matlab填充变换频率

Question

我试图比较一个cosinus的matlab fft和两个不同的零填充.我认为它不会改变频率响应,但是当我叠加两条曲线时,频率不一样.我想我做两个fft的方式有问题吗？

Fe = 8000;
F = 1680;
w = 2*pi*F;
N = 50;
P = 50;
T = 1/Fe;
t = (0:T:P*T);

x = real(exp(i*w*t))
x_reduced = x(1:P)

X = fft(x_reduced,N)
N = 1000;
Y = fft(x_reduced,N)


plot(abs(Y))
hold on
plot(abs(X),'*')

提前致谢

Answer 1

plot((0:999)/1000*Fe,abs(Y))
hold on
plot((0:49)/50*Fe,abs(X),'*')

您可能需要调整两种情况的频率.