Table 6 Optimization of Circuits I, II, and III using the suggested surrogate model.

I

f₀ = 1.0 GHz

Improve |S₁₁| and |S₄₁| at f₀; maintain 3 dB power split ratio (|S₂₁| – |S₃₁|= 3 dB) at f₀

RO4003 (ε_r = 3.38, h = 0.76 mm)

x* = [2.1 10.3 20.0 0.5 1.35 0.6]^T

II

f₀ = 1.25 GHz

Improve |S₁₁| and |S₄₁| at f₀; maintain equal power split ratio (|S₂₁| =|S₃₁|) at f₀

RO4003 (ε_r = 3.38, h = 0.76 mm)

x* = [0.4 0.65 12.5 13.5 0.9 0.4 0.25 0.16 3.31 0.55]^T

III

f₁ = 1.5 GHz

f₂ = 2.45 GHz

Improve matching |S₁₁|, |S₂₂| =|S₃₃|, and port isolation |S₂₁| =|S₃₂| at both f₁ and f₂; maintain equal power division ratio |S₂₁| =|S₃₁| at f₁ and f₂

AD250 (ε_r = 2.5, h = 0.81 mm)

x* = [31.3 9.8 31.2 8.85 4.6 0.7 4.3]^T