fftshift/ifftshift [英] fftshift/ifftshift

问题描述

请参阅fftshift和ifftshift的说明. 我想了解如何在Matlab中与fft和fftn关联地调用上述两个函数.

Please, see the the description of both fftshift and ifftshift. I would like to understand how to call the above two functions in relationship with fft and fftn in Matlab.

假设我的信号具有一定的频率成分；现在，频率数组通常可以存储为:

Let say that my signal has a certain frequency content; now, the frequency array can generally be stored as:

f = (-N/2:N/2-1)*df;

f = (1:N)*(df/2);

f = [(0:N/2-1) (-N/2:-1)];

对于前面提到的3个研究案例，调用fft以及fftshift和ifftshift的最佳方法是什么?

What is the best way to call fft, coupled with fftshift and ifftshift, for the 3 study cases early mentioned?

调用命令序列或命令序列错误对信号的标准偏差有什么影响?

What is the effect on the standard deviation of the signal of calling the sequence of commands or the wrong one?

推荐答案

fft的结果是(用您的符号表示)索引(0:N-1). fftshift只是将其转换为[(N/2:N-1) (0:(N/2-1))]. ^* ifftshift只是恢复原始索引.

The result of fft is (in your notation) indices (0:N-1). fftshift simply converts that to [(N/2:N-1) (0:(N/2-1))].^* ifftshift simply restores the original indexing.

由于这只是对样本进行重新排序，因此对标准偏差没有任何作用.

As this is simply reordering samples, it does nothing to the standard deviation.

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_{*请注意，由于周期性，样本k等同于样本k+N或k-N等.}

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_{* Note that due to periodicity, sample k is equivalent to sample k+N, or k-N, etc.}

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