DIELECTRIC RESONATOR, DIELECTRIC FILTER USING THE RESONATOR, AND PRODUCTION METHOD OF THE DIELECTRIC FILTER

Abstract

 A compact and high-performance dielectric resonator including a molded body (1) made of a dielectric material, a through hole (2), first and second earth electrodes (3a and 3b), and an inner conductor (4). The molded body (1) has an open end (5) and a terminated end (6) provided with the second earth electrode (3b). The through hole (2) has a larger diameter (15) at the open end (5), and an island-like electrode (8) is disposed on the side surface of the body (1) toward the open end.

Description

Field of Technology

[0001] The present invention relates to a dielectric resonator and a dielectric filter using it, which are primarily used in high frequency wireless equipment and the like, and also a fabrication method for the dielectric filter.

Background of the Invention

[0002] A prior art dielectric resonator comprises, as shown in Fig. 8 and Fig. 9, a molded body 30, a through hole 31 passing through the molded body 30 from its open end 35 to opposite end 36, a first grounding electrode 32 made of a conductor covering side surfaces of the molded body 30, an internal conductor 34 covering the inner surface of the through hole 31, and a second grounding electrode 33 made of a conductor covering the opposite end 36 of the molded body 30 and also connecting between the foregoing first grounding electrode 32 and internal conductor 34, and further includes a non-electrode formed section 37 located on part of a side surface of the molded body 30 towards the open end 35 thereof and an island shaped electrode 38 disposed within the non-electrode formed section 37.
As a result of employing the above structures, an LC parallel resonant circuit 40 as shown in Fig. 10 is realized.

[0003] However, the prior art dielectric resonator as described in the above has a notch capacitance 39, as shown in Fig 10 which exists between the island shaped electrode 38 and the internal electrode 34, and its magnitude is proportionate to the dimensions of the island shaped electrode 38.
Therefore, in order to gain a larger capacitance value from the notch capacitance 39, it is necessary to make the island electrode 38 larger. Since the dimensions of the island electrode 38 are restricted by the size of the dielectric resonator, the required capacitance may not be obtained from the notch capacitance 39, resulting in a failure to realize needed high frequency characteristics.

Summary of the Invention

[0004] The present invention provides a dielectric resonator of excellent performance by solving the problems as described in the above.

[0005] For achieving this object, the present invention discloses a structure for a dielectric resonator, wherein a through hole of the dielectric resonator has a larger diameter on its open end than the diameter on its opposite end and an island shaped electrode insulated from a first grounding electrode is disposed on part of a side surface of the resonator opposite to a position having the foregoing larger diameter on an internal conductor formed on the inner surface of the through hole.

[0006] Thus, the dielectric resonator of the present invention has an internal conductor which formed on the inner surface of the through hall having a larger diameter at the open end at a position opposite to the island shaped electrode.
Therefore, the distance between the internal conductor and the island shaped electrode becomes small, thereby facilitating the realization of a large notch capacitance without increasing the dimensions of the island shaped electrode. As a result, it has become possible to realize a dielectric resonator with excellent performance.

Brief Description of Drawings

[0007] Fig. 1 is a perspective view of a dielectric resonator in a first exemplary embodiment of the present invention.

[0008] Fig. 2 is a cross-sectional view of the same dielectric resonator as in Fig. 1.

[0009] Fig. 3 is an equivalent circuit diagram of the same dielectric resonator as in Fig. 1.

[0010] Fig. 4 is a fragmentary sectional view of the same dielectric resonator as in Fig. 1, when it is mounted on a substrate.

[0011] Fig. 5 is a perspective view of a dielectric filter in a second exemplary embodiment of the present invention.

[0012] Fig. 6 is an equivalent circuit diagram of the same dielectric filter as in Fig. 5.

[0013] Fig. 7 is an exploded perspective view showing the details of the same dielectric filter as in Fig. 5.

[0014] Fig. 8 is a perspective view of a prior art dielectric resonator.

[0015] Fig. 9 is a cross-sectional view of the same prior art dielectric resonator as in Fig. 8.

