shaped resonating element which is responsible for the two
resonances around 2.51 GHz and 5.18 GHz respectively.
The proposed 9-shaped monopole antenna was simulated
by using the IE3D full wave simulator [13].
For a printed monopole antenna, the resonant frequency
can be approximately calculated by equating its
area (in this case a folded 9-shaped printed monopole) to
that of an equivalent cylindrical monopole antenna[14] of
equivalent height Lc and equivalent radius rc as follows: