Ceramic waveguide filter with extracted pole

• US 5,926,079 A
• Filed: 12/05/1996
• Issued: 07/20/1999
• Est. Priority Date: 12/05/1996
• Status: Expired due to Term

• Current Assignee: CTS Corporation
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Ballance, Mark H., Sokola, Raymond, Pramanick, Protap, Heine, David R.
• Primary Examiner(s): Ham, Seungsook
• Application Number:
  US08/761,105
• Time in Patent Office: 957 Days
• Field of Search: 333/202, 333/206, 333/208, 333/212, 333/219.1
• US Class Current: 333/208
• CPC Class Codes: H01P 1/2088 Integrated in a substrate

Abstract

A ceramic waveguide filter made from a monolithic block of dielectric ceramic material which has longitudinally spaced resonators is described. Resonant structures having a grounded portion and ungrounded portion, each of the resonant structures being inductively coupled at the ungrounded portion describe the electrical schematic which corresponds to the waveguide filter. The positioning of the input and output on the block of dielectric ceramic material define a passband and also create a shunt resonant section. The shunt resonant section is associated with a shunt zero in the electrical schematic of the waveguide filter. Finally, the dielectric block of ceramic is mostly coated with an electrically conductive coating material with the exception of an uncoated area immediately surrounding the input and output. An extracted pole in the form of a shunt zero can provide a frequency response with a high side zero, low side zero, or both, and two extracted poles in the form of two shunt zeros can provide two high side zeros, two low side zeros, or one zero on each side of the passband. These features together provide a ceramic filter with a extracted pole.

Claims

1. A ceramic waveguide filter, comprising:

(a) a monolithic block of dielectric material having a plurality of longitudinally spaced resonant structures extending in a horizontal direction and providing a desired passband;

(b) an input and an output coupled to the plurality of longitudinally spaced resonant structures and at least one of the input and the output having a respective shunt resonant section immediately adjacent thereto and disposed in said block, said respective shunt resonant section having a resonant frequency which is outside the desired passband and providing a shunt zero;

(c) a first coupling resonant section disposed in said block having the input connected thereto and a second coupling resonant section disposed in said block having the output connected thereto, at least one of the first and second coupling resonant sections comprising a coupling interface, each of said coupling interfaces providing a first coupling means connected to the input or the output, a second coupling means connected to the plurality of longitudinally spaced resonant structures and a third coupling means connected to the shunt resonant section, and each of the first and second coupling resonant sections also being narrower in the horizontal direction than the plurality of longitudinally spaced resonant structures;

(d) the first and the second coupling resonant sections are respectively located between the plurality of longitudinally spaced resonant structures and the corresponding shunt resonant section and provide impedance matching and proper coupling of the plurality of longitudinally spaced resonant structures to the input and the output respectively; and

(e) the block being substantially covered by a conductive coating with the exception of an uncoated area immediately surrounding the input and the output.

2. The waveguide filter of claim 1 wherein the shunt resonant section provides at least one shunt zero outside the passband.

3. The waveguide filter of claim 1 wherein the input and the output are positioned in proximity to the end portions of the block such that respective shunt resonant sections are provided at both end portions of the block thereby providing two shunt zeros outside the passband.

4. The waveguide filter of claim 1 wherein a dimension of the shunt resonant section defines a halfwave shunt resonant section.

5. The waveguide filter of claim 1 wherein a dimension of the shunt resonant section defines a quarterwave shunt resonant section.

6. The waveguide filter of claim 1 wherein the input and the output comprise receptacles complementary configured to receive a conductor and the receptacles are connected to a circuit board.

7. The waveguide filter of claim 1 wherein the passband has a predetermined bandwidth which is in the range of about 0.5 to about 20 Giga-Hertz.

8. The waveguide filter of claim 1 wherein the number of longitudinally spaced resonant structures is substantially equal to a number of poles in the waveguide filter.

9. A ceramic waveguide filter, comprising:

(a) a monolithic block of dielectric material having side surfaces and having substantially vertical slots symmetrically placed on the side surfaces defining longitudinally spaced resonant structures extending in a horizontal direction and providing a desired passband;

(b) an input and an output having conductively coated blind holes disposed in said block defining receptacles, the input and the output coupled to the plurality of longitudinally spaced resonant structures and at least one of the input and the output having a respective shunt resonant section immediately adjacent thereto and disposed in said block, said respective shunt resonant section having a resonant frequency which is outside the desired passband and providing a shunt zero;

(c) a first coupling resonant section disposed in said block having the input connected thereto and a second coupling resonant section disposed in said block having the output connected thereto;

at least one of the first and second coupling resonant sections comprising a coupling interface, each of said coupling interfaces providing a first coupling means connected to the input or the output, a second coupling means connected to the plurality of longitudinally spaced resonant structures and a third coupling means connected to the shunt resonant section, and each of the first and second coupling resonant sections also being narrower in the horizontal direction than the plurality of longitudinally spaced resonant structures;

(d) the first and the second coupling resonant sections are respectively located between the plurality of longitudinally spaced resonant structures and the corresponding shunt resonant section and provide impedance matching and proper coupling of the plurality of longitudinally spaced resonant structures to the input and the output respectively; and

(e) the block being substantially covered by a conductive coating with the exception of an uncoated area immediately surrounding the receptacles.

11. The waveguide filter of claim 9 wherein the number of longitudinally spaced resonant structures is substantially equal to a number of poles in the waveguide filter.

12. The waveguide filter of claim 9 wherein the passband has a predetermined bandwidth which is in the range of about 500 to about 1000 Mega-Hertz.

10. A ceramic waveguide filter, comprising:

(a) a monolithic block of dielectric material having a plurality of longitudinally spaced resonant structures extending in a horizontal direction and providing a desired passband;

(b) an input and an output coupled to the plurality of longitudinally spaced resonant structures and at least one of the input and the output having a respective shunt resonant section immediately adjacent thereto and disposed in said block, said respective shunt resonant section having a resonant frequency which is outside the desired passband and providing a shunt zero, and

(c) a single coupling resonant section disposed in said block having the input or the output connected thereto;

the single coupling resonant section comprising a coupling interface providing a first coupling means connected to the input or the output and a second coupling means connected to the plurality of longitudinally spaced resonant structures and a third coupling means connected to the shunt resonant section, and the single coupling resonant section also being narrower in the horizontal direction than the plurality of longitudinally spaced resonant structures;

(d) the single coupling resonant section is between the plurality of longitudinally spaced resonant structures and the shunt resonant section and provides impedance matching and proper coupling of the plurality of longitudinally spaced resonant structures to the input or the output; and

(e) the block being substantially covered by a conductive coating with the exception of an uncoated area immediately surrounding the input and the output.