## 4 Antennas for Beam Steering and Beamforming
### Beam-Steering/Beamforming Techniques and Their Possible Features for CubeSat Communications
This method achieves precise control over beam direction by manipulating electromagnetic waves at the metasurface interface. The primary challenge in this approach is the complex fabrication and integration of metasurfaces into existing systems. However, the outcome showed significant potential for high-precision beam steering with minimal signal loss, indicating a promising avenue for future research. Integrated optical beam-steering devices have been developed using switchable liquid crystal metasurfaces. A study available in Ref. [85] depicts a method employing holography techniques to calculate the required phases, enabling dynamic beam steering in optical systems. The challenges of this approach include the precise control of the liquid crystal properties and the integration into compact optical devices. The outcomes demonstrated ultrafast beam-steering capabilities, which could revolutionize applications in optical communications and beyond (Figure 7). Reference [86] introduced a pattern-reconfigurable antenna that utilizes a metasurface for two-dimensional beam steering. The design integrates a reconfigurable metasurface with the antenna structure, enabling dynamic control over the radiation pattern in both the azimuth and elevation planes. This approach allows for efficient beam steering without the need for mechanical movement, offering potential advantages in applications such as wireless communications and radar systems. However, the available summary did not provide specific details regarding the operational frequency range, steering range, and the methods employed for reconfiguring the metasurface. Further information from the full text is necessary to comprehensively assess this design's performance and potential limitations. Reference [87] presents a dual-port, dual-beam, and pattern-reconfigurable antenna capable of independent two-dimensional (2D) beam scanning. The antenna features two feeding ports that allow for the independent control of each beam, enhancing flexibility in beam directionality. This design enables dynamic beam switching, making it well-suited for applications requiring adaptive beamforming, such as satellite communications and wireless networks. The proposed antenna achieves efficient 2D beam scanning without requiring mechanical movement, reducing system complexity and improving reliability. However, the design introduces challenges related to the feed network's complexity and potential mutual coupling between the two beams. Additionally, the extent of the beam-scanning coverage and its adaptability in real-time environments require further evaluation. While promising for advanced communication systems, its feasibility for CubeSat integration depends on the size, power consumption, and reconfiguration speed. Reference [88] proposes a low-cost multibeam switching antenna utilizing a reconfigurable hybrid metasurface for beamforming applications. The design integrates a hybrid metasurface with tunable elements, enabling beam switching without requiring complex phase-shifting networks. This approach enhances beamforming efficiency while maintaining a cost-effective and compact structure, making it suitable for wireless and satellite network applications. The proposed antenna achieves dynamic beam control with minimal power consumption, an advantage for power-constrained platforms like CubeSats. However, its reliance on discrete tuning elements introduces response-time limitations, potentially restricting real-time adaptability in highly dynamic environments. Additionally, practical implementation challenges, such as fabrication complexity and integration with existing satellite communication systems, must be addressed. While promising for adaptive beamforming, its scalability and performance under different operational conditions require further investigation. Figure 7: The design of metasurface antennas. Reference [89] proposes a beamforming technique for a linear antenna array using a reconfigurable frequency selective surface (FSS).