Figure 4. Measured and simulated return loss.
Figure 5 show the variations in return loss and impedance
bandwidth by varying size of central slot shown in Fig. 3(b). It
can be seen from Fig. 5 that increase in the area of central slot
improves return loss and increases an impedance bandwidth,
however the gain of the antenna is insufficient in the pass
band and the side of the patch opposite to the feed line also
becomes deficient of the current density.