Amplitude and phase modulation

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Constellation diagram of an APSK with 16 possible states and two amplitude levels

Amplitude and phase modulation (English amplitude and phase-shift keying ) or asymmetrical phase modulation (English asymmetric phase-shift keying ), (APSK) , is a digital type of modulation that encodes the data by changing the amplitude and phase angle of a carrier . This method combines amplitude shift keying (ASK) and phase shift keying (PSK) to expand the code word matrix . This method can also be viewed as a subgroup of quadrature amplitude modulation (QAM). The advantages over the usual (orthogonal) QAM are the lower number of amplitudes, which leads to fewer errors when using non-linear amplifiers, and the lower maximum amplitude, which allows better power utilization.


  • Helmut Röder, Heinz Ruckriegel, Heinz Häberle: Electronics 3rd part, communications electronics. 5th edition, Verlag Europa-Lehrmittel, Wuppertal, 1980, ISBN 3-8085-3225-4

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