用锁相环路作调频、调相器可以得到中心频率稳定度高、频移大的调频、调相信号。但是对应用频率合成器的调频发信机中怎样加入调制信号,加了调制信号后,环路参数怎样设计,调制频偏与环路参数的关系怎样确定,在电路设计上要注意些什么,怎样减小调制信号对环路的影响,这些问题在一般教科书和以前的一些锁相环方面的文章中都没有详细而系统的论述。因此本文在这方面做一些探讨。本文首先推出调频、调相波的数学表达式,然后对加了调制信号后锁相环路的特点及参数的确定进行 Phase-locked loop for FM, phase modulator can get the center frequency stability, frequency shift large FM, phase modulation signal. However, how to add the modulation signal to the frequency modulation transmitter of the frequency synthesizer and the modulation signal, how to design the loop parameters, how to determine the relationship between the modulation frequency offset and the loop parameters, what should be paid attention to in the circuit design, How to reduce the impact of the modulated signal on the loop, these issues in general textbooks and some of the previous phase-locked loop articles are not detailed and systematic exposition. So this article does some research in this aspect. In this paper, the mathematical expressions of FM and phase-modulated waves are first introduced, and then the characteristics and parameters of the PLL are added after the modulation signal is added