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摘要: 近年来衍射光学系统得到了快速发展,衍射器件(如二元光学器件和膜基透镜)相当于微波天线的固定移相器,微波相控阵天线成熟的理论和方法应可用于其性能分析。激光SAR和激光通信都具有单色且波长较长的特点,特别适合采用非成像衍射光学系统,通过衍射器件实现信号波前控制,减小焦距并有利于系统的轻量化。基于衍射光学系统,研究激光SAR和激光通信技术具有重要的理论意义和应用价值。该文给出了衍射光学系统的相控阵解释,介绍了基于衍射光学系统已开展的机载激光SAR和星载激光SAR研究工作。提出了艇载1 m衍射口径激光通信和干涉定位系统概念并分析了其性能,该系统在10 m短基线下,其作用距离将达到4×108 km,对应的定位精度在6 km量级,可用于深空探测。该文同时探讨了稀疏采样激光成像问题,在激光照射目标条件下,提出用傅里叶透镜将激光图像信号变换到频域,在低频区域利用小规模探测器实施稀疏采样,等效进行2维低通滤波处理,再用计算机重构目标图像的设想,给出了一些初步的仿真结果。Abstract: In recent years, the diffractive optical systems have developed rapidly. Diffractive devices such as binary optical device and membrane-based lens are equivalent to fixed phase shifters of microwave antennas. Thus, the mature theories and methods of a microwave phased-array antenna could be used for diffractive devices’ performance analysis. Both laser Synthetic Aperture Radar (SAR) and laser communication feature a single color and long wavelength, and they are specifically suitable for non-imaging diffractive optical systems. A signal wave front control realized by a diffraction device reduces the focal length and the weight of a system. Research on laser SAR and laser communication technology has important theoretical significance and application value for diffractive optical system. In this paper, we provide a phased-array interpretation of a diffractive optical system and introduce research that has been conducted on airborne and spaceborne laser SAR with respect to diffractive optical systems. We propose the concept of shipborne 1 m diffraction aperture laser communication and an interferometric positioning system and analyze its performance. The results indicated that, using a 10 m short baseline, this system can reach 400 million km with a corresponding positioning accuracy of 6 km that is suitable for use during deep space probes. We also discuss the sparse-sampling laser-imaging problem using a laser to illuminate the target, transforming the laser image signal into the frequency domain with Fourier lens, using the small-scale detector to perform sparse sampling in the low-frequency domain, and reconstructing the target image using a computer. Some preliminary simulation results are provided.
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表 1 激光通信系统参数
Table 1. Parameters of laser telecommunication system
下行参数 数值 上行参数 数值 波长 1.064 μm 波长 1.064 μm 带宽 15 kHz 带宽 15 kHz 探测器发射望远镜口径 0.1 m 艇载发射望远镜口径 1.0 m 艇载接收望远镜口径 1.0 m 探测器接收望远镜口径 0.1 m 探测器激光发射功率 10 W 艇载激光发射功率 15 W 探测器发射光学系统传输效率 0.9 艇载发射光学系统传输效率 0.7 艇载接收光学系统传输效率 0.8 探测器接收光学系统传输效率 0.9 光电探测器量子效率 0.5 光电探测器量子效率 0.5 外差探测效率 0.5 外差探测效率 0.5 光学系统的其他损耗 0.3 光学系统的其他损耗 0.3 电子学噪声系数 2 dB 电子学噪声系数 2 dB 下行数据信噪比 6 dB 上行数据信噪比 6 dB 作用距离 4.08×108 km 作用距离 4.32×108 km -
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