Dielectric filter, antenna duplexer, and communications appliance

• US 20030141943A1
• Filed: 01/08/2003
• Published: 07/31/2003
• Est. Priority Date: 05/30/2000
• Status: Active Grant

• Current Assignee: Hideaki Nakakubo, Hiroshi Kushitani, Hiroshi Shigemura, Tomoya Maekawa, Toru Yamada, Toshio Ishizaki
• Original Assignee: Hideaki Nakakubo, Hiroshi Kushitani, Hiroshi Shigemura, Tomoya Maekawa, Toru Yamada, Toshio Ishizaki
• Inventors: Maekawa, Tomoya, Ishizaki, Toshio, Yamada, Toru, Nakakubo, Hideaki, Kushitani, Hiroshi, Shigemura, Hiroshi
• Granted Patent: US 6,747,528 B2
• Time in Patent Office: Days
• US Class Current: 333/134
• CPC Class Codes: H01P 1/20345 Multilayer filters
• CPC Class Codes: H01P 1/2135 using strip line filters H01P1/2131 takes precedence

Abstract

A dielectric filter, has

a plurality of resonators; and

at least one transmissions line provided among said plurality of resonators,

wherein a band rejection characteristic is formed around a resonance frequency of said resonator, and a line length of said transmission line is shorter than ¼ of a wavelength corresponding to the resonance frequency of said resonator.

Claims

1. A dielectric filter, comprising:

a plurality of resonators; and

at least one transmission line provided among said plurality of resonators,

wherein a band rejection characteristic is formed around a resonance frequency of said resonator, and a line length of said transmission line is shorter than ¼

of a wavelength corresponding to the resonance frequency of said resonator.

2. The dielectric filter according to claim 1, wherein said plurality of resonators are coupled in electromagnetic field.

3. The dielectric filter according to claim 2, wherein:

a dielectric sheet and an electrode layer are layered and co-fired into one layered structure; and

said resonator and said transmission line are realized as an entire or a part of said electrode layer.

4. The dielectric filter according to claim 3, wherein

said dielectric sheet comprises at least one dielectric layer;

said electrode layer comprises;

a plurality of resonator electrodes provided on one primary surface of said dielectric layer; and

a transmission line electrode, provided on another primary surface of said dielectric layer, whose ends are input/output terminals;

said resonator electrode operates as said resonator; and

in a projection drawing where said resonator electrode and said transmission line electrode are viewing from a direction perpendicular to a surface of said dielectric layer, there are a plurality of overlapping portions of said transmission line electrode and adjacent said resonator electrodes, such portion of said transmission electrode that is positioned between each central point of said overlapping portions, corresponds to said transmission line, and a part of said transmission line electrode is positioned along central points of an overlapping portion of said resonator electrodes and said transmission line electrode, and corresponds to said transmission line.

5. The dielectric filter according to claim 3, wherein

said dielectric sheet comprises at least five dielectric layers from a first dielectric layer to a fifth dielectric layer;

said electrode layer comprises at least;

a first shield electrode provided between said first dielectric layer and said second dielectric layer;

a plurality of resonator electrodes provided between said second dielectric layer and said third dielectric layer;

a transmission line electrode which has input/output terminals at both ends and is provided between said third dielectric layer and said fourth dielectric layer; and

a second shield electrode provided between said fourth dielectric layer and said fifth dielectric layer;

said resonator electrode operates as a resonator; and

in a projection drawing where said resonator electrode and said transmission line electrode are viewing from a direction perpendicular to a surface of said dielectric layer, there are a plurality of overlapping portions of said transmission line electrode and adjacent said resonator electrodes, such portion of said transmission electrode that is positioned between each central point of said overlapping portions, corresponds to said transmission line, and a part of said transmission line electrode is positioned along central points of an overlapping portion of said resonator electrodes and said transmission line electrode, and corresponds to said transmission line.

6. The dielectric filter according to claim 5, further comprising:

a plurality of adjusting electrodes provided on a surface of said fifth dielectric layer on which said second shield electrode is not provided; and

side electrodes which are provided on sides of said layered structure of said first to fifth dielectric layers and are connected to the input/output terminals on both ends of said transmission line electrode, wherein

said plurality of adjusting electrodes and said side electrodes are interconnected.

