c4_4_1.m

dsp入门与实践一书的源代码

clear all;                    	     				
clc;                              				
N=256;                            			 	
fs=600;                            			     
dt=1/fs;                                        		
for k=1:N;                    
   f1=250;                         			 	
   f2=100;                         			 	
   f3=270;                       				
   y(k)=sin(2*pi*f1*k*dt)+sin(2*pi*f2*k*dt)+sin(2*pi*f3*k*dt);  
end
lp=200;                                   
wn1=2*lp/fs;                              
[z1,p1,k1] = CHEBY1(3,0.5,wn1);           
[b1,a1] = CHEBY1(3,0.5,wn1);              
b1=b1/(8*1.0711);                    		
a1=a1/(8*1.0711);                         

yy1=filter(b1,a1,y);                   	  

y=fft(y,N);                         	  
pyy=y.*conj(y);                     	  
f=(0:(N/2-1));
for i=1:N/2-1;
   f(i)=f(i)*fs/N;
end
figure(1);

plot(f,pyy(1:N/2))                        

y=fft(yy1,N);                      	 
pyy=y.*conj(y);
f=(0:(N/2-1));
for i=1:N/2-1;
   f(i)=f(i)*fs/N;
end
figure(2);
plot(f,pyy(1:N/2));