Radial Line Slot Array (RLSA) Antennas: A Systematic Review of Performance Enhancements, Design Challenges, and Future Research Directions

Radial Line Slot Array (RLSA) antennas are widely recognized for their low profile, high gain, and suitability in satellite communications and wireless applications. This paper presents a comprehensive and systematic literature review (SLR) of performance enhancements, design strategies, and research challenges related to RLSA antennas. Employing a rigorous SLR methodology, we identified, screened, and analyzed 72 relevant studies published over the last decade, selected from four major scientific databases: Scopus, IEEE Xplore, ScienceDirect, and Web of Science. The review follows a structured protocol, including keyword-based searches, duplication removal, title and abstract screening, and full-text evaluation. Key research trends are synthesized, including advancements in slot configuration, feeding mechanisms, integration with metamaterials, and performance optimization techniques. The study highlights recurring challenges such as bandwidth, gain, sidelobe level limitations, beam shaping complexity, and fabrication constraints. By consolidating findings from 72 systematically screened studies, this paper represents the first systematic review of RLSA antennas. It offers a clear roadmap of current technologies and identifies critical research gaps and future directions for next-generation antenna systems.