JPH0646082Y2 - Stripline filter - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement in the structure of a stripline filter used as, for example, a bandpass filter.

2. Description of the Related Art A typical stripline filter includes a dielectric substrate, a resonance electrode formed on one main surface of the dielectric substrate, a ground electrode formed over the entire other main surface and both side surfaces, and an external extraction electrode. The filter element is provided with, and is fixed to the metal base and is surrounded by the metal case.

In such a prior art, when changing the filter characteristics, it is necessary to change the design of the microstrip line, that is, the pattern of the resonance electrode according to the desired characteristics. However, it takes a lot of time and effort to design a pattern of the resonance electrode according to desired characteristics or to produce a printing screen pattern or a photo-etching mask for forming a resonance electrode having a new pattern. .

Therefore, in order to solve such a problem and to easily change the filter characteristic, the applicant of the present application has already proposed the stripline filter shown in FIG. This stripline filter 1 includes a dielectric substrate 2, a resonance electrode 3 formed on one main surface of the dielectric substrate 2, a full-face earth electrode 4 formed over the entire other main surface, and a dielectric substrate. 2 is provided with a side surface electrode 8 formed on both side surfaces and a filter element 5 having an external extraction electrode (not shown). The filter element 5 is surrounded by a metal case 6 and further has a metal case 6 An internal metal cover 7 that covers at least a part of the resonance electrode 3 in a non-contact manner is provided therein. By the way, in the stripline filter 1, a resonant electromagnetic field exists in the space above the stripline. Therefore, in this prior art, by arranging the inner metal cover 7 above the strip line, that is, above the resonance electrode 3, and changing the shape and position of the inner metal cover 7, the influence of the resonance electromagnetic field is changed, and as a result, the filter. The characteristics can be changed arbitrarily. Therefore, it is possible to construct a stripline filter having desired characteristics much more easily and in a shorter time as compared with the above-described stripline filter of the prior art which has to be redone from the stripline pattern design.

Problems to be Solved by the Invention By the way, in the prior art shown in FIG.
Is not in direct contact with the inner metal cover 7, and the distance to the metal base 9, which is the ground electrode, is relatively long. Therefore, stray inductance is generated between the side ground electrode 8 and the inner metal cover 7 to deteriorate the current characteristic, which causes a problem that the attenuation characteristic of the filter becomes unstable.

An object of the present invention is to solve the above-mentioned technical problems and to provide a stripline filter having a simple structure and good attenuation characteristics.

The present invention provides a dielectric substrate, a resonance electrode formed on one main surface of the dielectric substrate, a ground electrode formed over the entire other main surface and both side surfaces, and an external electrode. In a stripline filter including a filter element having an extraction electrode, and a metal case surrounding the filter element, an internal metal cover that covers at least a part of the resonance electrode in a non-contact manner is provided in the metal case. Bent pieces that resiliently contact the ground electrodes on both side surfaces of the filter element are formed on opposite side walls of the metal cover.

Operation According to the above configuration, the bent pieces are formed on the opposing side walls of the inner metal cover provided in the metal case,
This bent piece elastically contacts the ground electrodes on both sides of the filter element. As a result, the side ground electrode is directly connected to the inner metal cover, and the stray inductance can be prevented from occurring. In addition, since the bent piece elastically contacts the side surface ground electrode, the side surface ground electrode can always be reliably connected directly to the inner metal cover and can be contacted at a predetermined position of the side surface ground electrode. . Therefore, the contact position and contact pressure are always stable, and there is no variation between products. For this reason, the generation of stray inductance can be prevented as much as possible, and the damping characteristics can be significantly improved.

Embodiment FIG. 1 is a perspective view of an embodiment of the present invention, FIG. 2 is a transverse sectional view, and FIG. 3 is a longitudinal sectional view. With reference to these drawings, in this stripline filter 10, a resonance electrode 12 is formed on one main surface of a dielectric substrate 11, and a full-scale ground electrode 13a is formed on the other main surface. Side surface ground electrodes 13b are formed on both side surfaces of the dielectric substrate 11 so as to be continuous with the entire surface ground electrode 13a. Furthermore, the resonance electrode 1
An external extraction electrode 14 is formed on the same main surface as 2. The filter element thus configured is surrounded by a package composed of the metal base 18 and the metal case 17. The external extraction electrode 14 is electrically connected to the terminals 15 and 16 extending below the metal base 18.

