Coated ferrite RF filters

Abstract

In a low pass RF filter, a coating of barium titanate is applied to a ferrite substrate. In one embodiment, the RF filter is an extruded tube of ferrite coated with barium titanate. The tube is used as an RF filter for a connector pin. In another embodiment, a thin strip of ferrite is coated with barium titanate. This forms a filter strip for use on circuit boards or for use as a high capacity lossy power bus.

What is claimed is: 
     
       1. A .[.unitary.]. .Iadd.composite ceramic .Iaddend.low pass filter element for mounting on a conductor of a low frequency transmission line to attenuate high frequencies thereon comprising, a conductive tubular member for receiving a conductor therein,   a semiconductive substrate in the form of a sleeve secured to the outer surface of the tubular member in intimate engagement therewith,   a .Iadd.ceramic dielectric .Iaddend.layer .[.of dielectric material.]. covering the outer surface of the sleeve in direct intimate contact therewith,   and an outer conductive layer disposed about and secured to the dielectric .[.material.]. .Iadd.layer .Iaddend.substantially the length thereof for connecting the unitary filter element to ground.   
     
     
       2. The filter recited in claim 1 wherein said .[.substrate.]. .Iadd.semiconductive substrate .Iaddend.is a .[.semi-conducting.]. ceramic. 
     
     
       3. The filter recited in claim 2 wherein the .[.semiconducting ceramic.]. .Iadd.semiconductive substrate .Iaddend.is doped barium titanate. 
     
     
       4. The filter recited in claim 1 wherein said dielectric is undoped barium titanate. 
     
     
       5. The filter recited in claim 1 wherein the layer of dielectric material is coated thereon. 
     
     
       6. The filter recited in claim 1 wherein the tubular member is a metallic plating over the inner surface of the sleeve. 
     
     
       7. The filter recited in claim 5 wherein the outer conductive layer is metallic plating over said layer of dielectric material. 
     
     
       8. A .[.unitary.]. .Iadd.composite ceramic .Iaddend.low pass filter strip for mounting on a circuit board provided with a ground plane conductor comprising, a substrate in the form of a flat strip of semiconductive material,   a conductive metal plating on one surface of the substrate,   a coating of .Iadd.ceramic .Iaddend.dielectric material on the opposite surface of the substrate, and a conductive metal plating on the outer surface of the dielectric coating,   one of said platings being connected to one terminal of a low frequency source and load, and the other plating being in conductive engagement with the ground plane conductor.   
     
     
       9. The filter of claim 8 in which the substrate is a semiconductive ceramic. 
     
     
       10. The filter of claim 8 in which the substrate is doped barium titanate. 
     
     
       11. The filter of claim 8 in which the dielectric is undoped barium titanate. 
     
     
       12. A .[.unitary.]. .Iadd.composite ceramic .Iaddend.low pass filter element for mounting on a conductor of a low frequency transmission line to attenuate high frequencies thereon comprising, a conductive tubular member for receiving a conductor therein,   a substrate of ferrite in the form of a sleeve secured to the outer surface of the tubular member, in intimate engagement therewith,   a layer of .Iadd.ceramic .Iaddend.dielectric material covering the outer surface of the sleeve in direct intimate contact therewith,   and an outer conductive layer disposed about and secured to the dielectric material substantially the length thereof for connecting the unitary filter element to the ground.   
     
     
       13. The filter recited in claim 12 wherein said dielectric is undoped barium titanate. .Iadd. 14. The filter of claim 8 in which the substrate is a ferrite..Iaddend.