Performing Pulse Code Modulation and Demodulation using MATLAB Code

This is a MATLAB code for performing Pulse Code Modulation (PCM) on an analog signal. The code generates an analog signal, samples it, quantizes it, encodes it, and finally demodulates it back to obtain the original analog signal. Here is the complete code:

function pcm()

clc;

close all;

clear all;

n=input('Enter n value for n-bit PCM system :  ');

n1=input('Enter number of samples in a period : ');

L=2^n;

% % Signal Generation

x=0:2*pi/n1:4*pi;               

% n1 number of samples have to be selected

s=4*sin(x);

subplot(4,1,1);

plot(s);

title('Analog Signal');

ylabel('Amplitude--->');

xlabel('Time--->');

subplot(4,1,2);

stem(s);grid on;  

title('Sampled Signal');  

ylabel('Amplitude--->'); 

xlabel('Time--->');

 %  Quantization Process

 vmax=10;

 vmin=-vmax;

 del=(vmax-vmin)/L;

 part=vmin:del:vmax;                                 

 % level are between vmin and vmax with difference of del

 code=vmin-(del/2):del:vmax+(del/2);        

% Contaion Quantized values 

 [ind,q]=quantiz(s,part,code); 

                    

% Quantization process                                                              

% ind contain index number and q contain quantized  values

 l1=length(ind);

 l2=length(q);

  

 for i=1:l1

    if(ind(i)==0)                                            

           % To make index as binary decimal so started from 0 to N

       ind(i)=ind(i)-1;

    end 

  

 end   

  for i=1:l2

     if(q(i)==vmin-(del/2))    

                      

             % To make quantize value in between the levels

         q(i)=vmin+(del/2);

     end

 end    

 subplot(4,1,3);

 stem(q);

grid on;                       % Display the Quantize values

 title('Quantized Signal');

 ylabel('Amplitude--->');

 xlabel('Time--->'); 

 %  Encoding Process

 figure

 code=de2bi(ind,'left-msb');        % Convert the decimal to binary

 k=1;

for i=1:l1

    for j=1:n

        coded(k)=code(i,j);  

         

        % convert code matrix to a coded row vector

        k=k+1;

    end

end

 subplot(2,1,1);

 grid on;

 stairs(coded);                 % Display the encoded signal

axis([0 100 -2 3]); 

 title('Encoded Signal');

 ylabel('Amplitude--->');

 xlabel('Time--->');

 %   Demodulation Of PCM signal

 qunt=reshape(coded,n,length(coded)/n);

 index=bi2de(qunt','left-msb');         % Get back the index in decimal form

 q=del*index+vmin+(del/2);            % Get back Quantized values

 subplot(4,1,4); 

 plot(q);                                            % Plot Demodulated signal

 title('Demodulated Signal');

 ylabel('Amplitude--->');

 xlabel('Time--->');

end