# Analog Communication Manual

Sitapaila, Kathmandu

Laboratory Manual

Analog Communication Lab

BELX-6th sem

Everest Engineering and Management College

Experiment No.1: To generate AM wave without using matlab inbuilt function.

1. Objective: To generate AM wave.

2. Theory: Explain about MATLAB

MATLAB is a software package for high performance numerical computation and visualization. It provides an interactive environment with hundred of built in function for technical computation, graphics, and animation. Best of all, it also provide easy extensibility with its own high level programming language. The name MATLAB stands for MATrix LABoratory.

3. Program:

clear all

T=1/100;

fm=0.25;

fc=10;

mt=sin(2*pi*fm*[0:T:10]);

subplot(3,1,1);

plot(mt)

ct=sin(2*pi*fc*[0:T:10]);

subplot(3,1,2);

plot(ct)

yt=mt.*ct;

subplot(3,1,3);

plot(yt)

4. Program Output

[pic]

5. Questions

a) What do you mean by ‘.*’ in above program.

b) Explain following MATLAB command plot and sub plot.

c) List out the advantage of AM systems.

d) Why modulation is required in communicatioin system.

6. Discussion and Conclusion

Experiment No.2: To generate AM wave and plot it’s frequency spectrum using matlab.

1. Objective: To generate AM wave and draw frequency domain representation.

2. Theory:

3. Program

%setting

fm=20;

fc=500;

vm=1;

vc=1;

%x-axis: Time(second)

t=0:0.00001:0.099999;

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;

subplot(2,2,1);

plot(t,vm);

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;

subplot(2,2,2);

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;

subplot(2,2,3);

plot(t,vm);

title('AM modulating signal');

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

grid on;

% Plot carrier signal

%figure;

subplot(2,2,4);

plot(t,vc);

title('AM carrier signal');

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

grid on;

clear;

4. Program Output

[pic]

5. Question

a) Why frequency domain analysis is important in electronic and communication system?

b) Write the equation for AM wave.

6. Discussion and Conclusion...

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