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 base station antenna, comprising:
a first linear array of radiating elements that transmit and receive signals within an operating frequency band; and
a second linear array of radiating elements that transmit and receive signals within the operating frequency band, and
wherein a first of the radiating elements in the second linear array includes a common mode filter that is configured to shift a frequency of a common mode resonance that is generated in the first radiating element when the first linear array transmits signals to outside the operating frequency band.
2. The base station antenna of claim 1 , wherein the first radiating element includes a first dipole and a second dipole.
3. The base station antenna of claim 2 , wherein the common mode filter comprises a conductive plate that is mounted above central portions of the first and second dipoles.
4. The base station antenna of claim 3 , 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 corresponds to the center frequency of the operating frequency band.
5. The base station antenna of claim 3 , wherein the conductive plate is configured to capacitively couple with the first and second dipoles to shift a frequency of the common mode resonance that is generated in the first radiating element when the first linear array transmits signals from within the operating frequency band to outside the operating frequency band.
6. The base station antenna of claim 2 , wherein the first dipole includes first and second dipole arms and the second dipole includes third and fourth dipole arms, and wherein gaps separate each of the first through fourth dipole arms from adjacent ones of the first through fourth dipole arms, and wherein widths of the gaps are selected so that the gaps form the common mode filter.
7. The base station antenna of claim 2 , wherein the first radiating element includes a feed stalk, and the first dipole and the second dipole are mounted on the feed stalk.
8. The base station antenna of claim 7 , wherein the common mode filter comprises first and second lines on the feed stalk that are inductively coupled.
9. The base station antenna of claim 8 , wherein the feed stalk comprises a printed circuit board, and wherein the first line is on a first side of the printed circuit board and the second line is on a second side of the printed circuit board.
10. The base station antenna of claim 8 , wherein the first and second lines are each meandered lines.
11. The base station antenna of claim 7 , wherein the common mode filter is configured to suppress a common mode resonance that would otherwise arise in the feed stalk.
12. A base station antenna, comprising:
a first linear array of radiating elements that transmit and receive signals within an operating frequency band; and
a second linear array of radiating elements that transmit and receive signals within the operating frequency band, and
wherein a first of the radiating elements in the second linear array includes a common mode filter that is configured to shift a frequency of a common mode resonance that is generated in the first radiating element when the first linear array transmits signals to an unused portion of the operating frequency band.
13. The base station antenna of claim 12 , wherein the operating frequency band comprises at least a portion of the 696-960 MHz frequency band, and the unused portion of the operating frequency band comprises the 799-823 MHz frequency band.
14. The base station antenna of claim 12 , wherein the first radiating element includes a first dipole and a second dipole.
15. The base station antenna of claim 14 , wherein the first dipole includes first and second dipole arms and the second dipole includes third and fourth dipole arms, and wherein a plurality of gaps separate each of the first through fourth dipole arms from adjacent ones of the first through fourth dipole arms, and wherein widths of the gaps are selected so that the gaps form the common mode filter.
16. The base station antenna of claim 14 , wherein the common mode filter comprises a conductive plate that is mounted above central portions of the first and second dipoles.
17. The base station antenna of claim 16 , 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 corresponds to the center frequency of the operating frequency band.
18. A method of tuning a base station antenna having a first linear array of radiating elements that transmit and receive signals within an operating frequency band and a second linear array of radiating elements that transmit and receive signals within the operating frequency band, each of the radiating elements including first through fourth dipole arms, and the operating frequency band having at least a first sub-band in a first frequency range and a second sub-band in a second frequency range, the first and second sub-bands separated by a third frequency band that is not part of the operating frequency band, the method comprising:
selecting sizes of respective gaps between adjacent ones of the first through fourth dipole arms on the respective radiating elements in order to tune a common mode resonance that is generated on the second linear array when the first linear array transmits signals to be within the third frequency band.
19. The method of claim 18 , wherein the first and second sub-bands are both within the 694-960 MHz frequency band.
20. The method of claim 19 , wherein the third frequency band is the 799-823 MHz frequency band.