关键词: 锁相环, 调频信号, 跳变周期, 线性度

Abstract:

This paper introduces a method for generating triangular frequency modulated signal based on PLL systems,and the optimization of signal linearity is studied.By changing the ratio N of frequency divider in the phase locked loop system rapidly,a corresponding VCO control voltage to output the triangular frequency modulated signal is generated.The key of this method is the choice of transition period Δt of frequency division ratio N.Under the premise that the transition period Δt is greater than lock time,the shorter the Δt is,the higher the linearity.By measuring the actual circuit,the feasibility of this method has been verified.This method has the advantages of mature circuit structure,high reliability and convenient adjustment over other schemes.

Key words: PLL;frequency modulated signal;transition period;linearity