QAM (disambiguation)

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QAM stands for Quadrature amplitude modulation

QAM may also refer to:

QAM is a digital television standard using quadrature amplitude modulation. It is the format by which digital cable channels are encoded and transmitted via cable television providers. QAM is used in a variety of communications systems such as Dial-up modems and WiFi. In cable systems, a QAM tuner is linked to the cable in a manner that is equivalent to an ATSC tuner which is required to receive over-the-air (OTA) digital channels broadcast by local television stations when attached to an antenna. Most new HDTV digital televisions support both of these standards. QAM uses the same 6 MHz bandwidth as ATSC, using a standard known as ITU-T Recommendation J.83 Annex B ("J.83b").

In computational complexity theory, QMA, which stands for Quantum Merlin Arthur, is the quantum analog of the nonprobabilistic complexity class NP or the probabilistic complexity class MA. It is related to BQP in the same way NP is related to P, or MA is related to BPP.

Queer Azaadi Mumbai Pride March, also called Queer Azaadi March and Mumbai pride march, is an annual LGBTQIH pride parade that is held in the city of Mumbai, capital of Maharashtra, India. It usually begins from Gowalia Tank ending at Girgaum Chowpatty. It, along with the Pride Week, is organized by Queer Azaadi Mumbai, a collective of organizations and individuals working for the rights of LGBTQIA community. The participants of the march include people from the LGBTQIH community as well their "straight allies", from India and outside. In addition to being a celebration of queer pride, the pride march and related events are a platform to ask for equal rights.

See also

The Qaem refers to two completely separate Iranian weapons: an air-to-ground glide bomb and a ground-to-air missile. These two weapons are similarly sized and identically named, and are both developed from the Toophan missile, but are separate weapon systems.

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Related Research Articles

Amplitude modulation in amplitude modulation, the amplitude (signal strength) of the carrier wave is varied in proportion to the waveform being transmitted

Amplitude modulation (AM) is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. In amplitude modulation, the amplitude of the carrier wave is varied in proportion to that of the message signal being transmitted. The message signal is, for example, a function of the sound to be reproduced by a loudspeaker, or the light intensity of pixels of a television screen. This technique contrasts with frequency modulation, in which the frequency of the carrier signal is varied, and phase modulation, in which its phase is varied.

In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a modulating signal that typically contains information to be transmitted. Most radio systems in the 20th century used frequency modulation (FM) or amplitude modulation (AM) for radio broadcast.

Quadrature amplitude modulation (QAM) is the name of a family of digital modulation methods and a related family of analog modulation methods widely used in modern telecommunications to transmit information. It conveys two analog message signals, or two digital bit streams, by changing (modulating) the amplitudes of two carrier waves, using the amplitude-shift keying (ASK) digital modulation scheme or amplitude modulation (AM) analog modulation scheme. The two carrier waves of the same frequency are out of phase with each other by 90°, a condition known as orthogonality and as quadrature. Being the same frequency, the modulated carriers add together, but can be coherently separated (demodulated) because of their orthogonality property. Another key property is that the modulations are low-frequency/low-bandwidth waveforms compared to the carrier frequency, which is known as the narrowband assumption.

Quadrature may refer to:

Pulse-amplitude modulation form of signal modulation where the message information is encoded in the amplitude of a series of signal pulse

Pulse-amplitude modulation (PAM), is a form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses. It is an analog pulse modulation scheme in which the amplitudes of a train of carrier pulses are varied according to the sample value of the message signal. Demodulation is performed by detecting the amplitude level of the carrier at every single period.

8VSB is the modulation method used for broadcast in the ATSC digital television standard. ATSC and 8VSB modulation is used primarily in North America; in contrast, the DVB-T standard uses COFDM.

C-QUAM is the method of AM stereo broadcasting used in Canada, the United States and most other countries. It was invented in 1977 by Norman Parker, Francis Hilbert, and Yoshio Sakaie, and published in an IEEE journal.

