Ablative method for forming RF ceramic block filters

A method of forming RF ceramic block filters comprising the steps of:

• (1) coating the entire external surface area of a ceramic dielectric block with a conductive metal;
• (2) causing said conductive metal to adhere to said ceramic block;
• and
• (3) ablatively etching unwanted conductive metal and a corresponding portion of said ceramic block from a designated surface area of said coated ceramic block to form desired metallized filter circuit patterns.

A method of forming an RF filter comprising the steps of:

• forming a block of dielectric material having multiple surfaces including at least one planar surface;
• coating a layer of electrically conductive metallic material on all of the multiple surfaces of said block of dielectric material;
• and
• ablatively removing trenches of selected areas of dielectric material and metallic material from at least a portion of said at least one planar surface to form an electrical RF filter pattern of conductive metal providing a predetermined filter frequency response.

A method of forming a duplexer circuit for an RF transmit/receive circuit comprising the steps of:

• forming a block of dielectric material having multiple surfaces including at least one planar surface;
• adhering a layer of electrically conductive metallic material on all of the multiple surfaces of said block of dielectric material;
• ablatively removing a first selected area of metallic material and corresponding dielectric material from said at least one planar surface to first predetermined depths and widths to form a first electrical filter circuit pattern of electrically isolated conductive elements having a first predetermined filter frequency response;
• ablatively removing a second different selected area of metallic material and corresponding dielectric material from said at least one planar surface to second predetermined depths and widths to form a second electrical filter circuit pattern of electrically isolated conductive elements having a second predetermined filter frequency response;
• and
• forming a first terminal as an input terminal and a second terminal as an output terminal, said first and second terminals being formed on at least one of said block surfaces by removing surrounding metallic material and corresponding ceramic material sufficient to electrically isolate said input and said output terminals from the surrounding electrically conductive material.

An RF filter comprising:

• a block of dielectric material having multiple surfaces including at least one planar surface;
• a layer of electrically conductive material adhered to all of the multiple surfaces of said block of dielectric material;
• a ground plane formed by at least one of said electrically conductive surfaces;
• an electrical filter circuit pattern of multiple conductive elements being formed in said layer of electrically conductive material on at least said one planar surface;
• wherein said circuit pattern comprises:
• a trench at least partially surrounding each of said conductive elements, said trench comprising recessed areas that extend through said conductive material and into corresponding dielectric material, said trenches having a predetermined shape determining the coupling capacitance between said conductive elements and said ground plane, said coupling capacitance determining an operating characteristic of said filter.

A duplexer for an RF receiver/transmitter unit comprising:

• a block of dielectric material having multiple surfaces including at least one planar surface;
• a layer of metallic material coating all of the multiple surfaces of said block of dielectric material;
• a ground plane formed by at least some of said metallic surfaces;
• an RF receiver filter being formed in a first area of said at least one planar surface, and comprising:
• first plurality of conductive elements;
• a first trench completely surrounding at least some of said conductive elements to electrically isolate them;
• each first trench having a predetermined shape and comprising recessed areas having a predetermined depth and width and that extend through said metallic material and into corresponding dielectric material;
• and
• a first capacitive coupling between said first plurality of conductive elements and said ground plane that is determined by the depth and width of said recessed areas;
• said first capacitive coupling determining the operating frequency of said RF receiver filter;
• an RF transmitter filter formed in a second different area of said at least one planar surface, and comprising:
• a second plurality of conductive elements;
• a second trench completely surrounding at least some of said second plurality of conductive elements to electrically isolate them;
• said second trenches having a predetermined shape and comprising second recessed areas having a second predetermined depth and width that extend through said metallic material and into corresponding dielectric material;
• and
• a second capacitive coupling between said second plurality of conductive elements and said ground plane that is determined by the second predetermined depth and width of said second recessed areas;
• said second capacitive coupling determining the operating frequency of said transmitter filter;
• first and second terminals formed on at least one surface of said coated dielectric block for coupling RF signals to respective ones of said receiver filter and said transmitter filter;
• and
• a third terminal for receiving an antenna connection, said third terminal being electrically coupled to said receiver filter and said transmitter filter for conveying RF signals between said antenna and said RF receiver and said RF transmitter.

An RF filter comprising:

• a dielectric block having at least one planar surface;
• a layer of electrically conductive material disposed on at least a portion of said dielectric block planar surface;
• a ground plane formed on at least one other block surface;
• a pattern of dielectric material forming electrically conductive circuit elements on said dielectric block planar surface by electrically isolating said electrically conductive circuit elements from each other and from said ground plane;
• said electrically conductive circuit elements having a first elevation above said dielectric block planar surface;
• at least one ablatively etched trench forming at least a portion of said pattern of dielectric material that electrically isolates said electrically conductive circuit elements;
• and
• said trench extending into said dielectric material one or more predetermined depths below said dielectric planar surface to electrically isolate said electrical circuit pattern elements.