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(AM) Amplitute Modulation

Amplitude modulationn of a sine or cosine carrier results in avariation of the carrier amplitude that is proportional to theamplitude of the modulating signal. In the time domain (amplitude versus time), the amplitude modulation of onesinusoidal carrier by another sinusoid resembles Figure XX.The mathematical expression for this complex wave showsthat it is the sum of three sinusoids of different frequencies.One of these sinusoids has the same frequency andamplitude as the unmodulated carrier. The second sinusoidis at a frequency equal to the sum of the carrier frequencyand the modulation frequency; this component is the uppersideband. The third sinusoid is at a frequency equal to thecarrier frequency minus the modulation frequency; thiscomponent is the lower sideband. The two sidebandcomponents have equal amplitudes, which are proportionalto the amplitude of the modulating signal.

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