Independent sideband (ISB) is an AM single sideband mode which is used with some AM radio transmissions. Normally each sideband carries identical information, but ISB modulates two different input signals — one on the upper sideband, the other on the lower sideband. This is used in some kinds of AM stereo, but is generally otherwise prohibited in the U.S. by the FCC.

16VSB is an abbreviation for 16-level vestigial sideband modulation, capable of transmitting four bits (24=16) at a time.

Rate-adaptive digital subscriber line (RADSL) is a pre-standard asymmetric digital subscriber line (ADSL) solution. RADSL was introduced as proprietary technology by AT&T Paradyne, later GlobeSpan Technologies Inc., in June 1996. In September 1999, RADSL technology was formally described by ANSI in T1.TR.59-1999. RADSL supports downstream data rates of up to approximately 8 Mbit/s, upstream data rates up to approximately 1 Mbit/s, and can coexist with POTS voice on the same line.

Carrierless amplitude phase modulation (CAP) is a variant of quadrature amplitude modulation (QAM). Instead of modulating the amplitude of two carrier waves, CAP generates a QAM signal by combining two PAM signals filtered through two filters designed so that their impulse responses form a Hilbert pair. If the impulse responses of the two filters are chosen as sine and a cosine, the only mathematical difference between QAM and CAP waveforms is that the phase of the carrier is reset at the beginning of each symbol. If the carrier frequency and symbol rates are similar, the main advantage of CAP over QAM is simpler implementation. The modulation of the baseband signal with the quadrature carriers is not necessary with CAP, because it is part of the transmit pulse.

In-phase and quadrature components

In electrical engineering, a sinusoid with angle modulation can be decomposed into, or synthesized from, two amplitude-modulated sinusoids that are offset in phase by one-quarter cycle. All three functions have the same frequency. The amplitude modulated sinusoids are known as in-phase and quadrature components.  In some contexts it is more convenient to refer to only the amplitude modulation (baseband) itself by those terms.

The modulation order of a digital communication scheme is determined by the number of the different symbols that can be transmitted using it.

Higher-order modulation is a type of digital modulation usually with an order of 4 or higher. Examples: quadrature phase-shift keying (QPSK), and m-ary quadrature amplitude modulation (m-QAM).

Trellis-coded pulse-amplitude modulation (TC-PAM) is the modulation format that is used in HDSL2 and G.SHDSL. It is a variant of trellis coded modulation (TCM) which uses a one-dimensional pulse-amplitude modulation (PAM) symbol space, as opposed to a two-dimensional quadrature amplitude modulation (QAM) symbol space. Compared to the 2B1Q scheme used in the older HDSL and SDSL standards, TC-PAM improves range at a given bit-rate and provides enhanced spectral compatibility with ADSL.

Analog transmission is a transmission method of conveying information using a continuous signal which varies in amplitude, phase, or some other property in proportion to that information. It could be the transfer of an analog source signal, using an analog modulation method such as frequency modulation (FM) or amplitude modulation (AM), or no modulation at all.

Amplitude and phase-shift keying or asymmetric phase-shift keying (APSK) is a digital modulation scheme that conveys data by changing, or modulating, both the amplitude and the phase of a reference signal. In other words, it combines both amplitude-shift keying (ASK) and phase-shift keying (PSK) to increase the symbol-set. It can be considered as a superclass of quadrature amplitude modulation (QAM). The advantage over conventional QAM, for example 16-QAM, is lower number of possible amplitude levels.

A Web-to-TV installation provides a way to show web television or other over-the-top content from the Internet, to a television set. Various technologies to do this include Home theater PCs, digital media receivers, and Smart TVs.

Constellation shaping is an energy efficiency enhancement scheme for digital signal modulation that improves upon the amplitude and phase-shift keying (APSK) and the conventional quadrature amplitude modulation (QAM)) modulation schemes by transmitting low-energy signals more frequently than high-energy ones.