说明：  QAM是正交振幅调制，其幅度和相位同时变化，属于非恒包络二维调制。QAM是正交载波调制技术与多电平振幅键控的结合 。
(QAM is quadrature amplitude modulation, whose 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 and multilevel amplitude keying.)