Qam constellation _QAM constellation

What does QAM quadrature amplitude modulation mean? Draw a 6QAM constellation

Quadrature amplitude keying (QAM) is a method of combining two AM signals (2ask and 2psk) into one channel, so it will double the effective bandwidth. Quadrature amplitude modulation is used for pulse amplitude modulation, especially in wireless network applications.

Constellation diagram of QAM in different systems

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 can be 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.

QAM uses two independent baseband signals to suppress the amplitude modulation of two mutually orthogonal co-frequency carriers, and uses the orthogonality of the spectrum of this modulation signal in the same bandwidth to realize the transmission of two parallel digital information. This modulation method usually includes binary QAM(4QAM), quaternary QAM(l6QAM), octal QAM(64QAM), …, and the corresponding spatial signal vector endpoint distribution map is called constellation map, with 4, 16, 64, … vector endpoints respectively. The relationship between series M and signal state M is that for 4QAM, when the amplitudes of two signals are equal, its generation, demodulation, performance and phase vector are the same as those of 4PSK.