Page 287 - Antennas for Base Stations in Wireless Communications

260 Chapter Seven

E-plane, Co-pol
q = 0°
H-plane, Co-pol
f = 5.8 GHz

90°
0
10

180° (20 dBi)
(f)
Figure 7.6 A 16-dBi P2P antenna: (a) photo of antenna, (b) antenna specifications, (c)
schematic diagram, (d) return loss, (e) radiation patterns at 5.6 GHz, and (f) radiation
patterns at 5.8 GHz (Continued)

7.3.2 Outdoor Point-to-Multiple-Point
Antennas
Outdoor P2MP antennas include omnidirectional antennas, sectored
antennas, and arrays, such as the patch antennas, sleeve dipoles, colin-
ear dipoles, turnstile antennas, and corner reflector antennas. Figure 7.7
shows a 5.4–5.9 GHz, 17-dBi center-fed sectored antenna with a series
feed. The length and separation of the radiators are approximately half
a wavelength. The width of the microstrip line, soldered to the N-type
probe at the center, is widened for impedance matching. This center-fed
structure is almost symmetrical along the E-plane, thus it mitigates the
undesirable beam-squinting effect. By implementing it in a cylindrical
MIMO array fashion, various elements in the antenna array can be
switched to provide omnidirectional coverage in a multipath rich urban
environment, e.g., on campuses or in shopping malls.

7.3.3 Indoor Point-to-Multiple
Point Antennas
Indoor P2MP antennas require a broad beamwidth for maximum cover-
age. A base loaded monopole, e.g., a rubber duck antenna, is commonly
used due to the antenna’s omnidirectional radiation. Broadband sus-
pended patch antennas are also employed. Diversity antennas with
multiple elements are used to reduce the effects of fading. The multipath
rich indoor environment makes it favorable for MIMO antenna technol-
ogy deployment.
Figure 7.8 shows a 10-dBi dual-fed slotted planar antenna. This
antenna operates from 4.9–6.0 GHz, which covers the IEEE 802.11j
(Japan) band, public safety band (U.S.), and the IEEE 802.11a band.
The radiator is single-layered and easy to manufacture. The dual-fed