BANDPASS FILTER WITH DUAL BAND RESPONSE

• US 20100164651A1
• Filed: 12/30/2008
• Published: 07/01/2010
• Est. Priority Date: 12/30/2008
• Status: Active Grant

• Current Assignee: TDK Corporation
• Original Assignee: TDK Corporation
• Inventors: Erb, Jean-Luc
• Granted Patent: US 8,680,952 B2
• Time in Patent Office: Days
• US Class Current: 333/204
• CPC Class Codes: H01P 1/20345 Multilayer filters

Abstract

There is provided an improved bandpass filter having multiple passbands, and in one embodiment, two independent passbands are provided by a single filter. Embodiments of the present invention support communication architectures with several frequency bands without requiring one signal path per band, thus realizing improvements in size, cost, and weight. One aspect of the invention utilizes strongly overcoupled resonators to achieve multiple passband response, and in various embodiments, single-ended or differential mode inputs and outputs are accommodated.

Claims

1. A dual-band filter comprising:

a substrate; and

first and second resonators disposed within the substrate, each of the resonators respectively having an open circuit end and a short circuit end;

wherein the first and second resonators are connected through a low-reactance inter-resonator coupling, the inter-resonator coupling configuring the filter to provide dual-band response.

2. The dual-band filter as disclosed in claim 1 wherein the low-reactance inter-resonator coupling component comprises at least one of:

a transmission line substantially shorter than a quarter wavelength;

an inductor;

a capacitor; and

a resistor.

3. The dual-band filter as disclosed in claim 1 wherein the low-reactance inter-resonator coupling component is coupled between the first and second resonators at any predetermined location along the length of the first and second resonator.

4. The dual-band filter as disclosed in claim 1 comprising first and second low-reactance inter-resonator coupling components connected to the resonators in parallel.

5. The dual-band filter as disclosed in claim 1 wherein the first and second resonators respectively comprise transverse electromagnetic quarter-wave resonators.

6. The dual-band filter as disclosed in claim 1 wherein the first and second resonators respectively comprise one of a combline resonator, an interdigital resonator, and an edge-coupled resonator.

7. The dual-band filter as disclosed in claim 1 wherein the resonators are respectively loaded by respective capacitors at the open circuit end, wherein each respective capacitor connects a respective resonator to ground.

8. The dual-band filter as disclosed in claim 1 wherein the resonators are over-coupled at the short circuit end.

9. The dual-band filter as disclosed in claim 1 wherein the substrate comprises at least one of a low temperature co-fired ceramic substrate, a high temperature co-fired ceramic substrate, a silicon substrate, a gallium arsenide substrate, and an organic circuit substrate.

10. The dual-band filter as disclosed in claim 9 wherein the substrate comprises a multilayer structure.

11. The dual-band filter as disclosed in claim 10 wherein the first and second resonators are disposed on the same layer within the multilayer structure, wherein at least one conductive plane on a disparate layer of the multilayer structure configures the circuit as a microstrip architecture.

12. The dual-band filter as disclosed in claim 10 wherein the first and second resonators are disposed on the same layer within the multilayer structure, wherein at least two conductive planes on disparate layers of the multilayer structure configures the circuit as a stripline architecture.

13. The dual-band filter as disclosed in claim 10 wherein:

the first and second resonators are disposed on the same layer within the multilayer structure; and

the first and second resonators are respectively coupled to at least one loading capacitor formed by at least one top conductive plane disposed on a layer above the first and second resonators, the at least one top conductive plane situated above at least one lower conductive plane disposed on a layer below the first and second resonators.

14. The dual-band filter as disclosed in claim 1 wherein the low-reactance inter-resonator coupling component comprises a common transmission line to ground, the common transmission line coupled between a common tapping of the first and second resonators.

15. The dual-band filter as disclosed in claim 1 further comprising:

a third resonator disposed within the substrate, the third resonator having an open circuit end and a short circuit end;

wherein;

the first, second, and third resonators are connected through a low-reactance inter-resonator coupling, the inter-resonator coupling configuring the filter to provide dual-band response;

the low-reactance inter-resonator coupling component comprises a common transmission line to ground, the common transmission line coupled between a common tapping of the first, second, and third resonators;

the first, second and third resonators are respectively loaded by respective capacitors at the open circuit end, wherein each respective capacitor connects a respective resonator to ground; and

a feedback capacitor is coupled between the open circuit ends of the first and third resonators.

