%   Exercise 9.6
%   Program to graph some examples of information signals and the modulated
%   carriers created by phase modulation and by frequency modulation
%   Square-wave phase and frequency modulation
fc = 4e6 ; Tc = 1/fc ; dt = Tc/32 ; 
f0 = 2e5 ; T0 = 1/f0 ; w = T0/5 ; N = 2 ; T = N*T0 ;
ep = 10*eps ; 
t = [0:dt:T]' ;
for k = 1:N, t = [t ; k*T0-w/2-ep ; k*T0+w/2+ep] ; end
t = sort(t) ; I = find(t >= 0 & t <= T) ; t = t(I) ;
%	Rectwave is a function I wrote to generate rectangular waves
%	You can generate them your own way
x = rectwave(t,T0,0,1/5,0,1) ;  %   Rectangular wave, period T0, no shift,duty
xint = cumtrapz(t,x) ;
kp = pi ; cp = sin(2*pi*fc*t + kp*x) ;	%	Phase modulated result
kf = 2*pi*1e6 ; cf = sin(2*pi*fc*t + kf*xint) ;	%	Frequency modulated result

%	Exercise 9.16
fc = 1e6 ; Tc = 1/fc ; dt = Tc/32 ; 
f0 = 5e4 ; T0 = 1/f0 ; N = 1 ; T = N*T0 ;
t = [0:dt:T]' ;
x = sin(2*pi*f0*t) ;
xint = cumtrapz(t,x) ;
%	cp is the exact phase modulated result and cpa is the narrowband approximation
%	cf is the exact frequency modulated result and cfa is the narrowband approximation
kp = pi/5 ; cp = cos(2*pi*fc*t + kp*x) ;
kf = kp*fc/5 ; cf = cos(2*pi*fc*t + kf*xint) ;
cpa = cos(2*pi*fc*t) - kp*x.*sin(2*pi*fc*t) ;
cfa = cos(2*pi*fc*t) - kf*sin(2*pi*fc*t).*xint ;