There are 6 names in this directory beginning with the letter Q.
QAM: Quadrature Amplitude Modulation
Quadrature Amplitude Modulation (QAM) is a type of modulation where the signalling information is carried in the phase and amplitude of the modulated carrier wave. Specifically for QAM, the amplitude of two waves, 90 degrees out-of-phase with each other (in quadrature) are changed (modulated or keyed) to represent the data signal, in which each combination of phase and amplitude represents one of sixteen four-bit patterns.
QCIF: Quarter CIF
Quarter CIF (QCIF) is a video image format which employs 176 horizontal pixels and 144 vertical lines. Although resolution is courser than CIF, QCIF consumes less memory while still achieving an acceptable level of clarity on small displays such as those incorporated in mobile phones.
QPSK: Quadrature Phase Shift Keying
Quadrature Phase Shift Keying (QPSK) is a digital modulation scheme that conveys data by changing, or modulating, the phase of a reference signal (the carrier wave). Sometimes known as quaternary or quadriphase PSK or 4-PSK, QPSK uses four points on the constellation diagram, equispaced around a circle. With four phases, QPSK can encode two bits per symbol, shown in the diagram with Gray coding to minimize the BER.
The quadrature phase channel in a phase shift keyed system having more that 2 phase states.