FM modulation, demodulation Matlab code

problem statement

To be completed. . . . . It's too late, it's early morning, tomorrow will be the whole day.

%-------------------------------------
%2FSK调制

s=[1 0 1 1 0 0 1 0]; %原始数据
f1= 200 ;%261.6256*2*pi;
f2= 400 ;%391.9954*2*pi;
Fs =  11025;
t=0:1/(Fs-1)*10:1;
m1=[];
c1=[];
B1=[];
for n=1:length(s)
    if s(n)==0;
        m=ones(1,length(t));
        c=sin(2*pi*f1*t);
        b=zeros(1,length(t));
    else s(n)==1;
        m=ones(1,length(t));
        c=sin(2*pi*f2*t);
        b=ones(1,length(t));
    end
    m1=[m1 m]; 
    c1=[c1 c];
    B1=[B1 b];
end


fsk=c1.*m1;
gcf = figure(1);
subplot(311);
plot(B1,'r')
axis([1,length(B1),-0.2,1.2]);
title('原始信号');
%axis([0 100*length(s) -0.1 1.1]);
grid on;
subplot(312);
plot(fsk(1:1000))
title('2FSK信号');
grid on; 


%sound(fsk,Fs,8);
%wavwrite(fsk,Fs,8,'a.wav');
%------------------------
%高斯噪声
no=0.1*randn(1,length(fsk));        %噪声
fsk= 0.4*(fsk+no);%噪声加衰减
subplot(313);
plot(fsk(1:1000));
title('噪声加衰减信号');

saveas(gcf,'fm_01.png');
%---------------------------------------------------------------------------
%解调  


% 使用带通滤波进行过滤
b1=fir1(101,[0.1 0.6]);
b2=fir1(101,[0.6 0.8]);  %设置带通参数
H1=filter(b1,1,fsk);
H2=filter(b2,1,fsk);          %经过带通滤波器后的信号
gcf = figure(2);
subplot(211);

plot(H1);
title('带通0.1-0.6 结果');
subplot(212);
title('带通0.6-0.8 结果');
plot(H2);

saveas(gcf,'fm_02.png');


% 求绝对值（就是所谓的整流。。。）
H1 = abs(H1);
H2 = abs(H2);
gcf = figure(3);
subplot(211);
title('低频整流');
plot(H1);
subplot(212);
title('高频整流');
plot(H2);

%低通滤波器
b3=fir1(101,0.1);
H1_low=filter(b3,1,H1);
H2_low=filter(b3,1,H2);
saveas(gcf,'fm_03.png');

gcf = figure(4);
subplot(211);
plot(H1_low);
title('低频整流H1经过低频滤波');
subplot(212);
plot(H2_low);
title('高频整流H1经过低频滤波');

saveas(gcf,'fm_04.png');
% 表决器

z = ones(size(H1));
z(H1_low>H2_low) = 0;

%b4=fir1(101,0.1);
b3=fir1(101,0.05);
z=filter(b3,1,z);
z(z>=0.5) = 1;
z(z<0.5) = 0;
gcf = figure(5);

subplot(211);
plot(B1);
axis([1,length(z),-0.2,1.2]);
title('原始信号');
subplot(212);
plot(z);
axis([1,length(z),-0.2,1.2]);
title('解调后信号');
saveas(gcf,'fm_05.png');