Some Mathematics :
For simplicity, suppose both carrier wave and modulating signal are sinusoidal:
vc = Vc sin wc t (c denotes carrier)
vm = Vm sin wm t (m denotes modulation)
vc = (Vc + Vm sin wmt).sin wc t
where (Vc + Vm sin wm t) is the new, varying carrier amplitude.
Expanding this equation gives:
vc = Vc sin ωc t + Vm sin ωc t. sin ωm t
which may be rewritten as:
where m = Vm/Vc and is called the modulation index.
sin ωc t.sin ωm t = (1/2) [cos(ωc - ωm) t - cos(ωc + ωm) t]
vc = Vc [sin ωc t + m sin ωc t. sin ωm t]
we can express vc as:
- The original carrier waveform, at frequency ωc, containing no variations and thus carrying no information.
- A component at frequency (ωc - ωm) whose amplitude is proportional to the modulation index. This is called the Lower Side Frequency.
- A component at frequency (ωc + ωm) whose amplitude is proportional to the modulation index. This is called the Upper Side Frequency.
AMPLITUDE MODULATION USING MATLAB SIMULINK
Lets discuss step by step the implementation of amplitude modulation on simulink modulation :-
Start the new Simulink model
Open the Simulink library browser
Create the simulation model of the AM
A Sinusoidal signal of frequency 1 Hz, Amplitude=1
Carrier Signal of frequency 20 Hz and Amplitude=1
The above model is the equivalent of the mathematical expression:
m(t) represent the message signal
And cos(2πfct) represent the carrier
Run the Simulink model, the message, carrier and modulated output can be observed on the oscilloscope.
The above diagtam shows both supressed and without supressed carrier.You are recommended to see the following too :-
- Amplitude Modulation on Matlab Simulink Model
- Amplitude Demodulation on Matlab Simulink Model
- Real-time Amplitude Modulation and Demodulation on Texas Instrument DSK C6713
CERTIFICATE OF OWNERSHIP
This project named “AMPLITUDE MODULATION USING MATLAB SIMULINK AND TEXAS INSTRUMENT KIT C6713”, in all respect is the property of the following personnel who undertake this project as the term project in EE-322 ‘DSP & Filters’ in summer semester 2010. However the copy of the project can be distributed upon the approval of the following members:-
- Muhammad Ahmed (NUST-ELECTRONICS)
- Jamal Ahmed(NUST-ELECTRONICS)
- Muhammad Faisal (NUST-ELECTRONICS)