[0016] Fig. 10 is an equivalent circuit diagram of the same prior art dielectric resonator as in Fig. 8.

Detailed Description of Preferred Embodiments

(Example 1)

[0017] As shown in Fig. 1 and Fig. 2, a dielectric resonator comprises a molded body 1 made of a dielectric and having a through hole 2 passing through the molded body 1 from its open end 5 to opposite end 6, a first grounding electrode 3a disposed on outer side surfaces of the molded body 1, an internal conductor 4 disposed on the inner surface of the through hole 2 and a second grounding electrode 3b disposed on the opposite end 6 of the molded body 1 and connecting the first grounding electrode 3a to the internal conductor 4.
The through hole 2 includes a larger diameter cylindrical section 15 located towards the open end 5 and a smaller diameter cylindrical section 16 located towards the opposite end 6, and a non-electrode formed section 7 is disposed on a side surface of the molded body 1 at a position opposite to the larger diameter cylindrical section 15 and also an island shaped electrode 8 insulated from the first grounding electrode 3a is disposed within the non-electrode formed section 7.

[0018] In the dielectric resonator thus structured, an LC parallel resonance circuit 10 is formed by grounding the first grounding electrode 3a as shown in Fig. 3, and also a notch capacitance 11 is formed by the island shaped electrode 8 and internal conductor 4 with a dielectric inserted in between, and is connected in series to the foregoing LC parallel resonance circuit 10.

[0019] The through hole 2 is composed of the larger diameter cylindrical section 15 towards the side of the open end 5 and the smaller diameter cylindrical section 16 towards the side of the opposite end 6, thereby making it possible to vary the impedance of the dielectric resonator inside the through hole 2 and to make the length of the dielectric resonator smaller. Furthermore, since the island shaped electrode 8 is disposed on the outer surface of the molded body 1 at a position opposite to the larger diameter cylindrical section 15, the distance between the internal conductor 4 and the island shaped electrode 8 can be made small, thus realizing a large notch capacitance 11 without requiring a larger island shaped electrode 8.

[0020] An electrode protection film 9 made from an insulating glass material is applied to an area over the non-electrode formed sect ion 7 including the peripheral area of island shaped electrode 8, therefore an area 27 not covered by electrode protection film is formed on the island shaped electrode 8.
Thus, by providing the electrode protection film 9, a strong adhesion of the island shaped electrode 8 to the molded body 1 is assured.
In addition, when soldering is applied to the island shaped electrode 8, molten solder does not flow out of the island shaped electrode 8 since the peripheral area of the island shaped electrode 8 is covered by the electrode protection film 9, thus preventing such adverse effects as electrode peeling and the like from occurring and enabling a supply of a dielectric resonator having excellent reliability.

[0021] In the present exemplary embodiment, the electrode protection film 9 is applied only to cover the peripheral area of the island shaped electrode 8 and the non-electrode formed section 7. However, by applying the electrode protection film 9 to cover even the end of the first grounding electrode 3a located outside the island shaped electrode 8, it is made possible to prevent the electrode peeling of the end of the first grounding electrode 3a from taking place, thereby enabling a supply of a dielectric resonator with more excellent reliability.

[0022] Fig. 4 shows a dielectric filter constructed by mounting the dielectric resonator of Fig. 1 to Fig. 3 on a sub strate.

[0023] The substrate 14 has a grounding electrode pattern 12a and a connecting electrode pattern 12b formed thereon in advance, and the grounding electrode pattern 12a is connected to the first grounding electrode 3a of the dielectric resonator and at the same time the connecting electrode pattern 12b is connected to an area 27 not covered by electrode protection film located on the island shaped electrode 8 by reflow solder 13.

(Example 2)

[0024] Next, a second exemplary embodiment of the present invention will be explained with reference to drawings.

[0025] The second exemplary embodiment of the present invention is a band elimination filter of Fig. 6 constructed by mounting dielectric resonators 21a and 21b on a substrate 22 as shown in Fig. 5.

