Page 32 - Antennas for Base Stations in Wireless Communications

Fundamentals of Antennas 5

Sidelobes Color scale magnitude
0.00
-4.44
Main lobe
-8.89
Backlobe -13.33
-17.78
-22.22
-26.67
-31.11
Nulls -35.56
-40.00
Figure 1.3 3D radiation pattern

0 90°
120° 60°
-10
150° -20 30°

-30
-40
180° 0°

210° 330°

240° 300°
270°
Figure 1.4 Polar plot radiation

The same pattern can be presented in the rectangular coordinate
system, as shown in Figure 1.5. We should point out that these pat-
terns are normalized to the pattern’s peak, which is pointed to q = 0 in
this case and given in decibels.

1.1.3.1 Beamwidth The beamwidth of the antenna is usually considered
to be the angular width of the half power radiated within a certain cut
through the main beam of the antenna where most of the power is radi-
ating. From the peak radiation intensity of the radiation pattern, which
is the peak of the main beam, the half power level is −3 dB below such
a peak where the two points on the main beam are located; these points
are on two sides of the peak, which separate the angular width of the half
power. The angular distance between the half power points is defined
as the beamwidth. Half the power expressed in decibels is −3 dB, so the