differential quaternary phase shift keying (Modulation) (DQPSK)

Differential Quaternary PhaseShift Keying (DQPSK) is a quadrature phase shift keying technique that uses phase changes of the carrier frequency and modulates them with dibits.

Unlike quadrature phase shift keying( QPSK), where ambiguity can occur when the phase changes, DQPSK changes the phase with the signal, whereas QPSK fixes the phase. DQPSK resampling works with dibits.

DBPSK and DQPSK keying of the carrier phase angle

If "00" is transmitted as the dibit, the phase position does not change. With dibit "01", the phase position changes by +90°, with "10" by -90° and with "11" by 180°. The DQPSK method has a higher transmission rate than Differential Phase Shift Keying( DPSK).

DQPSK modulation is used in cellular networks and cable modems. InBluetooth, DQPSK keying is used to increase the data rate with Enhanced Data Rate( EDR).