本振信号较差的相干性限制了合成孔径激光雷达(SAL)对远距离目标成像的方位/横向分辨率。研究了SAL信号相干性保持问题, 提出了一种基于本振数字延时的SAL信号相干性保持方法。通过设置本振信号参考通道, 采用自外差探测的方式, 在数字域提取本振信号频率不稳引入的相位, 并将其在数字域延时后对目标回波信号实施相位补偿。建立了激光信号模型, 对所提出的SAL信号相干性保持方法进行了误差分析, 给出了自外差探测中光纤延时长度的选取原则。理论分析和仿真实验表明, 该方法能有效保持SAL信号的相干性。

Poor coherence of local oscillator signal restricts the azimuth/lateral resolution of long-range target imaging with synthetic aperture ladar (SAL). Coherence maintenance problem of SAL signal is studied, and a method for maintaining the coherence of SAL signal based on local oscillator digital delay is proposed. By setting the local oscillator signal reference channel and using the self-heterodyne detection method, the phase introduced by the frequency instability of the local oscillator signal is extracted in the digital domain, which is used to compensate the phase in target echo signal after the delay in the digital domain. The laser signal model is established, and the error analysis of the proposed SAL signal coherence maintenance method is given. The selection principle of the fiber delay length from the self-heterodyne detection is given. Theoretical analysis and simulation experiment show that the proposed method can effectively maintain the coherence of SAL signal.