Microstrip circuit with suspended substrate stripline regions embedded therein

A method of making a microstrip microwave circuit having embedded therein at least one suspended substrate stripline region for high Q circuit elements, said method comprising the steps of:

• disposing a dielectric layer on the top surface of a ground plane;
• forming a continuous microstrip circuit pattern on the exposed surface of said dielectric layer with at least one region for high Q circuit elements having at least one interconnecting circuit path to the remaining microstrip circuitry;
• removing portions of the dielectric layer through to the top surface of the ground plane to form channels substantially encircling each high Q region;
• removing the section of said ground plane which resides substantially underneath each high Q region to form openings in the bottom surface of said ground plane;
• covering the microstrip circuitry of each high Q region with a metallic housing having sidewalls by seating the sidewalls of each metallic housing in the removed channels of its corresponding high Q region to make physical contact with the top surface of the ground plane to form an upper ground plane separated correspondingly from a high Q region by an air pocket;
• providing an opening in each metallic housing for each interconnecting path of the corresponding high Q region being covered to permit passage therethrough;
• and
• enclosing each opening of the bottom surface of said ground plane with a metallic cover to form a lower ground plane separated from each high Q region by said dielectric layer thickness and a pocket of air, whereby each high Q region has an upper and lower ground plane separated from the microstrip circuitry and dielectric layer thereof by air which formation constitutes a suspended substrate stripline region.