PDMS-Based Angle-Stable and Flexible Reconfigurable Frequency Selective Surface for Shielding in GSM, 5G Sub-6 GHz, and 5 GHz Bands

This paper proposes a highly compact reconfigurable Frequency Selective Surface (RFSS) having frequency and mode agility. The conventional square-loop FSS is designed for 5G sub-6 GHz shielding applications. Subsequently, three capacitors, along with an RF-PIN diode, are incorporated to achieve on-demand reconfigurability, switching from a single band at 3.5 GHz to a dual-band response at 1.8 GHz and 4.9 GHz. The unit cell is fabricated using a highly flexible silicone-based substrate, polydimethylsiloxane (PDMS), with a thickness of 1 mm and a dielectric constant of 2.7, while the FSS structure is realized using nickel–copper-coated ripstop conductive fabric. The proposed FSS features a highly compact size of 0.12 λs × 0.12 λs, where λs corresponds to the free-space wavelength at the lower resonance of 1.8 GHz. Moreover, analysis shows that in the diode-On state, the FSS provides broadband shielding, covering 2.78–4.2 GHz. In contrast, in the diode-Off state, the FSS exhibits a dual-band response with bandwidths of 1.69–1.99 GHz and 4.52–5.34 GHz. Furthermore, a comparative analysis with state-of-the-art reconfigurable FSS designs is presented, highlighting the unique contributions of the proposed work for shielding applications.