emd分解仿真信号找不到周期冲击频率

mrmagiclu

fs=4000;
t=0:1/fs:1;
x=sin(2*pi*100*t)+sin(2*pi*20*t)+sin(2*pi*140*t)+randn(1,length(t));
x(1:8:length(t))=x(1:8:length(t))+1;
imf=emd(x);
bl=hilbert(imf(1,:));
ydate=abs(bl);
bl=bl-mean(bl);
p=abs(fft(ydate,4000));
figure
plot((0:4000/2-1)*4000/4000,p(1:2000));
xlabel('频率');
ylabel('gonglvpu')