離散フーリエ変換

信号

フーリエ変換

逆フーリエ変換

clear; close all; clc;

N=2^8;
fs = 100;
T=1/fs;
f1=10;f2=20;f3=40;
A1=1;A2=0.5;A3=0.8;
t=0:T:(N-1)*T;
scale = 0.3;
noise = rand(1,length(t))*scale;
x=A1*sin(2*pi*f1*t)+A2*sin(2*pi*f2*t)+A3*sin(2*pi*f3*t)+noise;
plot(t,x);
xlim([0,0.5]);


F = fft(x);
amp = 2*abs(F)/N;
freq = linspace(0,fs,N);
figure();
plot(freq(1:N/2+1),amp(1:N/2+1));

figure();
y = ifft(F);
plot(t,y,'--');
xlim([0,0.5]);