[0026] The foregoing substrate 22 has connecting electrode patterns 23a and 23b and a grounding electrode pattern 25 formed thereon in advance, and the foregoing connecting electrode patterns 23a and 23b are connected with each other by an air-core coil 24.
Furthermore, as shown in Fig. 7, a resist pattern 26 is formed on the surface of the foregoing substrate 22 in such a way as non-resist sections 28 and 29 are formed on the resist pattern 26 at the places corresponding to the ones where the foregoing connecting electrode patterns 23a and 23b and also the grounding electrode pattern 25 are located.

[0027] The foregoing dielectric resonators 21a and 21b have the same structures as the dielectric resonator as explained in Example 1 has.

[0028] As illustrated in Fig. 7, when the dielectric resonators 21a and 21b are mounted on the substrate 22, the first grounding electrode 3a of each of the dielectric resonators 21a and 21b is connected to the non-resist section 29 of the substrate 22 by reflow soldering and also the area 27 not covered by electrode protection film of each of the dielectric resonators 21a and 21b is connected to the non-resist section 28 of the substrate 22 by reflow soldering. Since the same shape is used for both of the foregoing area 27 not covered by electrode protection film and non-resist section 28, a shift in position of the dielectric resonators 21a and 21b is prevented even if reflow soldering is adopted in putting together the dielectric resonators 21a and 21b on the substrate 22, thus enabling a precision assembly of the band elimination filter.

Possible Applications in Industry

[0029] According to the present invention as described in the above, an internal conductor located opposite to an island shaped electrode is formed on a larger diameter cylindrical section of a through hole, thereby making the distance between the internal conductor and the island shaped electrode smaller and realizing a large notch capacitance without use of a larger island shaped electrode.
Also, the impedance of the dielectric resonator is changeable in the through hole 2 of the dielectric resonator to make it possible to use a shorter dielectric resonator, thereby enabling a supply of a dielectric resonator of excellent performance.

Key to Reference Numerals Used in Drawings

[0030] 

1

Molded Body

2

Through Hole

3a

First Grounding Electrode

3b

Second Grounding Electrode

4

Internal Conductor

5

Open End

6

Opposite End

7

Non-Electrode Section

8

Island Shaped Electrode

9

Electrode Protection Film

10

LC Parallel Resonance Circuit

11

Notch Capacitance

12a

Grounding Electrode Pattern

12b

Connecting Electrode Pattern

13

Reflow Solder

14

Substrate

15

Larger Diameter Cylindrical Section

16

Smaller Diameter Cylindrical Section

21a

Dielectric Resonator

21b

Dielectric Resonator

22

Substrate

23a

Connecting Electrode Pattern

23b

Connecting Electrode Pattern

24

Air-Core Coil

25

Grounding Electrode Pattern

26

Resist Pattern

27

Area Not Covered by Electrode Protection Film

28

Non-Resist Section

29

Non-Resist Section

30

Molded Body

31

Through Hole

32

First Grounding Electrode

33

Second Grounding Electrode

34

Internal Conductor

35

Open End

36

Opposite End

37

Non-Electrode Section

38

Island Shaped Electrode

39

Notch Capacitance

40

LC Parallel Resonance Circuit

Claims

1. A dielectric resonator comprising:

a molded body including a through hole that passes through said molded body from the open end to opposite end thereof and is composed of a larger diameter cylindrical section located towards the open end side of said molded body and a smaller diameter cylindrical section located towards the closed end side of said molded body;

a first grounding electrode disposed on the outer side surfaces of said molded body;

an internal conductor disposed on the inner surface of said through hole; and

a second grounding electrode disposed on the opposite end of said molded body and connecting said first grounding electrode to internal conductor,

and further comprising an island shaped electrode disposed on one of the outer side surfaces of said molded body at a place opposite to said larger diameter cylindrical section of the through hole and separated from said first grounding electrode.

