说明：  采用Maxim公司的可编程滤波器MAX264设计的锁相跟踪滤波器，能够实现自动跟踪频率功能，使得滤波范围增加，免去调整滤波中心频率的麻烦，采用单片机编程。
(The programmable filter Maxim MAX264 design phase-locked tracking filter, automatic tracking frequency, the increase in filter range, eliminating the need to adjust the filter center frequency of trouble, microcontroller programming.)