# A Novel L-Shaped Metalens for Ultra-Wide Band (UWB) Antenna Gain Improvement
## 4 Experimental Section  
Antenna prototypes, AVA, and AVA L-shaped#1 have been fabricated with Rogers RO4350B dielectric substrate, with \(\varepsilon_{r}=3.66\) and \(tan\delta=0.0037\), by using the standard PCB process. The prototype of AVA is shown in Figure 13a. The prototype AVA L-shaped#1 is shown in Figure 13b. The scattering parameter \(S_{11}\), input impedance \(Z_{ant}\), and voltage standing-wave ratio (\(VSWR\)) versus the frequency of the two antennas have been measured with the Agilent Technologies N5224A PNA Network Analyzer. The calibration of the PNA has been performed with an N4693A 2-Port Electronic Calibration Module, setting the IF bandwidth to \(IF_{BW}=1\) KHz and the stimulus power to \(P_{s}=-10\) dBm. The uncertainty in the measured \(S_{11}\) parameter is \(\pm 0.04\) dB for the magnitude and \(\pm 0.264^{\circ}\) for the phase. The radiation performance characterization has been performed with the antenna measurement system in an anechoic chamber, StarLab SATIMO. The system has been calibrated in gain with reference horn antennas. The uncertainty band of the instrument is \(e_{gain}=\pm 0.7\) dB. For the measurements, we have set a step of \(\Delta f=10\) MHz for linear frequency distribution and a grid size of \(\Delta\theta=\Delta\phi=4.5^{\circ}\) for spatial resolution. The simulated (solid curves) and the measured (dotted curves) moduli of the scattering parameter \(S_{11}\) as a function of the frequency, for the AVA (black curves) and AVA L-shaped#1 (green curves) are illustrated in Figure 14a. The metalens allows an increase in the antenna bandwidth at high frequencies. A band of \(f_{AVA}=3\div 13.5\) GHz for the AVA and an increased band of \(f_{maxL\#1}=3\div 14.7\) GHz for the AVA L-shaped#1 have been measured. The simulated and measured curves are in good agreement. The measured VSWR of AVA and AVA L-shaped#1 prototypes is \(VSWR<2\) in almost the whole operating frequency band. The introduction of the metalens reduces the VSWR for frequencies \(f>9.5\) GHz. The measured antenna impedance of both prototypes varies around the characteristic impedance of the feed line \(Z_{c}=50\)\(\Omega\). The introduction of metalens slightly reduces the  
Figure 12: Full-wave simulation of the gain \(G\) as a function of frequency for AVA L-shaped#1 (solid curve) and AVA with EHL, having thickness \(d_{EHL}=0.832\) mm and values of permittivity \(\varepsilon_{r}=4.98\) and permeability \(\mu_{r}=0.75\) (dashed curve). impedance mismatch at high frequencies, in agreement with the measured parameter \(S_{11}\) reported in Figure 14a. The simulated and measured gain of AVA and AVA L-shaped#1 as a function of the frequency is illustrated in Figure 14b. A maximum gain \(G_{max}=10.7\) dB at a frequency of \(f=8.4\) GHz for the AVA and \(G_{max}=14.21\) dB at a frequency of \(f=14.6\) GHz for the AVA L-shaped#1 have been measured. The AVA L-shaped#1 has an improved gain with respect to the AVA over the whole bandwidth, especially for the frequencies \(f>8\) GHz, where the measured average gain increase is about \(\Delta G_{avg}=3\) dB and the maximum measured gain increase is \(\Delta G_{max}=4.8\) dB at a frequency of \(f=13.8\) GHz. Additionally, for the gain, a good agreement between the simulation and measurement is obtained. The E-plane and H-plane radiation patterns of the antenna prototypes have been measured and compared in the whole operating frequency band.