使用FFT校正频率轴 [英] Correct frequency axis using FFT

问题描述

如何使用MATLAB的 FFT 绘制正确的频率矢量?

How can I get the correct frequency vector to plot using the FFT of MATLAB?

我的问题:

N      = 64;
n      = 0:N-1; 
phi1   = 2*(rand-0.5)*pi; 
omega1 = pi/6;
phi2   = 2*(rand-0.5)*pi; 
omega2 = 5*pi/6;
w      = randn(1,N); % noise
x      = 2*exp(1i*(n*omega1+phi1))+4*sin(n*omega2+phi2);
h      = rectwin(N).';
x      = x.*h;
X      = abs(fft(x));

通常我会这样做:

 f = f     = Fs/Nsamples*(0:Nsamples/2-1); % Prepare freq data for plot

问题是这一次我没有Fs(采样频率).

The problem is this time I do not have a Fs (sample frequency).

在这种情况下如何正确执行?

How can I do it correctly in this case?

推荐答案

如果您没有 Fs ，只需将其设置为1(如每个样本一个样本).这是我一直使用并看到其他所有人使用的典型解决方案.您的频率从0到1(或-0.5到0.5)，没有单位.每个人都将其理解为每个样本的期间".

If you don't have a Fs, simply set it to 1 (as in one sample per sample). This is the typical solution I've always used and seen everybody else use. Your frequencies will run from 0 to 1 (or -0.5 to 0.5), without units. This will be recognized by everyone as meaning "periods per sample".

修改

根据您的评论，我得出结论，您对径向频率感兴趣.在这种情况下，您想将绘图的x轴设置为

From your comment I conclude that you are interested in radial frequencies. In that case you want to set your plot x-axis to

omega = 2*pi*f;

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