四相相移键控(QPSK)调制体制是近十几年来在数据通信中研究如何更有效的利用信道带宽,即提高通信有效性的一个极重要的方向,研究很活跃,进展也很大。从目前的研究结果来看,对于带宽受限制的信道,偏移键控(Offset keyed)式四相相移键控(OKQPSK)体制与最小频移键控(MSK)体制是比较理想的两种调制体制,它们已在数字通信系统中 Quadrature phase shift keying (QPSK) modulation is one of the most important directions in the field of data communications to study how to use channel bandwidth more effectively in the recent decade. That is to say, research is very active and progressing tremendously. From the current research results, Offset keyed four-phase shift keying (OKQPSK) system and minimum frequency shift keying (MSK) systems are the ideal two for the limited channel bandwidth Modulation systems, which are already in digital communication systems