中文说明：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十分重要的调制解调方式。
English Description：
QPSK is a kind of digital modulation. It can be divided into absolute phase shift and relative phase shift. Because of the phase ambiguity in absolute phase shift, DQPSK is mainly used in practice. At present, it has been widely used in wireless communication and has become a very important modulation and demodulation method in modern communication.