# Generation of Sparse Antennas and Scatterers Based on Optimal Current Grid Approximation
## 2 Review of Approaches for Reducing Mass and Surface of Various Antenna Structures Using the OCGA
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Antenna** & \(f\), **GHz** & **GEET, \%** & **Approach** & \multicolumn{3}{c}{**Reductions, Times**} & \multicolumn{3}{c}{**Maximum Difference in Characteristics**} \\  & & & & **Mass and Surface** & **Memory** & **Time** & \(\mathcal{G}_{max}\)** & **dB** & **VSWR** & \(\mathbf{1}_{S1}\)**, \(\mathbf{dB}\)** & \(\mathbf{1}_{Z1}\)**, \(\mathbf{Ohm}\)** \\ \hline \multirow{6}{*}{Reflector} & \multirow{3}{*}{3.4-3.7} & \multirow{3}{*}{30} & OCGA & 1.39 & 1.94 & 2.71 & 0.14 & 0.007 & 2.83 & 0.34 \\  & & & EOCGA & 1.99 & 3.97 & 7.91 & 3.91 & 0.018 & 8.78 & 0.72 \\  & & & NCOCGA & 1.37 & 1.88 & 2.58 & 0.09 & 0.006 & 3.30 & 0.29 \\ \cline{2-10}  & & & OCGA & 1.51 & 2.28 & 3.44 & 0.12 & 0.01 & 0.26 & 0.08 \\  & & & EOCGA & 1.80 & 3.24 & 5.84 & 2.20 & 0.01 & 0.13 & 0.46 \\  & & & NCOCGA & 1.49 & 2.21 & 3.27 & 0.10 & 0.01 & 0.25 & 0.09 \\ \cline{2-10}  & & & OCGA & 1.37 & 1.87 & 2.57 & 0.30 & 0.014 & 0.63 & 0.54 \\  & & & EOCGA & 1.78 & 3.17 & 5.64 & 3.47 & 0.032 & 0.85 & 1.48 \\  & & & NCOCGA & 1.36 & 1.86 & 2.53 & 0.28 & 0.016 & 0.61 & 0.70 \\ \hline \multirow{6}{*}{Hom} & \multirow{3}{*}{0.7–1.3} & \multirow{3}{*}{75} & OCGA & 1.86 & 3.45 & 6.40 & 2.38 & 1.20 & 14.64 & 30.45 \\  & & & EOCGA & 2.03 & 4.11 & 8.32 & 3.14 & 1.11 & 12.51 & 31.02 \\  & & & NCOCGA & 1.83 & 3.35 & 6.14 & 2.33 & 1.22 & 13.00 & 28.14 \\ \cline{2-10}  & & & OCGA & 1.58 & 2.50 & 3.94 & 2.75 & 3.62 & 0.19 & 7.28 \\  & & & COCGA & 1.56 & 2.44 & 3.82 & 2.04 & 3.17 & 0.16 & 7.33 \\ \cline{2-10}  & & & & OCGA & 2.36 & 5.56 & 13.11 & 2.22 & 0.51 & 3.24 & 6.51 \\  & & & EOCGA & 2.46 & 6.05 & 14.89 & 2.41 & 0.48 & 3.22 & 6.74 \\  & & & NCOCGA & 2.32 & 5.38 & 12.48 & 2.20 & 0.46 & 3.14 & 6.15 \\ \hline \multirow{6}{*}{Conical horn} & \multirow{3}{*}{5.3–6.3} & \multirow{3}{*}{20} & OCGA & 1.19 & 1.42 & 1.69 & 1.67 & 0.53 & 2.32 & 22.98 \\  & & & EOCGA & 1.19 & 1.42 & 1.69 & 1.67 & 0.53 & 2.32 & 22.98 \\ \cline{1-1}  & & & EOCGA & 1.26 & 1.60 & 2.02 & 0.55 & 0.03 & 0.21 & 0.24 \\ \cline{1-1}  & & & EOCGA & 2.75 & 7.55 & 20.75 & 3.91 & 0.22 & 1.44 & 29.28 \\ \cline{1-1}  & & & NCOCGA & 1.25 & 1.56 & 1.96 & 0.57 & 0.03 & 0.22 & 0.20 \\ \hline \multirow{2}{*}{Patch} & \multirow{2}{*}{2-3} & \multirow{2}{*}{30} & OCGA & 1.52 & 2.31 & 3.51 & 0.22 & 2.79 & 6.04 & 41.49 \\ \cline{1-1}  & & & EOCGA & 1.72 & 2.95 & 5.07 & 1.54 & 11.52 & 15.88 & 66.63 \\ \cline{1-1}  & & & NCOCGA & 1.49 & 2.22 & 3.31 & 0.88 & 3.08 & 15.81 & 136.12 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The improvements and maximum differences from the original sparse structure after applying different approaches to different antenna types. and size. In addition, they can be used in applications that require hidden antennas so as not to affect the overall landscape. The conditions for performing antenna measurements must fully meet the requirements and criteria specified in [62]. WG antenna structures have been widely developed and studied in previous studies, and the far zone was considered for these types of antennas. Although there are changes in the number of wires in sparse WG antenna structures, they are basically not much different from the original WG structure. Therefore, the measurement conditions and far zone requirements for these structures are still the same as those for the original WG structures; they can be measured in an anechoic chamber or in outdoor areas, depending on the purpose of testing the real-life performance of the antenna. Figure 1 presents the setup for antenna measurements, the configuration of the sparse antennas, and the results of main characteristic measurements for both sparse and original antennas. In [63], we created actual sparse horn antennas based on OCGA using the horn antenna from [64] operating in the UHF band with a central frequency of 0.915 GHz. A total of 1062 copper wires are employed to form the WG structure. To connect the WG structure and the excitation wires, a 50-Ohm SMA connector is used.