## 3 Results and Discussion  
The designed antenna is built as shown in Figure 3a to validate the simulation results that are obtained through high-frequency structure simulator (HFSS) software, which were fine-tuned using an intense parametric optimization procedure to generate the reflection coefficient displayed in Figure 3b, where the simulated and measured S\({}_{11}\) are in good agreement. The antenna 6-dB bandwidth ranges from 2.52 GHz to 13.83 GHz, and its 10-dB bandwidth spans over 2.55-10.94 GHz, which satisfies UWB requirements. Due to the multi-band behavior of the proposed antenna; the 6-dB bandwidth can be considered to provide seven resonating bands. These bands have bandwidths of (2.52-2.68) GHz, (3.9-4.4) GHz, (4.9-5.2) GHz, (5.8-6.7) GHz, (6.8-7.4) GHz, (7.6-8.2) GHz, and (9.3-13.8) GHz, respectively, in addition to an acceptable 10-dB impedance bandwidth in both simulation and measurements if they were considered. Besides these resonating bands, the suggested antenna was also acquired with six frequency notches with a notch level \(\geq\)\(-\)5 dB. The rejecting bands' centered frequencies '\(f_{c}\)' are 3.24 GHz, 4.71 GHz, 5.48 GHz, 6.81 GHz, 7.51 GHz, and 8.7 GHz and the percentage bandwidths (PBW) are 41.36%, 14.65%, 15.15%, 5.29%, 5.99%, and 18.04%, respectively. Together, several resonances modes and notch-band techniques have been used in this design to pass or suppress different communication services. Figure 2: (a) Proposed antenna design steps; (b) reflection coefficient comparison for the design steps. Figure 3: _Cont._  
The simulated and measured peak realized gain graph is depicted in Figure 3c. A good agreement is noticed between the two traces where the gain tends to increase as the frequency increases with a sharp reduction at the rejecting band's center frequencies. The simulated results of the gain at the six notches' center frequencies are \(-8.2515\) dB, \(-0.6843\) dB, \(-0.2025\) dB, \(1.6513\) dB, \(2.5284\) dB, and \(0.78\) dB, respectively. Table 2 summarizes the measured values of different aspects of the proposed antenna at these rejecting bands and the seven resonant frequencies. The proposed antenna peak realized gains within each resonance are tabulated in Table 2, where the maximum gain reaches \(4.46\) dB at \(13.74\) GHz. The graphs of the simulated and measured radiation efficiency are depicted in Figure 3d, and the results well agreed with the efficiencies attained at the operating band and a reduction at the rejecting bands. The maximum efficiency is found to be \(90.3\%\) at \(9.82\) GHz, while the lowest radiation efficiency reaches \(50.14\%\) at \(6.53\) GHz, which belongs to the fourth notch. The fabricated antenna is tested in its characteristics by mounting the antenna in a suitable anechoic chamber to conduct the required measurements as shown in Figure 4a. The radiation pattern at all resonances-centered frequencies is measured and compared with the simulation. The pattern at eight selected frequencies in which the S\({}_{11}\) curve has deepest locations is plotted in Figure 4b-i for both the E-plane, which represent the YZ-plane (\(\phi=90^{\circ}\)), and the H-plane, which represents the XZ-plane (\(\phi=0^{\circ}\)). In the H-plane, the antenna has shown an omnidirectional pattern at the first two resonances and starts to exhibit directional radiation pattern towards single or multiple orientations. The E-plane demonstrates an omnidirectional radiation pattern at the first resonant while the beam starts to acquire different directional patterns at the other resonances, and this is due to the partial ground and other modes being involved as frequency was increased. A good agreement between the simulated and measured patterns are noticed for the shown patterns. The radiation pattern at the rejection band-centered frequencies is also monitored, and it has a similar behavior but with much less power compared to the resonating band, and the pattern at the first notch-centered frequency is plotted in Figure 4j.