7. The dielectric filter according to claim 3, wherein

said dielectric sheet comprises at least five dielectric layers from a first dielectric layer to a fifth dielectric layer;

said electrode layer comprises at least;

a first shield electrode provided between said first dielectric layer and said second dielectric layer;

a plurality of first resonator electrodes provided between said second dielectric layer and said third dielectric layer;

a transmission line electrode which has input/output terminals at both ends and is provided between said third dielectric layer and said fourth dielectric layer;

a second shield electrode provided between said fourth dielectric layer and said fifth dielectric layer;

a second resonator electrode provided on a surface of said fifth dielectric layer on which said second shield electrode is not provided; and

a third resonator electrode which are provided on outer peripheral sides of said layered structure of said first to fifth dielectric layers and are connected to one end of said first resonator electrode and one end of said second resonator electrode;

said resonator electrode operates as a resonator; and

in a projection drawing where said resonator electrode and said transmission line electrode are viewing from a direction perpendicular to a surface of said dielectric layer, there are a plurality of overlapping portions of said transmission line electrode and adjacent said resonator electrodes, such portion of said transmission electrode that is positioned between each central point of said overlapping portions, corresponds to said transmission line, and a part of said transmission line electrode is positioned along central points of an overlapping portion of said resonator electrodes and said transmission line electrode, and corresponds to said transmission line.

8. The dielectric filter according to claim 3, wherein

said dielectric sheet comprises at least seven dielectric layers from a first dielectric layer to a seventh dielectric layer;

said electrode layer comprises at least;

a first shield electrode provided between said first dielectric layer and said second dielectric layer;

a plurality of first resonator electrodes provided between said second dielectric layer and said third dielectric layer;

a third shield electrode provided between said third dielectric layer and said fourth dielectric layer;

a second resonator electrode provided between said fourth dielectric layer and said fifth dielectric layer;

a transmission line electrode which has input/output terminals on both ends and provided between said fifth dielectric layer and said sixth dielectric layer;

a second shield electrode provided between said sixth dielectric layer and said seventh dielectric layer; and

a third resonator electrode which are provided on outer peripheral sides of said layered structure of said first to seventh dielectric layers and are connected to one end of said first resonator electrode and one end of said second resonator electrode;

said resonator electrode operates as a resonator; and

in a projection drawing where said resonator electrode and said transmission line electrode are viewing from a direction perpendicular to a surface of said dielectric layer, there are a plurality of overlapping portions of said transmission line electrode and adjacent said resonator electrodes, such portion of said transmission electrode that is positioned between each central point of said overlapping portions, corresponds to said transmission line, and a part of said transmission line electrode is positioned along central points of an overlapping portion of said resonator electrodes and said transmission line electrode, and corresponds to said transmission line.

9. The dielectric filter according to any one of claims 1 to 3, wherein an open end of said resonator is a wide portion and a short circuit side is a narrow portion with a line width on the short circuit side made narrower halfway of said resonator.

10. The dielectric filter according to any one of claims 1 to 3, wherein a central portion of said resonator is a wide portion, and a short circuit side and an open end side are narrow portions.

11. The dielectric filter according to any one of claims 1 to 3, 9, and 10, wherein one end of said plurality of resonators is short circuited, and another end is set open.

12. The dielectric filter according to any one of claims 1 to 3, 9, and 10, wherein both ends of said plurality of resonators are open or short circuited.

13. The dielectric filter according to any one of claims 5, 7, and 8, wherein all or a part of said first to third shield electrodes are connected and grounded.

14. The dielectric filter according to any one of claims 5, 7, and 8, wherein said first to fifth dielectric layers or said first to seventh dielectric layers have different thicknesses.

15. The dielectric filter according to any one of claims 5, 7, and 8, wherein said first to fifth dielectric layers or said first to seventh dielectric layers comprise dielectrics having relative dielectric constant.

16. A antenna duplexer, wherein a dielectric filter according to anyone of claims 1 to 15 is used as one or both of a transmission filter and a reception filter.

17. A communications appliance using a dielectric filter according to any one of claims 1 to 15.

18. The dielectric filter according to any one of claims 1 to 8 used in microwave bands.

19. The dielectric filter according to any one of 1 to 8, wherein a line length of said transmission line is at least equal to or longer than {fraction (1/102)} of a wavelength corresponding to a resonance frequency of said resonator.

20. A dielectric filter comprising at least one transmission line, a plurality of resonators connected to said transmission line, and a plurality of capacitors provided between said resonator and said transmission line, and forming a band rejection characteristic around the resonance frequency of the resonator,

wherein a plurality of values of capacitances of said capacitors are different to each other.

21. The dielectric filter according to claim 20, wherein:

said transmission line has input/output terminals at both ends; and

said each capacitor of plurality of capacitors has different capacity values depending on impedance conditions at each input/output terminal of said transmission line.

22. The dielectric filter according to claim 21, wherein among said plurality of input/output terminals, capacity values of input/output terminals having higher impedance are smaller than capacity values of input/output terminals having lower impedance.

