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一、引言锁相环的用途很广,用于不同场合的环路指标要求可以差别很大,因而测量方法也不相同。例如,在接收机中用作跟踪滤波器的锁相环,要求很窄的噪声带宽B_n,同时要求尽量好的动态特性,于是等效噪声带宽B_n就成了环路的主要指标,且对阻尼系数ζ也有一定要求。但用在频率合成器中的锁相环,对V C O输出信号的相位抖动或频谱纯度有比较严格的要求,而对B_n和ζ却不太注重。此外,即使是同一项指标,对不同环路往往需要采用不同的测
I. INTRODUCTION The use of PLLs is very broad. The requirements for loop indexes used in different occasions can vary widely and the measurement methods are different. For example, a phase-locked loop used as a tracking filter in a receiver requires a very narrow noise bandwidth B_n while requiring as good a dynamic characteristic as possible, and thus the equivalent noise bandwidth B_n becomes the main index of the loop, The coefficient ζ also has certain requirements. However, the phase-locked loop used in the frequency synthesizer has more stringent requirements on the phase jitter or spectral purity of the VCO output signal, but less on the B_n and ζ. In addition, even the same indicator often requires different measurements for different loops