JPH0645868A - Ultra thin sheet multistage cascaded multimode filter - Google Patents

Abstract

PURPOSE:To sufficiently suppress the spurious generated on the high band side of a filter passage band by giving different directions and shapes to electrode leads which are extended from both of divided electrodes of each multimode filter element toward the end part of an element plate. CONSTITUTION:Directions and leading-out shapes of electrode lead parts 6, 7 extended from both of divided electrodes 5 formed on a very thin plate oscillation part 2 toward the end part of an element plate 1 are made different from each other. That is, the electrode lead part 6 is led out in the oscillation propagating direction and is bent at right angles and is extended to the end part of the element plate 1, and the electrode lead part 7 is extended in the direction inclined at about 45 deg. to the oscillation propagating direction. Thus, the spurious generated between electrode lead parts 6, 7 and an overall electrode 4 is different by generation position in accordance with directions and shapes of electrode lead parts 6, 7, and therefore, the spurious level is reduced by mutual cancelling when both filter elements are cascaded, and a very thin plate multistage cascaded multimode filter defect is removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an ultra-thin plate multi-stage cascade connection multi-mode filter.

[0002]

2. Description of the Related Art Conventionally, as shown in FIGS. 4 (a) and 4 (b), one surface of a piezoelectric element plate, for example, an AT-cut quartz crystal element plate 1 is recessed by, for example, etching, and the bottom surface thereof is made into a thin plate-shaped vibrating portion 2. In addition, in the ultra-thin plate crystal resonator in which a thick annular surrounding portion 3 that supports the periphery of the vibrating portion 2 is integrally formed with the vibrating portion 2 and the mechanical strength of the vibrating portion 2 is maintained, A conductive electrode is vapor-deposited on the concave side to form a full-surface electrode 4, and a pair of divided electrodes 5 and electrodes extending from the both electrodes toward the end of the blank plate are formed substantially in the center of the vibrating portion 2 on the opposite flat surface. A multi-stage cascade connection filter in which ultra-thin plate multiple mode filter elements provided with lead portions 6 and 6 are cascade-connected in multiple stages increases the attenuation amount in the attenuation band near the pass band and has steep skirt characteristics. High frequency due to excellent filter characteristics Is used in the field of communication devices such as compact is strictly required. However, in the ultra-thin plate multi-stage cascade connection multiple mode filter constructed as described above, resonance occurs between the electrode lead portion and the entire surface electrode of each filter element, but each multiple mode filter When the lead arrangement of the elements is the same, there is a defect that a spurious with a high level is generated on the high band side of the filter pass band.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in order to eliminate the defects of the conventional ultra-thin plate multi-stage cascade connection multi-mode filter as described above. The present invention provides an ultra-thin plate multi-stage cascade connection multi-mode filter capable of sufficiently suppressing spurious.

[0004]

SUMMARY OF THE INVENTION In order to achieve the above object, an ultra-thin plate multi-stage cascade connection multiple mode filter according to the present invention extends from both electrodes of a split electrode of each multiple mode filter element toward the end of a blank plate. The direction and shape of the electrode lead portion are different from each other.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings showing the embodiments. Prior to the description of the embodiments, the super thin plate multiplexing (2
A filter configuration in which two (heavy) mode filter elements are connected in cascade and their characteristics will be briefly described with reference to FIG.
That is, as shown in FIG. 4 (a), the spurious characteristics shown in FIG. 4 (c) are completely the same because the filter element having the same electrode configuration has been used in the related art. As described above, there is a problem that spurious characteristics occur at the same position as in the case of one filter element and cannot be suppressed as shown in d). In order to solve this problem, the ultra-thin plate multistage cascade connection multimode of the present invention is used.
The defilter has the following configuration. 1A and 1B are a plan view and a sectional view taken along line AA showing an embodiment of an ultrathin plate multistage cascade connection multimode filter according to the present invention, showing a divided electrode 5 formed on an ultrathin plate vibrating portion 2. The directions of the electrode lead portions 6, 6 and 7 and 7 extending from both electrodes toward the end portions of the base plate and the shapes of the lead portions are different, that is, the electrode lead portions 6, 6 are different.
Is bent in a direction perpendicular to the vibration propagation direction and then bent at a right angle to extend to the end of the base plate 1.
It is an extension of about 5 degrees in the oblique direction. The spurious generated between the electrode lead portions 6 and 7 and the entire surface electrode 4 is shown in FIG.
As shown in (a) and (b), since the generation position differs depending on the direction and shape of the electrode lead portions 6 and 7, when these two filter elements are connected in cascade, they cancel each other as shown in FIG. The level can be reduced. By the way, in the filter element, there is an increasing demand for miniaturization together with higher frequency, and as one means for responding to this, a multi-stage multi-mode filter in which a plurality of sets of split electrodes are cascade-connected to the surface of the vibrating portion of an ultra-thin plate has long been available. Is proposed. FIG. 3 is a plan view showing an embodiment in which the present invention is applied to this ultra-thin plate multi-stage cascade connection multi-mode filter.
The directions and shapes of the electrode lead portions 8 and 9 extending from one of the two electrodes are different from each other, and the same effect as the above-described embodiment is achieved. Although the present invention has been described with reference to the embodiment of the ultra-thin plate multi-stage cascade connection multi-mode filter using the AT-cut quartz crystal plate, the present invention is not limited to this and other piezoelectric element plates may be used. It is self-evident.

[0006]

Since the present invention is constructed as described above, spurious can be suppressed only by changing the direction and shape of the electrode lead portion extending from both electrodes of the divided electrode toward the end of each blank plate. It has a remarkable effect in realizing the ultra-thin plate multi-stage cascade connection multi-mode filter.

[0007]

[Brief description of drawings]

FIG. 1 is a plan view and an AA sectional view showing an embodiment of an ultrathin plate multistage cascade connection multiple mode filter according to the present invention.

2 (a), (b) and (C) are schematic diagrams for explaining the basic spurious characteristics of each multi-mode filter element of the filter of the present invention and a multi-stage cascade-connected filter, respectively.

FIG. 3 is a plan view showing an embodiment of an ultrathin plate multistage cascade connection multiple mode filter in which a plurality of sets of divided electrodes are cascaded on the vibrating portion of the ultrathin plate according to the present invention.

FIG. 4A is a plan view showing the structure of a conventional ultra-thin plate multistage cascade connection multiple mode filter, FIG. 4B is a sectional view taken along line AA, and FIGS. FIG. 5 is a schematic diagram illustrating basic spurious characteristics in the case of a single filter element and basic spurious characteristics in a configuration in which each element is connected in cascade.

[0008]

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... AT cut quartz crystal plate 2 ... Vibrating part 3 ... Annular surrounding part 4 ... Full surface electrode 5, 10 ... Divided electrode 6, 7, 8, 9 ... Electrode lead Department

Claims (2)

[Claims] 1. An ultra-thin vibrating portion and a thick annular surrounding portion that supports the periphery of the vibrating portion are integrally formed of a piezoelectric element plate, and a predetermined gap is provided on the surface of the vibrating portion. In a multi-stage cascade-connected multi-mode filter in which multi-mode filter elements provided with divided split electrodes are arranged in cascade connection in multiple stages, an electrode lead portion extending from the split electrodes of each of the multi-mode filter elements An ultra-thin plate multi-stage cascade-connected multi-mode filter characterized in that the directions and shapes of the two are different. 2. The ultra-thin plate multi-stage cascade connection multiple mode filter according to claim 1, wherein a plurality of sets of the divided electrodes are arranged in cascade connection on the surface of the ultra-thin vibrating portion.