Ceramic filter with a coplanar shield

• US 5,745,018 A
• Filed: 07/09/1996
• Issued: 04/28/1998
• Est. Priority Date: 07/09/1996
• Status: Expired due to Term

• Current Assignee: CTS Corporation
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Vangala, Reddy R.
• Primary Examiner(s): LEE, BENNY T
• Application Number:
  US08/677,154
• Time in Patent Office: 658 Days
• Field of Search: 333/203, 333/206, 333/207, 333/202, 333/202 DB
• US Class Current: 333/202
• CPC Class Codes: H01P 1/2056 Comb filters or interdigital filters with metallised resonator holes in a dielectric block

Abstract

A ceramic filter with a coplanar shield which has: a filter body (302) comprising a block of dielectric material having top (304), bottom (306) and side surfaces (308,310,312,314), and having a plurality of metallized through holes (316) extending from the top (304) to the bottom (306) surfaces defining resonators; a metallization layer substantially coating the bottom (306) and the side surfaces (306,310,312,314), and the top surface (304) having a metallized pattern thereon defining a top pattern; input-output pads (318); and a conductive shield (322) having standoff legs (324) which maintain the conductive shield at a predetermined height above the top pattern of the filter body, the standoff legs (324) are connected to a portion of the top pattern on the top surface of the filter at a desired distance from the side surface having the input-output pads.

Claims

1. A ceramic filter with a coplanar shield, comprising:

a filter body comprising a block of dielectric material having top, bottom and side surfaces, and having a plurality of metallized through holes extending from the top to the bottom surfaces defining resonators in the filter body;

a metallization layer substantially coating the bottom and the side surfaces, and the top surface having a metallized pattern thereon defining a top pattern;

at least a first and a second input-output pad comprising an area of conductive material on one of the side surfaces and substantially surrounded by an unmetallized area of the metallization layer on the one side surface of the metallization layer; and

a conductive shield having a plurality of standoff legs which maintain the conductive shield at a predetermined height above the top pattern of the filter body, the standoff legs are connected to a portion of the top pattern on the top surface of the filter at a predetermined distance from the one side surface having the at least first and second input-output pads.

2. The ceramic filter of claim 1, wherein the conductive shield has openings therein defining tuning windows on at least one of a front and a rear section thereof.

3. The ceramic filter of claim 1, wherein the conductive shield comprises a tin-coated steel metal.

4. The ceramic filter of claim 1, wherein the conductive shield comprises a thickness of about 0.005 inches to about 0.01 inches.

5. A ceramic filter with a coplanar shield, comprising:

a filter body comprising a block of dielectric material having top, bottom and side surfaces, and having a plurality of metallized through holes extending from the top to the bottom surfaces defining resonators in the filter body;

a metallization layer substantially coating the bottom and the side surfaces, and the top surface having a metallized pattern thereon defining a top pattern;

at least a first and a second input-output pad comprising an area of conductive material on one of the side surfaces and substantially surrounded by an unmetallized area of the metallization layer on the one side surface of the metallization layer; and

a conductive shield having a first and a second plurality of standoff legs which maintain the conductive shield at a predetermined height above the top pattern on the top surface of the filter body, the first plurality of standoff legs are coupled to the top pattern and the second plurality of standoff legs are coupled to the metallization layer on the side surface of the filter body opposite the one side surface having the at least first and second input-output pads.

6. The ceramic filter of claim 5, wherein the second plurality of standoff legs comprise a continuous sheet of metal, in a generally L-shape.

7. The ceramic filter of claim 5, wherein the conductive shield has openings therein defining tuning windows.

8. The ceramic filter of claim 5, wherein the conductive shield has openings therein defining tuning windows on at least one of a front and a rear section thereof.

9. The ceramic filter of claim 5, wherein the conductive shield comprises a tin-coated steel metal.

10. The ceramic filter of claim 5, wherein the conductive shield comprises a thickness of about 0.005 inches to about 0.01 inches.

11. A ceramic filter with a coplanar shield, comprising:

a filter body comprising a block of dielectric material having top, bottom and side surfaces, and having a plurality of metallized through holes extending from the top to the bottom surfaces defining resonators in the filter body;

a metallization layer substantially coating the bottom and the side surfaces, and the top surface having a metallized pattern thereon defining a top pattern;

at least a first and a second input-output pad comprising an area of conductive material on one of the side surfaces and substantially surrounded by an unmetallized area of the metallization layer on the one side surface of the metallization layer; and

a conductive shield having a first plurality of standoff legs on a front section thereof which maintain the conductive shield at a predetermined height above the top pattern on the top surface of the filter body, the first plurality of standoff legs are connected directly to a portion of the metallized pattern on the top surface of the filter, and the conductive shield having a second plurality of standoff legs connected to a plurality of substantially complimentarily-configured troughs on the side surface of the filter body opposite the one side surface having the at least first and second input-output pads.

12. The ceramic filter of claim 11, wherein the conductive shield has openings therein defining tuning windows.