JPH0685503A - Dielectric filter - Google Patents

Abstract

PURPOSE:To provide satisfactory filter characteristics preventing a Q value from being lowered when the load of a coaxial resonator is high by eliminating a ridge line part formed by the two faces of a face, which forms the inter-step coupling window of the resonator, and a face adjacent to this face in counter to a substrate. CONSTITUTION:A dielectric block 1 composed of dielectric ceramic is compacted and sintered by a die almost in a prismatic shape eliminating a ridge line part 1c formed by a first face 1a and a second face 1b and afterwards, an outer conductor 3 and an inner conductor 4 are formed by covering the outer and inner peripheral faces with a conductive member while remaining an open end face 2. Further, a window 5 for inter-step coupling is formed by removing the outer conductor on the second face 1b and removing one part of the outer conductor on the first face 1a adjacent to the second face 1b so that a coaxial resonator 6 can be completed. Thus, even when the inter-step coupling window 5 is formed on the second face 1b by a dicing saw 7, the leakage of an electromagnetic substance is suppressed by the outer conductor 3 remained between the first face 1a and the second face 1b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric filter used in a microwave band used for mobile communication equipment and the like.

[0002]

2. Description of the Related Art Conventionally, as a dielectric filter using a coaxial resonator, for example, Japanese Utility Model Publication No. 62-44566 (H).
01P1 / 205) is known.
This conventional dielectric filter is provided with a through hole in a dielectric member, and a plurality of single-sided short-circuit type formed by coating a conductive member on the outer peripheral surface of the dielectric member and the inner peripheral surface of the through hole. The coaxial resonator is connected to a dielectric substrate, and the coaxial resonators are capacitively coupled by electrodes formed on the dielectric substrate.

[0003]

In recent years, mobile communication equipment is required to be smaller and lighter, and accordingly, the dielectric filter, which is one of the components, is also required to be smaller. ing.

By the way, in order to obtain a high Qu (Q value when no load is applied) when miniaturizing the dielectric filter, if the inner coaxial diameter is a and the outer conductive shaft diameter is b, then b / a = It is desirable to set it to 3.6, but if the outer coaxial diameter is 4 mm or less,
The inner coaxial diameter is 1.2 mm or less, and it is extremely difficult to insert the external connection member into the through hole of the coaxial resonator to connect to the external circuit as in the above-described conventional art, and it is limited to miniaturization. There is a drawback that there is. In order to improve this, the present applicant has already filed Japanese Patent Application No. 4-82106. In this prior art, the open surfaces of the coaxial resonator including the input / output stages are staggered on a dielectric substrate having input / output coupling striplines and a coplanar ground conductor provided so as to surround these striplines. The size of the dielectric substrate is made equal by making the area of the dielectric substrate equal to the cross-sectional area of the coaxial resonator array direction.
In this conventional technique, as shown in FIG.
The outer conductor 15 and the inner conductor 16 are formed by covering the outer peripheral surface and the inner peripheral surface of the dielectric block 12 having the open end surface 14 with the conductive member, and the outer surface of the surface 17 facing the dielectric substrate is outside. While removing the conductor, a part of the outer conductor of the surface 18 adjacent to the dielectric substrate facing surface 17 is removed by a dicing saw or the like to form a window 19 for interstage coupling.

However, in this prior art, since the interstage coupling window 19 is formed by a dicing saw, the outer conductor of the surface 18 is removed until it reaches the dielectric substrate facing surface 17. As a result, the Qu of the coaxial resonator 12 is lowered and the characteristics of the dielectric filter are deteriorated.

[0006]

In view of the above-mentioned drawbacks of the prior art, the dielectric filter according to the present invention is composed of a dielectric substrate having an input / output coupling stripline and a plurality of dielectric coaxial resonators. In the filter, the coaxial resonator has an outer peripheral surface except an open end surface of a substantially rectangular columnar dielectric block in which a ridge line portion formed by a first surface and a second surface adjacent to the first surface is removed. An outer conductor and an inner conductor are formed by coating the inner peripheral surface with a conductive member, and the outer conductor on the first surface is removed and a part of the outer conductor on the second surface is removed. It is characterized in that a window for intercoupling is formed.

[0007]

According to the present invention, since the coaxial resonator has a substantially prismatic shape in which the ridge portion formed by the first surface and the second surface adjacent to the first surface is deleted, Even if the inter-step coupling window is formed on the second surface by a dicing saw, the outer conductor is not removed to the first surface, and the outer conductor remaining between the first surface and the second surface is the electromagnetic field. Of the resonator Qu to prevent the resonator Qu from decreasing.

