Phase modulation - definition
Phase modulation - definition
Phase Modulation (PM) is an analogue modulation technique in which the phase of the carrier wave is changed in a way that depends on the instantaneous value of the information signal. Unlike amplitude modulation or frequency modulation, here the amplitude and frequency of the carrier remain constant and the information is carried by changes in phase. Phase modulation is directly related to frequency modulation - both are categorised as angle modulation because they are based on changes in parameters related to the phase angle of the carrier wave.
In communication systems, PM allows data to be carried over long distances with high immunity to interference, especially those affecting the amplitude of the signal. However, its effectiveness depends on precise synchronisation of the receiver with the phase of the transmitted signal, which introduces specific design requirements for demodulation circuits. Phase modulation is the basis of many modern digital transmission techniques, such as phase-shift-keying, where specific bit values are assigned to discrete phase changes.
PM is used in both analogue and digital transmission, especially where it is crucial to increase spectral efficiency and minimise the impact of noise. In digital technology, this modulation enables the implementation of complex coding schemes, allowing more information to be transmitted in the same frequency band. The analysis and implementation of PM requires knowledge of signal theory, Fourier transforms and bandpass filtering, as phase-modulated signals have a complex spectral structure and require advanced processing in the receive path.
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