Compact combline resonator and filter

A method of forming a pair of coupled inductive posts, each of the coupled inductive posts having a respective annular radius terminating at a radial end at a circumference of the inductive post, used as a pair of series inductive capacitive resonators in a combline microwave filter, comprising:

• modulating the annular radius of a first inductive post along the length of the first inductive post to establish a desired inductive value for a first series inductive capacitive resonator;
• and
• modulating the annular radius of a second inductive post along the length of the second inductive post to establish a desired inductive value for a second series inductive capacitive resonator;
• wherein the annular radius of the first inductive post along the length of the first inductive post and the annular radius of the second inductive post along the length of the second inductive post are respectively established such that when the first inductive post and the second inductive post are parallel adjacent to each other one or more respective radial ends of the first inductive post and the second inductive post interleave without making contact between the first inductive post and the second inductive post.

A combline microwave filter comprising:

• a waveguide channel having an input port and an output port;
• and
• one or more inductive posts located in the waveguide channel, the one or more inductive posts providing filter poles and coupling the input port to the output port, each inductive post being electrically connected at one post end to a wall of the waveguide channel and providing a capacitance gap between an other post end and an opposing wall of the waveguide channel to provide a series inductive capacitive resonator;
• wherein the one or more inductive posts each have an annular radius terminating at a radial end located at a circumference of the inductive post, the annular radius curvedly modulating along the length of the inductive post to establish a desired inductive value.

A combline microwave filter comprising:

• a waveguide channel having an input port and an output port;
• one or more inductive posts, each inductive post having an annular radius terminating at a radial end at the circumference of the inductive post, located in the waveguide channel, the one or more inductive posts providing filter poles and coupling the input port to the output port, each inductive post being electrically connected at one post end to a wall of the waveguide channel and providing a capacitance gap between an other post end and an opposing wall of the waveguide channel to provide a series inductive capacitive resonator;
• wherein the one or more inductive posts have an annular radius which modulates along the length of the inductive post to establish a desired inductive value,
• wherein a pair of adjacent coupled inductive posts are each formed such that:
• the annular radius of a first inductive post is modulated along the length of the first inductive post to establish a desired inductive value for a first series inductive capacitive resonator and the annular radius of a second inductive post is modulated along the length of the second inductive post to establish a desired inductive value for a second series inductive capacitive resonator;
• and
• wherein the annular radius of the first inductive post along the length of the first inductive post and the annular radius of the second inductive post along the length of the second inductive post are respectively established such that when the first inductive post and the second inductive post are parallel adjacent each other one or more respective radial ends of the first inductive post and the second inductive post interleave without making contact between the first inductive post and the second inductive post.