(a) Proposed unit cell geometry along with its physical dimensions: a = 6 mm, b = 2.2 mm, c = 0.8 mm, g = 0.5 mm, w = 2.3 mm, α = 90°, and thickness (t) = 0.6 mm. (b) Simulated reflection coefficient, transmission coefficient, and absorptivity of the optimized structure. (c) Angle-sensitivity (S_A ) of the topology for different values of the inner angle (α) and corresponding geometries [31].