相敏检测系统中自动移相的实现方法

Implementation of Automation Phase-Shifting Method in Phase-Sensitive-Detection System

在分析现有的多种可调移相方法基础之上，针对相敏检测系统中输入信号的特点，在保证准确度的前提下，提出了采用高性能的准１６位单片机８０９８进行移相控制，实现正交搜寻快速自动移相的方法。该方法是通过将采入单片机中的一组正交测量数据进行比值运算、查表并进行三次变换来完成最佳移相角度的选取。将该法应用于大时间常数的同步外差相敏检测系统中，使移相速度大为提高，从而改善了系统的动态特性。

fter analyses of several present adjustable phase-shifting methods according to the characteristics of the input signal in a Phase-Sensitive-Detection system, an orthogonal-seeking phase-shifting method, in which phase shifting is controlled by a quasi-16-bit single-chip microcomputer 8098 of high performance, is proposed. At the same time, accuracy is ensured. Choice of the optimum phase-shifting angle is completed through the following processes making the ratio computation for a couple of orthogonal quantities sampled into the microcomputer, searching the table and transforming three times. When this method is applied to a synchronous heterodyne Phase-Sensitive-Detection system with a long time constant,the phase-shifting speed is increased greatly, so that the dynamic characteristic is improved.