The question is like this:(adsbygoogle = window.adsbygoogle || []).push({});

a.The amplitude modulation(AM)waveform in time and frequency domain.

fm=20HZ,fc=500HZ,Vm=1V,Vc=1V,t=0:0.00001:0.09999

a.The frequency modulation(FM)waveform in time and frequency domain.

fm=250HZ,fc=5KHZ,Vm=1V,Vc=1V,m=10,t=0:0.00001:0.09999

Then my program is like this:

% setting

fm=20;

fc=500;

vm=1;

vc=1;

interval=0.001;

% x-axis:Time(second)

t=0:0.00001:0.09999;

f=0:1:9999;

% y-axis:Voltage(volt)

wc=2*pi*fc;

wm=2*pi*fm;

V1=vc+vm*sin(wm*t);

V2=-(vc+vm*sin(wm*t));

Vm=vm*sin(wm*t);

Vc=vc*sin(wc*t);

Vam=(1+sin(wm*t)).*(sin(wc*t));

Vf=abs(fft(Vam,10000))/10000;

% Plot figure in time domain

figure;

plot(t,Vam);

hold on;

plot(t,V1,'r'),plot(t,V2,'r');

title('AM waveform time-domain');

xlabel('time'), ylabel('amplitude');

grid on;

% Plot figure in frequency domain

figure;

plot(f*10,Vf);

axis([(fc-2*fm) (fc+2*fm) 0 0.6]);

title('AM waveform frequency-domain');

xlabel('frequency'), ylabel('amplitude');

grid on;

%Plot modulating signal

figure;

plot(t,Vm);

title('AM modulating signal');

xlabel('time'), ylabel('amplitude');

grid on;

%Plot carrier signal

figure;

plot(t, Vc);

title('AM carrier signal');

xlabel('time'), ylabel('amplitude');

grid on;

clear;

Is it correct?It is AM program.If it is wrong can u help me correct it?

% setting

vc=1;

vm=1;

fm=250;

fc=5000;

m=10;

% x-axis:Time(second)

t=0:0.00001:0.09999;

f=0:10:99990;

% y-axis:Voltage(volt)

wc=2*pi*fc;

wm=2*pi*fm;

sc_t=vc*cos(wc*t);

sm_t=vm*cos(wm*t);

kf=1000;

s_fm=vc*cos((wc*t)+10*sin(wm*t));

vf=abs(fft(s_fm,10^4))/5000;

% Plot figure in time domain

figure;

plot(t,s_fm);

hold on;

plot(t,sm_t,'r');

axis([0 0.01 -1.5 1.5]);

xlabel('time(second)'),ylabel('amplitude');

title('FM time-domain');

grid on;

% Plot figure in frequency domain

figure;

plot(f,vf);

axis([ 0 10^4 0 0.4]);

xlabel('frequency'), ylabel('amplitude');

title('FM frequency-domain');

grid on;

%Plot modulating signal

figure;

plot(t,sm_t);

axis([0 0.1 -1.5 1.5]);

title('FM modulating signal');

This is FM.

And can let me know what can i get discussion and conclution from this two program?I not very sure i understand what is it doing......

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# Matlab problem about AM and FM

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