JP2750389B2 - Dielectric filter - Google Patents

Description

The present invention relates to a dielectric filter.

(B) Conventional technology Conventionally, a plurality of one-end-open type in which an outer conductor and an inner conductor are formed by coating a conductive material on an outer surface of a dielectric block having one hole and an inner surface of the hole. A dielectric filter including a coaxial resonator is known (for example, see Japanese Patent Publication No. 62-42521).

In recent years, with the development of mobile communication, there has been a demand for the development of small and lightweight devices. In addition, in order to realize such a small and lightweight device, high-density mounting of components is required, and a shift to a surface-mount type dielectric filter is also required.

As a dielectric filter for solving such a problem, one having the configuration shown in FIG. 4 can be considered.

In FIG. 4, reference numerals 1 and 2 denote outer conductors and inner conductors by coating a conductive material on outer surfaces of dielectric blocks 1b and 2b having holes 1a and 2a and inner surfaces of the holes 1a and 1b, respectively. The open-ended coaxial resonator 3 removes part of the outer conductor of the coaxial resonators 1 and 2 or part of the outer conductor including the dielectric blocks 1b and 2b so as to be parallel to the inner conductor. The coupling substrate 4 has coupling electrodes 4a and 4b formed to couple with the inner conducting shafts of the coaxial resonators 1 and 2, respectively, and is mounted in the concave portion 3 with an adhesive or the like. It is.

(C) Problems to be Solved by the Invention According to the dielectric filter shown in FIG. 4, surface mounting is possible, but since the distance between the coupling electrodes is small, direct coupling occurs between the coupling electrodes and the filter characteristics are reduced. May be deteriorated.

(D) Means for Solving the Problems A dielectric filter according to the present invention provides an outer conductor and an inner conductor by coating a conductive material on an outer surface of a dielectric block having one hole and an inner surface of the hole. Are formed on a coupling substrate having input / output electrodes, wherein the two open-ended coaxial resonators each have an open end. A cutout in which a part of the connected outer conductor is removed, or a cutout in which a part of the outer conductor connected to the open end is removed together with the underlying dielectric member; The resonator is disposed on the coupling substrate such that each cutout portion faces one end of each of the input / output electrodes provided on the coupling substrate, and the open ends face in opposite directions to each other. I / O power provided on the coupling board The other end of each is characterized in that to be used for connection with the external circuit at a position away from the two open ended coaxial resonator.

(E) Function According to the present invention, since two resonators are arranged on the coupling substrate with their open ends facing in opposite directions, the distance between the input and output electrodes coupled to the inner conductor of the resonator is reduced. As a result, the direct coupling between the input and output electrodes is suppressed.

In addition, since the filter characteristics are determined by placing the two resonators on the coupling substrate, the filter characteristics do not change even if the filter is mounted on a printed circuit board or the like.

(F) Embodiment The structure of a dielectric filter according to an embodiment of the present invention is described as follows.
Shown in the figure. This dielectric filter has one hole 10a, 1
The two open-ended coaxial resonators 10, in which an outer conductor and an inner conductor are formed by coating a conductive material on the outer surfaces of the dielectric blocks 10b and 11b and the inner surfaces of the holes,
11 is a dielectric filter mounted on a coupling substrate 14 having input / output electrodes 14a and 14b, wherein the two resonators 10 and
11 is provided with cutouts 12 and 13 each having a part of the outer conductor connected to the open end removed, and further includes the two resonators 10 and 11
Are arranged on the coupling substrate such that each notch faces one end of each of the input / output electrodes 14a and 14b provided on the coupling substrate, and the open ends face in opposite directions,
The other end of each of the input / output electrodes 14a and 14b provided on the coupling substrate is connected to the two open-ended coaxial resonators 10 and 11 respectively.
And provided for connection with an external circuit at a position away from the external circuit.

Here, the outer shape of the two resonators 10 and 11 is 3 m in cross section.
m square, resonator length 4.8 mm, the dielectric blocks 10a, 1
The material of 0b has a relative dielectric constant of 38 (TiO2 + Sr2O3 + ZrO2)
A system dielectric is used, and alumina is used as a material of the coupling substrate 14, and a ground conductor is provided on the back surface of the coupling substrate 14.

A window 15 from which a part of the outer conductor is removed is formed on the surfaces of the two resonators 10 and 11 facing each other, and coupling between the two resonators is formed through the window. Done.
When the open ends of the two resonators 10 and 11 are oriented in opposite directions, the mode of each resonator changes, and when the coupling between the resonators is reduced, the shape of the window 15 is changed. Then, the degree of coupling may be adjusted.

The cutouts 12, 13 and the window 15 of the resonator may be formed by removing a part of the outer conductor together with the underlying dielectric member.

The external dimensions of the resonator in the conventional example shown in FIG.
In the case of 3 mm square as in the embodiment of the figure, while the distance between the input and output electrodes is 2.5 mm, according to the present invention, the distance between the input and output electrodes can be expanded to 3.8 mm, Direct coupling between the input and output electrodes is suppressed.

FIG. 2 shows the characteristics of the filter of FIG. 4 and the filter of FIG. 1. The solid line shows the characteristics of the filter of FIG. 1 (that is, the filter of the present invention), and the broken line shows the characteristics of the filter of FIG. Is shown.

As is clear from FIG. 2, according to the present invention, the amount of attenuation outside the pass band is larger than in the conventional case, and good filter characteristics are provided.

FIG. 3 shows another embodiment of the coupling substrate, in which a mounting electrode 14c is provided between the input electrode 14a and the output electrode 14b.

If the coupling substrate shown in FIG. 3 is used, the separation between the input and output electrodes becomes more reliable, and the filter characteristics are improved.

Note that the present invention is not limited to the embodiment, and it is possible to change the dielectric material, the outer dimensions, and the like.

(G) Effects of the Invention According to the present invention, even when the resonator shape is reduced, direct coupling between input and output electrodes is suppressed, and good filter characteristics can be obtained.

Even when the dielectric filter according to the present invention is mounted on a printed circuit board or the like, the filter characteristics do not change.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing filter characteristics, FIG. 3 is a diagram showing another example of a coupling substrate, and FIG. It is a figure showing an example. 10, 11, a coaxial resonator, 12, 13, a notch, 14, a coupling substrate, 14a, an input electrode, 14b, an output electrode, and 15 a window.

Claims (2)

(57) [Claims] 1. An open-ended coaxial resonator having an outer conductor and an inner conductor formed by coating an outer surface of a dielectric block having one hole and an inner surface of the hole with a conductive material. However, in the dielectric filter disposed on the coupling substrate having the input and output electrodes, wherein the two open-ended coaxial resonators, respectively, a cutout portion in which a part of the outer conductor connected to the open end is removed, Alternatively, a notch portion in which a part of the outer conductor connected to the open end is removed together with the underlying dielectric member is provided, and each of the two open-end coaxial resonators has a notch portion on the coupling substrate. The other end of each of the input / output electrodes provided on the coupling substrate is disposed so as to face one end of each of the provided input / output electrodes and to have open ends facing in opposite directions. The ends are coaxial with the two open ends. Dielectric filter characterized in that it is provided for connection to an external circuit at a position away from the vessel. 2. The dielectric filter according to claim 1, wherein a ground electrode is provided on the coupling substrate at a position between the input / output electrodes.