# Compact Planar Super-Wideband Monopole Antenna with Four Notched Bands
## 3 Results and Discussion  
The fabricated prototype of the proposed quadruple notched-band SWB antenna is displayed in Figure 1c. A tapered feed line is used to excite the antenna and to provide better impedance matching. Figure 8 displays the measured and simulated reflection coefficient curves of the proposed antenna. The antenna covers a wide frequency range from 2.5-40 GHz. In the resonating frequency band,  
Figure 7: Simulated reflection coefficients of the antenna: (**a**) when \(b_{1}\) is varied, (**b**) when \(l_{3}\) is varied, (**c**) when \(l_{4}\) is varied, (**d**) when \(l_{9}\) is varied. four notched bands (at 3.5 GHz, 5.5 GHz, 7.5 GHz, and 10.5 GHz) are achieved to remove interfering frequencies from the SWB. The notched frequency bands can be controlled by varying the lengths of the slots. This simulated and measured reflection coefficient curves show reasonably good agreement between them. Figure 9 shows the measured and simulated plots of the antenna gain. The simulated peak gain of the presented quad-notched band antenna is 7 dBi. The gain steadily increases from 2.5 GHz to 15 GHz, and remains almost constant up to 40 GHz. It is also observed that the gain sharply falls in the vicinity of the notched bands. The simulated efficiency curve of the proposed quadruple notched-band antenna is depicted in Figure 10a. The efficiency is more than 90% in the passband region and it decreases sharply at the rejection bands. The group delay is an important parameter used to characterize the degree of distortion of the pulse signal [30]. Figure 10b shows the simulated group delay of the proposed  
Figure 8: Reflection coefficients of the proposed quad band-notched SWB antenna. Figure 9: Gain of the proposed quad band-notched SWB antenna. quadruple notched-band antenna. The group delay curve is stable over the SWB range except at four rejection bands. The co-polar and cross-polar patterns of the proposed SWB antenna are shown in Figure 11. It is noticed that omni-directional co-polar radiation patterns are obtained in the H-plane, while bi-directional patterns in the E-plane. Furthermore, the cross-polarization level is lesser than the co-polarization level in both the E- and H-planes. Figure 11: _Cont._  
Figure 10: Proposed quadruple band-notched SWB antenna: (a) efficiency, (b) group delay. A comparison of the proposed quad notched-band antenna with the recently reported SWB antenna designs is shown in Table 2. The antennas presented in References [9; 10; 11; 12; 13; 14; 15; 16] did not have band rejection features. The elimination of unwanted frequency bands improves the quality of communication. The SWB antennas in References [20; 21] rejected only one frequency band, while the antennas in References [22; 23] rejected two frequency bands. The antenna designs in References [24; 25; 26] showed triple-band rejection characteristics. However, the drawbacks of these notched band antennas were their poor selectivity and complicated ground planes embedded with parasitic elements and stubs. Furthermore, the sizes of the SWB antennas in References [9; 11; 13; 14; 15; 22; 24; 25] were quite large, which may limit their applications in monolithic microwave integrated circuits and portable high-frequency devices. The radiating patch designs in References [11; 12; 26] were practically complex, due to the fractal shape and integrated active elements. Furthermore, most of the SWB antennas proposed in the literature were printed on the FR-4 substrate, which is a lossy substrate and exhibits poor performance at high frequency. In the proposed antenna design, the four notched bands are obtained without using any filter/active elements, thus simplifying the antenna design process. The total area occupied by the proposed SWB antenna is comparatively small, and it can be easily integrated into portable RF devices. Thus, the proposed antenna outperforms the reported SWB antennas in terms of bandwidth ratio, simple design, compact size, and the number of notch bands.