Modulation method used by modems and DSL equipment. Combines two amplitude-modulated (AM) signals into a single channel. The modem inserts the signals 90 degrees (one-quarter cycle) out of phase with each other. Engineers call this 90-degree phase shift "quadrature." QAM modulates both carrier phase and amplitude. Doubles effective bandwidth.
uadrature Am plitude odulation - A method of modulating digital signals onto a radio-frequency carrier signal in which the value of a symbol consisting of multiple bits is represented by amplitude and phase states of the carrier.
A digital modulation format used for downstream transmission in cable TV systems â€” commonly used for cable HDTV.
A modulation technique used to transmit 9,600 bits per second over a 2,400-baud line. See modulation.
The method of modulation that encode multiple analog signal to bit pattern.
Quadrature amplitude modulation. Quadrature modulation in which the two carriers are amplitude modulated. In analog communications, the representation (i.e., transmission) of digital information by encoding bit sequences of fixed, specified length (number of bits), and representing these bit sequences as a function of (a) the amplitude of an analog carrier; or (b) a phase shift of the analog carrier with respect to the phase that represented the preceding bit sequence, and where the permissible phase shift is an integral multiple of /2 radians (90°, or one-quarter unit interval); or (c) both.
Quadrature amplitude modulation. Method for modulating two carriers. The carriers can be analog or digital.
Quadrature Amplitude Modulation. A method of modulating digital signals onto a radio-frequency carrier signal in which the value of a symbol consisting of multiple bits is represented by amplitude and phase states of the carrier. QAM is a modulation scheme mostly used in the downstream direction (64-QAM, 256-QAM); 16-QAM is often usable in the upstream direction. Numbers indicate number of code points per symbol. The QAM rate or the number of points in the QAM constellation can be computed by 2 raised to the power of number of bits/symbol. For example, 16-QAM has 4 bits per symbol, 64-QAM has 6 bits per symbol, and 256-QAM has 8 bits per symbol.
Quadrature amplitude modulation. A modulation method used by cable DTV that combines changes in phase and amplitude to send four bits with each baud. Quadrature phase shift keying (QPSK) A modulation method used by satellite DTV that transmits information by varying the phase of a sine wave.
Quadrature Amplitude Modulation. A modulation scheme which is used either on its own (in cable transmission) or with COFDM. QAM Clear is unscrambled cable broadcast signal. Scrambled QAM is scrambled Premium and/or Pay per View cable broadcast.
Quadrature Amplitude Modulation. This digital frequency modulation technique is primarily used for sending data downstream over a coaxial cable network.
Quadrature Amplitude Modulation - Modulation / demodulation system for digital cable TV in the US.
The signal modulation system used for digital cable TV.
Quadrature amplitude modulation. A sophisticated modulation technique, or compression technique, using variations in signal amplitude and phase, that allows multiple bits to form a single "symbol," which is then impressed on a single sine wave. Return
Quadrature Amplitude Modulation. Modulation standard used for cable transmission.
Quadrature Amplitude Modulation. A method of combining two Amplitude Modulated (AM) signals - each having the same frequency, but differing in phase by 90 degrees, into a single channel, thereby doubling the effective bandwidth.
Quadrature Amplitude Modulation. A method of encoding digital data in an analog signal in which each combination of phase and amplitude represent one of sixteen four-bit patterns.
Quadrature Amplitude Modulation. A variation of PSK that incorporates AM to increase the number of bits per baud.
Quadrature Amplitude Modulation. This is an efficient way of transferring binary data over cable. It is used for multiple dwelling unit installations. They set up a few LNB dishes and send the output to a QAM converter rack. Then they send the signals into the cable entering the apartment building. The people wanting to receive these signals connect their satellite receiver to the cable and they can then receive satellite TV. The downfalls are that mostly everyone working for the satellite company knows nothing about it. Also, misalignment of a dish will affect everyone and you probably don't have direct access to re-align that dish.
Quadrature Amplitude Modulation. System that greatly increases the amount of information which can be carried within a given bandwidth.
The acronym for Quadrature Amplitude Modulation. A form of Amplitude Modulation that uses two carriers that are modulated by separate signals. QAM is the most viable transmission line code for VDSL modems.
Quadrature amplitude modulation. A coding system that allows many bits per signal element Close this window
(Quadrature Amplitude Modulation). modulation method where the carrier amplitude is modulated, together with two carriers of 90-degree phase difference. The information signal is divided into two independent components, termed I and Q, so each carrier describes the value of alternate bits in a bit stream.
Quandrature Amplitude Modulation.
Quadrature Amplitude Modulation is a modulation technique which uses different phases such as 16, 32, 64, and 256 and each state is defined by a specific amplitude and phase.
Quadrature Amplitude Modulator.
Quadrature Amplitude Modulation. A two-dimensional modulation used for ADSL, cable modems and proposed for VDSL. CAP is a special case of QAM. In QAM, a single carrier frequency is modulated in both sine and cosine components.
(quadrature amplitude modulation) - a method of combining two amplitude-modulated (AM) signals into a single channel, thereby doubling the effective bandwidth. QAM is used with pulse amplitude modulation (PAM) in digital systems. In a QAM signal, there are two carriers, each having the same frequency but differing in phase by 90 degrees (one quarter of a cycle, from which the term quadrature arises). One signal is called the I signal, and the other is called the Q signal. Mathematically, one of the signals can be represented by a sine wave, and the other by a cosine wave. The two modulated carriers are combined at the source for transmission. At the destination, the carriers are separated, the data is extracted from each, and then the data is combined into the original modulating information. CAP is very similar to QAM.
Quadrature amplitude modulation - A digital modulation method in which the value of a symbol consisting of multiple bits is represented by amplitude and phase states of a carrier. 64 or 256 QAM is used for downstream transmission in cable systems.
Quadrature Amplitude Modulation; a multi-level modulation technique.
See quadrature amplitude modulation.
quadrature amplitude modulation : a modulation scheme which conveys data by changing (modulating) the amplitude of two carrier waves, usually sinusoids which are out of phase with each other by 90° (called quadrature carriers). In digital QAM, the sets of modulated amplitudes and selected phases of two carrier waves are used to transmit some binary numeral; then each signal transmitted can carry two or more bits (as many as 256 in 256-QAM modulation). Latin acronym
A single-carrier scheme that modulates both the amplitude and phase to yield higher spectral efficiency. Various levels of QAM exist, and they are referred to as QAM nn, where nn indicates the number of states per Hertz. The number of bits per symbol time is k, where 2k = nn. So, 4 bits/Hz is equivalent to QAM 16, 6 bits/Hz is equivalent to QAM 64, and 8 bits/Hz is equivalent to QAM 256.