cft.m

现代信号处理里的一些内容

function [Fw,f]=CFT(ft,dt,t0);
if nargin==1
    dt=1;
    t0=0;
elseif nargin==2
    t0=0;
end
N=length(ft);
T=N*dt;
t=t0+[0:N-1]*dt;
NFFT = 2^nextpow2(N);%计算比N大2的整数次方的数;
k=-NFFT/2:NFFT/2-1;
f=k./T;
W1=dt.*exp(-i*2*pi*t0.*k./T);
F1=fft(ft,NFFT);
Fw=F1.*W1;
Fw=fftshift(Fw);
if nargout==0
    subplot(2,2,1);
    plot(t,real(ft));
    title('信号时域波形实部');
    xlabel('Time(s)');
    ylabel('f(t)');
    grid on;
    % Plot single-sided amplitude spectrum.
    subplot(2,2,2);
    plot(f,abs(Fw));
    title('双边功率谱密度幅度');
    xlabel('Frequency (Hz)');
    ylabel('|F(f)|');
    grid on;
    subplot(2,2,3);
    plot(f,angle(Fw));
    title('双边功率谱密度相位');
    xlabel('Frequency (Hz)');
    ylabel('\phi(f)');
    grid on;
    subplot(2,2,4);
    plot(f,20.*log10(abs(Fw)));
    title('双边功率谱密度波特图');
    xlabel('Frequency (Hz)');
    ylabel('Magnitude(dB)');
    grid on;
end