testfft.m

this base on DSP a iir design

%writen by Ziwei Chen 
clc;close all;clear all;

N=128;f=4;
fo=fopen('d:\MATLAB701\work','w');
for i=1:N
    x(i)=1+cos(2.*pi*i*f/N)+4*cos(2.*pi*4*i*f/N);
    x(i)=x(i)*4096;
    fprintf(fo,'  .word %d\r\n',fix(x(i)));
end 
fclose(fo);
XF=fft(x)/N;
figure(1);
plot(0:N-1,real(XF));
hold on;
plot(0:N-1,imag(XF),'r');
zoom on;
figure(2);
load c:\tic2xx\myproject\dsp.dat;
XF1(1:N)=dsp(1:2:2*N)+j*dsp(2:2:2*N);
err0=(XF1-XF);
err1=abs(XF1-XF)./abs(XF);
subplot(3,1,1);
plot(0:N-1,abs(XF),'r',0:N-1,abs(XF1),'k');
zoom on;
subplot(3,1,2);plot(abs(err0));zoom on;
subplot(3,1,3);plot(abs(err1));zoom on;