int_m(i+1)=int_m(i)+m(i)*ts
hi to all ..............
im doing my project in frequency demodualtion using pll our project has been strucked as we are not able to correct the error in this program we r getting frequency modulated wave same as carrier wave i request u all to solve my program i will be thankful if u provide any other example i would be workin on it.................
% Signal generation
t0 = .15; % signal duration
ts = 0.0005; % sampling interval
fc = 200; % carrier frequency
kf = 50; % modulation index
fs = 1/ts; % sampling frequency
t = [0:ts:t0]; % time vector
df = 0.25; % required frequency resolution
c = cos(2*pi*fc*t); % carrier signal
m = [2*ones(1,t0/(3*ts)),-2*ones(1,t0/(3*ts)),zeros(1,t0/(3*ts)+1)];
% Frequency modulation
int_m(1) = 0;
for (i = 1 : length(t)-1) % integral of m
int_m(i+1) = int_m(i) + m(i)*ts;
end
u = cos(2*pi*fc*t + 2*pi*kf*int_m); % modulated signal
figure
subplot (3,1,1)
plot (m(1:300))
TITLE ('Modulating Signal')
grid on;
subplot (3,1,2)
plot (c(1:300))
TITLE ('Carrier Signal')
grid on;
subplot (3,1,3)
plot (u(1:300))
TITLE ('Frequency Modulated Signal')
grid on;
% Frequency demodulation
t = [0:ts:ts*(length(u)-1)]; % finding phase of modulated signal
x = hilbert(u);
z = x.*exp(-j*2*pi*250*t);
phi = angle(z);
phi = unwrap(phi); % restoring original phase
dem = (1/(2*pi*kf))*(diff(phi)/ts); % demodulated signal
figure
subplot (3,1,1)
plot (c(1:300))
TITLE ('Carrier Signal')
grid on;
subplot (3,1,2)
plot (u(1:300))
TITLE ('Frequency Modulated Signal')
grid on;
subplot (3,1,3)
dem = smooth(dem,7) + 1;
plot (dem(1:300))
axis ([0 300 -2 2]);
TITLE ('De-Modulated Signal')
grid on;
end