中文说明：
正交振幅调制是将两个振幅调制信号组合成单个信道的方法，从而使有效带宽加倍。在数字系统中，特别是在无线应用中，QAM与脉冲幅度调制一起使用。
English Description：
Quadrature amplitude modulation is a method to combine two amplitude modulation signals into a single channel, so as to double the effective bandwidth. In digital systems, especially in wireless applications, QAM is used together with pulse amplitude modulation