help on demodulating a signal in matlab

%% create DATA

fc=13.56E6;   % carrier frequency  

fm=fc/32;       % modulation frequency

fs=fc*4;        %sampling frequency

tb=512/fc;      %time length of 1 bit

To=8*tb;       %length of 8 bit


hex_string='AF';   % string in hexadecimal format

dec_string= hex2dec(hex_string); % convert hexadecimal string to decimal

input=dec2bin(double(dec_string),8); % convert decimal string to binary  



dataCh=0;

for j=1:length (dec_string)
    dataCh=[dataCh input(j,1:8)];   
end;
dataCh=dataCh(2:length(dataCh));

input=double(dataCh)-48;         


Ns=tb*fs; %The required number of sample to 1 bit                       

%% MANCHESTER CODING

i=1;
while i<=length(input)
    
    switch input(i)
        case 0
            
       for j=1:2:15
           output((i-1)*Ns+1+(j-1)*Ns/32:(i-1)*Ns+j*Ns/32)=4;        
       end
       for j=2:2:16
           output((i-1)*Ns+1+(j-1)*Ns/32:(i-1)*Ns+j*Ns/32)=0; 
       end   
       for j=16:32
           output((i-1)*Ns+1+(j-1)*Ns/32:(i-1)*Ns+j*Ns/32)=0; 
       end   
    
       case 1
            
       for j=1:16
           output((i-1)*Ns+1+(j-1)*Ns/32:(i-1)*Ns+j*Ns/32)=0; 
       end   
       for j=17:2:31
           output((i-1)*Ns+1+(j-1)*Ns/32:(i-1)*Ns+j*Ns/32)=4;            
       end
       for j=18:2:32
           output((i-1)*Ns+1+(j-1)*Ns/32:(i-1)*Ns+j*Ns/32)=0; 
       end     
       
    end
    i=(i+1);
end


figure
plot(output);
axis([0 1.65E4*length(dec_string) -25 25]);
    title('Unmodulated signal'); 
    ylabel ('U [V]');
    
    
 

m=1; %modulation index 100%
a=4/2;          
opt=a*(1-m)/(1+m);


signal = modulate(sign,fc,fs,'amdsb-tc',opt); 
 
 figure 
 plot(signal)


z=demod(signal,fc,fs,'amdsb-sc',opt);

figure 
plot(z);