%顯示模擬調制的波形及解調方法SSB
    %信源
    close all;
    
    clear all;
    
    dt=0.001;       %采樣時間間隔
    
    fm=1;           %信源最高頻率
    
    fc=10;          %載波中心頻率
    
    T=5;            %信號時長
 
    am=sqrt(2);     %頻譜

    sn=4;         %信噪比
    
    t=0:dt:T;
    
%%%%%%%%% 畫畫調制信號波形 %%%%%%%%%%%%%%
    
    mt=am*cos(2*pi*fm*t);     %信源
    
    subplot(5,2,1);
    
    plot(t,mt);         %畫調制信號波形
    
    axis([0,5,-2,2]);
    
    xlabel('t');
    
    ylabel('幅度 V');
    
    title('調制信號');
    
%%%%%%%%% 畫畫調制信號頻譜 %%%%%%%%%%%%%%

    [f,sf]=T2F(t,mt);
    
    subplot(5,2,2);
    
    plot(f,sf);         %畫調制信號頻譜
    
    axis([-2*fm,2*fm,0,4]);
    
    xlabel('f');
    
    axis([-3,3,0,4]);
    title('調制信號頻譜');
    

    
%%%%%%%%% 畫載波信號波形 %%%%%%%%%%%%%%
    
    mtt=am*cos(2*pi*fc*t);     %信源
    
    subplot(5,2,3);
    
    plot(t,mtt);                    %畫載波信號波形
    
    axis([0,1,-2,2]);
    
    xlabel('t');
    
    title('載波信號');

%%%%%%%%% 畫畫載波信號頻譜 %%%%%%%%%%%%%%

    [f,sff]=T2F(t,mtt);
    
    subplot(5,2,4);
    
    plot(f,sff);         %畫調制信號頻譜
    
    axis([-2*fm,2*fm,0,4]);
    
    xlabel('f');
    
    axis([-12,12,0,2]);
    title('調制信號頻譜');
    
%%%%%%%%% 畫出已調信號波形 %%%%%%%%%%%%%%    
    
    s_ssb=0.5*am*cos(2*pi*(fc-fm)*t);
    
    subplot(5,2,5);
    
    plot(t,s_ssb);                  %畫出SSB信號波形
    
    title('已調調制信號');
    
    xlabel('t');
    
    axis([0,1,-1,1]);
    
    
%%%%%%%%% 畫畫已調信號頻譜 %%%%%%%%%%%%%%

    [f,sff]=T2F(t,s_ssb);
    
    subplot(5,2,6);
    
    plot(f,sff);         %畫SSB信號頻譜
    
    axis([-12,12,0,2]);
    
    xlabel('f');
    
    
    title('已調信號頻譜');
%%%%%%%%% 畫出SSB信號波形 %%%%%%%%%%%%%%    
     
   
   s_ssb=0.5*am*cos(2*pi*(fc-fm)*t); 
   db=2*sn/am^2;      
   noise=sqrt(db)*randn(size(t));
   s_ssb=s_ssb+noise;
   subplot(5,2,7);
   plot(t,s_ssb);                  %畫出SSB信號波形
   title('SSB調制信號');
   xlabel('t');
   axis([0,1,-1,1]);

%%%%%%%%% 畫畫SSB信號頻譜 %%%%%%%%%%%%%%

    [f,sfff]=T2F(t,s_ssb);
    
    subplot(5,2,8);
    
    plot(f,sfff);         %畫SSB信號頻譜
    title('SSB調制信號頻譜');
    axis([-12,12,0,2]);
    xlabel('f');
    
 %%%%%%%%% 畫出解調波形 %%%%%%%%%%%%%%     
    %SSB  demodulation
    rt=4*s_ssb.*cos(2*pi*fc*t);
    
    rt=rt+mean(rt);
        
    [f,rf]=T2F(t,rt);
    
    [t,rt]=lpf(f,rf,fm);
    
    subplot(5,2,9);
    
    plot(t,rt);
    
    title('相干解調后的波形'); 
     axis([0,5,-2,2]);
    xlabel('t');
%%%%%%%%% 畫畫解調信號頻譜 %%%%%%%%%%%%%%

    [f,sffff]=T2F(t,rt);
    
    subplot(5,2,10);
    
    plot(f,sffff);         %畫SSB信號頻譜
    title('解調信號頻譜');
    xlabel('f');
    axis([-3,3,0,4]);