(a), (b) Effective constitutive parameters at the design angular frequency ω = ω₀. Red-dashed curves represent the optimized blueprints, obtained from equations (4) and (6), with , , and β₀ = 0.46k₀. Blue-solid curves pertain to the nonlocal effective model of the synthesized multilayered metamaterial [four-layer unit cell shown in the inset of panel (b)] with ε₁ = 7.089, given in equation (9) (with ε₂ = −1.104 and κ₂ = 0.0365), ε₃ = 3.35, ε₄ = −1.957, d₁ = 0.252λ₀, d₂ = 0.0815λ₀, d₃ = 0.102λ₀, d₄ = 0.0648λ₀. The parameter matching is enforced at k_x = 0 and within the (yellow-shaded) range 0.9β₀ ≤ k_z ≤ 1.1β₀.