III. EXPERIMENTAL RESULTS AND DISCUSSION
In order to obtain the uni-directional radiation, a plane
reflector is placed parallel to the slot surface on the side of the
dielectric substrate. The return loss of the CPW-fed slot
antennas is calculated for different sizes of a finite reflector
plate and an infinite reflector. The simulated return losses of
the CPW-fed slot antennas with and without the reflector are
presented in Fig. 2. It can be seen that the matching of the
antenna is affected by the size of the reflector. As the
thickness of the air reflector substrate is relatively large, the
reflector element has little effect on the input impedance of
the antenna.
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