激光测距微弱信号检测方法研究

三峡大学

硕士学位论文

激光测距微弱信号检测方法研究

姓名：田桂平

申请学位级别：硕士

专业：控制理论与控制工程

指导教师：万钧力

20050401

内容摘要

在激光测距系统中，光电探测器接收激光回波信号时,信号受限于光电探测元件的噪声以及背景光干扰等原因,往往淹没在噪声之中,给实际应用带来了很多的困难,因而寻找合适的信号检测方法来提高信噪比,对许多应用场合来说,都是至关重要的。

本文以激光测距回波信号为研究对象，分析信号和噪声的特性，比较不同探测方法对改善信噪比的效果，探讨以提高信噪比为目的的激光测距微弱信号检测技术。论文共六章。第一章介绍了激光测距原理，概述了激光测距技术的发展与应用，讨论了信噪比与测程的关系。

论文第二章讨论了相关检测技术在激光测距微弱信号检测中的应用。相关检测技术是应用信号周期性和噪声随机性的特点，通过自相关或互相关运算，达到去除噪声,提取信号的目的。根据相关检测的原理，设计了一种基于相关检测的光电探测器的激光回波探测系统。仿真表明，对于淹没在噪声中的信号，互相关处理可以减少噪声,提高信噪比。该方法对脉冲式或相位式激光测距微弱信号检测均有效。论文第三章提出了一种用于相位式激光测距鉴相的新方法：向量内积法检相，理论仿真表明，该方法可消除信号幅值变化带来的测量影响，有很高的相位差检测精度。论文第四章介绍了信号积累技术的原理，设计了一种用于微弱信号检测的硬件电路方案，仿真表明该

m

方案的信噪改善比为m(是积累次数)。论文第五章介绍了小波变换用于激光脉冲回波微弱信号检测原理和方法，其中对小波多分辨率分析方法、小波阀值去噪算法几方面进行了详细的分析和研究；重点讨论了含噪脉冲信号的小波分解与重构，仿真表明，小波分解与重构方法能有效消除噪声。论文第六章对全文进行了总结。

关键词：微弱信号检测相关检测信号积累 小波变换

Abstract

In the laser measurement system, when the electrophotonic detector received the laser echo signal, Signal is always submerged into noise because of the noise of electrophotonic detector and background interference. It makes practical application difficult. So, it is very important for lots of practical applications to find suitable techniques to detect weak signal.

In this dissertation, to detect weak signal submerged into noise, Several technology problems of weak signal detecting of laser ranging are dealt with, and the cause and rule to producing noise is analyzed, and the features and correlation of the signal detected are studied. The focus on research effort is the laser weak signal detecting techniques for improving signal noise ratio (SNR). This dissertation has five chapters. In Chapter 1, the relationship between SNR and range is discussed, and the principle of laser ranging is introduced, the development and application of the techniques of laser ranging is descript.

In Chapter 2, the application of correlation detection to detect weak signal of laser ranging is discussed. Based on self-correlation or cross-correlation calculation, the correlation detecting technique can de-noise by means of the characteristics of signal and noise. The photoelectric detector is used to received the laser echo signal with，and the signal with the circuit designed on the basis of correlation detection is dealt with. The experimental results show that the cross-correlation can de-noise and improve SNR while the signal submerged in noise is processed by the circuit, and it fits the laser phase or pulse signal de-noising. In Chapter 3, a new way of phase detector applied to the phase difference measurement is introduced in accordance with the characteristic of phase signal and the theory of inner product. The simulation shows that it can enhance the measurement precision through eliminating the effect that is brought because of the range changing of signal. In Chapter 4, the theory of signal integration is introduced. Based on the theory, a kind of hardware circuit is designed. The simulation shows that the signal noise improved m

ratio is about m(is the integration times).In Chapter 5,the principle and approach to detect weak signal of laser ranging by wavelet transform is introduced, and multi-scale analysis and wavelet threshold de-noising is studied and analyzed detailed. The simulation shows that multi-scale analysis can de-noise effectively. In Chapter 6, the whole dissertation is generalized.

Key words: weak signal detecting correlation detection signal integration wavelet transform