shows the simulated radiation patterns with
different reflector sizes, which are obtained from IE3D at
1700 MHz, 2100 MHz, and 2700 MHz, respectively. It can be
seen that the back-lobe level decreases when the size of the
reflector is increased. The antenna radiates bi-directionally
with equal power when there is no reflector. It is obvious that
there is no backward radiation in the case of an infinite
reflector plate. The reflector plate is then modified to reduce