[0008]

1 shows a coaxial resonator used in a dielectric filter according to the present invention. Reference numeral 1 denotes a dielectric block made of a dielectric ceramic, which is molded by a mold into a substantially prismatic shape in which a cross section 1c indicated by a two-dot chain line formed by the first surface 1a and the second surface 1b is removed. After being sintered and sintered, the outer conductor 3 and the inner conductor 4 are formed by covering the outer peripheral surface and the inner peripheral surface with a conductive member while leaving the open end surface 2.
Further, while removing the outer conductor of the surface facing the substrate, that is, the second surface 1b, the first conductor adjacent to the second surface 1b is removed.
A part of the outer conductor of the surface 1a is removed to form the window 5 for interstage coupling, and the coaxial resonator 6 is completed.

The inter-stage coupling window 5 has a rotating dicing saw 7 with a predetermined height with respect to the resonator fixed with the first surface 1a facing upward, as shown by the chain double-dashed line in FIG. By sliding it in the direction of the arrow, the first surface 1a is formed substantially at the center. At this time, since the ridge line portion 1c is deleted, it is possible to perform processing without the inter-stage coupling window 5 reaching the second surface 1b, and thereby the part 3a of the outer conductor 3 is covered.

The ridge line portion formed by the first surface 1a and the second surface 1b has the same effect even if it is deleted in a rectangular shape as shown in FIG. 2 or an arc shape as shown in FIG.・
The effect can be obtained.

FIG. 4 shows a dielectric filter formed by using two coaxial resonators 6 manufactured as described above.
Two coaxial resonators 6, 6 are arranged on the dielectric substrate 8 so that the open end surfaces 2 are staggered, and the second surfaces 1b are attached to each other with an adhesive such as an epoxy resin. Dielectric substrate 8
Are made of a dielectric material and have the same area as two coaxial resonators 6 arranged in a staggered and parallel manner.

FIG. 5 shows this dielectric substrate 8, FIG. 5 (A) shows the surface on which the coaxial resonator 6 is mounted, and FIG. 5 (B) shows the back surface. . Reference numerals 9 and 10 denote input / output coupling strip lines. By disposing the coaxial resonator 6 with the open end face 2 sides thereof facing each other, the coaxial resonator 6 and the external circuit are coupled to each other by input / output. Reference numeral 11 denotes a ground electrode, which is electrically connected on the front surface and the back surface and prevents electrical interference between the input coupling strip line 9 and the output coupling strip line 10.

In the thus-formed dielectric filter according to the present invention, the resonator Qu is less deteriorated as compared with the conventional one. That is, in the dielectric filter using two coaxial resonators as in this embodiment, when the conventional resonator shown in FIG. 6 is used, there is a deterioration of 15 to 18% in Qu. When the coaxial resonator is used, it can be suppressed to around 10%. In addition, the insertion loss, which is one of the filter characteristics, becomes 1.7 dB smaller than that of the conventional filter.

Although a two-stage dielectric filter using two dielectric resonators 6 has been described in this embodiment, FIG.
The intermediate stage resonator is interposed between the two coaxial resonators 6 shown in Fig. 6, and the interstage coupling windows are formed on both sides of the intermediate stage resonator in the same manner as described above, and the dielectric substrate is expanded to provide multistage resonance. It goes without saying that you can get a vessel.

[0015]

In the dielectric filter according to the present invention, the ridge line portion formed by the surface forming the inter-stage coupling window of the coaxial resonator and the two surfaces facing the substrate adjacent to this surface is eliminated. When the inter-stage coupling window is formed, the removal of the outer conductor does not reach the surface facing the substrate, and leakage of the electromagnetic field can be suppressed by the remaining outer conductor. Can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a coaxial resonator used in the present invention.

FIG. 2 is a diagram showing a coaxial resonator used in the present invention.

FIG. 3 is a diagram showing a coaxial resonator used in the present invention.

FIG. 4 is a diagram showing an embodiment of a dielectric filter according to the present invention.

FIG. 5 is a diagram showing a dielectric substrate used in the present invention.

FIG. 6 is a view showing a coaxial resonator which has been conventionally used.

[Explanation of symbols]

 1 Dielectric Block 1a First Surface 1b Second Surface 1c Ridge Line Part 2 Open End Face 3 Outer Conductor 4 Inner Conductor 5 Interstage Coupling Window 6 Coaxial Resonator 8 Dielectric Substrate

Claims (1)

[Claims] 1. A dielectric filter comprising a dielectric substrate having an input / output coupling stripline and a plurality of dielectric coaxial resonators, wherein the coaxial resonator has a first surface and a first surface.
Of the outer conductor and the inner peripheral surface of the substantially rectangular prism-shaped dielectric block from which the ridge line portion formed by the second surface adjacent to the outer surface is removed, and the outer peripheral surface and the inner peripheral surface are covered with a conductive member. An inner conductor is formed, the outer conductor on the first surface is removed, and a part of the outer conductor on the second surface is removed to form a window for interstage coupling. .