Patent ID: 8184057

Claim:
An antenna system comprising: at least one linearly polarized antenna having an axis and a direction of linear polarization orthogonal to the axis; a parallel plate polarizer disposed on the axis in front of the at least one linearly polarized antenna, the parallel plate polarizer comprising parallel metal vanes secured by a supporting structure, each of the parallel metal vanes having a breadth and an axial thickness and each of the parallel metal vanes being separated from adjacent metal vanes by a distance, and the parallel plate polarizer having a phase advance orientation substantially orthogonal to the axis; and an anisotropic dielectric polarizer disposed on the axis in front of the at least one linearly polarized antenna, the anisotropic dielectric polarizer having a phase advance orientation substantially orthogonal to the axis, wherein, when the phase advance orientation of the parallel plate polarizer is at an angle of about 45° or about 135° with respect to the direction of linear polarization, and the phase advance orientation of the anisotropic dielectric polarizer is at an angle of about 45° or about 135° with respect to the direction of linear polarization, the parallel plate polarizer and the anisotropic dielectric polarizer have a combined differential phase shift for a first frequency f 1 of about 90° and a combined differential phase shift for a second frequency f 2 of about 90%, wherein the breadth and the axial thickness of each of the parallel metal vanes, and the distance separating adjacent metal vanes are selectable to provide a differential phase response.