1. In
digital transmission,
angle modulation in which the
phase of the
carrier is discretely varied in relation either to a reference phase or to the phase of the immediately preceding
signal element, in accordance with
data being transmitted. (
188 ) 2. In a
communications system, the representing of characters, such as bits or quaternary digits, by a shift in the phase of an electromagnetic carrier wave with respect to a reference, by an amount corresponding to the symbol being encoded. Note 1: For example, when encoding bits, the
phase shift could be 0° for encoding a "0," and 180° for encoding a "1," or the phase shift could be -90 for "0" and +90° for a "1," thus making the representations for "0" and "1" a total of 180° apart. Note 2: In PSK systems designed so that the
carrier can assume only two different
phase angles, each change of phase carries one
bit of
information, i.e., the
bit rate equals the
modulation rate. If the number of recognizable phase angles is increased to 4, then 2 bits of information can be encoded into each
signal element; likewise, 8 phase angles can
encode 3 bits in each signal element. Synonyms biphase modulation, phase-shift signaling.
psk.
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