卷積是 f(τ) 與反轉函數 g(t-τ) 的相關函數。
卷積運算符是星號*。
f(t) 和 g(t) 的捲積等於 f(τ) 乘以 f(t-τ) 的積分:
2個離散函數的捲積定義為:
二維離散卷積通常用於圖像處理。
我們可以通過與脈衝響應 h(n) 卷積對離散輸入信號 x(n) 進行濾波,得到輸出信號 y(n)。
y(n) = x(n) * h(n)
2 個函數相乘的傅里葉變換等於每個函數的傅里葉變換的捲積:
ℱ{f ⋅ g} = ℱ{f } * ℱ{g}
2 個函數的捲積的傅里葉變換等於每個函數的傅里葉變換的乘積:
ℱ{f * g} = ℱ{f } ⋅ ℱ{g}
ℱ{f (t) ⋅ g(t)} = ℱ{f (t)} * ℱ{g(t)} = F(ω) * G(ω)
ℱ{f (t) * g(t)} = ℱ{f (t)} ⋅ ℱ{g(t)} = F(ω) ⋅ G(ω)
ℱ{f (n) ⋅ g(n)} = ℱ{f (n)} * ℱ{g(n)} = F(k) * G(k)
ℱ{f (n) * g(n)} = ℱ{f (n)} ⋅ ℱ{g(n)} = F(k) ⋅ G(k)
ℒ{f (t) * g(t)} = ℒ{f (t)} ⋅ ℒ{g(t)} = F(s) ⋅ G(s)