.7
We prototyped a MHz dual mode filter. This is the fifth
Shown in Figure (,).

The filter characteristics are shown in FIG. 5(b). The 3 dB specific bandwidth of this filter is 1.5%, and the passband loss is 2 dB.
Met. On the high frequency side, 4th and 5th order wide longitudinal vibrations (WB2 and 5) and thickness shear vibrations (TS) spurious occur, but over a wide frequency range - 20 dBB1
0 Attenuation is ensured 0 The element dimensions of this filter are L o = 4 mm, 2 H = 0.5 wn
.

2 t = 45 firn, t = 0.3 mm +
21'=0.2 tan.

The conventional 10.7 MHz energy confinement filter using plate thickness longitudinal vibration has a side of about 5 mm and a thickness of 0.
Although it is composed of a square piezoelectric ceramic plate of 2 RAN, this filter is very small compared to this, and the element size has been significantly reduced.

As described above, the two inventions have been described, and by utilizing high-order vibration, it has become possible to provide a piezoelectric filter that is extremely small and has good characteristics. The filter of the present invention has several MH
It can be said that it is extremely useful as a piezoelectric filter in the short wave band of 100 MHz to 10 MHz, and that it has an extremely large effect on industry.

[Brief explanation of the drawing]

FIG. 1 shows the structure of a single mode filter using high-order width vertical vibration and high-order width shear vibration using the piezoelectric longitudinal effect in the present invention. The diagram shows the relationship between (a) when using the quadratic mode, (b) when using the cubic mode, and (C) when using the cubic mode.
The figures each show the case of using the 4th mode. FIG. 2 is a diagram showing the configuration of a transverse effect type single mode filter, showing a top view, a bottom view, and the relationship between the stress distribution of each order mode. FIG. 3 shows the structure of another embodiment of the present invention, showing the structure of the electrodes on the front and back surfaces, and the structure of the electrodes on the front and back surfaces, showing the structure of a dual mode filter using high-order width vertical vibration of the piezoelectric transverse effect. The diagram shows the relationship between the mode and the stress distribution. (a) Figure is when the second mode is used, (b) Figure is when the third mode is used,
(C) shows the case of using the fourth mode. FIG. 4 is a diagram showing the third-order width characteristic of the piezoelectric longitudinal effect according to the present invention, where (a) is a circuit configuration diagram thereof, and (b) is a filter characteristic thereof. FIG. 5 is a diagram showing the characteristics of a 10.7 MHz band dual mode filter using third-order width vertical vibration using piezoelectric transverse effect according to the present invention, and FIG. 5 (a) is a circuit configuration diagram thereof. (b) Figure shows the filter characteristics. In the figure, 1... input lead terminal, 2... output lead terminal, 3... common ground lead terminal, 10... rectangular piezoelectric thin plate, 11.13, 15, 17, 19, 21. 111.112...input/output electrode, 11', 13'
, 15'. 17', l9', 21'... Same as above extraction electrode, 12°14.16, 18.20.22... Common ground electrode. 12', 14', 16', 18', 20', 22', 1
15゜118.122.125... Same as above extraction electrode. Figure 1 (b) Procedural amendment (spontaneous) Date of λ/2, 1960 Director General of the Japan Patent Office Shima 1) Haruki Tono1, Indication of the case Patent application No. 158427, filed in 1982, 2, Title of the invention High order range Piezoelectric filter 3 that uses vibration, and its relationship to the case of a person making corrections Patent applicant Address: No address in Sendai City, Miyagi Prefecture Name: Hiroshi Shimizu 4, Agent: 105 Address: 1-4 Nishi-Shinbashi, Minato-ku, Tokyo 10 No. 5, Subject of amendment 1) Claims column of the specification 2) Detailed explanation of the invention column of the specification 6) Brief explanation of drawings column of the specification 6. Contents of amendment 1) As shown in the attachment 2) (1) "1-piezo electromagnetic plate" on page 2, line 9 is corrected to "1-piezo electromagnetic plate." (2) On page 5, line 16, ``What is the usage mode?'' is corrected to ``11 historical mode.'' (6) Insert "once" before "Figure (b)" on page 9, line 11. (4) Page 9, bottom line “Pb'(Zr, Ti)CO3
Correct j to "Pb(Zr, Ti)03 J." 3) Correct "bottom view" on page 11, line 11 to "1 bottom view." (Attachment) Claim 1: A plurality of strip-shaped electrodes for high-order width vibration excitation formed in the longitudinal center of a rectangular piezoelectric thin plate are used as input/output and common grounding electrodes, and A single-mode piezoelectric filter that utilizes high-order vibration, characterized in that extraction electrodes from the electrodes are provided at the periphery on both sides. 2. Two or more high-order width vibration energy trapping resonators are formed close to each other in the center of the rectangular piezoelectric thin plate in the length direction, and extraction electrodes from the drive electrodes of the resonators at both ends of the length direction are formed in the periphery. A multi-mode piezoelectric filter that utilizes high-order vibration, characterized in that it is configured to be provided in a portion.

Claims (1)

[Claims] 1. A plurality of strip-shaped electrodes for high-order width vibration excitation formed in the longitudinal center of a rectangular piezoelectric thin plate are used as input/output and common grounding electrodes. Furthermore, a single-mode piezoelectric filter utilizing high-order vibration is characterized in that lead-out electrodes from these electrodes are provided at the periphery on both sides. 2. Two or more high-order width vibration energy trapping resonators are formed close to each other in the center of the rectangular piezoelectric thin plate in the length direction, and extraction electrodes from the drive electrodes of the resonators on both sides of the length are connected to the periphery. Multi-mode piezoelectric filter 0 utilizing high-order width vibration, characterized in that it is configured such that it is provided in a section.