Change of transmission characteristics of FSSs in hybrid composites due to residual stresses

Design of Active Frequency Selective Surface with Curved Composite Structures and Tunable Frequency Response

“…This structure gained impedance and stability with respect to the incidence angle and distance between the unit cell and bias circuits given its composition, which includes the diode, symmetric, and bias circuits, for a grid-type power supply. Based on the proposed design, we fabricated the structure with a single-curvature and fiberreinforced composite materials, which are strong, dense, and feature high modulus, dimensional stability, and less fatigue [16][17][18]. To verify the design results, we analyzed the impact of the dielectric properties and curvature radius of the composite materials through electromagnetic transmission measurements.…”

“…In general, an AFSS needs additional circuits, an RF choke, or resistors coupled to the bias circuits to control plane waves. However, we designed a grid-type bias circuit along with the via hole, and by using the resulting resistance and inductance, the proposed AFSS guaranteed adequate isolation between the unit cell and bias circuit and minimized the possibility of a parasitic effect [5,17]. For this study, we considered the MADP-000907-14020 PIN diode manufactured by MACOM, which can be switched on and off in the X-band.…”

“…This method does not increase the weight and evenly distributes the load in the area between the adhesively bonded joints. To prevent any alteration of the PIN diode, we metalized it at a temperature below 120 ∘ C and subsequently applied a foam-core sandwich structure as it slowly cooled down to room temperature [17]. This structure provides an optimized design factor, which minimizes the variation and delamination between the composite material and the FSS structure to reduce the thermal induced residual stress due to the difference in the coefficients of thermal expansion.…”