16. The dual-band filter as disclosed in claim 15 further comprising a feedback capacitor coupled between open circuit ends of at least two of the first, second, and third resonators.

17. A dual-band filter comprising:

a substrate;

first and second resonators disposed within the substrate, each of the resonators respectively having an open circuit end and a merging end;

wherein the first and second resonators are connected to ground by a transmission line at their respective merging ends.

18. The dual-band filter as disclosed in claim 17 further comprising a coupling element coupled between the first and second resonators proximate to the respective short-circuit ends of the resonators.

19. The dual-band filter as disclosed in claim 18 wherein the coupling element comprises at least one of a capacitor and an inductor.

20. The dual-band filter as disclosed in claim 18 wherein the coupling element comprises a transmission line substantially shorter than a quarter wavelength.

21. The dual-band filter as disclosed in claim 17 further comprising a coupling element coupled between the first and second resonators proximate to the respective merging ends of the resonators.

22. The dual-band filter as disclosed in claim 17 wherein each of the first and second resonators is a transverse electromagnetic quarter-wave resonator.

23. The dual-band filter as disclosed in claim 17 wherein the first and second resonators respectively comprise one of a combline resonator, an interdigital resonator, and an edge-coupled resonator.

24. The dual-band filter as disclosed in claim 17 wherein the first and second the resonators are strongly over-coupled at the open circuit end.

25. The dual-band filter as disclosed in claim 17 wherein the first and second resonators are respectively loaded by respective capacitors coupled between the respective open circuit ends and ground.

26. The dual-band filter as disclosed in claim 17 wherein the substrate comprises at least one of a low temperature co-fired ceramic substrate, a high temperature co-fired ceramic substrate, a silicon substrate, a gallium arsenide substrate, and an organic circuit substrate.

27. The dual-band filter as disclosed in claim 26 wherein the first and second resonators are disposed on the same layer within the multilayer structure, wherein at least one conductive plane on a disparate layer of the multilayer structure configures the circuit as a microstrip architecture.

28. The dual-band filter as disclosed in claim 26 wherein the first and second resonators are disposed on the same layer within the multilayer structure, wherein at least two conductive planes on disparate layers of the multilayer structure configures the circuit as a stripline architecture.

29. The dual-band filter as disclosed in claim 26 wherein:

the first and second resonators are disposed on the same layer within the multilayer structure; and

the first and second resonators are respectively coupled to at least one loading capacitor formed by at least one top conductive plane disposed on a layer above the first and second resonators, the at least one top conductive plane situated above at least one lower conductive plane disposed on a layer below the first and second resonators.

30. The dual-band filter as disclosed in claim 25 further comprising a third resonator disposed within the substrate and having an open circuit end and a merging end, the merging end connected to the transmission line, and a third loading capacitor coupled between the open circuit end of the third resonator and ground.

31. The dual-band filter as disclosed in claim 30 further comprising a coupling element coupled between two of the three resonators at their respective open circuit ends.

32. The dual-band filter as disclosed in claim 31 wherein the coupling element comprises at least one of a capacitor and an inductor.

33. The dual-band filter as disclosed in claim 30 wherein the third resonator is coupled to the first and second resonators through a transmission line substantially shorter than a quarter wavelength.

34. The dual-band filter as disclosed in claim 31 wherein the coupling element comprises a transmission line substantially shorter than a quarter wavelength and at least one of a capacitor and an inductor.

35. A dual-band differential filter comprising:

a substrate;

a first input coupled to a first overcoupled resonator assembly disposed within the substrate and including a first plurality of resonators having a short circuit end and a merging end;

a second input coupled to a second overcoupled resonator assembly disposed within the substrate comprising a second plurality of resonators having a short circuit end and a merging end;

an output coupled to the first overcoupled resonator assembly; and

wherein the first plurality of resonators are respectively disposed in vertically offset substantially parallel proximity to the second plurality of resonators.

