# A Novel L-Shaped Metalens for Ultra-Wide Band (UWB) Antenna Gain Improvement
## 5 Conclusions  
Metalenses have been designed and optimized in the frequency band of \(f=3\div 15\) GHz in order to enhance the radiation performance of an antipodal Vivaldi antenna. The metalens L-shaped#1 improves both the pristine AVA bandwidth and the gain, especially at high frequencies. A maximum gain increase of \(\Delta G_{max}=4.8\) dB and a maximum HPBW reduction of \(\Delta HPBW_{max}=31.3^{\circ}\) have been measured at the frequency of \(f=13.8\) GHz with respect to the pristine AVA. A frequency band of \(f_{xu\mu 1\#1}=3\div 14.7\) GHz, slightly larger than that of the pristine AVA, has been measured. The metalens L-shaped#2 can give better results at lower frequencies. The experimental results are in good agreement with the simulations. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Ref**} & **Size** & **Operating** & **Min-Max Gain** & **Min-Max Gain** & **Min-Max \(\Delta HPBW\)** \\  & **(\(\lambda\times\lambda\)) (\({}^{\text{th}}\))** & **Bandwidth (GHz)** & **G (dB)** & **\(\Delta G\) (dB)** & **(deg)** \\ \hline \hline \multirow{4}{*}{[1]} & \(286\times 300\) & \multirow{4}{*}{\(0.7\div 2.1\)} & \multirow{4}{*}{nr (\({}^{\text{2}}\))} & \multirow{4}{*}{\(1.0\div 1.9\)} & E plane: \\  & \(1.3\lambda\times 1.4\lambda\) & & & & & \(4.8^{\circ}\div 9.9^{\circ}\) \\  & \(200\times 390\) & & & & & \(14.7^{\circ}\div 30.3^{\circ}\) \\  & \(2.8\lambda\times 5.5\lambda\) & \(1\div 7.5\) & nr & \(0.1\div 4.8\) & nr \\  & \(138.2\times 69.6\times 31.7\) & \multirow{4}{*}{\(7.55\div 22.85\)} & \multirow{4}{*}{\(6.98\div 11.54\)} & nr & nr \\  & \(7\lambda\times 3.5\lambda\times 1.6\lambda\) & & & & \\  & \(120\times 260\) & & & & \\  & \(5.8\lambda\times 12\lambda\) & & \(1\div 28\) & \(4.9\div 14.6\) & nr & nr \\  & \(60\times 28.6\) & & & & & \\  & \(5.3\lambda\times 2.5\lambda\) & & & & & \\  & \(42\times 78\) & & & & & \(-3^{\circ}\div 17^{\circ}\) \\  & \(1.7\lambda\times 3.1\lambda\) & & \(6\div 18\) & \(7.2\div 12\) & \(1.3\div 3.6\) & H plane: \\  & & & & & & \(23^{\circ}\div 33^{\circ}\) \\  & \(52\times 93\) & & & & & \\  & \(2.1\lambda\times 3.7\lambda\) & & \(6\div 18\) & nr & \(1\div 2.5\) & nr \\  & & & & & & E-plane: \\  & \(140\times 96\) & & & & & \\  & \(3.1\lambda\times 2.1\lambda\) & & \(1.4\div 12\) & \(9.5\div 12.4\) & \(2.5\div 4\) & \(11.3^{\circ}\div 23.2^{\circ}\) \\  & \(80\times 148.5\) & & & & & \(-24^{\circ}\div 33.2^{\circ}\) \\  & \(1.75\lambda\times 3.2\lambda\) & & & & & \(nr\) \\  & & & & & & E-plane: \\  & \(48\times 120\) & & & & & \(1.7^{\circ}\div 31.3^{\circ}\) \\  & \(1.4\lambda\times 3.5\lambda\) & & & & & \(1.7^{\circ}\div 28.3^{\circ}\) \\  & & & & & & \\  & & & & & & \\  & & & & & & \\  & & & & & & \\ \hline \hline \end{tabular} \({}^{(\text{th})}\) \(\lambda\) represents the wavelength at the center frequency of the operating bandwidth. (\({}^{\text{2}}\)) nr: not reported.  
\end{table} 
Table 3: Experimental results comparison of the metalens investigated in this work and similar published work. **Author Contributions:** Conceptualization, investigation, and methodology, V.P., A.M.L., A.C., F.A. and F.P. ; writing--original draft preparation, V.P. and F.P. ; writing--review and editing, V.P., A.M.L., F.A. and F.P. ; supervision, F.P. All authors have read and agreed to the published version of the manuscript. **Funding:** This work was partially supported by the European Union under the Italian National Recovery and Resilience Plan (NRRP) of NextGenerationEU, with particular reference to the partnership on \"Telecommunications of the Future\" (PE00000001--program \"RESTART\", CUP: D93C22000910001)--STRUCTURAL PROJECT MINDS DREAMS Millimeter wave aNtennas Disruptive Solutions and Devices foR mixing, dEtction And Manipulation of mm Waves.