A circularly polarized patch antenna, comprising:
- a first patch radiator, comprising a substantially uniform, planar, conductive surface having extents proportional to a wavelength of an electromagnetic signal within a specified frequency band of the antenna, wherein a positive direction along a first-patch reference axis, passing through a centroid of the first patch radiator perpendicular to the surface thereof, is parallel to a principal direction of propagation of signals emitted from the antenna;
- a first coaxial feed point and a second coaxial feed point on the first patch radiator, located at prescribed stations with reference to dimensions of the first patch radiator;
- a first backing conductor, substantially parallel to and coextensive with the first patch radiator, wherein a distance from the first patch radiator to the first backing conductor is negative with reference to the principal direction of propagation of signals emitted from the antenna;
- a first parasitic radiator, substantially parallel to and aligned with the first patch radiator, wherein a distance from the first patch radiator to the first parasitic radiator is positive with reference to the principal direction of propagation of signals emitted from the antenna;
- a second patch radiator, substantially identical to and oriented equivalently to and coplanar with the first patch radiator, wherein a positive direction along a second-patch reference axis, passing through a centroid of the second patch radiator perpendicular to the surface thereof, is parallel to the principal direction of propagation of signals emitted from the antenna;
- a third coaxial feed point and a fourth coaxial feed point on the second patch radiator, located at prescribed stations with reference to dimensions of the second patch radiator;
- a second backing conductor, substantially parallel to and coextensive with the second patch radiator, wherein a distance from the second patch radiator to the second backing conductor is negative with reference to the principal direction of propagation of signals emitted from the antenna;
- a second parasitic radiator, substantially parallel to and aligned with the second patch radiator, wherein a distance from the second patch radiator to the second parasitic radiator is positive with reference to the principal direction of propagation of signals emitted from the antenna;
- a power divider, configured to accept an applied broadcast signal on a coaxial input port and to provide a first two divider output signals, having prescribed relative phase and amplitude, on a first two divider coaxial output ports, and a second two divider output signals, having prescribed relative phase and amplitude, on a second two divider coaxial output ports;
- first two interconnecting coaxial signal lines between the first two coaxial output ports of the power divider and the radiator coaxial feed points of the first patch radiator, wherein the first two interconnecting coaxial signal lines have prescribed relative lengths and propagation times;
- second two interconnecting signal lines between the second two coaxial output ports of the power divider and the radiator coaxial feed points of the second patch radiator, wherein the second two interconnecting coaxial signal lines have prescribed relative lengths and propagation times;
- a conductive frame distal to the parasitic radiator and located further from the first patch radiator than is the backing conductor;
- and
- passage apertures through the frame for the coaxial feed stems at prescribed locations, wherein the respective feed stem outer conductors are connected electrically and mechanically to the frame at the passage locations;
- wherein the respective interconnecting signal lines include:
- coaxial feed stems that pass through the first backing conductor, with electrical connections therebetween substantially coinciding with the first backing conductor passthrough locations, wherein the respective feed stems are straight cylindrical coaxial line segments having longitudinal axes substantially parallel to the first-patch reference axis at least from respective passthrough locations to the first patch radiator,
- coaxial feed lines directed from the first two divider output ports to respective inputs of the coaxial feed stems,
- termination loci for respective coaxial feed stem outer conductors, located between the first backing conductor and the first patch radiator, wherein gap distances from the respective termination loci to the first patch radiator surface proximal to the backing conductor are prescribed, and
- respective coaxial feed stem inner conductors that extend from the feed lines through the respective feed stem outer conductors, beyond the termination loci, and connect to the first patch radiator at the respective feed points, and
- wherein spacing along the principal propagation axis between the first backing conductor and the first patch radiator is approximately one thirty-second of the wavelength, between the first patch radiator and the first parasitic radiator is approximately one sixteenth of the wavelength, and between the first backing conductor and the frame is approximately one quarter of the wavelength.