www.pudn.com > PSK.zip > scatter_plot.m

function scatter_plot(m, type_of_mod, fc, fs, d) 
 
%this program is to test the QAM and PSK modulation and demodulation 
%techniques, with csatter plot and input / output signals. here 
%type_of_modulation may be QAM or PSK, m is the type of M. fc is carrier 
%and fs is sampling frequency and, d is the signal duration. 
 
%santosh shah, The LNM IIT Jaipur (India)(santosh.jnt@gmail.com) 25/04/07 
 
%==================MODULATION======================================== 
if nargin < 5 
    d = .01; % default for 0.1 second signal duration 
end 
if nargin < 4 
    fs = 100e3 ; % default value of sampling frequency 100kHz 
end 
if nargin < 3 
    fc = 500; % default value of carrier frequency 
end 
 
t= linspace(0, d, d*fs); 
 
%signal selection for mod / demod. 
xin = sin(2*pi*fc*t); 
x= floor(m/2 + m/2*xin); 
subplot(2, 1, 1);plot(t,xin), title('original signal'); 
grid on ; 
 
if (type_of_mod == 'qam') 
y = my_qammod(x, m) ; 
elseif (type_of_mod == 'psk') 
    y = my_pskmod(x, m) ; 
end 
 
 
%==================DEMODULATION=================================== 
if (type_of_mod == 'qam') 
z = my_qamdemod(y, m); 
elseif (type_of_mod == 'psk') 
    z = my_pskdemod(y, m); 
end 
 
subplot(2, 1, 2); 
plot(t, (2*z/m) ), title('Recovered signal'); 
grid on; 
 
%==================SCATTER PLOT=================================== 
scale = modnorm(y,'peakpow',1); 
y = scale*y; % Scale the constellation. 
scatterplot(y); % Plot the scaled constellation. 
grid on; 
 
 
%tfplot(z, fs, 'Vin','modulated signal');