在现代电子技术的设计与开发过程中，特别是在通信、雷达、航空、航天以及仪器仪表等领域,都需要进一步提高一系列高精度、高稳定度的频率源的频率精度。这样，一般的振荡器已经无法满足各种应用的发展要求，而晶体振荡器的性能虽然比较好,但其频率单一，或只能在极小的范围内进行微调。 

锁相环是一个相位误差控制系统。它比较输入信号和振荡器输出信号之间的相位差，从而产生误差控制信号来调整振荡器的频率，以达到与输入信号同频同相。本设计主要针对特定场合的安检任务设计，采用基于线圈感应来实现对金属的探测。本设计选用的是51系列单片机，在硬件电路设计中，完成单片机选型及外部电路元件的选用，设计了硬件接线图，提出了接线要求，使之具有控制和保护的功能；在软件设计中，给出了程序流程图，编程语言采用了C语言，将硬件和软件有机的结合在一起，使系统运行可靠，达到预期的设计目的。

 

关键词：频率合成器；锁相环；51单片机；C语言

    In modern electronics design and development process, particularly in communications, radar, aviation, aerospace and instrumentation, and other fields, we need to further improve the range of high-precision, high-precision frequency stability frequency source. Thus, the general oscillator has been unable to meet the development requirements of various applications, and the crystal oscillator performance although better, but the single frequency or fine tune only in a very small range.

    Phase-locked loop is a phase error control system. It compares the input signal and the phase difference between the oscillator output signal to produce a frequency error control signal to adjust the oscillator to achieve with the input signal with the same frequency. This design is mainly designed for security tasks specific occasions, based on the induction coil to achieve metal detection. The design choices are 51 series, the hardware circuit design, selection and external microcontroller to complete the selection of circuit elements, the design of the hardware wiring diagram, proposed wiring requirements, so that it has control and protection functions; in software design given the program flow chart, using the programming language C language, the organic combination of hardware and software, the system is reliable, is designed to achieve the desired.

    Keywords:frequency synthesizer; phase-locked loop; 51 microcontroller; C language

 

 

 

 

 

 

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