tits_3_4

Gs=tf(0.7157,[1 1.253 1.535 0.7157]);
% bode(Gs);
fgc=500;
fp=1500;
tp=1/fp;
wgc=2*pi*fgc;
wga=1.38;
bode(Gs);
B=wga*tan(wgc*tp/2);
Gz=tf([0.7157 -2.1471 2.1471 -0.7157], [(B*B*B+1.2535*B*B+ 1.535*B +0.7157) (3*B*B*B +1.2535*B*B -1.535*B -2.1471) (3*B*B*B -1.2535*B*B-1.535*B+2.1471) (B*B*B -1.2535*B*B +1.535*B - 0.7157)],tp);
figure;
bode(Gz);
hold;


a1=100;
t=0:tp:5;
y1=a1*sin(2*pi*fgc*t)+a1*sin(2*pi*(0.3*fgc)*t)+a1*sin(2*pi*fgc*1.4*t);

y1fft=fft(y1);
n=length(y1fft);
y1fft=(2*abs(fft(y1)))/n;
osf=(0:n-1)*fp/n;
figure;
plot(osf,y1fft);

y1f=filter([0.7157 -2.1471 2.1471 -0.7157], [(B*B*B+1.2535*B*B+ 1.535*B +0.7157) (3*B*B*B +1.2535*B*B -1.535*B -2.1471) (3*B*B*B -1.2535*B*B-1.535*B+2.1471) (B*B*B -1.2535*B*B +1.535*B - 0.7157)],y1);
y1ffft=fft(y1f);
n=length(y1ffft);
y1ffft=(2*abs(fft(y1f)))/n;
osf=(0:n-1)*fp/n;
figure;
plot(osf,y1ffft);

[h,w]=freqz([0.7157 -2.1471 2.1471 -0.7157], [(B*B*B+1.2535*B*B+ 1.535*B +0.7157) (3*B*B*B +1.2535*B*B -1.535*B -2.1471) (3*B*B*B -1.2535*B*B-1.535*B+2.1471) (B*B*B -1.2535*B*B +1.535*B - 0.7157)],1000,fp);
figure;
plot(w,abs(h));
grid;