Base station antennas having parasitic assemblies for improving cross-polarization discrimination performance
Base station antennas include a reflector, a first array of cross-polarized radiating elements that are mounted to extend forwardly from the reflector, and a parasitic assembly. The parasitic assembly includes a base that is mounted on the reflector, a horizontal component shaping element, and a forwardly projecting member that projects forwardly from the base that is coupled between the base and the horizontal component shaping element. The horizontal component shaping element may extend substantially parallel to a plane defined by the reflector and may include a proximate side that is directly connected to the forwardly projecting member and a distal side that is opposite the proximate side. The distal side of is only electrically connected to the reflector through the proximate side.
1. A base station antenna, comprising:
a reflector that defines a substantially vertical plane;
a plurality of cross-polarized radiating elements that form a first array of radiating elements, the cross-polarized radiating elements mounted to extend forwardly from the reflector, and each cross-polarized radiating element including a −45° dipole radiator and a +45° dipole radiator; and
a parasitic assembly mounted to extend forwardly from the reflector, the parasitic assembly including a base that is mounted on the reflector, a horizontal component shaping element, and a forwardly projecting member that projects forwardly from the base that is coupled between the base and the horizontal component shaping element,
wherein the horizontal component shaping element is slanted less than 45° from the substantially vertical plane defined by the reflector,
wherein the horizontal component shaping element includes a proximate side that is directly connected to the forwardly projecting member and a distal side that is opposite the proximate side, and
wherein the distal side of the horizontal component shaping element is only electrically connected to the reflector through the proximate side of the horizontal component shaping element.
2. The base station antenna of claim 1 , wherein the horizontal component shaping element is slanted between 0° and 15° with respect to the substantially vertical plane defined by the reflector.
3. The base station antenna of claim 2 , wherein the parasitic assembly is mounted directly adjacent a first of the cross-polarized radiating elements and is between the first of the cross-polarized radiating elements and a transverse edge of the reflector.
4. The base station antenna of claim 1 , wherein the horizontal component shaping element is slanted between 0° and 45° with respect to the substantially vertical plane defined by the reflector.
5. The base station antenna of claim 4 , wherein the parasitic assembly comprises one of a plurality of parasitic assemblies, and the parasitic assemblies are mounted adjacent the respective cross-polarized radiating elements in the first array of radiating elements.
6. The base station antenna of claim 4 , wherein an extent to which the forwardly projecting member projects forwardly is selected so that the horizontal component shaping element will primarily alter a cross-polarization discrimination performance of the first array in a selected sub-band of an operating frequency range of the first array of radiating elements.
7. The base station antenna of claim 4 , wherein the horizontal component shaping element includes at least one slot.
8. The base station antenna of claim 4 , wherein the horizontal component shaping element is positioned a first distance forwardly of the reflector, and a bottom edge the −45° dipole radiator is positioned a second distance forwardly of the reflector, wherein the second distance is greater than the first distance.
9. The base station antenna of claim 4 , wherein the first array of radiating elements is configured to form a first antenna beam having a −45° polarization and a second antenna beam having a +45° polarization that each provide coverage to a predefined sector, and wherein the parasitic assembly is configured to alter horizontal components of portions of the first and second antenna beams that are within the sector at least twice as much as respective vertical components of portions of the first and second antenna beam that are within the sector.
10. The base station antenna of claim 4 , wherein the parasitic assembly is capacitively coupled to the reflector.
11. The base station antenna of claim 4 , wherein the horizontal component shaping element extends substantially parallel to the reflector.
12. A base station antenna, comprising:
a reflector that defines a substantially vertical plane;
a plurality of cross-polarized radiating elements that form a first array of radiating elements, the cross-polarized radiating elements mounted to extend forwardly from the reflector, and each cross-polarized radiating element including a −45° dipole radiator and a +45° dipole radiator;
a parasitic assembly mounted to extend forwardly from the reflector, the parasitic assembly including a base that is mounted on the reflector, a horizontal component shaping element, and a forwardly projecting member that projects forwardly from the base that is coupled between the base and the horizontal component shaping element,
wherein the horizontal component shaping element is slanted between 0° and 45° with respect to the substantially vertical plane defined by the reflector, and
wherein the parasitic assembly is mounted directly adjacent the first array of radiating elements and is between the first array of radiating elements and a transverse edge of the reflector.
13. The base station antenna of claim 12 , wherein the horizontal component shaping element is slanted between 0° and 20° with respect to the substantially vertical plane defined by the reflector.
14. The base station antenna of claim 13 , wherein the parasitic assembly comprises one of a plurality of parasitic assemblies, and the parasitic assemblies are mounted between the first array of radiating elements and the transverse edge of the reflector.
15. The base station antenna of claim 12 wherein the horizontal component shaping element extends substantially parallel to the reflector.
16. The base station antenna of claim 12 , wherein the horizontal component shaping element includes at least one vertically-extending slot.
17. The base station antenna of claim 12 , wherein the first array of radiating elements is configured to form a first antenna beam having a −45° polarization and a second antenna beam having a +45° polarization that each provide coverage to a predefined sector, and wherein the parasitic assembly is configured to alter horizontal components of portions of the first and second antenna beams that are within the sector at least twice as much as respective vertical components of portions of the first and second antenna beam that are within the sector.
18. A base station antenna, comprising:
a reflector that defines a substantially vertical plane;
a plurality of cross-polarized radiating elements that form a first array of radiating elements, the cross-polarized radiating elements mounted to extend forwardly from the reflector, and each cross-polarized radiating element including a −45° dipole radiator and a +45° dipole radiator;
a first parasitic assembly mounted forwardly from the reflector on a first side of the first array of radiating elements and a second parasitic assembly mounted forwardly from the reflector on a second side of the first array of radiating elements, the first and second parasitic assemblies each including a base that is mounted on the reflector, a horizontal component shaping element that extends substantially parallel to the reflector, and a forwardly projecting member that projects forwardly from the base that is coupled between the base and the horizontal component shaping element,
wherein the first array of radiating elements is configured to form a first antenna beam having a −45° polarization and a second antenna beam having a +45° polarization that each provide coverage to a predefined sector, and wherein the first parasitic assembly is configured to alter horizontal components of portions of the first and second antenna beams that are within the sector at least twice as much as respective vertical components of portions of the first and second antenna beam that are within the sector.
19. The base station antenna of claim 18 , wherein the first array of radiating elements comprises a column of radiating elements that extend along a first axis, and the first parasitic assembly is a first of a plurality of parasitic assemblies that comprise a column of parasitic assemblies that extends along a second axis that is substantially parallel to the first axis.
20. The base station antenna of claim 18 , wherein the horizontal component shaping element is slanted less than 20° from the substantially vertical plane defined by the reflector.
21. The base station antenna of claim 18 , wherein an extent to which the forwardly projecting member of the first parasitic assembly projects forwardly is selected so that the horizontal component shaping element of the first parasitic assembly will primarily alter a cross-polarization discrimination performance of the first array of radiating elements in a selected sub-band of an operating frequency range of the first array of radiating elements.
22. The base station antenna of claim 18 , wherein the first parasitic assembly is capacitively coupled to the reflector, and the first parasitic assembly comprises a monolithic sheet metal assembly.