fázismodulációnál

Phase modulation, often abbreviated as PM, is a modulation technique used in telecommunications and signal processing. It is a type of angle modulation, where the phase of the carrier signal is varied in proportion to the instantaneous amplitude of the message signal. In simpler terms, the information is encoded by changing the timing or alignment of the carrier wave.

The key characteristic of phase modulation is that the phase of the carrier wave changes directly with the amplitude of the modulating signal. This is distinct from frequency modulation (FM), where the frequency of the carrier wave changes with the amplitude of the modulating signal, and amplitude modulation (AM), where the amplitude of the carrier wave changes. Phase modulation is often used in digital communication systems where it can be implemented efficiently. It offers good noise immunity compared to amplitude modulation.

The mathematical representation of a phase-modulated signal involves modifying the phase angle of a sinusoidal carrier wave. The instantaneous phase of the carrier is shifted by an amount proportional to the instantaneous amplitude of the message signal. The bandwidth required for a phase-modulated signal is generally larger than that for amplitude modulation but can be comparable to or less than that for frequency modulation, depending on the specific parameters. Applications of phase modulation include certain radio communication systems, satellite communications, and digital data transmission.