###### Abstract
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline
**Ref** & **Freq** & **Substrate** & **Sub** & **Patch** & **Gain** & **Bandwidth** & **Efficiency** & **Transp-** & **Transmi-** \\  & **(GHz)** & **Material** & **Thickness** & **(Mesh)** & **(dBi)** & **Bandwidth** & **(\%)** & **arency** & **trance** \\ \hline
[35] & 2.46–2.94 & Fused silica & - & \
\begin{tabular}{c} Tortuous \\ MM \\ \end{tabular} & \(-3.4\) &
\begin{tabular}{c} 2.82– \\ 3.0 GHz \\ \end{tabular} & 81 & - & 30–45 \\ \hline
[36] & 3.45 & PDMS & 2–4 mm & \
\begin{tabular}{c} EGaIn \\ (liquid \\ metal) \\ \end{tabular} &
\begin{tabular}{c} 3.3– \\ 3.5 GHz \\ \end{tabular} & 60 & - & - \\ \hline
[37] &
\begin{tabular}{c} 2.4–2.48, \\ 5.15–5.8 \\ \end{tabular} & Glass & 1.09 mm & MMMC & 0.74, 2.30 & - & 43, 46 & - & 75 \\ \hline
[38] & 2.43–2.48 & \begin{tabular}{c} Borosilicate \\ glass \\ \end{tabular} & \begin{tabular}{c} 4, 3.5, 3, \\ 2.5 mm \\ \end{tabular} & \
\begin{tabular}{c} Meshed \\ patch \\ \end{tabular} & 4.4 &
\begin{tabular}{c} 2.39– \\ 2.58 GHz \\ \end{tabular} & - & 74 & - \\ \hline
[39] & 2.3–3 & PET/PMMA & 4–5 mm & \
\begin{tabular}{c} Metal \\ mesh \\ \end{tabular} & 6 &
\begin{tabular}{c} 2.4– \\ 2.9 GHz \\ \end{tabular} & 90 & 70 & - \\ \hline
[40] & \
\begin{tabular}{c} 2.33–2.53, \\ 4.7–5.6 \\ \end{tabular} & PDMS & 3 mm & Mesh & 2.2, 3.1 &
\begin{tabular}{c} 170– \\ 200 MHz, \\ 700– \\ \end{tabular} & 37, 44 & - & 50–70 \\ \hline
[41] & 2.4–2.5 & Acrylic & 1 mm & Micromesh & \
\begin{tabular}{c} 4.75, \\ \(-4.23\), \\ and 2.63 \\ \end{tabular} &
\begin{tabular}{c} 2.4– \\ 2.6 GHz \\ and 42.69 \\ \end{tabular} & 66.32, & \multirow{2}{*}{80} & 6 & 6.32, \\
[42] & 60 &
\begin{tabular}{c} Thick \\ fused \\ silica 7980 \\ Corning \\ \end{tabular} & 0.2 mm & Al-MM & 3.20 & 53.55 GHz & - & 78 & - \\ \hline
[43] & 2.4, 2.55 & Quartz & 2.25 mm & \
\begin{tabular}{c} Silver \\ epoxy \\ mesh \\ \end{tabular} & 4.94, 7.23 &
\begin{tabular}{c} 2.4– \\ 2.6 GHz \\ \end{tabular} & - & 90 & - \\ \hline
[44] & 28 & Glass & 0.7 mm & \
\begin{tabular}{c} Ag-alloy \\ (diamond- \\ shaped) \\ \end{tabular} & 9.16 &
\begin{tabular}{c} 27.5– \\ 29.5 GHz \\ \end{tabular} & 52 & 41 & - \\ \hline
[45] & 2–2.5 & Plexiglass & 2.03 mm &
\begin{tabular}{c} Meshed \\ copper \\ \end{tabular} & 7.32 & - & 78 & 70–95 & - \\ \hline
[46] & 27–35 & Acrylic & 2 mm & \
\begin{tabular}{c} Cu micro- \\ grids \\ \end{tabular} & - &
\begin{tabular}{c} 27– \\ 35 GHz \\ \end{tabular} & - & - & - \\ \hline
[47] & 0.5–20 & PET & 0.1 mm & \
\begin{tabular}{c} Metal \\ mesh \\ \end{tabular} & 10.4 &
\begin{tabular}{c} 0.78– \\ 20 GHz \\ \end{tabular} & - & - & 72 \\ \hline
[48] & 22–40 & COPs & 0.1 mm & Thin MM & 1.12 &
\begin{tabular}{c} 24– \\ 29 GHz, \\ 35.5– \\ 37.5 GHz \\ \end{tabular} & 34–43 & 92–98 & \\ \hline
[49] & \
\begin{tabular}{c} 6.63, \\ 7.291, \\ 7.29, 7.22 \\ \end{tabular} & FR-4 & 1.62 mm & MWCNT & 8.8 &
\begin{tabular}{c} 4.5– \\ 8.5 GHz \\ \end{tabular} & 86 & - & - \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._In the urban environment, transparent antennas embedded into the glass of high-rise buildings may work as a camouflage antenna to provide connectivity in the dead zones. However, this may affect the gain, efficiency, and radiation pattern of the antenna adversely. The process used to convert an opaque to a transparent antenna causes the inefficacy of the antenna due to the meshing of the conducting part or material resistivity of thin films [52]. Gain and Bandwidth for Various Antenna ApplicationsAntennas are designed for several applications working at different frequency bands. The RF spectrum is shown in Figure 2, where the spectrum is differentiated based on different applications. Therefore, the bandwidth and gain requirement also depends on the type of antenna, choice of substrate, patch material, the electrical length of the antenna, and feeding techniques. Some applications require low gain and bandwidth, while others have higher requirements. Figure 1: Examples of optically transparent antennas.