2. A dielectric resonator comprising:

a molded body including a through hole that passes through said molded part from the open end to opposite end thereof and is composed of a larger diameter cylindrical section located towards the open end side of said molded body and a smaller diameter cylindrical section located towards the opposite end side of said molded body;

a first grounding electrode disposed on the outer side surfaces of said molded body;

an internal conductor disposed on the inner surface of said through hole; and

a second grounding electrode disposed on the opposite end of said molded body and connecting said first grounding electrode to internal conductor,

and further comprising an island shaped electrode disposed on one of the outer side surfaces of said molded body at a place opposite to said larger diameter cylindrical section of the through hole and separated from said first grounding electrode, the periphery of which is further covered with an electrode protection film made of an insulating material.

3. A dielectric resonator comprising:

a molded body including a through hole that passes through said molded part from the open end to opposite end thereof and is composed of a larger diameter cylindrical section located towards the open end side of said molded body and a smaller diameter cylindrical section located towards the opposite end side of said molded body;

a first grounding electrode disposed on the outer side surfaces of said molded body;

an internal conductor disposed on the inner surface of said through hole; and

a second grounding electrode disposed on the closed end surface of said molded body and connecting said first grounding electrode to internal conductor,

and further comprising an island shaped electrode disposed on one of the outer side surfaces of said molded body at a place opposite to said larger diameter cylindrical section of the through hole and separated from said first grounding electrode, the periphery of which and the end of the first grounding electrode located outside of which are covered with an electrode protection film made of an insulating material.

4. A dielectric filter comprising a substrate and

dielectric resonators mounted on said substrate, each of which includes:

a dielectric molded body having a through hole that passes through said molded body from the open end to opposite end thereof and is composed of a larger diameter cylindrical section located towards the open end side of said molded body and a smaller diameter cylindrical section located towards the opposite end side of said molded body;

a first grounding electrode disposed on the outer side surfaces of said molded body;

an internal conductor disposed on the inner surface of said through hole; and

a second grounding electrode disposed on the opposite end of said molded body and connecting said first grounding electrode to internal conductor,

and further includes:

an island shaped electrode disposed on one of the outer side surfaces of said molded body at a place opposite to said larger diameter cylindrical section of the through hole and separated from said first grounding electrode,

and said substrate having a connecting electrode pattern, a grounding electrode pattern and an electrode protection film covering said connecting electrode pattern formed on the surface thereof,

and also a place of said connecting electrode pattern located opposite to the island shaped electrode of said dielectric resonator having an area not covered by electrode protection film, which is shaped almost like the exposed area of said island shaped electrode.

5. The dielectric filter according to Claim 4, wherein the periphery of the island shaped electrode disposed on each respective dielectric resonator is covered with an electrode protection film made of an insulating material.

6. The dielectric filter according to Claim 5, wherein the edge surface of the first grounding electrode located outside the island shaped electrode disposed on each respective dielectric resonator is covered with an electrode protection film made of an insulating material.

7. A fabrication method for a dielectric filter comprising a substrate and dielectric resonators mounted on said substrate, each of which includes:

a dielectric molded body having a through hole that passes through said molded body from the open end to opposite end thereof and is composed of a larger diameter cylindrical section located towards the open end side of said molded body and a smaller diameter cylindrical section located towards the opposite end side of said molded body;

a first grounding electrode disposed on the outer side surfaces of said molded body;

an internal conductor disposed on the inner surface of said through hole; and

a second grounding electrode disposed on the opposite end of said molded body and connecting said first grounding electrode to internal conductor,

and further includes:

an island shaped electrode disposed on one of the outer side surfaces of said molded body at a place opposite to said larger diameter cylindrical section of the through hole and separated from said first grounding electrode,

and said substrate having a connecting electrode pattern, a grounding electrode pattern and an electrode protection film covering a part of said connecting electrode pattern formed on the surface thereof,

and also a place of said connecting electrode pattern located opposite to the island shaped electrode of said dielectric resonator having an area not covered by electrode protection film, which is shaped almost like the exposed area of said island shaped electrode,

and further the connections between the first grounding electrode of said dielectric resonator and the grounding electrode pattern of said substrate and between an exposed area of the island shaped electrode of said dielectric resonator and the area not covered by electrode protection film of the connecting electrode pattern of said substrate being simultaneously performed by means of reflow soldering.

Drawing