In our design, a rectangular monopole was used as the initial
design. The dimensions are shown in Fig. 1(a). A FR4 board
with permittivity 4.5 was used as the substrate. All the
simulations were done with Microstripes 3D electromagnetic
simulation software. The rectangular antenna has a bandwidth
from 2.5GHz to 3.1GHz (about 23.3%) which is located in the
antenna’s anti-resonance region, see Fig.2. While due to the low
real part and capacitive imaginary part of the impedance caused
by the small ground plane, the resonance area (1.6GHz-2.1GHz)
has a worse match. To counteract this effect without increasing
the ground plane size or adding an extra matching circuit, two
12mm long wings are added to the ground plane. See Fig. 1(b).