Phase modulation (PM) is an angular modulation of a carrier oscillation in which the phase angle of the modulated oscillation deviates from that of the carrier oscillation by an amount proportional to the primary sign oscillation. This amount of deviation is referred to as phase deviation.
"0" corresponds to 90 degrees phase angle and binary "1" to 270 degrees.
modulation In phase difference modulation, which is used almost exclusively because phase modulation is not susceptible to interference, the binary characters are encoded by the phase difference of two successive AC pulses. In this process, several binary characters are combined into an alternating current signal and transmitted. Phase modulation is used in data transmission technology with modems in the form of phase shift keying (PSK) and in a further variant as phase jitter modulation (PJM) with the smallest phase changes in RFID.