Amplitude Modulation

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매트랩을 이용한 AM 실험 그래프와 과정설명입니다.This experiment examines the characteristic of the amplitude modulation process. The modulation is performed by an envelope detector. Overmodulated AM signals and its requirement for coherent detection are also considered. DSB signal were generated by the multiplication of the message signal with a carrier wave form.

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Experiment : Amplitude Modulation
Experiment : Amplitude Modulation
Abstract
This experiment examines the characteristic of the amplitude modulation process. The modulation is performed by an envelope detector. Overmodulated AM signals and its requirement for coherent detection are also considered. DSB signal were generated by the multiplication of the message signal with a carrier wave form.
Laboratory
AM signal generation
-Result from preplab
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☞Result in laboratory
Signal 1: 8V with 500Hz, signal 2: 5V with 9kHz
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Signal 1: 2V with 500Hz, signal 2: 5V with 9kHz
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Analysis 2. (a) Estimate the modulation index of each AM signal.
P1 : m=
?????
??+??
=??.??, there is no distortion because m is less than 1.
P2 : m=
?????
??+??
=??.?? , there is no distortion because m is less than 1.
(b) Describe the effect of the modulation index on the magnitude of the sideband in the spectra of these signals.
Modulation index impacts on the magnitude of the sideband. P2 has lower modulation index thus it has smaller magnitude of the sidebands.

Demodulation of AM signals using envelop detection
Message signal : sine, 5V, 1kHz, Carrier signal : sine, 5V, 98kHz
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Message signal : sine, 5V, 1kHz, Carrier signal : sine, 5V, 450kHz
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Analysis 3. (a) Explain why the signal of P4 shows less ripple.
The requirement for best operation of this modulator is fc>>fx. P4 has much larger carrier frequency than P3 thus it shows less ripple. This is because LPF filter can clearly remove very higher frequency.

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