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一、前言运用砷化镓发光二极管作光源和APD雪崩光电二极管作接收元件所组成的红外测距仪系统中均有一个本地振荡器,与主振荡器在频率数值上差几千赫芝的低频,并且在这个频率上完成相位差的检测,以此得到被测距离的数值.该本地振荡器应与主振荡器保持严格的同步,即主振、本振频率之差应保持恒定值.这也是相位差检测的首要条件,使用TTL锁频环可以很容易达到这一要求.锁频环的应用框图见图1,图中虚线框内即为锁频环的框图.图中所示差频值为:LF=f_1′-f_1.主振、本振信号经混频器后得到差频信号,再经
I. Introduction The use of gallium arsenide light-emitting diodes and APD avalanche photodiodes for receiving components of the infrared range finder system consists of a local oscillator, and the main oscillator in the frequency difference between a few thousand Hertz’s low frequency , And at this frequency to complete the phase difference detection, in order to get the value of the measured distance. The local oscillator should be kept strictly synchronized with the main oscillator, that is, the difference between the main oscillator, the local oscillator frequency should be kept constant. But also the primary condition of the phase difference detection, the use of TTL frequency lock loop can be easily achieved this requirement.Load frequency loop application block diagram shown in Figure 1, the dashed box is the block diagram of the frequency locked loop .Figure shown in the difference frequency The value is: LF = f_1’-f_1. The main oscillator, local oscillator signal obtained by the frequency difference signal, and then by