简单的包络检波

当 Ui(t) > Uo(t-) 时 Uo(t) = Ui(t)
当 Ui(t) < Uo(t-) 时
RC dUo/dt = Uo
化成差分方程为：

把这个过程用程序来实现就有了下面的代码。

clear all;
x = 0:0.000001:0.005;
y = sin(200000.*pi.*x) .* (sin(2000.*pi.*x)*0.2 + 0.5);
mold = 0.0;
out = x;
rc = 400;
for i=1:5000
    if y(i) > mold
        mold = y(i);
    else
        mold = (mold * rc)/(rc + 1);
    end
    out(i) = mold; 
end
subplot(211);
plot(y);
subplot(212);
plot(out);

% 半波
% void env_half(double in[], double out[], int N)  
% {  
%     for(int i = 0; i < N; i++)  
%     {  
%         if( in[i] > m_old)  
%         {  
%             m_old = in[i];  
%             out[i] = m_old;  
%         }  
%         else  
%         {  
%             m_old *= m_rct / ( m_rct + 1 );  
%             out[i] = m_old;  
%         }  
%     }  
% } 
% 全波
% void env_full(double in[], double out[], int N)  
% {  
%     double abs_in;  
%     for(int i = 0; i < N; i++)  
%     {  
%         abs_in = fabs(in[i]);  
%         if( abs_in > m_old)  
%         {  
%             m_old = abs_in;  
%             out[i] = m_old;  
%         }  
%         else  
%         {  
%             m_old *= m_rct / ( m_rct + 1 );  
%             out[i] = m_old;  
%         }  
%     }  
% }