Multi-band base station antennas having crossed-dipole radiating elements with generally oval or rectangularly shaped dipole arms and/or common mode resonance reduction filters
A dual-polarized radiating element for a base station antenna includes a first dipole that extends along a first axis, the first dipole including a first dipole arm and a second dipole arm and a second dipole that extends along a second axis, the second dipole including a third dipole arm and a fourth dipole arm and the second axis being generally perpendicular to the first axis, where each of the first through fourth dipole arms has first and second spaced-apart conductive segments that together form a generally oval shape.
1. A dual-polarized radiating element, comprising:
a first dipole that extends along a first axis, the first dipole including a first dipole arm and a second dipole arm;
a second dipole that extends along a second axis, the second dipole including a third dipole arm and a fourth dipole arm and the second axis being generally perpendicular to the first axis,
wherein each of the first through fourth dipole arms has first and second spaced apart-current paths, and
wherein central portions of each of the first and second spaced apart-current paths of the first and second dipole arms extend in parallel to the first axis, and central portions of each of the first and second spaced apart-current paths of the third and fourth dipole arms extend in parallel to the second axis.
2. The dual-polarized radiating element of claim 1 , wherein each of the first through fourth dipole arms has first and second spaced-apart conductive segments, and wherein the first current path is along the first conductive segment and the second current path is along the second conductive segment.
3. The dual-polarized radiating element of claim 2 , wherein the first and second spaced-apart conductive segments on each of the first through fourth dipole arms together form a generally oval shape.
4. The dual-polarized radiating element of claim 2 , wherein the first and second spaced-apart conductive segments on each of the first through fourth dipole arms together form a generally rectangular shape.
5. The dual-polarized radiating element of claim 2 , wherein each of the first and second conductive segments of the first through fourth dipole arms includes a first widened section that has a first average width, a second widened section that has a second average width and a narrowed section that has a third average width, the narrowed section being between the first widened section and the second widened section, wherein the third average width is less than half the first average width and less than half the second average width.
6. The dual-polarized radiating element of claim 5 , wherein the narrowed section creates a high impedance for currents that are at a frequency that is approximately twice the highest frequency in the operating frequency range of the dual-polarized radiating element.
7. The dual-polarized radiating element of claim 5 , wherein the narrowed section comprises a meandered conductive trace.
8. The dual-polarized radiating element of claim 2 , wherein a combined surface area of the first and second conductive segments that form the first dipole arm is greater than a combined surface area of the first and second conductive segments that form the second dipole arm.
9. The dual-polarized radiating element of claim 8 mounted on the base station antenna, wherein the first dipole arm is closer to a side edge of a base station antenna than is the second dipole arm.
10. The dual-polarized radiating element of claim 2 , wherein the first conductive segment of the first dipole arm includes a first meandered trace and the second conductive segment of the first dipole arm includes a second meandered trace, and wherein the first and second meandered traces extend into an interior section of the first dipole arm that is between the first and second conductive segments of the first dipole arm.
11. The dual-polarized radiating element of claim 2 , wherein the first and second conductive segments of the first dipole arm together include a plurality of meandered trace segments, and wherein all of the meandered trace segments included in the first and second conductive segments of the first dipole arm extend towards an interior section of the first dipole arm that is between the first and second conductive segments of the first dipole arm.
12. The dual-polarized radiating element of claim 2 , wherein distal ends of the first and second conductive segments of the first dipole arm are electrically connected to each other so that the first dipole arm has a closed loop structure.
13. The dual-polarized radiating element of claim 12 , wherein the distal ends of the first and second conductive segments of the first dipole arm are electrically connected to each other by a meandered conductive trace.
14. The dual-polarized radiating element of claim 2 , wherein a distal end of the first conductive segment of the first dipole arm is spaced-apart from a distal end of the second conductive segment of the first dipole arm so that the first and second conductive segments of the first dipole arm are only electrically connected to each other through proximate ends of the first and second conductive segments of the first dipole arm.
15. The dual-polarized radiating element of claim 2 , wherein, at least half of an area between the first and second conductive segments of the first dipole arm comprises open area.
16. The dual-polarized radiating element of claim 1 in combination with a base station antenna, wherein the base station antenna extends along a longitudinal axis, wherein the first axis is angled at about +45 degrees with respect to the longitudinal axis, and the second axis is angled at about −45 degrees with respect to the longitudinal axis.
17. The dual-polarized radiating element of claim 1 , wherein the first dipole directly radiates radio frequency (“RF”) signals at a +45° polarization and the second dipole directly radiates RF signals at a −45° polarization.
18. The dual-polarized radiating element of claim 1 , wherein a conductive plate is mounted above central portions of the first and second dipoles.
19. The dual-polarized radiating element of claim 18 , wherein the conductive plate is positioned within a distance of 0.05 times an operating wavelength of the first and second dipoles, where the operating wavelength is the wavelength corresponding to the center frequency of an operating frequency band of the dual-polarized radiating element.
20. A base station antenna having a first linear array of the dual-polarized radiating elements of claim 19 and a second linear array of the dual-polarized radiating elements of claim 19 , wherein the conductive plates included on each dual-polarized radiating element are configured to shift a frequency of a common mode resonance that is within an operating frequency band of the first and second linear arrays and that is generated on the second linear array when the first linear array transmits signals so that the common mode resonance falls outside the operating frequency band.