Signal Modulation! ~ Dan Chiarlone ッ

ASK

Interactive canvas

Matlab Graphs

Matlab Code

                
                    close all;
                    clear;
                    clc;
                    
                    %  bit sequence 
                    
                    K = 40;
                    data_rate = 20;
                    b_k = zeros(1, K*data_rate);
                    
                    for i = 0:(K-1)
                        curr = round(rand());
                        for j = 1:data_rate
                            b_k(data_rate*i+j) = curr;
                        end
                    end
                    
                    %  /bit sequence 
                    
                    %  carrier 
                    
                    fc = 315;
                    N = 800;
                    OSR = 4;
                    fs = OSR*fc;
                    Ts = 1/fs;
                    n = 0:(N-1);
                    
                    carrier = cos(2*pi*fc*n*Ts);
                    
                    %  /carrier 
                    
                    %  x(t) 
                    
                    %  time 
                    
                    x = b_k.*carrier;
                    
                    figure(1);
                    plot(x);
                    title('ASK in time domain');
                    ylabel('magnitude');
                    xlabel('time');
                    
                    %  /time 
                    
                    %  frequency 
                    
                    k = n; % frequency index;
                    
                    deltaf = fs/N;
                    
                    if mod(N,2) == 0
                        f_shift = (k-(N)/2)*deltaf; % k = N/2
                    else 
                        f_shift = (k-(N -1)/2)*deltaf; % k = (N-1)/2
                    end 
                    
                    X = fftshift(fft(x));
                    figure(2);
                    plot(f_shift, abs(X)/N);
                    title('ASK in frequency domain');
                    ylabel("magnitude");
                    xlabel("frequency");
                    
                    %  /frequency 
                    
                    %  /x(t)

PSK

Matlab Graphs

Matlab Code

                
                    %  x(t) 

                    %  time 
                    
                    x_psk = cos(2*pi*fc*n*Ts + pi.*b_k);
                    
                    figure(3);
                    plot(x_psk);
                    title('PSK in time domain');
                    ylabel('magnitude');
                    xlabel('time');
                    
                    %  /time 
                    
                    %  frequency 
                    
                    X_PSK = fftshift(fft(x_psk));
                    figure(4);
                    plot(f_shift, abs(X_PSK)/N);
                    title('PSK in frequency domain');
                    ylabel("magnitude");
                    xlabel("frequency");
                    
                    %  /frequency 
                    
                    %  /x(t)

FSK

Matlab Graphs

Matlab Code

                
                    %  x(t) 

                    %  time 
                    
                    Deltaf = 25;
                    
                    x_fsk = cos(2*pi*n*Ts.*(fc+Deltaf*b_k));
                    
                    figure(5);
                    plot(x_fsk);
                    title('FSK in time domain');
                    ylabel('magnitude');
                    xlabel('time');
                    
                    %  /time 
                    
                    %  frequency 
                    
                    X_FSK = fftshift(fft(x_fsk));
                    figure(6);
                    plot(f_shift, abs(X_FSK)/N);
                    title('FSK in frequency domain');
                    ylabel("magnitude");
                    xlabel("frequency");
                    
                    %  /frequency 
                    
                    %  /x(t)