Phase-shift keying
![Constellation diagram example for BPSK.](/Images/godic/202501/28/BPSK_Gray_Coded.svg3238.png")
![Constellation diagram for QPSK with Gray coding. Each adjacent symbol only differs by one bit.](/Images/godic/202501/28/QPSK_Gray_Coded.svg3238.png")
![Conceptual transmitter structure for QPSK. The binary data stream is split into the in-phase and quadrature-phase components. These are then separately modulated onto two orthogonal basis functions. In this implementation, two sinusoids are used. Afterwards, the two signals are superimposed, and the resulting signal is the QPSK signal. Note the use of polar non-return-to-zero encoding. These encoders can be placed before for binary data source, but have been placed after to illustrate the conceptual difference between digital and analog signals involved with digital modulation.](/Images/godic/202501/28/Transmisor_QPSK_23239.png")
![Receiver structure for QPSK. The matched filters can be replaced with correlators. Each detection device uses a reference threshold value to determine whether a 1 or 0 is detected.](/Images/godic/202501/28/Receiver_QPSK3239.PNG")
Phase-shift keying (PSK) is a digital modulation scheme that conveys data by changing (modulating) the phase of a reference signal (the carrier wave). The signal is impressed into the magnetic field x,y area by varying the sine and cosine inputs at a precise time. It is widely used for wireless LANs, RFID and Bluetooth communication.