为什么我的希尔伯特谱显示的频率比理论的大10倍？

lijing4006

如题，为什么？

lijing4006

我的模拟信号：x=2*sin(2*pi*15*t)+sin(2*pi*5*t);

求希尔伯特谱程序：
imf=emd(x);
emd_visu(x,1:length(x),imf)
[A,f,t]=hhspectrum(imf);         
[E,t,Cenf]=toimage(A,f,t,length(t));           
disp_hhs(E,[],fs)
colormap(flipud(gray))
图形file:///C:/DOCUME%7E1/mac/LOCALS%7E1/Temp/moz-screenshot-2.pngfile:///C:/DOCUME%7E1/mac/LOCALS%7E1/Temp/moz-screenshot-3.pngfile:///C:/DOCUME%7E1/mac/LOCALS%7E1/Temp/moz-screenshot-4.pngfile:///C:/DOCUME%7E1/mac/LOCALS%7E1/Temp/moz-screenshot-5.pngfile:///C:/DOCUME%7E1/mac/LOCALS%7E1/Temp/moz-screenshot-6.pngfile:///C:/DOCUME%7E1/mac/LOCALS%7E1/Temp/moz-screenshot-7.pngfile:///C:/DOCUME%7E1/mac/LOCALS%7E1/Temp/moz-screenshot-8.pngfile:///C:/DOCUME%7E1/mac/LOCALS%7E1/Temp/moz-screenshot-9.pngfile:///C:/DOCUME%7E1/mac/LOCALS%7E1/Temp/moz-screenshot.pngfile:///C:/DOCUME%7E1/mac/LOCALS%7E1/Temp/moz-screenshot-1.png