Sectorized Panel Antenna
Although there are many different style of antennas possible for WLANs and wireless bridging, one specific antenna is particularly well suited for local outdoor coverage: a sectorized panel antenna (see Figure C-2). Many of the cellular telephone base-station sites use a type of sectorized antenna.
Figure C-2. Sectorized Antenna
 Wall-mounted omnidirectional antennas can suffer from multipath components created by the wall itself. Covering a large area for local coverage, such as a parking area, neighborhood, or educational or industrial campuses, can also be a challenge for an omnidirectional antenna placed on a building. Sectorized antennas, although similar in nature to omni antennas, offer a solution for these situations. These antennas use a wide horizontal coverage angle with ranges from as little as 60 degrees to as much as 180 degrees. Figure C-3 shows how using three 120-degree sectorized antennas can provide a 360-degree range of coverage providing higher gain than possible from an single omni, while having a very broad vertical radiation angle.
 sector antennas on a single mounting mast. Notice that you can angle the antennas slightly downward with the mounting brackets to obtain down tilt (discussed in Chapter 2).
Figure C-4. Mounting Sectorized Antennas
Chapter 5, "Selecting the WLAN Architecture and Hardware." An alternative method is to mount these at some greater physical distance apart, such as at the edges of a building, or separate them using longer horizontal support arms similar to those found on cellular phone towers. |
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