CBSE Class 12-science Answered
With the help of diagram, explain the term amplitude modulation qualitatively.
In amplitude modulation the amplitude of the carrier wave is changed in accordance with the amplitude of the frequency modulating signal. The carrier frequency and phase remain constant.The frequency of modulated wave remains same as that of the carrier wave.
Fig (a) represents the unmodulated continuous carrier wave radiation of constant frequency fc, and constant amplitude V c .
Fig (b) shows the waveform of the input signal, an audio frequency modulating voltage of frequency fm and amplitude Vm. The input signal will, in practice, rarely be a simple pure sine wave, but this form serves to illustrate the concept clearly.
Fig (c) illustrates the waveform of the Radio Frequency (RF) carrier after amplitude modulation by the audio frequency modulating signal. The outline of the modulated wave (dotted line), known as the modulation envelope, is an exact replica of the modulating signal.