Inside the metal case 17, an internal metal cover 19 is further provided. The internal metal cover 19 is provided so as to cover all the resonance electrodes 12 in a non-contact manner, and is fixed to the metal base 18.

4 is a perspective view of the inner metal cover 19, FIG. 5 is a plan view of the inner metal cover 19, and FIG. 6 is a side view of the inner metal cover 19. With reference to these drawings, the inner metal cover 19 has a cross section perpendicular to the axis formed in a substantially inverted U shape, and has an upper wall 20 and side walls 21 hanging from both ends of the upper wall 20. Notches 22 and 23 are formed in the side wall 21,
As a result, a bent piece 24 is formed which is bent inward along the folding curve 28. The tip of the bent piece 24 is formed to be bent outward, and the bent portion 25 elastically contacts the side ground electrode 13b as shown in FIG. Side wall 21 bent piece 2
In the remaining part 29 other than 4, its tip is about 90 ° outward.
The attachment piece 27 is formed by being bent. This mounting piece
27 is soldered to the metal base 18, and the inner metal cover 19 is fixed to the metal base 18.

In this way, the bent piece 24 is brought into contact with the side surface ground electrode 13b, so that the side surface ground electrode 13b is directly connected to the inner metal cover, whereby the ground line can be made the shortest. Therefore, compared with the prior art, it is possible to prevent the occurrence of stray inductance as much as possible and stabilize the damping characteristics.

In addition, the bending piece 24 has a side ground electrode 13 due to its elastic force.
Since it comes into contact with b elastically, it always comes into contact with the side ground electrode 13b. Therefore, it is possible to obtain stable damping characteristics without variation among products. In the prior art, when the whole-face ground electrode 13a and the metal base 18 are soldered, the spread of the solder is not always constant, which causes stray inductance and deteriorates the attenuation characteristics. However, in the present embodiment, since the side surface ground electrode 13b can be directly connected to the inner metal cover by the bent piece 24 contacting the side surface ground electrode 13b, the generation of stray inductance can be significantly reduced. .

An adjustment hole 26 is formed in the upper wall 20. The adjusting hole 26 is used, for example, for trimming the resonance electrode 12.

7 is a perspective view of a stripline filter according to another embodiment of the present invention, FIG. 8 is a plan view of an inner metal cover 19a used in the embodiment of FIG. 7, and FIG. 9 is an inner metal cover. FIG. 10 is a front view of the cover 19a, and FIG. 10 shows the inner metal cover 1
FIG. 9b is a side view of 9a. Although the inner metal cover 19 that covers the entire surface of the resonance electrode 12 is used in the above-described embodiment, the inner metal cover 19a used in this embodiment is, so to speak, the first metal cover 19a after the inner metal cover 19 is divided into a plurality of pieces. It has dimensions, and partially covers the resonance electrode 12, and the filter characteristics can be changed depending on the fixing position of the inner metal cover 19a and its shape, as described later. The inner metal cover 19a has an upper wall 20a and side walls 21a hanging from both ends of the upper wall 20a. The side wall 21a has a notch 22a,
23a is formed, which forms bent pieces 24a, 24b that are bent inward along folding curves 28a, 28b. The tip ends of the bent pieces 24a, 24b are formed by being bent outward. The bent portions 25a and 25b resiliently contact the side surface ground electrode 13b. At the remaining portion 29a of the side wall 21a other than the bent pieces 24a, 24b, the tip end is bent outward and the mounting piece 2
7a is formed.

By providing such an internal metal cover 19a,
The filter characteristics of the stripline filter change as compared with the case where the internal metal cover 19a is not provided. This will be described below with reference to FIGS. 11 and 12.

