## 4 Antennas for Beam Steering and Beamforming
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**References** & **Gain (dBi)** & \begin{tabular}{c} **Efficiency** \\ **(\%)** \\ \end{tabular} & \
\begin{tabular}{c} **CubeSat** \\ **Unit** \\ \end{tabular} & **Polarization** &
\begin{tabular}{c} **Dimensions** \\ **(mm \(\times\) mm2)** \\ \end{tabular} & **Feeding Tech** & **f\({}_{\text{f}}\) (GHz)** & **Mass (kg)** \\ \hline
[30] & \textless{}13 & N/A & 1 & CP & N/A &
\begin{tabular}{c} coaxial \\ probe \\ coaxial \\ probe \\ \end{tabular} & 8.27 & N/A \\
[31] & \textless{}7 & N/A & \(3\times 1\) & CP & \(100\times 100\) &
\begin{tabular}{c} coaxial \\ probe \\ \end{tabular} & 8, 11.5 & N/A \\
[32] & 15 & 65 & 1 & CP & \textless{}300 & Fabry–Perot cavity & 10 & N/A \\
[33] & 20 & 97.5 & 1 & CP (RHCP) & \(100\times 100\) &
\begin{tabular}{c} unequal series parallel \\ power dividers \\ offset fed reflect array \\ \end{tabular} & 8.2 & N/A \\
[34] & 29.2 & 45 & 6 & CP (RHCP) & \(100\times 200\times 340\) & offset fed reflect array & 8.425 & \textless{}1 \\
[35] & 4.31 & \textless{}78.8 & N/A & N/A & \(40\times 40\) &
\begin{tabular}{c} coaxial \\ probe \\ \end{tabular} & 8-12 & N/A \\
[36] & 8.07 & N/A & N/A & N/A & \(16\times 16\) &
\begin{tabular}{c} coaxial \\ probe \\ \end{tabular} & 7.6, 12 & N/A \\
[37] & 35 & N/A & N/A & N/A &
\begin{tabular}{c} coaxial \\ probe \\ \end{tabular} & 7.89–10.49 & N/A \\
[38] & \textless{}5.5 & 90.90 & N/A & N/A & \(20\times 17.2\) &
\begin{tabular}{c} coaxial \\ probe \\ \end{tabular} & 9, 11 & N/A \\
[39] & 12.5 & N/A & N/A & N/A & \(70\times 70\) & patch rod & 8 & N/A \\
[40] & 10.5 & N/A & N/A & N/A & \(95\times 95\) &
\begin{tabular}{c} coaxial \\ probe \\ \end{tabular} & 8.15 & N/A \\
[41] & 6.1 & \textgreater{}80 & N/A & N/A & \(35\times 33\) &
\begin{tabular}{c} coaxial \\ probe \\ \end{tabular} & 9.3 & N/A \\
[42] & \textless{}10 & \textgreater{}80 & N/A & LP & \(27\times 22\) &
\begin{tabular}{c} coaxial \\ probe \\ \end{tabular} & 8.5, 10 & N/A \\
[48] & 39 & N/A & \(3\times 2\) & N/A & \(1500\times 1500\) &
\begin{tabular}{c} diagonal cord feed \\ \end{tabular} & 8.4 & 1.75 \\
[55] & \textless{}11.5 & N/A & N/A & N/A & \(49.6\times 53\) & PBG & 2.5, 8 & N/A \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Utilized planar antennas for CubeSat communication operations in the X-band. improving the communication range and reducing interference. On the other hand, beam steering is the ability to dynamically change the direction of the main lobe (i.e., focus) of an antenna's radiation pattern without physically moving the antenna. It involves electronically controlling the phase of signals in an antenna array to steer the beam in the desired direction. Beam steering allows for the flexible coverage of a specific area or tracking of a moving target, such as a satellite or mobile device, without mechanical movement (Figure 6). The feasibility of dynamic beam-steering in Low Earth Orbit (LEO) satellite communications is heavily impacted by power limitations. Directing communication beams toward ground targets demands precise antenna array control, which requires considerable power for signal transmission and steering operations. This challenge is particularly pronounced in small satellites like CubeSats, which have minimal energy resources due to their size. Consequently, the power used for beam-steering must be shared with other vital tasks, such as managing onboard systems and regulating thermal conditions. To tackle these constraints, researchers have introduced energy-efficient strategies that optimize beam handovers and switching within multi-LEO satellite networks, aiming to maximize power efficiency without compromising communication reliability [68]. Moreover, studies on beam scheduling and beamforming design under individual feed power limitations emphasize the difficulties in distributing power effectively across multiple beams. The goal is to optimize data rates while ensuring the overall power consumption remains within the designated limits [69].