## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Ref**} & \multirow{2}{*}{**Geometry**} & \multirow{2}{*}{**Optimization**} & \multirow{2}{*}{**Domain**} & \multicolumn{2}{c}{**Resonant**} & \multirow{2}{*}{**Antenna Size**} & \multirow{2}{*}{**Efficiency**} & \multirow{2}{*}{**Gain (dBi)**} & \multicolumn{2}{c}{\(-10\) dB} \\  & & & & **(GHz)** & & & **(\%)** & & **Bandwidth** \\ \hline
[47] & Microstrip & PSO + Curve & \multirow{2}{*}{Real} & \multirow{2}{*}{2.37} & \multirow{2}{*}{\(39\times 47.6\times 1.6\)} & \multirow{2}{*}{93.9} & \multirow{2}{*}{3.5} & \multirow{2}{*}{13.5} \\  & Patch & Fitting & & & & & & \\ Microstrip & HBCPSO + & \multirow{2}{*}{Real} & \multirow{2}{*}{3.1} & \multirow{2}{*}{\(29\times 20.5\times 1.6\)} & \multirow{2}{*}{N/A} & \multirow{2}{*}{N/A} & \multirow{2}{*}{13.8} \\  & Patch & Curve Fitting & & & & & \\ Microstrip & \multirow{2}{*}{HPSO} & \multirow{2}{*}{Binary} & \multirow{2}{*}{2.39} & \multirow{2}{*}{\(189\times 261.87\times 1.6\)} & \multirow{2}{*}{N/A} & \multirow{2}{*}{4.56} & \multirow{2}{*}{16.3} \\  & Patch & & & & & & \\ \cline{1-1}
[48] & Planar & BPSO + DGF & \multirow{2}{*}{Binary} & \multirow{2}{*}{4.2} & \multirow{2}{*}{\(16\times 19.2\times 1.6\)} & \multirow{2}{*}{N/A} & \multirow{2}{*}{4.71} & \multirow{2}{*}{27.4} \\  & Monopole & & & & & & & \\ \cline{1-1}
[49] & PLPDA & PSO & \multirow{2}{*}{Real} & \multirow{2}{*}{7.2} & \multirow{2}{*}{\(46\times 33\times 1.6\)} & \multirow{2}{*}{N/A} & \multirow{2}{*}{7.6} & \multirow{2}{*}{48.0} \\ Proposed & IFA & DH-BPSO & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Comparison of DHBPSO with other applications in literature of PSO algorithms towards bandwidth enhancement. **Author Contributions:** Conceptualization, [PERSON] and N.J.; methodology, [PERSON], G.G. and N.J.; software, [PERSON] and G.G. ; validation, J.A. ; formal analysis, [PERSON], G.G. and N.J.; investigation, J.A., G.G. and N.J.; resources, N.J.; data curation, [PERSON], G.G., and N.J.; writing--original draft preparation, [PERSON], G.G. and N.J.; writing--review and editing, [PERSON], G.G. and N.J.; visualization, [PERSON], G.G. and N.J.; supervision, N.J.; project administration, N.J.; funding acquisition, N.J. All authors have read and agreed to the published version of the manuscript. This research was funded by the Remote Sensing Center of the University of Alabama. **Informed Consent Statement:** Not Applicable. **Acknowledgments:** We would like to acknowledge [PERSON] for his assistance in the antenna fabrication process. **Conflicts of Interest:** The authors declare no conflict of interest. * [PERSON] and [PERSON] (1997) [PERSON]; [PERSON] A discrete binary version of the particle swarm algorithm. In Proceedings of the 1997 IEEE International Conference on Systems, Man, and Cybernetics. Computational Cybernetics and Simulation, Orlando, FL, USA, 12-15 October 1997; Volume 4105, pp. 4104-4108. * [PERSON] and [PERSON] (1997) [PERSON]; [PERSON] Genetic algorithm optimization applied to electromagnetics: A review. _IEEE Trans. Antennas Propag._**1997**, _45_, 343-353. [CrossRef]
* [PERSON] and [PERSON] (2006) [PERSON]; [PERSON] Novel method of UWB antenna optimization for specified input signal forms by means of genetic algorithm. _IEEE Trans. Antennas Propag._**2006**, _54_, 2216-2225. [CrossRef]
* [PERSON] and [PERSON] (2015) [PERSON]; [PERSON] Antenna array optimization using surrogate-model aware evolutionary algorithm with local search. In Proceedings of the 2015 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting, Vancouver, BC, Canada, 19-24 July 2015; pp. 1330-1331. [CrossRef]
* [PERSON] et al. (2004) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Space mapping: The state of the art. _IEEE Trans. Microw. Theory Tech._**2004**, _52_, 337-361. [CrossRef]
* [PERSON] et al.