109450.fig.004
Figure 4: Simulated return loss of the proposed antenna with different values of gap length between the rectangular ring, open-ended antenna and the ground plane ( ). (Other parameters:  mm;  mm;  mm;  mm;  mm;  mm;  mm;  mm;  mm;  mm;  mm;  mm;  mm;  mm;  mm;  mm;  mm; and  mm.)