fft(DFT)x轴的单位 [英] unit of fft(DFT) x axis

问题描述

可能重复:
如何从FFT结果中获取频率

Possible Duplicate:
How to get Frequency from FFT result

在某种程度上，我对Matlab中的fft(DFT)命令的x轴感到困惑.当我们对在n点采样的信号执行fft命令时，会得到x轴为0到n-1的图.它是指以Hz为单位的频率吗?例如，当我在n = 2上有一个尖峰时，是否意味着信号频率为2Hz?

I am somehow confused with the x axis of fft(DFT) command in Matlab. When we do a fft command for a signal which has sampled in n point, we get a plot in which the x axis is 0 to n-1. Does it mean frequency in Hz? For example when I have a spike on n=2 is it mean that the signal frequency is 2Hz?

推荐答案

X轴是无量纲的.要获得bin索引与频率之间的对应关系，您需要知道(a)采样率(以Hz为单位)Fs，以及(b)FFT中的点数N.这样，垃圾箱的中心频率为:

The X axis is dimensionless. To get the correspondence between bin index and frequency you need to know (a) the sample rate (in Hz), Fs, and (b) the number of points in the FFT, N. The centre frequency for the bin is then:

f = i * Fs / N

其中f是bin频率，单位为Hz，i是bin索引.

where f is the bin frequency in Hz and i is the bin index.

请参阅此答案以获取更完整的信息解释.

See this answer for a more complete explanation.

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