7.4 AN ASTABLE MULTIVIBRATOR AS A FREQUENCY MODULATOR
In communication systems, a modulator is used to transmit information from one end to the other. A modulator is a circuit that changes one of the parameters of the high-frequency signal in accordance with the instantaneous amplitude of the low-frequency signal—that is intelligence. If the frequency of the high-frequency signal, called the carrier, is varied in accordance with the instantaneous amplitude of the low-frequency signal, the process is called frequency modulation.
If the voltage VBB varies in accordance with the amplitude of the modulating signal (say, a sine wave), the frequency of the astable multivibrator varies in accordance with the instantaneous amplitude of the sinusoidal ...
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