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New Unidirectional Antennas for Various Wireless Base Stations 231

5

4

SWR 3 T-strip
Sq-Cap
L-strip

2

1
1.5 1.75 2 2.25 2.5 2.75 3 3.25 3.5 3.75
Freq/GHz
Figure 6.25 SWRs for three different feeding structures: T-strip, L-strip, and square-cap

9
8
7

6
Gain/dB 5 4

3
2 T-strip
Sq-Cap
1 L-strip
0
1.5 1.75 2 2.25 2.5 2.75 3 3.25 3.5 3.75
Freq/GHz
Figure 6.26 Gain curves for three different feeding structures: T-strip, L-strip,
and square-cap

higher frequency within the operating bandwidths in these two cases.
As a result, we can conclude the antenna gain is very stable across the
operating bandwidth for the L-strip coupled feed. Additionally, there
is an approximately 1.5-dB variation in the antenna gains for the two
cases of T-strip and square-cap coupled feeds.
Figure 6.27 shows the measured and simulated SWRs of the T-strip
case. As seen from the SWR curves, the antenna has a wide impedance