# Ultra-Wideband Antenna Design for 5G NR Using the Bezier Search Differential Evolution Algorithm
## 4 Conclusions  
In this research paper, a novel ultra-wideband patch antenna with a stub and partial grounding is proposed for RF energy harvesting applications (Figure 3). This antenna is the result of an optimization process, using the Bezier Search Differential Evolution Algorithm [3] (Algorithm 1), which was tested with benchmark functions and outperformed all other candidate algorithms (Tables 2 and 3). The optimization goal was to expand the operational bandwidth of the initial antenna design proposed in [1] (Figure 2) to include the 5G FR1 band. In order to implement the optimization, a novel CST-Matlab API was designed, containing all the functions to manipulate the CST antenna structure and capable of calculating the cost function from the corresponding \(S_{11}\) graph of each agent.The optimal antenna operates from 1.4 GHz to 3.9 GHz, successfully broadening the bandwidth of the initial design which was from 1.7 GHz to 2.7 GHz and allowing harvesting from all the vastly used technologies like GSM at 1.8 GHz, UMTS at 2.1 GHz, Wi-Fi at 2.4 GHz, LTE at 2.6 GHz, and 5G NR at 3.5 GHz, which is a feature not yet present in the literature, making it one of the most useful broad-band antennas for rectenna applications (Table 1). The ultra-wideband characteristics, along with its omnidirectionality, are confirmed from the impedance response graph, the \(S_{11}\) graph, the efficiency table, and the 3D radiation pattern. More specifically, the \(S_{11}\) graph in Figure 4 has values lower than \(-10\) dB in the entire operational frequency band; the impedance graph in Figure 5 depicts appropriate matching, with a mean reactance value less than 30 \(\Omega\) and resistance close to 50 \(\Omega\); the efficiency is above 84% across the frequency band and up to 96% for specific frequency points (Table 5); and last but not least, the 3D radiation pattern shows omnidirectional behavior as expected from antennas for RF harvesting application (Figures 6 and 7). In conclusion, the optimization process was utterly successful, resulting in an optimal antenna design suitable for the majority of RF energy harvesting applications, as it presents both ultra-wideband and omnidirectional characteristics in the operation band, which spreads from 1.4 to 3.9 GHz, including the frequencies of all vastly used wireless telecommunications technologies, like GSM, UMTS, Wi-Fi, LTE, and 5G NR. Future research will focus on finding complex matching networks that will allow rectifiers to convert RF energy from more than one of these technologies to DC.  
Conceptualization, G.K. and K.S.; methodology, G.K.; software, G.K. and A.D.B.; validation, G.K. and Z.D.Z.; formal analysis, G.K. and M.S.P.; investigation, G.K. and P.S.; resources, G.K. and P.S.; data curation, G.K. and M.A.M.; writing--original draft preparation, G.K. and S.K.G.; writing--review and editing, G.K. and Z.D.Z.; visualization, G.K. and M.A.M.; supervision, S.K.G.; project administration, S.K.G. All authors have read and agreed to the published version of the manuscript. This research received no external funding.  
Not applicable.  
The raw data supporting the conclusions of this article will be made available by the authors on request.  
The authors declare no conflicts of interest.