基于MATLAB的FIR滤波器性能仿真,包括矩形窗、汉明窗，海宁窗，布莱克曼窗，含仿真操作录像

clc,clear; N=input('输入窗函数阶数N=:'); w1=input('输入通带频率(输入值应小于1):'); w2=input('输入截止频率(输入值应小于1):'); w1=w1*pi; w2=w2*pi; %========================================================================== alpha=(N-1)/2; n=[0:(N-1)]; m=n-alpha+eps; h1=sin(w1*m)./(pi*m); h2=sin(w2*m)./(pi*m); h=h1-h2; %========================================================================== k=input('请选择窗的类型:\n 1、矩形窗\n 2、汉宁窗\n 3、汉明窗\n 4、布拉克曼窗\n 5、凯泽窗\n'); switch k case 1 x=win(0,N-1,0,N-1); %矩形窗 figure, subplot(1,2,1); stem(n,x,'.'); %得到数字信号波形表示方法函数STEM xlabel('n'); %X坐标标签 ylabel('x'); %Y坐标标签 string=['矩形窗时域图形','N=',num2str(N)];%波形标题 text((0.6*N),0.8,string); %波形标题 [H,m]=freqz(x,[1],1024,'whole'); %求其频率响应 mag=abs(H); %得到幅值 db=20*log10((mag+eps)/max(mag)); subplot(1,2,2); plot(m/pi,db); xlabel('w/pi'); ylabel('dB'); title('矩形窗的频率特性(db)'); axis([0,1,-100,0]); string=['矩形窗','N=',num2str(N)]; case 2 x=win(0,N-1,0,N-1); x=(0.5-0.5*cos(2*pi*n/(N-1))).*x; figure, subplot(1,2,1); stem(n,x,'.'); xlabel('n'); ylabel('x'); string=['汉宁窗时域图形','N=',num2str(N)]; text((0.6*N),0.8,string); [H,m]=freqz(x,[1],1024,'whole'); %求其频率响应 mag=abs(H); %得到幅值 db=20*log10((mag+eps)/max(mag)); subplot(1,2,2); plot(m/pi,db); xlabel('w/pi'); ylabel('dB'); title('汉宁窗的频率特性(db)'); axis([0,1,-100,0]); string=['汉宁窗','N=',num2str(N)]; case 3 x=win(0,N-1,0,N-1); x=(0.54-0.46*cos(2*pi*n/(N-1))).*x; figure, subplot(1,2,1); stem(n,x,'.'); xlabel('n'); ylabel('x'); string=['汉明窗时域图形','N=',num2str(N)]; text((0.6*N),0.8,string); [H,m]=freqz(x,[1],1024,'whole'); %求其频率响应 mag=abs(H); %得到幅值 db=20*log10((mag+eps)/max(mag)); subplot(1,2,2); plot(m/pi,db); xlabel('w/pi'); ylabel('dB'); title('汉明窗的频率特性(db)'); axis([0,1,-100,0]); string=['汉明窗','N=',num2str(N)]; case 4 x=win(0,N-1,0,N-1); x=(0.42-0.5*cos(2*pi*n/(N-1))+0.08*cos(4*pi*n/(N-1))).*x; figure, subplot(1,2,1); stem(n,x,'.'); xlabel('n'); ylabel('x'); string=['布拉克曼窗时域图形','N=',num2str(N)]; text((0.6*N),0.8,string); [H,m]=freqz(x,[1],1024,'whole'); %求其频率响应 mag=abs(H); %得到幅值 db=20*log10((mag+eps)/max(mag)); subplot(1,2,2); plot(m/pi,db); xlabel('w/pi'); ylabel('dB'); title('布拉克曼窗的频率特性(db)'); axis([0,1,-100,0]); string=['布拉克曼窗','N=',num2str(N)]; otherwise x=win(0,N-1,0,N-1); a=input('请输入a(典型值为4<a<9)='); b=a*sqrt(1-(2*n/(N-1)-1).^2); x=(besseli(0,b)/besseli(0,a)).*x; figure, subplot(1,2,1); stem(n,x,'.'); xlabel('n'); ylabel('x'); string=['凯泽窗时域图形','N=',num2str(N)];text((0.6*N),0.8,string); [H,m]=freqz(x,[1],1024,'whole'); %求其频率响应 mag=abs(H); %得到幅值 db=20*log10((mag+eps)/max(mag)); subplot(1,2,2); plot(m/pi,db); xlabel('w/pi'); ylabel('dB'); title('凯泽窗的频率特性(db)'); axis([0,1,-100,0]); string=['凯泽窗','N=',num2str(N)]; end h3=h.*x; %========================================================================== figure; subplot(2,1,1); stem(n,h,'.'); axis([0,N-1,-0.31,0.31]); hold on; x1=zeros(N); plot(n,x1,'r-'); xlabel('n'); ylabel('h(n)'); title('理想信号'); text((0.3*N),0.2,string); subplot(2,1,2); stem(n,h3,'.'); axis([0,N-1,-0.31,0.31]); hold on; x1=zeros(N); plot(n,x1,'r-'); xlabel('n'); ylabel('h(n)*win'); title('实际低通滤波器的h(n)'); text((0.3*N),0.2,string); figure; [H,m]=freqz(h,[1],1024,'whole'); %求其频率响应 mag=abs(H); %得到幅值 db=20*log10((mag+eps)/max(mag)); subplot(2,1,1); plot(m/pi,db); title('理想信号频谱'); axis([0,1,-100,0]); [H,m]=freqz(h3,[1],1024,'whole'); %求其频率响应 mag=abs(H); %得到幅值 db=20*log10((mag+eps)/max(mag)); subplot(2,1,2); plot(m/pi,db); title('通过滤波器以后的频谱'); axis([0,1,-100,0]);