Fig.11Simulated and measured group delay of the proposed antenna
Figure 12 exhibits the surface current distribution of the proposed antenna at 3.5 GHz, 4.4 GHz, 5.5 GHz, 8.8 GHz, and 12 GHz. At 3.5 GHz and 4.4 GHz shown in the figure 12 (a), (b) respectively, the increased current density is visible in the microstrip feed-line and inner edges of the square slot in the circular radiating element. Because of this amount of current density, proper radiation is possible by the proposed UWB antenna that radiates properly in these operating frequencies. At notch frequency 5.5 GHz because of the thick rectangular protruding stub and a SRR printed in the left side of the microstrip feed-line the proposed UWB notch antenna cannot able to radiate considerably as depicted in figure 12 (c). At this operating frequency of 5.5 GHz the current density is very low in the whole structure of the proposed UWB notch antenna. Similarly, at other frequencies of 8.5 GHz and 12 GHz as in figure 12 (d), (e) proper radiation happened as the enhanced current density is visible again in the inner edges of the square slot and around the edges of the open-ended slit ring.