FM modulation

Ac=1;
fc=1;

Am=1;
fm=0.1;
kf=1.5;
B=kf*Am/fm;

t=[0:0.1:20];
ct=Ac*cos(2*pi*fc*t);
mt=Am*cos(2*pi*fm*t);
FMt=Ac*cos(2*pi*fc*t+B*sin(2*pi*fm*t));

subplot(2,2,1);
plot(mt);
ylabel('message signal');
grid on;

subplot(2,2,2);
plot(ct);
ylabel('carrier');
grid on;

subplot(2,2,3);
plot(FMt);
ylabel('FM signal');
grid on;