receiv2.m

双音多频编解码系统

%带通滤波法
function num =Receiv2(hn)
phone='123A456B789C*0#D';
fs=8000;
fl=[697 770 852 941];
fh=[1209 1336 1447 1633];

alfa=[-1 -5];
omega1=[0.15*pi 0.25*pi 0.1*pi 0.3*pi];
omega2=[0.3*pi 0.45*pi 0.25*pi 0.5*pi];

[Bn1,An1,N1]=bandpIIR(alfa,omega1,fs)
[Bn2,An2,N2]=bandpIIR(alfa,omega2,fs)
dn1=filter(Bn1,An1,hn);
dn2=filter(Bn2,An2,hn);
% figure,freqz(dn1);
% title('dn1');
% figure,freqz(dn2);
% title('dn2');
[nn1,w]=freqz(dn1);
[nn2,w]=freqz(dn2);

am=25;
bm=25;
ffl=mean(w(nn1>=am)*fs/(2*pi));
ffh=mean(w(nn2>=bm)*fs/(2*pi));

for i=1:4
    if abs(ffl-fl(i))<=fl(i)*0.03
        a=i;
    end
end
for j=1:4
    if abs(ffh-fh(j))<=fh(j)*0.03
        b=j;
    end
end
num=phone((a-1)*4+b);