Continuous Phase Modulation
(CPM) is a phase modulation in which the phase changes continuously. Unlike other phase modulations such as phase shift ke
ying(PSK), CPM modulation does not jump back to zero
degrees phase, or switch between a sine function and a cosine function asin quadrature phase shift keying
(QPSK). Continuous CPM modulation has better spectral efficiency because phase hopping methods require a large amount of energy outside the transmission band.
In addition, CPM modulation operates at a constant signal level, which means that the transmitted power remains constant.