线性调频相干激光探测技术仿真分析及实验研究

发布时间：2018-05-14 14:23

本文选题：激光雷达 + 相干探测　；参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：随着社会的发展,小型飞行器在军用及民用领域扮演着越来越重要的角色,如果能够研制出小型化、远距离探测、高分辨率的激光雷达将会进一步推动小型飞行器的发展。本文研究方案为对长脉冲激光进行强度线性调频,接收端采用相干探测,采集后的信号进行脉冲压缩处理。从仿真分析和实验验证两方面对该方案同时增加探测距离和提高距离分辨率进行了初步验证。首先,在对比分析国内外各科研机构在相干激光雷达及激光雷达波形调制方面研究成果的基础上,对线性调频信号的频谱和时频谱、匹配滤波的调制带宽与脉冲压缩宽度及抗噪声能力进行了仿真分析;讨论了应用匹配滤波方法时如何计算距离及由此导致的误差;根据相干探测基本理论,对幅度线性调频激光信号的相干探测进行了理论推导。其次,为了解决在进行多目标探测时采用匹配滤波进行脉冲压缩会造成强反射物体距离旁瓣太高而引起临近弱目标无法识别的问题,对不同压缩比信号使用7种不同窗函数,详细讨论了探测目标的主旁瓣比及脉冲压缩宽度;对不同回波强度的多目标分别采用匹配滤波,加窗处理,基于LS的脉冲压缩和基于RMMSE的自适应脉冲压缩进行信号处理,并从不同角度分析了这4种方法的优缺点。最后,搭建实验装置,对线性调频相干激光探测技术进行实验验证。实验结果显示调制带宽为5 MHz,脉冲宽度为500μs的发射信号,经过相干探测及匹配滤波后信号的主旁瓣比为12.71 dB,脉冲压缩后的宽度为183.2 ns,脉冲压缩比为2729。证实了采用线性调频强度调制信号进行脉冲压缩,采用相干探测进行接收能够提高距离分辨率。
[Abstract]:With the development of society, small aircraft play an increasingly important role in military and civil fields. If miniaturization, long-range detection and high-resolution lidar can be developed, the development of small aircraft will be further promoted. The scheme of this paper is to carry out intensity linear frequency modulation (LFM) of long pulse laser. Coherent detection is used at the receiving end and the collected signal is processed by pulse compression. Both simulation analysis and experimental verification are used to verify the proposed scheme, which increases both the detection range and the range resolution. First of all, on the basis of comparing and analyzing the research results of coherent lidar and laser radar waveform modulation, the frequency spectrum and time spectrum of LFM signal are analyzed. The modulation bandwidth, pulse compression width and anti-noise ability of matched filtering are simulated and analyzed, and how to calculate the distance and the resulting errors when applying the matched filtering method is discussed. The coherent detection of amplitude LFM laser signal is theoretically deduced. Secondly, in order to solve the problem that pulse compression by using matched filter in multi-target detection will cause the high distance sidelobe of strong reflected object and lead to unrecognizable near weak target, seven different window functions are used for signals with different compression ratios. The main sidelobe ratio and pulse compression width of the detected target are discussed in detail, and the matched filter, windowed processing, LS based pulse compression and adaptive pulse compression based on RMMSE are used to process the signal for the multiple targets with different echo intensity. The advantages and disadvantages of these four methods are analyzed from different angles. Finally, an experimental device is built to verify the LFM coherent laser detection technology. The experimental results show that the modulation bandwidth is 5 MHz and the pulse width is 500 渭 s. After coherent detection and matched filtering, the main sidelobe ratio of the signal is 12.71 dB, the width of pulse compression is 183.2 ns, and the pulse compression ratio is 2729. It is proved that the range resolution can be improved by pulse compression using LFM signal and receiving by coherent detection.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN957.51

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