Figure 5. Effects of the central slot on return loss.
The feed line is extended from feed point to the top of the
patch to form a straight printed patch (LS3 x SW1). This helped
in attaining omni-directional high gain patterns but introduced
a dip at high frequency due to the introduction of more
radiating edges. A comparative study of the width variation of
the straight slot is shown in Fig. 6, from which it can be seen
that reduction in the width of the extended line improves the
return loss characteristics significantly.