为了便于信号发射，提高信道利用率、发射功率效率以及改善通信质量，人们研制出各种通信信号的调制样式。尽管调制样式多种多样，但实质上调制不外乎用调制信号去控制载波的某一个（或几个）参数，使这个参数按照调制信号的规律而变化。调制信号可以分别“寄生”在已调信号的振幅、频率和相位中，相应的调制就是调幅、调频和调相这三大类熟知的调制方式。
MSK信号就是调频这一大类中的一种相位连续的移频键控。其主要特点是包络恒定，带外辐射小，实现较简单，可用于移动通信中的数字传输
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