锁相调频发生器

The Research of a Phase-Locked FM Generator

采用锁相技术,可以使一个调频信号发生器有十分稳定的中心频率;但理论分析指出:这样一个环路对二阶滤波器来说并非无条件稳定,其稳定范围与滤波器类型有关。当输入等幅正弦调制信号时,输出信号的最大频偏是调制信号频率的函数。此外,尚有其他的附加失真。尽管如此,当对中心频率要求较严格时,仍不失为一个尚可利用的线路。 (一)概述利用锁相环路可以使本机振荡信号锁定在外来信号上,使得本机振荡信号频率与外来信号频率相等,而两个信号之间只存在一个固定的相位差。此相位差的大小视环路特性而异,但在环内噪声作用下会引起本机振荡器相位的抖动。

This paper presents a method for obtaining the FM signal, the centre frequency of which is very stable, and it is proved that the loop filter of phase lag type there are unstable states Finally, the distortions are discussed and curves of pre-quulization are given to reduce the distortions.