针对大动态范围下运动目标速度测量受限的问题，提出四光相干混频探测方法，通过提取多普勒频率以及移频量与多普勒差频可以实现更大动态范围的速度测量。在四光相干混频探测过程中，存在输出信号多和信号判别难度大的问题。为了解决以上问题，提出并设计空间偏振分光结构的四光相干混频探测结构，使用偏振分光技术实现四路输出信号的完全空间分离，可以避免信号之间的相互影响，降低信号处理的难度。从理论上对结构进行原理分析，并使用光学仿真软件对其进行仿真分析，验证理论和结构的可行性，同时可根据不同探测器输出信号判断目标的运动方向。

Aiming at the problem of limited speed measurement of moving targets in a large dynamic range， a four-light coherent mixing detection method is proposed. By extracting the Doppler frequency and the difference frequency between frequency shift and Doppler frequency， the speed measurement with a larger dynamic range can be achieved. In the process of four-optical coherent mixing detection， there are many output signals and the problem of difficult signal discrimination. In order to solve the above problems， a four-light coherent mixing detection structure with spatial polarization splitting structure is proposed and designed. Polarization splitting technology is used to achieve complete spatial separation of four output signals， avoiding mutual influence between signals and reducing the difficulty of signal processing. In theory， the structure is analyzed in principle， and the optical simulation software is used to simulate and analyze it to verify the feasibility of the theory and structure. At the same time， the direction of the target movement can be judged according to the output signals of different detectors.