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Research on Resolution of Terahertz Coded-aperture Imaging
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摘要: 太赫兹孔径编码成像综合了光学孔径编码成像和微波关联成像的基本原理，通过孔径编码天线改变目标区域太赫兹波空间幅相分布来实现高分辨、高帧率、前视凝视成像。基于孔径编码天线，该文设计了雷达成像系统和准光扫描光路，可同时实现系统孔径编码和波束扫描功能，理论推导并仿真分析了其成像质量影响因素，并在此基础上比较了不同算法对孔径编码成像分辨性能的影响，证明了稀疏重构类算法对孔径编码成像的优势，最后对比了孔径编码成像和同尺寸阵列实孔径成像的结果，论证出孔径编码成像系统具有高分辨，易于小型化，成本较低等优点。该成像方式可广泛应用于战场侦查、安检反恐和末制导等领域。Abstract: Terahertz coded-aperture imaging follows the basic principles of optical coded-aperture imaging and microwave coincidence imaging and is a novel imaging technique. Herein, the wave spatial distribution or illumination pattern is usually obtained by a sub-reflector antenna. Terahertz coded-aperture imaging has some significant advantages such as a high frame rate, high resolution, and ability of forward-looking and staring imaging. To achieve simultaneous functions of aperture coding and beam scanning, we designed a terahertz coded-aperture imaging system that utilizes digital sub-reflector antenna and quasi-optical techniques. Based on this system, we deduce and simulate the influencing factors on its resolution. Then, different algorithms are applied to the imaging model in order to verify the superiority of sparse reconstruction for coded-aperture imaging. Finally, we compare the imaging results of our imaging system and that of a traditional real aperture imaging structure for the same simulation parameters. The results prove that our imaging system performs better with high resolution, small volume, and low cost. This new imaging technique can be applied to areas such as battlefield reconnaissance, security checks, anti-terrorism, and terminal guidance.
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Key words:
- Terahertz /
- Coded-aperture /
- Staring /
- Forward-looking
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图 5 不同调相范围下的参考信号矩阵空间相关性
Figure 5. Space correlations of the reference signal matrix under different phase modulation ranges
图 6 不同调相范围下的参考信号矩阵时间相关性
Figure 6. Time correlations of the reference signal matrix under different phase modulation ranges
图 7 不同调频系数下的参考信号矩阵空间相关性
Figure 7. Space correlations of the reference signal matrix under different frequency modulation coefficients
图 8 不同时间采样间隔下的参考信号矩阵空间相关性
Figure 8. Space correlations of the reference signal matrix under different time-sampling intervals
图 9 不同采样次数下的参考信号矩阵空间相关性
Figure 9. Space correlations of the reference signal matrix under different sampling times
图 10 不同载频下的参考信号矩阵空间相关性
Figure 10. Space correlations of the reference signal matrix under different carrier frequencies
图 11 不同编码孔径阵元数量下的参考信号矩阵空间相关性
Figure 11. Space correlations of the reference signal matrix under different reflector array-element numbers
图 12 不同编码孔径阵元尺寸下的参考信号矩阵空间相关性
Figure 12. Space correlations of the reference signal matrix under different sizes of coding-aperture element
图 13 不同成像距离下的参考信号矩阵空间相关性
Figure 13. Space correlations of the reference signal matrix under different imaging ranges
图 14 待成像手枪目标及参考信号矩阵的时空非相关性
Figure 14. The imaging target of gun, space and time correlations of the reference signal matrix
图 16 阵列实孔径成像和孔径编码成像对比
Figure 16. The comparisons of real array aperture and coded-aperture imaging
表 1 成像基本参数
Table 1. The basic imaging parameters
参数 取值 孔径编码天线阵元数量 20×20 孔径编码天线阵元边长lh×lv 0.02 m×0.02 m 孔径编码天线边长 0.3 m×0.3 m 信号振幅 A 1 信号中心频率 fc 340 GHz 信号线性调频系数 k 5×1012 随机调相范围 [– ${\rm{{{π}} }}$/2 ${\rm{{{π}} }}$/2] 采样间隔ts 2×10–6 s 采样次数N 2×103 目标中心斜距R 5 m 成像单元尺寸lc×lc 0.01 m×0.01 m 信噪比(SNR) 20 dB 
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表 2 成像时间比较
Table 2. The imaging time comparisons
成像算法 运行时间(s) 匹配滤波法 0.350714 最小二乘法 0.679656 Tikhonov法 1.239225 OMP法 0.850584
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表 3 关键成像参数
Table 3. The key imaging parameters
成像方式 编码孔径阵列
尺寸(m×m)编码孔径阵元数量 载频(GHz) 信噪比(dB) 成像距离(m) 阵列实孔径1 0.4×0.4 40×40 340 20 7 阵列实孔径2 0.4×0.4 400×400 340 20 7 孔径编码 0.4×0.4 40×40 340 20 7
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