Fig. 4 Chronological developenent of the proposed antenna with last two iterative processes.
Figure 5 shows the simulated reflection coefficient (|S11|) of iteration five and six of the final proposed design of the UWB notch antenna. In iteration five shown in figure 4 (a), an open-ended slit ring is created on the top of the protruding stub in the square slot of the circular radiating element. Due to the open-ended slit ring in the top portion of the protruding stub, the operation band is extended from 2.8 GHz to 12.8 GHz with impedance bandwidth 10 GHz which is 0.6 GHz more than the impedance bandwidth obtained in iteration four. The reason for the enhancement of the impedance bandwidth is due to creation of the extra current paths through open ended slit ring. This enhanced current path helps in the constructive addition of currents in the edges of the open-ended slit ring and the protruding stub. But in this iteration the position of the center of notch frequency is unmoved at fns1= 4.7 GHz as in fourth iteration. Hence there is no improvement of the position of the center frequency of the notch i.e.fns1= 4.7 GHz.