Page 243 - Antennas for Base Stations in Wireless Communications

216 Chapter Six

Parallel
stripline
Port 1

Dielectric
l 0 /4 substrate
Microstrip
line
+
Port 2 Microstrip
line
Resistor −
Port 3
Ground
plane

Figure 6.8 Geometry of the wideband 180° out-of-phase power divider 51

4

3.5
Measured SWR
Simulated SWR
3
SWR 2.5
74%
2

1.5

1
1 1.5 2 2.5 3 3.5
Frequency (GHz)
50
Figure 6.9 Simulated and measured SWRs of the proposed antenna
(© 2007 IEEE)
Figure 6.9 reveals that the proposed antenna can operate from 1.37 to
2.97 GHz with a measured impedance bandwidth (SWR ≤ 2) of 74%.
In Figure 6.10, the resonances of two modes are also obtained for the
proposed DFPA. Over the operating band, ranging from 1.37 GHz
to 2.97 GHz, the input resistance varies from 30 Ω to 63 Ω, while
the input reactance changes interiorly between –10 Ω and 27 Ω. In
Figure 6.11, the antenna gain is stable across the operating band and
has an average value of 8.5 dBi. The performance of high and stable
antenna gain is mostly owing to the high polarization purity.