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QPSK [Quadrature Phase-Shift Keying] is a system of modulating digital signals onto a radio-frequency carrier signal using four phase states to code two digital bits.

DQPSK [Dual Quadrature Phase-Shift Keying] is phase modulation using two pairs of unique carrier phases using a differential characteristic which indicates the use of a different phase from the last change or symbol to determine the current symbol’s value, rather than any absolute measurement of the phase change.

DBPSK [Dual Binary Phase-Shift Keying] is a phase modulation system using two distinct carrier phases for data signaling providing one bit per symbol.

QAM [Quadrature Amplitude Modulation] is a system modulating digital signals onto a radio-frequency carrier signal involving both amplitude and phase coding.

These technologies are critical to modem data transmission, cable modems, and other digital data transmission systems.

For more details, see TECHtionary QAM.

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