PSK is Phase shift keying is a digital modulation process that conveys data by changing the phase of a constant frequency reference signal which is the carrier wave. PSK technique is commonly used for wireless LANs, biometric, contactless operations along with RFID and BlueTooth communications. PSK is of two types depending upon the phases of the signal that gets shifted: BPSK (Binary Phase Shift Keying ) and QPSK (Quadrature Phase Shift keying). In Differential Phase shift keying, the phase of the modulated signal is shifted relative to the previous signal element. It does not need a reference oscillator. DPSK is basically a technique of BPSK in which there is no reference phase signal. It encodes two distinct signals, the carrier and the modulating signal with a 180-degree phase shift each.