傅里叶变换公式是否被视为卷积或相关?

信息处理 傅里叶变换 转换
2022-02-07 05:04:12

傅里叶变换的表达式为

(1)F(ω)=+f(t) ejωt dt

现在,让一个函数f(x)和其他是ejωt然后他们的卷积在p(0)给出为

(2)p(0)=+f(t) ejωt dt
与中相同(1).

此外,如果我们将指数项拆分为正弦,则表达式(1)变成

(3)F(ω)=+(f(t)cosωtjf(t)sinωt) dt

f(t)cosωt是2个功能。所以它们的价值相关性 q(0) 给出为

(4)q(0)=+(f(t)cosωt) dt
与中相同(3). (我们也可以使用 f(t) 和正弦函数。)

所以我想知道

  1. 傅里叶变换公式是否被视为卷积或相关?

  2. 还有,什么意思p(0)q(0)条款?

1个回答

相关和卷积基本上是相同的操作。你可以表达两个函数的互相关F()G()通过卷积:

Rfg(τ)=f(τ)g(τ)

where denotes convolution, and denotes complex conjugation.

If you evaluate the cross-correlation at τ=0 you get the inner product of f(t) and g(t), and that's exactly what the Fourier transform is: it is the projection of f(t) on the complex exponential ejωt.

So, to answer your questions:

  1. It is actually an inner product. Due to the equivalence of convolution and correlation, it can be seen as both, evaluated at τ=0.
  2. As already mentioned, the meaning of these terms is an inner product.