rectwindow.m

用matlab编写的数字信号处理程序

clc,clear all,close all;
n=[0:1:999];
xn=10*cos(0.2*pi*n)+1.2*cos(0.25*pi*n)+4.6*cos(0.6328*pi*n);    %先定义一个长序列，处理时再截取

%(11111111)用矩形窗截获进行频谱分析%%%%%%%%%%%%%%%%%%%%%%%%%
%32点的DFT
w1=rectwin(32);           %生成一个32点的矩形窗，为列矢量
xn1=xn(1:32);             %截取xn的前32个点
xn11=xn1.*w1';            %将截取的序列和矩形窗相乘
X1=fft(xn11,32);          %做32点的DFT，其中DFT函数已定义
subplot(2,2,1);
plot([0:1:31],X1);
xlabel('n=0:31 32-point dft');
ylabel('the result of dft --w');

%64点的DFT%%%%%%%%%%%%%%%%%%%%%%%%%
w2=rectwin(64);
xn2=xn(1:64);
xn22=xn2.*w2';
X2=fft(xn22,64);
subplot(2,2,2);
plot([0:1:63],X2);
xlabel('n=0:63 64-point dft');
ylabel('dft result --w');

%128点DFT%%%%%%%%%%%%%%%%%%%%%%%%%
w3=rectwin(128);
xn3=xn(1:128);
xn33=xn3.*w3';
X3=fft(xn33,128);
subplot(2,2,3);
plot([0:1:127],X3);
xlabel('n=0:127 128-point dft');
ylabel('dft result --w');

%256点DFT%%%%%%%%%%%%%%%%%%%%%%%%%
w4=rectwin(256);
xn4=xn(1:256);
xn44=xn4.*w4';
X4=fft(xn44,256);
subplot(2,2,4);
plot([0:1:255],X4);
xlabel('n=0:255 256-point dft');
ylabel('dft result --w');