Apparatus for providing desired coupling in dual-mode dielectric resonator filters

• US 5,495,216 A
• Filed: 04/14/1994
• Issued: 02/27/1996
• Est. Priority Date: 04/14/1994
• Status: Expired due to Term

• Current Assignee: Allen Telecom LLC (CommScope Holding Company, Inc.)
• Original Assignee: Allen Telecom Group, Inc.
• Inventors: Jachowski, Douglas
• Primary Examiner(s): Pascal, Robert J.
• Assistant Examiner(s): GAMBINO, DARUIS
• Application Number:
  US08/227,739
• Time in Patent Office: 684 Days
• Field of Search: 333/202, 333/219.1, 333/208-212, 333/230
• US Class Current: 333/208
• CPC Class Codes: H01P 1/2086 multimode

Abstract

A dual-mode dielectric-resonator-loaded cavity filter comprises a generally cylindrical cavity, at least two longitudinally-spaced dielectric resonator elements coaxially aligned within the cavity, and at least one coupling obstacle disposed between the resonators and extending a distance from the cavity wall. The coupling obstacles are preferably conductive and are electrically connected to the cavity wall. However, the obstacles may be constructed of a dielectric material in some applications. Each obstacle may be aligned with one of the reference planes corresponding to a resonant mode of the resonators to effectively control or reduce the coupling between the parallel resonant modes of adjacent resonators. The reduction in coupling between resonant modes of adjacent resonators allows large coupling differentials to be produced, allowing a filter designer to implement a wide variety of high-performance filters without expensive irises. The coupling obstacle achieves the reduction in coupling without requiring large spacing between adjacent resonators. The coupling obstacles may be conveniently and inexpensively produced in bar, wire, hemi-disk, and other configurations. Several adjustments allow the resonators to be tuned, and the couplings to be adjusted, after the filter is assembled, reducing the complexity and expense of manufacture. In particular, the coupling obstacles arc mounted for limited translation along the longitudinal axis of the cavity, and for rotation about their own longitudinal axes, thereby adjusting the amount of coupling reduction they provide.

Claims

1. A radio-frequency filter comprising:

an enclosure;

at least first and second dielectric resonators disposed coaxially within said enclosure in a spaced longitudinal relationship;

each of said resonators being adapted to resonate in first and second resonant modes;

said first and second resonant modes being orthogonal;

said first resonant modes of said first and second resonators being parallel;

said first resonant modes of said first and second resonators being subject to electromagnetic coupling;

said coupling having an electric field component and a magnetic field component;

obstacle means disposed within said enclosure and positioned longitudinally between said first and second resonators to reduce said coupling;

said obstacle means predominantly disposed parallel to said electric field component of said coupling;

wherein said enclosure has at least one wall surface and said coupling obstacle means is a volumetric solid having at least first and second exterior edge contour sections, said first contour section having a shape matching that of said wall surface, said obstacle means being disposed within said enclosure such that said first contour section contacts said wall surface substantially over the entire extent of said first contour section, and said second contour section is substantially out of contact with any wall section.

2. The device of claim 1 wherein said enclosure is a generally cylindrical conductive cavity.

3. The filter of claim 1 wherein said coupling obstacle means is formed as a substantially solid bar of conductive material.

4. The filter of claim 1 wherein said coupling obstacle means is formed as a thin conductive wire.

5. The filter of claim 1 wherein said coupling obstacle means is formed as a truncated disk.

6. A radio-frequency filter comprising:

an enclosure;

said enclosure having at least one wall surface;

first and second dielectric resonator means disposed within said enclosure in a spaced relationship;

said first and second dielectric resonator means defining therebetween an interstitial region;

each of said first and second dielectric resonator means having a center of mass;

said centers of mass defining a longitudinal axis extending therebetween;

at least one coupling obstacle means extending from said wall surface into said interstitial region;

said coupling obstacle means occluding less than half of the cross-sectional area within said enclosure as measured along a plane perpendicular to said longitudinal axis and with said plane intersecting at least a portion of said coupling obstacle means;

wherein said coupling obstacle means is a volumetric solid having at least first and second exterior edge contour sections, said first contour section having a shape matching that of said wall surface, said obstacle means being disposed within said enclosure such that said first contour section contacts said wall surface substantially over the entire extent of said first contour section, and said second contour section is substantially out of contact with any wall section.

7. The filter of claim 6 wherein said coupling obstacle means is formed as a substantially solid bar of conductive material.

8. The filter of claim 6 wherein said coupling obstacle means is formed as a thin conductive wire.

9. The filter of claim 6 wherein said coupling obstacle means is formed as a truncated disk.

10. A radio-frequency filter comprising:

an enclosure;

said enclosure having at least one wall surface;

first and second dielectric resonator means disposed within said enclosure in a spaced relationship;

said first and second dielectric resonator means defining therebetween an interstitial region within said enclosure;

each of said first add second dielectric resonator means having a center of mass;

said centers of mass defining a filter longitudinal axis extending therebetween;

and at least one coupling obstacle means extending from said wall surface into said interstitial region;

said coupling obstacle means being formed as a substantially solid elongate member having first and second longitudinally spaced ends;

said coupling obstacle means contacting wall surfaces of said enclosure substantially exclusively at said first and second ends;

wherein said coupling obstacle means has a longitudinal axis and said coupling obstacle means has means for adjusting the size of a cross-sectional area defined by the intersection of the exterior surface of the coupling obstacle with a plane parallel to said obstacle longitudinal axis and perpendicular to said filter longitudinal axis.

11. The filter of claim 10 wherein said elongate member has a rectangular cross section.

12. The filter of claim 10 wherein said elongate member has a non-circular cross section.

13. The filter of claim 12 wherein said elongate member has an elliptical cross section.

14. The filter of claim 10 wherein said elongate member has means permitting rotation of said coupling obstacle about its longitudinal axis.

15. The filter of claim 10 wherein said filter has means permitting rotation of said elongate member about an axis non-co-linear with its longitudinal axis.

16. The filter of claim 10 further comprising means for permitting adjustable displacement of said coupling obstacle through a range of positions along said longitudinal axis.

17. A radio-frequency filter comprising:

an enclosure;

said enclosure having at least one wall surface;

first and second dielectric resonator means disposed within said enclosure in a spaced relationship;

said first and second dielectric resonator means defining therebetween an interstitial region within said enclosure;

and at least one coupling obstacle means extending from said wall surface into said interstitial region;

said coupling obstacle means being formed as a volumetric solid having at least first and second exterior edge contour sections, said first contour section having a shape matching that of said wall surface, said obstacle means being disposed within said enclosure such that said first contour section contacts said wall surface substantially over the entire extent of said first contour section, and said second contour section is substantially out of contact with any wall section.