Quadrature amplitude modulation
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Quadrature amplitude modulation (QAM) combines amplitude and phase modulation to transmit digital data.[1] Digital communications systems, including those based on 802.11 Wi-Fi standards, extensively employ QAM as a modulation scheme.[2]
Quick Facts
- Carrier phase offset
- 90°
- Orthogonality condition
- quadrature
- Carrier waves
- two
Facts from the source article.
Key facts and history
QAM modulates both the amplitude and phase of a carrier signal.[1] In a QAM signal, two carriers are 90° out of phase, providing an in-phase and a quadrature component.[1] Constellation points in digital QAM are typically arranged in a square grid with equal spacing.[1] Common square constellations include 16-QAM, 64-QAM, and 256-QAM.[1]
The number of constellation points is usually a power of two, corresponding to bits per symbol.[1] ADSL technology uses very dense constellations, up to 32768-QAM, equivalent to 15 bits per tone.[3] Moving to higher-order QAM in hostile RF environments increases multipath interference and reduces noise immunity.[4] Constellations that are not square, for example Cross-QAM, can provide greater efficiency, but the added modem complexity makes them uncommon.[1]
What the cited sources add
The Kylia product catalog states that the company can adapt any catalog product to customer needs, including operating wavelength and specific packaging design.[5]
References
- Wikipedia, "Quadrature amplitude modulation" (CC BY-SA 4.0), which cites: Xiong, "Digital Modulation Techniques", Artech House, 2000, p. 426-432 (we also read that source) en.wikipedia.org
- Wikipedia, "Quadrature amplitude modulation" (CC BY-SA 4.0), which cites: "Digital Modulation Efficiencies", Barnard Microsystems; "Ciena tests 200G via 16-QAM with Japan-U.S. Cable Network", lightwave, April 17, 2014; Kylia products , dwdm mux demux, 90 degree optical hybrid, d(q) psk demodulatorssingle polarization (we also read that source) en.wikipedia.org
- Wikipedia, "Quadrature amplitude modulation" (CC BY-SA 4.0), which cites: "G.992.3 : Asymmetric digital subscriber line transceivers 2 (ADSL2)", www.itu.int (original not read by us) en.wikipedia.org
- Wikipedia, "Quadrature amplitude modulation" (CC BY-SA 4.0), which cites: Howard Friedenberg and Sunil Naik, "Hitless Space Diversity STL Enables IP+Audio in Narrow STL Bands", 2005 National Association of Broadcasters Annual Convention (original not read by us) en.wikipedia.org
- Kylia products , dwdm mux demux, 90 degree optical hybrid, d(q) psk demodulatorssingle polarization. facts only, no text reused. kylia.com
Each numbered sentence above was checked against the source it cites before publication. Sentences citing Wikipedia adapt text from the English Wikipedia article Quadrature amplitude modulation (contributors), used under CC BY-SA 4.0; this entry is available under the same licence. Other sources were used for facts only; no text or images are copied from them.
More in Radio Modulation Modes
Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: Quadrature amplitude modulation (CC BY-SA 4.0).
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