# Frequency Selective Surfaces: Design, Analysis, and Applications
###### Abstract  
This paper aims to provide a general review of the fundamental ideas, varieties, methods, and experimental research of the most advanced frequency selective surfaces available today. Frequency-selective surfaces are periodic structures engineered to work as spatial filters in interaction with electromagnetic (EM) waves with different frequencies, polarization, and incident angles in a desired and controlled way. They are usually made of periodic elements with dimensions less than the operational wavelength. The primary issue examined is the need for more efficient, compact, and adaptable electromagnetic filtering solutions. The research method involved a comprehensive review of recent advancements in FSS design, focusing on structural diversity, miniaturization, multiband operations, and the integration of active components for tunability and reconfigurability. Key findings include the development of highly selective miniaturized FSSs, innovative applications on flexible and textile substrates, and the exploration of FSSs for liquid and strain sensing. The conclusions emphasize the significant potential of FSS technology to enhance wireless communication, environmental monitoring, and defense applications. This study provides valuable insights into the design and application of FSSs, aiming to guide future research and development in this dynamic field. frequency selective surfaces; spatial filters; periodic structures; electromagnetic waves +
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Researchers have also investigated incorporating active components into FSS designs to enable tunability and reconfigurability. Active FSSs with convoluted elements have been suggested for Ultra-High Frequency (UHF) applications, showcasing the potential for dynamic control over the surface's frequency response [15]. Moreover, studies on switchable and frequency-tunable active FSSs have shown promise in achieving versatile electromagnetic modulation capabilities, allowing for independent adjustments of frequency and amplitude responses [16]. These developments pave the way for adaptive FSS solutions that can cater to diverse operational requirements in communication and sensing systems. In addition to traditional rigid substrates, the impact of flexible and textile substrates on FSS performance has been explored. Investigations into FSSs on flexible substrates have revealed the potential for conformal applications, enabling the development of highly efficient and miniaturized shields for electromagnetic compatibility in X-band frequencies [17]. Furthermore, studies on paper-based FSS designs utilizing slotlines have demonstrated the feasibility of implementing FSS technology on unconventional substrates, opening up possibilities for cost-effective and environmentally friendly electromagnetic filters [18]. The versatility of FSSs extends beyond conventional electromagnetic applications, with emerging research focusing on innovative functionalities. For instance, liquid sensors based on FSS principles have been proposed, showcasing the adaptability of these surfaces for sensing applications by modifying electromagnetic signals based on intrinsic resonant frequencies [19]. Moreover, popup tunable FSSs have been investigated for strain sensing, highlighting the potential for integrating FSS technology into structural engineering for diverse sensing and monitoring applications [20]. Recent studies have explored the development of high-performance frequency selective surfaces (FSSs) with advanced characteristics. Notably, high-temperature-resistant FSS metasurfaces have been designed to exhibit low backward scattering at lower frequencies and efficient transmission at higher frequencies, making them suitable for applications that require robust performance under extreme environmental conditions [21]. These advancements are critical for applications such as radar cross-section reduction and stealth technology, where maintaining performance under varying conditions is paramount [22].