phase modulation

Phase modulation (PM) is a telecommunications technique where the phase of a carrier wave is altered in response to an information signal. It is closely related to frequency modulation (FM), as changing the phase inherently changes the frequency, and vice versa.12

In digital communications, phase-shift keying (PSK) is a form of digital modulation where the phase of the carrier wave is changed to represent binary data (0s and 1s). The simplest form of PSK uses a 180° phase shift to distinguish between a 0 and a 1. PM and FM are often used together and are effective at minimizing interference, particularly in microwave radio relays and some Wi-Fi and satellite television systems.32