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Modulation is the process of embedding a message signal, for example a digital bit stream or an analog audio signal, inside another signal that can be physically transmitted.
- Amplitude modulation (AM)
- Frequency modulation (FM)
- Phase modulation (PM)
In digital modulation, an analog carrier signal is modulated by a discrete digital signal.
- Phase-Shift Keying (PSK): a finite number of phases are used.
- Frequency-Shift Keying (FSK): a finite number of frequencies are used.
- Amplitude-Shift Keying (ASK): a finite number of amplitudes are used.
- Quadrature Amplitude Modulation (QAM):