我在 MATLAB 中编码, 我需要获得一个 2d 数组的正确频谱 x( 就像Fourier 的连续变换一样 ) 。
我尝试了以下两种方式。
fftshift(fft2(x));
fftshift(fft2(fftshift(x)));
两者似乎都给出了 x 频谱的正确密度分布, 我想知道哪一个给出了正确的 x 频谱 。
非常感谢你的帮助!
我在 MATLAB 中编码, 我需要获得一个 2d 数组的正确频谱 x( 就像Fourier 的连续变换一样 ) 。
我尝试了以下两种方式。
fftshift(fft2(x));
fftshift(fft2(fftshift(x)));
两者似乎都给出了 x 频谱的正确密度分布, 我想知道哪一个给出了正确的 x 频谱 。
非常感谢你的帮助!
正如Christoph Rackwitz指出的,ffttraft
是指按频率域的顺序运行的实用功能,不打算按时间/空间域的信号运行。
原因在于 < code> fft < / code > 是如何包装的 。 通常, 在 Matlab 函数的情况下, DFT 执行会将正频率包在矢量负频率之前。 I. 也就是说, 0 th 频率(DC) 在 bin < code> 1 , < code> sr/n (
< code> < /code> is DFT > in bin
2 < code >
le, et. leg. 直到最高combutele 频率( < code> - sr/2 - sr/ncode>) 在 bin " code " - (code > -s- sr/n < code > is bindcode > in this dcode > in the mind a frode a fir lic> licle ride ride a trex in the mess.
图片值一千字。为了便于视觉化, 这是一个 1D 案例 :
t = 0:1/512:1;
x = chirp(t,0,1,10);
figure;
subplot(2,1,1);
plot(x);
hold;
plot(fftshift(x));
legend( x , fftshift x );
subplot(2,1,2);
plot(abs(fft(x)));
hold;
plot(fftshift(abs(fft(x))));
legend( abs(fft(x)) , fftshift(abs(fft(x))) );
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