In stripline filters, the line or resonant electrode 12
A resonance electromagnetic field (indicated by an arrow) is present in the space above the as shown in FIG. On the other hand, as shown in FIG. 12, when the inner metal cover 19a is arranged above the resonance electrode 12 so as to cover the resonance electrode 12, the resonance electromagnetic field on the resonance electrode 12 changes as shown by the arrow. . That is, the coupling between the resonance electrodes 12 becomes small. This is because the electric field causing the coupling is pulled by the inner metal cover 19a. However, since the effective dielectric constant is lowered, the resonance frequency is slightly increased. However, it is understood that the shift of the resonance frequency to the wide band side is negligible and can be ignored, and therefore it can be considered that the coupling coefficient is simply reduced.

In this way, when the inner metal cover 19a is arranged in the space above the resonance electrode 12, the filter characteristic changes. Therefore, it can be understood that filters having various characteristics can be constructed by changing the shape, size and fixing position of the inner metal cover 19a shown in FIG. 7 and changing the region covering the resonance electrode 12. Therefore, when a stripline filter having different characteristics is configured, it is not necessary to design a pattern of the resonance electrode 12 and a mask for forming a new pattern, and it is possible to easily obtain a filter having desired characteristics. it can.

In this way, the filter characteristics of the stripline filter can be variously changed by changing the shape, size, and fixing position of the inner metal cover 19a.

As described above, according to the present invention, since the bent piece that abuts the side ground electrode is formed on the inner metal cover, the side ground electrode can be directly connected to the inner metal cover. Therefore, the stray inductance hardly occurs between the side ground electrode and the inner metal cover, so that good damping characteristics can be obtained. Further, since the bent piece has an elastic force, it is possible to keep the bent piece always in contact with the predetermined position of the side surface ground electrode simply by attaching the inner metal cover to the predetermined position of the metal base. Therefore, the work for bringing the bent pieces into contact with each other is not particularly required, and the work of attaching the inner metal cover can be performed with the conventional labor, while the bent pieces prevent the damping characteristics from varying from product to product. You can get the effect.

As described above, according to the present invention, it is possible to surely reduce the generation of the stray inductance with a simple structure, and thus it is possible to provide a remarkable effect that a stripline filter having a remarkably stable attenuation characteristic can be provided.

Also, by disposing the inner metal cover in the space above the resonance electrode, the resonance electromagnetic field existing in the space above the resonance electrode is changed by changing the shape, size and position of the inner metal cover, and Stripline filters having various characteristics can be obtained.

[Brief description of drawings]

1 is a perspective view of a stripline filter according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of the stripline filter shown in FIG. 1, and FIG. 3 is a vertical sectional view of the stripline filter shown in FIG. 4 is a perspective view of the inner metal cover 19, FIG. 5 is a plan view of the inner metal cover 19, FIG. 6 is a side view of the inner metal cover 19, and FIG. 7 is a perspective view of a stripline filter of another embodiment. FIG. 8 is a plan view of the inner metal cover 19a used in the stripline filter shown in FIG. 7, FIG. 9 is a front view of the inner metal cover 19a, and FIG. 10 is a side view of the inner metal cover 19a. The figure is a cross-sectional view for explaining the resonance electromagnetic field when the internal metal cover 19a is not provided, FIG. 12 is a cross-sectional view for explaining the resonance electromagnetic field when the internal metal cover 19a is provided, and FIG. It is sectional drawing which shows a prior art example. 11 ... Dielectric substrate, 12 ... Resonance electrode, 13a ... Whole surface ground electrode, 13b ... Side ground electrode, 14a ... External extraction electrode, 17 ... Metal case, 19a ... Inner metal cover, 24, 24a, 24b ... Bent piece.

Claims (1)

[Scope of utility model registration request] 1. A filter element having a dielectric substrate, a resonance electrode formed on one main surface of the dielectric substrate, a ground electrode formed over the entire other main surface and both side surfaces, and an external extraction electrode. And a metal case surrounding the filter element, wherein an inner metal cover that covers at least a part of the resonance electrode in a non-contact manner is provided in the metal case, and the metal cover faces each other. A stripline filter, characterized in that each side wall is formed with a bent piece that elastically contacts the ground electrodes on both sides of the filter element.