IC解密MATLAB仿真程序
窗函数设计法：
Fs=100;
t=(1:100)/Fs;
s1=sin(2*pi*t*5);
s2=sin(2*pi*t*15);
s3=sin(2*pi*t*30);
s=s1+s2+s3;
figure(1);
subplot(2,2,1);
plot(t,s)%画出信号的时域波形
xlabel('Time(seconds)')
ylabel('Time waveform')
title('原始信号的时域波形')%程序功能：画出信号的频谱图。
S=fft(s,512);%对s进行快速傅立叶变换
w=(0:255)/256*(Fs/2);
subplot(2,2,2);
plot(w,abs(S(1:256)))%画出信号的幅度图
xlabel('Frequency(Hz)')
ylabel('幅度')
title('幅度谱')
axis([0 35 0 60]);
subplot(2,2,3);
plot(w,angle(S(1:256)))%画出信号的相位图
xlabel('Frequency(Hz)')
ylabel('相位')
title('相位谱')%程序功能：设计低通滤波器并画出其频谱图：
%%%%%%%%%%%%%%低通
fb=10;
fc=13;%设置滤波器截止频率
fs=100;
wb=2*pi*fb/fs;
ws=2*pi*fc/fs;
wc=0.5*(wb+ws);
tr_width=ws-wb;%过渡带宽
%%%%%%%%%%%%%%高通
%fb=25;
%fc=22;%设置滤波器截止频率
%fs=100;
%wb=2*pi*fb/fs;
%ws=2*pi*fc/fs;
%wc=0.5*(wb+ws);
%tr_width=wb-ws;%过渡带宽
%%%%%%%%%%%%%%%%%%%带通
%fc1=9;fb1=12;fb2=18;fc2=21;fs=100;
%wb1=2*pi*fb1/fs;ws1=2*pi*fc1/fs;wb2=2*pi*fb2/fs;
%ws2=2*pi*fc2/fs;wc1=0.5*(wb1+ws1);wc2=0.5*(wb2+ws2);
%tr_width=min((wb1-ws1),(ws2-wb2));
M=ceil(1.8*pi/tr_width);
n=[0:1:M-1];
hd=ideal_lp(wc,M);
%w_box=(boxcar(M))'
%w_box=(triang(M))'
%w_box=(hamming(M))'
w_box=(kaiser(M,2.5))'
h=hd.*w_box;
[H,w]=freqz(h,[1],1000,'whole');
H=(H(1:501))';
w=(w(1:501))';
mag=abs(H);
db=20*log10((mag+eps)/max(mag));
pha=angle(H);
grd=grpdelay(h,[1],w);
figure(2);
subplot(2,2,1);stem(n,hd);%理想脉冲响应
xlabel('n');
ylabel('hd(n)');
title('Ideal Impulse Response');
subplot(2,2,2);stem(n,w_box);%矩形窗