Equation Icon  ∫ ∞ ′ iΩ(t−t′) S 𝒳𝒳 (Ω ) = dt⟨𝒳ˆ(t) ∘ 𝒳ˆ(t)⟩e , (145 ) ∫−∞∞ ˆ ˆ ′ iΩ (t−t′) S ℱℱ (Ω ) = −∞ dt⟨ℱ (t) ∘ ℱ (t)⟩e , (146 ) ∫ ∞ S 𝒳ℱ (Ω ) = dt⟨𝒳ˆ(t) ∘ ℱˆ(t′)⟩eiΩ (t−t′), (147 ) −∞