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摘要:
信号检测是激光多普勒测速(LDV)系统实现高精度的关键技术，针对LDV中微弱多普勒信号的检测，本文从噪声在频域中的统计特性出发，对多普勒信号进行带阻滤波，结合雷达的恒虚警(CFAR)检测技术，设计了基于频域的单元平方和自适应阈值检测算法以解决在低信噪比(SNR)的环境中LDV的信号检测问题，提高LDV的信号探测能力，同时降低其虚警概率。仿真与实验的结果表明：该算法与固定阈值相比可以在SNR为-12 dB时实现信号的完全检测，保持低虚警概率，运算简单，工程适用性强。
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关键词:
- 激光多普勒测速(LDV)系统 /
- 频域信号检测 /
- 恒虚警(CFAR) /
- 低信噪比(SNR) /
- 自适应阈值
Abstract:Signal detection is the key technology for the high precision of laser Doppler velocimetry (LDV) system. In order to achieve the accurate detection of the weak Doppler signal in LDV, we carried out a band-stop filtering toward the Doppler signal on the ground of the statistical characteristics of the noise in frequency domain. Combined with the constant false alarm rate (CFAR) detection technology of radar, an algorithm of adaptive threshold detection based on the sum of unit square in frequency domain is proposed so as to address the difficulty in signal detection within the atmosphere of low signal noise ratio (SNR), improving the detection performance and decreasing the probability of false alarm. Compared with the fixed threshold through simulations and experiments, this algorithm boasts the advantage of complete detection under the circumstance of SNR -12 dB while maintaining a relatively lower false alarm rate and simple operation as well as great applicability.
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图 2 不同参考单元数下检测概率随信噪比变化
Figure 2. Variation of detection probability with SNR under different reference cells
图 4 不同虚警概率下检测概率随信噪比变化
Figure 4. Variation of detection probability with SNR under different false alarm probabilities
图 6 固定阈值及自适应阈值虚警概率实验结果
Figure 6. Experimental results of false alarm probability of fixed threshold and adaptive threshold
图 7 固定阈值及自适应阈值检测概率实验结果
Figure 7. Experimental results of detection probability of fixed threshold and adaptive threshold
表 1 仿真参数
Table 1. Simulation parameters
参数 数值 采样频率/Hz 1000 信噪比/dB -30~0 噪声功率/W 0~25 信号频率/Hz 200 滤波器带宽 0.2 
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表 2 实验参数
Table 2. Experimental parameters
参数 数值 波长/nm 1550 采样频率/MHz 10 采样点数 1000 光斑面积/mm2 19.6 入射角/rad π/3 滤波器带宽 0.2
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