双基雷达系统因其拥有较好的隐蔽性、抗干扰性、灵活性而应用广泛。舰船目标由于受海情影响存在三维运动,瞬时投影平面容易反复叠加,使图像出现严重散焦,大大降低成像分辨率,因此选取最优的成像时间段成为逆合成孔径雷达(ISAR)成像研究领域的热门话题。在双基几何构型下,文中结合图像对比度评判指标,提出一种基于短时分数阶傅里叶变换(FrFT)时频分析的成像时间段选取方法,获得在不同阶次下的时频分析曲线信息,利用估计频率分布的概率密度函数(PDF)选取多普勒频率较平稳的连续时间段,通过最大化图像对比度确定阶次与成像时间段,自适应地获得最佳的成像结果。该方法为最优成像时刻与时间长度的选取提供解决方案,仿真实验结果论证了该成像方法的有效性。

Bistatic radar system has good concealment, anti-interference and flexibility, and is widely used. The ship target has three-dimensional motion due to the influence of sea conditions, the instantaneous projection plane is easy to be repeatedly superimposed, resulting in serious defocus of the image and greatly reducing the imaging resolution. Therefore, selecting the optimal imaging time period has become a hot topic in the field of inverse synthetic aperture radar (ISAR) imaging research. In this paper, a method of selecting the imaging time period based on short-time Fractional Fourier transform (FrFT) time-frequency analysis is proposed in combination with the image contrast evaluation index under the bistatic geometry. The time-frequency analysis curve information of different orders is obtained. The probability density function (PDF) of the estimated frequency distribution is used to select the continuous time period with relatively stable Doppler frequency. The order and imaging time period are determined by maximizing the image contrast, and the best imaging results are obtained adaptively. This method provides a solution for selecting the optimal imaging moment and time duration. Simulation results demonstrate the effectiveness of this imaging method.

TN957. 51