36. The dual-band differential filter as disclosed in claim 35 wherein:

the plurality of resonators of the first overcoupled resonator assembly are respectively connected at the merging end through a first low-reactance inter-resonator coupling;

the plurality of resonators of the second overcoupled resonator assembly are respectively connected at the merging end through a second low-reactance inter-resonator coupling; and

wherein the first and second inter-resonator couplings configure the filter to provide dual-band response.

37. The dual-band differential filter as disclosed in claim 36 wherein the first and second low-reactance inter-resonator coupling components respectively comprise at least one of:

a transmission line substantially shorter than a quarter wavelength;

an inductor;

a capacitor; and

a resistor.

38. The dual-band differential filter as disclosed in claim 36 wherein the plurality of resonators of the first and second overcoupled resonator assemblies respectively comprise transverse electromagnetic quarter-wave resonators.

39. The dual-band differential filter as disclosed in claim 36 wherein the plurality of resonators of the first and second overcoupled resonator assemblies respectively comprise one of a combline resonator, an interdigital resonator, and an edge-coupled resonator.

40. The dual-band differential filter as disclosed in claim 36 wherein:

the first overcoupled resonator assembly and the second overcoupled resonator assembly are respectively disposed on adjacent signal layers within a multilayer structure;

the second overcoupled resonator assembly comprises substantially similar resonator dimensions and spacing as the first overcoupled resonator assembly; and

the second overcoupled resonator assembly is disposed so as to be 180 degrees rotated about an axis perpendicular to the signal layers with respect to the first overcoupled resonator, wherein;

the respective resonators of the first and second pluralites of resonators are respectively proximal and substantially parallel; and

first and second low-reactance inter-resonator couplings are substantially removed from one another.

41. The dual-band differential filter as disclosed in claim 35 wherein a spatial arrangement of the first plurality of resonators is substantially similar to a spatial arrangement of the second plurality of resonators.

42. The dual-band differential filter as disclosed in claim 41 wherein the merging end of the first plurality of resonators is proximate to the short circuit end of the second plurality of resonators.

43. The dual-band differential filter as disclosed in claim 36 wherein the first plurality of resonators includes two resonators and the second plurality of resonators comprises two resonators.

44. The dual-band differential filter as disclosed in claim 36 wherein the first plurality of resonators includes three resonators and the second plurality of resonators comprises three resonators.

45. The dual-band differential filter as disclosed in claim 36 further comprising a second output coupled to the second overcoupled resonator assembly.

46. The dual-band differential filter as disclosed in claim 35 wherein the substrate comprises at least one of a low temperature co-fired ceramic substrate, a high temperature co-fired ceramic substrate, a silicon substrate, a gallium arsenide substrate, and an organic circuit substrate.

47. The dual-band differential filter as disclosed in claim 46 wherein the substrate comprises a multilayer structure.

48. The dual-band differential filter as disclosed in claim 47 wherein the first overcoupled resonator assembly and the second overcoupled resonator assembly are respectively disposed on adjacent signal layers within the multilayer structure, wherein at least one conductive plane on a disparate layer of the multilayer structure configures the circuit as a microstrip architecture.

49. The dual-band differential filter as disclosed in claim 48, wherein the adjacent signal layers are separated by approximately 20-40 μ

m.

50. The dual-band differential filter as disclosed in claim 47, wherein the first overcoupled resonator assembly and the second overcoupled resonator assembly are respectively disposed on adjacent signal layers within the multilayer structure, wherein at least two conductive planes on a disparate layers of the multilayer structure configures the circuit as a stripline architecture.

51. The dual-band differential filter as disclosed in claim 50, wherein the adjacent signal layers are separated by approximately 20-40 μ

m.

52. The dual-band differential filter as disclosed in claim 47 wherein:

the first overcoupled resonator assembly and the second overcoupled resonator assembly are respectively disposed on adjacent signal layers within the multilayer structure; and

the first and second overcoupled resonator assemblies are respectively coupled to at least one loading capacitor formed by at least one top conductive plane disposed on a layer above the first and second resonators, the at least one top conductive plane situated above at least one lower conductive plane disposed on a layer below the first and second overcoupled resonator assemblies.

53. The dual-band differential filter as disclosed in claim 52, wherein the at least one loading capacitor further comprises dielectric medium disposed between the top conductive plane and the loser conductive plane, the dielectric comprising ceramic substrate material.