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 conductive segments that together form a generally oval shape,
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.
2. The dual-polarized radiating element of claim 1 , 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.
3. 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.
4. The dual-polarized radiating element of claim 1 , 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.
5. The dual-polarized radiating element of claim 1 , wherein a conductive plate is mounted above central portions of the first and second dipoles.
6. The dual-polarized radiating element of claim 5 , 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.
7. A base station antenna having a first linear array of the dual-polarized radiating elements of claim 5 and a second linear array of the dual-polarized radiating elements of claim 5 , 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.
8. The dual-polarized radiating element of claim 1 , further comprising at least one feed stalk that extends generally perpendicular to a plane defined by the first and second dipoles.
9. The dual-polarized radiating element of claim 1 , wherein the narrowed section comprises a meandered conductive trace.
10. The dual-polarized radiating element of claim 1 , 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.
11. The dual-polarized radiating element of claim 1 , wherein the first and second conductive segments of each dipole arm comprise conductive segments of a printed circuit board.
12. The dual-polarized radiating element of claim 1 , wherein, at least half of an area between the first and second conductive segments of the first dipole arm comprises open area.
13. The dual-polarized radiating element of claim 1 , wherein a first meandered trace of the first conductive segment of the first dipole arm and a second meandered trace of the second conductive segment of the first dipole arm extend into an interior section of the first dipole arm that is between the first and second conductive segments of the first dipole arm.
14. The dual-polarized radiating element of claim 1 , wherein all of the meandered trace segments on 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.
15. 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 conductive segments that together form a generally oval shape,
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.
16. The dual-polarized radiating element of claim 15 mounted on a base station antenna, wherein the first dipole arm is closer to a side edge of the base station antenna than is the second dipole arm.
17. The dual-polarized radiating element of claim 15 , 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 15 , wherein a first meandered trace of the first conductive segment of the first dipole arm and a second meandered trace of the second conductive segment of the first dipole arm extend into an interior section of the first dipole arm that is between the first and second conductive segments of the first dipole arm.
19. The dual-polarized radiating element of claim 15 , 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.