The modified ground plane is used to achieve the
WiMAX band at 3.5GHz and obtain a better impedance
matching. The design evolution process is shown in Fig. 2.
Firstly, by adding the L-strip at the top of the rectangle ground
plane in Antenna1, a broad band from 3.37GHz to 6.70GHz
can be obtained, as shown in Fig. 3. Secondly, a narrow
rectangle strip has been added at the side of the L-strip in
Antenna2 to split the wide frequency band into two bands,
3.363.86GHz and 4.376.36GHz respectively, and then the
Antenna3 (proposed antenna) is able to generate three
resonant bands to cover the 2.4/5.2/5.8GHz WLAN bands and
the 3.5/5.5GHz WiMAX bands. The geometrical parameters
of the proposed antennas are described in Table 1.