Dual circularly polarized antenna
An antenna includes a waveguide having an aperture at a first end and a conducting component at a second end, the conducting component shorting the waveguide and a first set of two orthogonal dipoles, fed in quadrature, the orthogonal dipoles located near the aperture of the waveguide operating close to its dominant mode cut off frequency.
1. An antenna comprising:
a waveguide having an aperture at a first end and a conducting component at a second end, the conducting component shorting the waveguide;
a first set of two orthogonal dipoles, fed in quadrature, the orthogonal dipoles located near the aperture of the waveguide operating at a first frequency that is close to the waveguide's dominant mode cut off frequency; and
a second set of two orthogonal dipoles, connected in parallel to the first set of orthogonal dipoles, to resonate and match at a frequency band different from the first frequency.
2. The antenna of claim 1 wherein a connecting plate connects the two orthogonal dipoles to the conducting component.
3. The antenna of claim 2 wherein the connecting plate has mounted thereon one or more components selected from the group consisting of LNAs (low noise amplifiers), matching circuits, filters, hybrid devices, and combinations thereof.
4. The antenna of claim 1 wherein the two orthogonal dipoles are made of relatively thin conductors extending in a horizontal direction.
5. The antenna of claim 4 wherein the orthogonal dipoles include signal feed structures that are positioned at or near the connecting plate.
6. The antenna of claim 5 wherein the signal feed structures are comprised of a component selected from the group consisting of microstrip lines, striplines, coplanar waveguides, and miniature coaxial cables bonded to the connecting plate.
7. The antenna of claim 1 further comprising:
one or more additional sets of two orthogonal dipoles wherein multiple sets of two orthogonal dipoles are mounted adjacent to each other and fed in parallel with each other.
8. The antenna of claim 1 wherein one or more amplifiers are attached to an output of a quadrature hybrid to preserve an amplitude balance and a phase differential of the hybrid and preserve an axial ratio and RHCP (right hand circular polarized) over LHCP (left hand circular polarized) ratios of the antenna.
9. The antenna of claim 1 wherein the waveguide is filled with a dielectric configured to allow a reduction of the area of the aperture.
10. The antenna of claim 1 configured as a transmitting antenna.
11. The antenna of claim 1 further comprising:
one or more disks placed on a negative axis of the antenna to reduce the response of the antenna to cross-polarized signals approaching from the back of the antenna.
12. The antenna of claim 11 further comprising two or more disks, the disks having a spacing and changing radius.
13. The antenna of claim 11 wherein the disks are supported by a conducting rod or tube.
14. The antenna of claim 13 wherein disks are supported by a conducting tube, the tube containing one or more signal and power feed lines to and from the antenna.