Carrier recovery

A carrier recovery is a circuit used to recover the carrier  and it is implemented using a phase-locked loop, or PLL. In the transmitter of a communications system, a carrier signal is modulated by a baseband signal. When the frequency spectrum of the modulated waveform is analyzed, it is often seen that the carrier frequency is suppressed. This is done intentionally in order to optimize the energy efficiency of the transmitter. At the receiver the baseband information is extracted from the incoming modulated waveform. To that end, it is necessary to reproduce or recover the suppressed carrier signal at the receiver.
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