What modulation is 256QAM?

QAM is the abbreviation of quadrature amplitude modulation, which is translated as "quadrature amplitude modulation" in Chinese. Its amplitude and phase change at the same time, which belongs to non-constant envelope two-dimensional modulation QAM is a combination of orthogonal carrier modulation technology and multilevel amplitude keying.

Quadrature amplitude keying (QAM) is a method of combining two amplitude modulation signals (2ASK and 2PSK) into one channel, which will double the effective bandwidth. QAM is used for pulse amplitude modulation. The quadrature amplitude modulation signal has two carriers with the same frequency, but the phase difference is 90 degrees (a quarter period, according to the integral term). One signal is called I signal and the other signal is called Q signal. Mathematically, one signal is expressed as sine and the other as cosine. Two modulated carriers have been mixed at the time of transmission. After reaching the destination, the carrier is separated, the data is extracted separately, and then mixed with the original modulation information.

Extended data:

In QAM (Quadrature Amplitude Modulation), the data signal is represented by the amplitude variation of two orthogonal carriers. The phase modulation of analog signal and PSK (phase shift keying) of digital signal can be considered as a special quadrature amplitude modulation with constant amplitude and only phase change. Therefore, the phase modulation of analog signals and PSK (phase shift keying) of digital signals can also be considered as special cases of QAM, because it is essentially phase modulation.

Baidu encyclopedia-amplitude keying

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