dtmf.m

基于matlab的DTMF仿真 DTMF为行频和列频（697Hz 770Hz 852Hz 941Hz 1209Hz 1336Hz 1477Hz 1633Hz）组合代表按键输入

f = [697 770 852 941 1209 1336 1477 1633];
coef = [27980 26956 25701 24219 19073 16325 13085 9315];
fs = 8000;
N = 125;
k = 8;
lf = 1;
hf = 8;
is = cos(0 : (2*pi*f(lf))/fs : (2*N*pi*f(lf))/fs) + sin(0 : (2*pi*f(hf))/fs : (2*N*pi*f(hf))/fs);
is = (is)*2^14;
%plot(is);
v(1:k,1:2) = zeros(k,2);
X2(1:k) = zeros(k,1);
for i = 1:N    
    for j = 1:k
        % vk(n) = 2*coef*vk(n-1) - vk(n-2) + x(n)
        tmp = 2*coef(j)*v(j,2)/2^15-v(j,1)+is(i),
        v(j,1) = v(j,2),
        v(j,2) = tmp;        
    end
    %test= input('prompt','s');
end
for j = 1:k
    % y(N)*y(N) = vk(N)*vk(N) - 2*coef*vk(N)*vk(N-1) + vk(N-1)*vk(N-1)
    X2(j) = v(j,2)*v(j,2)+v(j,1)*v(j,1)-2*coef(j)*v(j,1)*v(j,2)/2^15;
end
X2,
plot(X2,'+');