23. The dielectric filter according to claim 20, wherein said transmission line is formed by said resonator and said transmission line, which are plane electrodes, on a plurality of dielectric sheets as a layered structure co-fired into laminated structure.

32. A antenna duplexer, comprising:

a transmission filter and a reception filter,

wherein said transmission filter and/or said reception filter comprises the dielectric filter according to any one of claims 20 to 31.

33. A communications appliance, comprising:

an antenna;

a matching circuit connected to said antenna;

a transmission filter connected to said matching circuit;

a transmission circuit connected to said transmission filter;

a reception filter connected to said matching circuit; and

a reception circuit connected to said reception filter,

wherein said transmission filter and/or said reception filter comprise the dielectric filter according to any one of claims 20 to 31.

24. A dielectric filter having a layered structure, comprising:

a first shield electrode;

a dielectric layer (1) provided on said first shield electrode;

a plurality of resonator electrodes provided on said dielectric layer (1);

a dielectric layer (2) provided on said plurality of resonator electrodes;

a transmission line electrode which are provided on said dielectric layer (2) and whose both ends are input/output terminals;

a plurality of capacitors connected to said transmission line electrode, provided on same dielectric layer (2), positioned opposite said plurality of resonator electrodes partially through said dielectric layer (2);

a dielectric layer (3) provided on said transmission line electrode and said plurality of capacitor electrodes;

a second shield electrode provided on said dielectric layer (3); and

side electrodes provided on sides, wherein

a band rejection characteristic is formed around a resonance frequency of said resonator; and

an area of said resonator electrode opposite said capacitor electrode through said dielectric layer (2) is different each other from an area of said capacitor electrode.

25. The dielectric filter according to claim 24, wherein open ends of said plurality of resonator electrodes are connected to other respective side electrodes.

26. The dielectric filter according to claim 25, wherein a dielectric layer (4) is provided on said second shield electrode, adjusting electrodes equal in number to said resonator electrodes are provided on a top surface of said dielectric layer (4), and, among said plurality of side electrodes, said adjusting electrodes are connected to side electrodes connected to said resonator electrode respectively.

27. The dielectric filter according to claim 24, wherein said side electrodes are connected to both input/output terminals of said transmission line electrode, a dielectric layer (4) is provided on said second shield electrode, an adjusting electrode is provided on a top surface of said dielectric layer (4), and said side electrodes connected to said transmission line electrode are connected to said adjusting electrodes respectively.

28. The dielectric filter according to claim 24, wherein one end of each of said plurality of resonator electrodes is connected to a predetermined side electrode through a short circuit end, and another end of each of said plurality of resonator electrodes is an open end.

29. The dielectric filter according to claim 24, wherein both ends of said plurality of resonator electrodes are open ends.

30. The dielectric filter according to claim 24, wherein among said plurality of resonator electrodes, a thickness of at least one resonator electrode is different from thicknesses of other resonator electrodes.

31. The dielectric filter according to claim 24, wherein

each of said dielectric layers has a dielectric material having a different specific inductive capacity.

34. A dielectric filter, comprising:

a plurality of resonators;

at least one transmission line provided among said plurality of resonators; and

a capacitor provided between said resonator and said transmission line,

wherein;

a band rejection characteristic is formed around a resonance frequency of said resonator;

a line length of said transmission line is shorter than ¼

of a length of a waveform corresponding to a resonance frequency of said resonator; and

said plurality of capacitors have different capacity values.

35. The dielectric filter according to claim 34, wherein:

said plurality of resonators are coupled in electromagnetic field;

said transmission line has input/output terminals at both ends; and

each capacitor of said plurality of capacitors has different capacity values depending on impedance conditions at each input/output terminal of said transmission line.

36. The dielectric filter according to claim 35, wherein among said plurality of input/output terminals, capacity values of input/output terminals having higher impedance are smaller than capacity values of input/output terminals having lower impedance.

37. The dielectric filter according to any one of claims 34 to 36, wherein:

a dielectric sheet and an electrode layer are layered and co-fired into one layered structure; and

said resonator and said transmission line are realized as an entire or a part of said electrode layer.

38. A dielectric filter, comprising:

a plurality of resonators; and

at least one transmission line provided among said plurality of resonators,

wherein a band rejection characteristic is formed around a resonance frequency of said resonator, and a line length of said transmission line is longer than ¼

of a wavelength corresponding to the resonance frequency of said resonator.

39. The dielectric filter according to claim 38, wherein said plurality of resonators are coupled in electromagnetic field.

40. The dielectric filter according to claim 39, wherein:

a dielectric sheet and an electrode layer are layered and co-fired into one layered structure; and

said resonator and said transmission line are realized as an entire or a part of said electrode layer.