2 Basic modulation techniques
The amplitude, frequency and/or phase of the RF or baseband signal described by equations (2) to (6) are modified by the data signal so that the information it represent is impressed on the RF signal. The terms M-ary amplitude, frequency or phase modulation are used to indicate which parameter is varied to represent the information. The term keying is used for digital modulation. The abbreviations ASK for amplitude-shift keying, FSK for frequency-shift keying and PSK for phase-shift keying are widely used internationally.
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