Excitation method of coaxial horn for wide bandwidth and circular polarization

A coaxial feed horn comprising:

• a dielectric substrate including a top surface and a bottom surface;
• at least one microstrip feed line deposited on the bottom surface of the substrate;
• a ground plane deposited on the top surface of the substrate;
• a cylindrical outer conductor electrically coupled to the ground plane and including an internal chamber, said outer conductor including an opening opposite to the substrate defining an aperture of the feed horn;
• an embedded conductor positioned within the chamber and being coaxial with the outer conductor;
• and
• a plurality of dielectric layers positioned within the chamber and being external to the embedded conductor, said plurality of dielectric layers having defined dielectric constants where a first dielectric layer is positioned at a lower end of the outer conductor and has a lowest dielectric constant and a last dielectric layer is positioned proximate the aperture and has a highest dielectric constant to provide impedance matching and to allow propagation of a TE12 difference mode.

A coaxial feed horn comprising:

• a dielectric substrate including a top surface and a bottom surface;
• four microstrip feed lines deposited on the bottom surface of the substrate and being spaced 90° apart;
• a ground plane deposited on the top surface of the substrate;
• a cylindrical outer conductor electrically coupled to the ground plane and including an internal chamber, said outer conductor including an opening opposite to the substrate defining an aperture of the feed horn;
• an embedded conductor positioned within the chamber and being coaxial with the outer conductor, said embedded conductor including a conical section in electrical contact with the at least one microstrip line, a cylindrical section opposite the substrate and a tapered section extending out of the outer conductor at the aperture;
• and
• a plurality of dielectric layers positioned within the chamber and being external to the embedded conductor, said plurality of dielectric layers having defined dielectric constants where a first dielectric layer is positioned at a lower end of the outer conductor and has a lowest dielectric constant and a last dielectric layer is positioned proximate the aperture and has a highest dielectric constant, wherein the first dielectric layer has a dielectric constant selected to allow propagation of a TE11 sum mode and the last dielectric layer has a dielectric constant selected to allow propagation of a TE12 difference mode.