fázismodulációval

Phase modulation (PM) is a type of angle modulation where the phase of a carrier signal is varied in accordance with the instantaneous amplitude of the modulating signal. It is a continuous digital modulation technique. In phase modulation, the phase deviation is directly proportional to the amplitude of the modulating signal. The amplitude and frequency of the carrier wave remain constant.

The mathematical representation of a phase-modulated signal can be expressed as s(t) = Ac cos(ωc t + mP m(t)), where Ac is the amplitude of the carrier, ωc is the carrier angular frequency, mP is the phase sensitivity index, and m(t) is the modulating signal. The phase of the carrier is shifted by an amount proportional to the amplitude of the message signal at any given instant.

Phase modulation is closely related to frequency modulation (FM). In fact, an FM signal can be generated by first integrating the modulating signal and then phase modulating it. Conversely, a PM signal can be obtained by differentiating an FM signal. However, PM and FM are not identical. For instance, if the modulating signal is a constant DC voltage, FM would result in a frequency shift, while PM would cause a constant phase shift.

PM has applications in various communication systems, including some digital modulation schemes like BPSK (Binary Phase Shift Keying) and QPSK (Quadrature Phase Shift Keying). It offers good noise immunity and spectral efficiency in certain scenarios.