JPS63127602A - Strip line filter - Google Patents

Abstract

PURPOSE:To improve the electric characteristic by providing a conductor between the outer circumference and the inner circumference of the cylindrical dielectric base along the axial direction and connecting a resonance electrode and a ground electrode by said conductor thereby reducing the outer diameter. CONSTITUTION:The ground electrode 2 is formed on the entire inner circumferential face of the dielectric base 1 made of a cylindrical ceramics. A notch A is formed along the axial direction to the base 1 between the outer and inner circumferential faces and a conductor 2a in continuity to the ground electrode 2 is formed on one side face of the notch. Five resonance electrodes 4-8 are formed on the outer circumferential face of the base 1, one terminal is connected to the conductor 2a and the other terminal is an opened and they are formed to be so-called comb-line form. Thus, the ground electrode and the resonance electrode are connected by the conductor, the current is spread over the entire face of conductor thereby improving the Q of the band-pass filter.

Description

DETAILED DESCRIPTION OF THE INVENTION +a) Industrial Application Field The present invention relates to a stripline filter used, for example, as a bandpass filter.

(b) Prior Art Conventionally, stripline filters in which ink digital type or combline type resonant electrodes are provided on a rectangular flat dielectric substrate have been known. Such conventional flat strip line filters have the disadvantage that when the number of resonant electrodes is large, the outer diameter of the entire bandpass filter becomes thick and the area required for installation increases. For example, a stripline filter as shown in the perspective view of FIG. 3 has been proposed.

The stripline filter in this figure is a five-stage ink-digital type, and reference numeral 1 in the figure is a dielectric substrate, which is made of cylindrical ceramics.

A ground electrode 2 is formed on the entire inner peripheral surface of this dielectric substrate 1, and from a portion of each of both ends of this ground electrode 2,
Extending portions 'la, 2b of a predetermined width are pulled out.

These extending portions 2a and 2b are arranged on both end faces of the dielectric substrate 1 facing each other, and have a predetermined width formed on the outer peripheral surface of the dielectric substrate l in the direction along the cylindrical axis of the dielectric substrate 1. They are connected by an extended electrode 3.

From one side of the extended electrode 3, three resonant electrodes 4 to 6 are drawn out in parallel at predetermined intervals in one circumferential direction (downward in the figure) along the outer peripheral surface of the dielectric substrate 1. .

Note that terminal electrodes 9.10 as input or output electrodes extend from each of the resonant electrodes 4.6 arranged on both sides, and the resonant electrodes 9.10 extend from the other side of the extended electrodes 3. Two resonant electrodes 7°8 in the opposite direction to 4-6
are drawn out in parallel and arranged between the resonant electrodes 4 to 6.

(C) Problems to be Solved by the Invention In a bandpass filter using such a stripline filter, the outer circumferential surface is Since the extended electrode 3 formed on the inner circumferential surface is connected to the ground electrode formed on the inner circumferential surface, there is a problem in that current is concentrated on the extended parts 2a and 2b, resulting in a decrease in Q.

The present invention is a means for solving the fd1 problem, which aims to solve such conventional problems and provide a stripline filter with a reduced outer diameter and improved electrical characteristics. , a cylindrical dielectric substrate is provided, a ground electrode is formed on either the inner circumferential surface or the outer circumferential surface of the dielectric substrate, and a resonant electrode is formed on the other surface of the dielectric substrate. The stripline filter is characterized in that a conductor is provided along the axial direction between the outer peripheral surface and the inner peripheral surface of the cylindrical dielectric, and the resonant electrode and the ground electrode are connected by this conductor.

(e) Effect With the above configuration, the conductor provided along the axial direction between the outer circumferential surface and the inner circumferential surface of the cylindrical dielectric substrate is connected to the inner circumferential surface or the outer circumferential surface of the cylindrical dielectric substrate. The ground electrode provided on the surface and the resonant electrode provided on the other surface are electrically connected.

At that time, since the outer circumferential surface and the inner circumferential surface of the cylindrical dielectric are fully connected along the axial direction, the current is dispersed and the Q is improved. It is a perspective view of one embodiment in which the invention is applied to a five-stage combline type stripline filter. In this figure, reference numeral 1 denotes a dielectric substrate, which is made of cylindrical ceramics. This dielectric substrate +N 1 A ground electrode 2 is formed on the entire inner circumferential surface of the cylindrical dielectric substrate.As shown in the figure, a notch A is formed along the axial direction between the outer circumferential surface and the inner circumferential surface. A conductor 2a continuous with the ground electrode 2 is formed on one side of the section.

Five resonant electrodes 4 to 8 are formed on the outer peripheral surface of the dielectric substrate 1, one end of which is connected to the conductor 2a, and the other end of which is formed as an open end in a so-called combline type. Note that terminal electrodes 9 and 10 as input or output electrodes extend from each of the resonant electrodes 4.8.

FIG. 2 is a partially cutaway perspective view showing another embodiment of the invention. In this figure, a ground electrode 2 is formed on the outer peripheral surface of a dielectric substrate 1, and resonant electrodes 4 to 8 are formed on the inner peripheral surface thereof. Note that the explanation for each is the same as the explanation in FIG. 1, and will therefore be omitted. When the ground electrode 2 is formed on the entire outer peripheral surface of the dielectric substrate 1 as in this embodiment, the entire filter is shielded by the ground electrode 2, and internal and external electromagnetic waves are blocked.

In the above embodiment, a notch was provided along the axial direction between the outer circumferential surface and the inner circumferential surface of the cylindrical dielectric substrate, and a conductor was formed on the side surface of the notch. There is no need to provide a gap as a notch (as long as the conductor is disposed along the axial direction between the outer circumferential surface and the inner circumferential surface. Although this was an example, it is also possible to use a rectangular cylindrical dielectric substrate.Furthermore, although all of the embodiments have been explained based on a 5-stage combline type stripline filter, filters having a number of stages other than 5 can also be used. The present invention can be similarly configured, and can be applied not only to the combline type but also to other types of stripline filters such as the ink digital type.

(g) Effects of the invention As described above, according to the invention, a conductor is provided along the axial direction between the outer peripheral surface and the inner peripheral surface of the cylindrical dielectric substrate, and the ground electrode and the resonant electrode are connected by this conductor. Therefore, the current is distributed over the entire surface of this conductor, and the Q of the bandpass filter can be improved.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the present invention, FIG. 1 is a perspective view of a case where a ground electrode is formed on the inner peripheral surface of a cylindrical dielectric substrate, and FIG. It is a partially cutaway perspective view when a ground electrode is formed. Moreover, FIG. 3 is a perspective view of a conventional example: 1-dielectric substrate, 2-ground electrode, 2a-conductor, 4-8-resonant electrode. : 4 <r N

Claims (1)

[Claims] (1) A cylindrical dielectric substrate is provided, a ground electrode is formed on either the inner peripheral surface or the outer peripheral surface of the dielectric substrate, and a resonant electrode is formed on the other surface of the dielectric substrate. In the strip line filter, a conductor is provided along the axial direction between the outer peripheral surface and the inner peripheral surface of the cylindrical dielectric, and the resonant electrode and the ground electrode are connected by this conductor. line filter.