What is mean by PSK ( phase shift keying)?

The PSK stand for phase-shift keying is the most efficient of three modulation technique. It is used for high bit rates. In PSK, phase of the sinusoidal carrier is changed according to the data bit to be transmitted. The simplest method of PSK, also called Binary PSK (BPSK) modulation, uses two signal phases – 0 degrees and 180 degrees. The digital signal is broken up time wise into individual bits (binary digits). The state of each bit is determined according to the state of the preceding bit. If the phase of the bit does not change then the state of the signals stays the same. If the phase of the signal changes by 180 degrees, then the signal state changes (from 0 to 1, or 1 to 0).There are more complex forms of PSK that rely on four or eight phases to transmit data at a faster rate.

phase shift keying