Continuous phase modulation: Difference between revisions

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== Continuous-phase frequency-shift keying ==

'''Continuous-phase frequency-shift keying''' (CPFSK) is a commonly used variation of [[frequency-shift keying]] (FSK), which is itself a special case of digitalanalog [[frequency modulation]]. FSK is a method of modulating [[digital data]] onto a [[sinusoidal]] [[carrier wave]], encoding the information present in the data to variations in the carrier's [[instantaneous phase#Instantaneous frequency|instantaneous frequency]] between one of two frequencies (referred to as the [[space frequency]] and [[mark frequency]]). In general, a standard FSK signal does not have [[continuous function|continuous]] phase, as the modulated waveform switches instantaneously between two sinusoids with different frequencies.

As the name suggests, the phase of a CPFSK is in fact continuous; this attribute is desirable for signals that are to be transmitted over a [[bandlimited]] channel, as discontinuities in a signal introduce [[wideband]] frequency components. In addition, some classes of amplifiers exhibit nonlinear behavior when driven with nearly discontinuous signals; this could have undesired effects on the shape of the transmitted signal.