说明：  正交相移键控（Quadrature Phase Shift Keyin，QPSK）是一种数字调制方式。它分为绝对相移和相对相移两种。由于绝对相移方式存在相位模糊问题，所以在实际中主要采用相对移相方式DQPSK。目前已经广泛应用于无线通信中，成为现代通信中一种
(Quadrature phase shift keying is a kind of digital modulation method. It is divided into two types, the absolute phase shift and the relative phase shift. Because of the phase ambiguity of the absolute phase shift method, the relative phase shift mode is adopted in practice DQPSK. At present, widely used in wireless communication, has become a very important modern communication modulation and demodulation.)