Communications: radio wave antennas – Antennas – With support for antenna – reflector or director
Reexamination Certificate
2000-05-10
2001-07-10
Ho, Tan (Department: 2821)
Communications: radio wave antennas
Antennas
With support for antenna, reflector or director
C343S893000, C455S562100
Reexamination Certificate
active
06259419
ABSTRACT:
FIELD OF THE INVENTION
A new configuration for a multi-sector base station/cell-site is presented.
BACKGROUND OF THE INVENTION
Usually, a three sector cell-site with standard vertical polarization uses space diversity to improve the system reliability (via horizontal space diversity effective gain). This traditional approach often requires nine separate antennas. A newer approach uses three dual slant polarized antennas to give just about the same system reliability, depending on the surrounding environment, using polarization diversity effective gain. One example of this approach is the Microsite™ scheme, offered by Andrew Corporation, the assignee of this invention.
Polarization diversity works best for congested urban areas, but is less efficient for rural and less congested suburban areas. Typically, in less congested areas, the random polarization scattering levels or multipath encountered are relatively lower than in an urban area and often, the polarization diversity gain is minimal.
However, using space diversity usually implies 10 to 20 &lgr;
0
(the wavelength in free space) spacing between the two receive antennas for each sector in order to achieve meaningful diversity gain. This spacing implies a relatively large, generally triangular-cross-section support frame which can be expected to lead to generally higher windloading problems at the tower. A relatively larger support frame also can have a negative impact on cell-site aesthetics for purposes of obtaining zoning board approval, and the like. Moreover, the large number of antennas (typically nine antennas for a three-sector cell site using space diversity) implies higher windloading on the numerous antennas, as well as a further negative impact on cell-site aesthetics.
Also, the expense of providing and installing individual antenna units is multiplied by the number of antenna units required for a given multi-sector site. In this regard, operators often lease tower space for their antennas, based on the number of antenna units to be installed. Therefore, reducing the number of antenna units required for a given multi-sector coverage, reduces operator expense.
If the triangular antenna support frame can be made smaller for the same effective diversity gain, less wind loaded is expected. Correspondingly, if a fewer number of antennas can be utilized for the same effective diversity gain, less windload with respect to the antennas, better cell-site aesthetics and less overall cell-site expense can be expected.
OBJECTS OF THE INVENTION
Accordingly, it is a general object of this invention to provide a novel and improved multi-sector cell-site configuration which overcomes the above-noted limitations of both the horizontal space diversity approach and the polarization diversity approach.
SUMMARY OF THE INVENTION
In accordance with one aspect of the invention, the antennas are recombined in a scheme using spatial diversity, but requiring fewer than the nine vertical polarized antennas in a typical three sector cell-site configuration using horizontal space diversity.
In accordance with another aspect of the invention a tower-top multi-sector scheme is presented which combines both horizontal space diversity and polarization diversity using just three antenna units. As suggested above, a scheme which offers a combination of polarization and space diversity, may be a useful approach for suburbs and less densely populated areas when the random polarization scattering levels are low, and therefore, the polarization diversity gain is minimal.
In accordance with another aspect of the invention, a multiple sector cell-site configuration comprises a support frame, a plurality of antennas mounted on the support frame, the antennas including at least one transmit antenna element and at least two receive antenna elements for each sector of the multiple sector cell-site, one of the receive antenna elements for each of two adjacent sectors being located in a common housing mounted adjacent a given point on the support frame located substantially along a boundary between the two adjacent sectors, each of the receive antenna elements mounted in each said common housing having an offset azimuthal beam directed toward its associated sector, and each of the transmit antenna elements having an azimuthal beam directed toward its associated sector.
REFERENCES:
patent: 5291211 (1994-03-01), Tropper
patent: 5787673 (1998-08-01), Noble
patent: 5872548 (1999-02-01), Lopez
patent: 5999145 (1999-12-01), Niekamp
patent: 6088003 (2000-07-01), Bassirat
Mobile Antenna Systems Handbook, Chapter 3, pp. 115-174, Fugimoto et al., 1994.
Skypath™ Base Station Antennas, pp. 3-8 and 21-66, Andrew Corporation, 2/99.
Andrew Corporation
Ho Tan
Jenkens & Gilchrist
Rudisill Stephen G.
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