Highly Selective and Polarization-Independent Band-Pass FSS with Robust Angular Stability for Secure CubeSat Communications

This paper presents the design, fabrication, and experimental validation of a highly selective, polarization-independent band-pass Frequency Selective Surface (FSS) tailored for secure CubeSat communications. As the electromagnetic (EM) spectrum becomes increasingly congested, mitigating unintentional interference and intentional jamming in space-based systems is critical. The proposed FSS unit cell, featuring a compact footprint of 10 x 10 mm², is developed through a hybrid geometric approach combining a square loop with straight and cross-dipoles. At normal incidence, it exhibits a high-selectivity pass-band in the 6.2–9.1 GHz range with a fractional bandwidth of 40.03% and a maximum roll-off rate of 40.15 dB/GHz, supporting selective transmission within the targeted satellite communication band. Simultaneously, it provides dual band-stop responses at 4–4.7 GHz and 15–17.3 GHz, with a peak shielding effectiveness exceeding 45 dB for out-of-band EM suppression. Full-wave TE/TM simulations indicate that the structure maintains a stable center-resonance behavior for oblique incidence angles up to 60°, while the four-fold rotational symmetry contributes to polarization-insensitive operation with cross-polarization levels below -20 dB. To verify the design, a physical prototype was manufactured and characterized using a free-space measurement setup within a controlled clean-room environment. The agreement between the simulated and measured normal-incidence responses supports the potential of the proposed FSS as a compact EM filtering and shielding candidate for CubeSat-oriented communication systems.