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EECB353 COMMUNICATION SYSTEM
SEMESTER 3 2015/2016
GROUP PROJECT - PART A
LECTURER’S NAME: DR. SAVITHRY A/P K. THANGARAJU
SECTION: 01
GROUP: 03
GROUP MEMBERS:
1 HANIF BIN ABDUL AZIZ EP093691
2 MUHAMMAD ARIFF BIN MUHAMMAD EP094516
DATE OF SUBMISSION: 27TH APRIL 2016
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TABLE OF CONTENTS
1. POWER SPECTRUM ...................................................................................................................3
2. AM SYSTEM SIMULATION USING MATLAB/SIMULINK ................................................4
2.1 Block Diagram ............................................................................................................................4
2.2 Relevant Specifications ..............................................................................................................4
2.3 Waveforms from the Transmitter Section ..................................................................................6
2.4 Waveforms from the Receiver Section .......................................................................................8
3. COMPARISON BETWEEN DEMODULATED AND MODULATING SIGNAL ...............9
3.1 Optional MATLAB Coding to Show Demodulated Signal is Equal to Modulating Signal ...10
4. FREQUENCY SPECTRUM ......................................................................................................12
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1. Power Spectrum
Total power, Ptotal = 1000 W
Given efficiency = 0.33
o
Where efficiency = (PUSB + PLSB) ÷ (Pusb + Plsb + Pcarrier )
0.33 = Psidebands ÷ 1000
Psideband = 330W
Pcarrier = Ptotal – Psidebands
= 1000 – 330
= 660 watts
Pusb = Plsb = Psidebands/2 = 330/2 = 165 watts
165
670
165
0
100
200
300
400
500
600
700
800
1.95 2 2.05
Power, P (Watts)
Frequency, f (MHz)
Power Spectrum
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2. AM SYSTEM SIMULATION USING MATLAB/SIMULINK
2.1 Block Diagram
Figure 1: Block Diagram of the complete AM system
2.2 Relevant Specifications
Message (modulating) signal frequency = 5 kHz, assumed to be 5 Hz for ease of simulation
Carrier signal frequency = 1.2 MHz, assumed to be 1200 Hz for ease of simulation
Carrier signal II frequency = 1.2 MHz, assumed to be 1200 Hz for ease of simulation
Carrier signal amplitude = 6 Volts
Maximum amplitude of DSB-FC waveforms = 6*2 = 12 Volts
Analog filter design method used to demodulate DSB signal – Butterworth:
- Lowpass Filter: Order 8, Passband edge Frequency: 2*π*5.2 = 32.67 rad/s
- Highpass Filter: Order 5, Passband edge frequency: 2*π*8.635 = 54.25 rad/s
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Some of the specifications used in the design
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2.3 Waveforms from the Transmitter Section
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3. DEMODULATED OUTPUT SIGNAL AND COMPARISON WITH ORIGINAL
MODULATING SIGNAL
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3.1 Optional MATLAB Coding to Show Demodulated Signal is Equal to Modulating Signal
fs = 8000; % Assume sampling rate is 8000 samples per second
fc = 1200; % Carrier frequency in Hz
t = [0:0.1*fs]'/fs; % Sampling times for 0.1 second
m = sin(2*pi*5*t); % Representation of the modulating signal
v = ammod (m,fc,fs); % Modulate m to produce v
figure(2)
subplot(2,1,1); plot(t,m); % Plot m on top
subplot(2,1,2); plot(t,v) % Plot v below
mr = amdemod (v,fc,fs); % Demodulate v to produce m
figure(3)
subplot(2,1,1); plot(t,m); % Plot m on top
subplot(2,1,2); plot(t,mr) % Plot mr below
Figure 2 : Top - Modulating Signal, Bottom - Modulated Signal
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Figure 3: Top – Original Modulating Signal, Bottom - Demodulated Signal
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