合成孔径激光成像雷达啁啾非线性的测量和抑制

Measurement and Overcoming of Nonlinear Chirp in Synthetic Aperture Imaging Ladar

合成孔径激光成像雷达系统中可调谐激光器的非线性啁啾,引起回波信号傅里叶频谱的展宽和相位的误差,影响距离向和方位向分辨率。实际测量了激光器的频率非线性,利用光纤法布里-珀罗干涉仪,测量激光器频率随时间的变化,得到高阶非线性项,给出了实验结果。以此为依据,研究了点目标回波外差信号的傅里叶频谱。通过改变分析信号的时间采样窗口宽度,压缩频谱宽度和相位误差,降低了非线性影响。在保证相位精度π/4时,得到了优化的时间采样窗口宽度。

The nonlinear chirp of tunable laser in synthetic aperture imaging ladar （SAIL） can degrade the range resolution and influence the azimuth resolution. The polynomial nonlinear coefficients of laser frequency changed with time are measured by a fiber Fabry-Perot interferometer. The results of experiment are presented. Based on the data the Fourier frequency spectrum of the point target is discussed on the condition of the different frequency linearity. The spectral width and phase errors are reduced through changing the sampling pulse width. It is one method to compensate the degradation of resolution. The optimized sampling pulse width is derived at the phase error better than π/4 corresponding to the optical diffraction limit.