The BPSK method, BinaryPhase Shift Keying, is a phase shift keying with two phase states, hence the abbreviation 2-PSK. It is the simplest form of phase shift keying, in which the carrier frequency
can assume two phase positions 0° and 180°. Each time the state of the digital signal changes, the phase of the carrier signal is rotated by 180°. For example, the Hi level is always assigned the phase position 0° and the ''Lo level that of 180°. The receiver evaluates the phase shifts and can determine from them whether it is a Lo or a Hi state. A total of 256 (2exp8) codewords
can be generated with an 8BPSK keying.Differential Binary Phase Shift Key ing (DBPSK) or Differential Quaternary Phase Shift Keying (DQPSK).