基于乘积型高阶相位函数的复杂运动目标ISAR成像

在逆合成孔径雷达(inverse synthetic aperture radar, ISAR)成像中,当目标存在非匀速转动甚至是三维转动时,散射点回波中高次相位项造成方位聚焦质量下降,基于目标匀速旋转模型的传统距离〖CD*2〗多普勒(range Doppler, RD)算法已经无法获得目标的清晰图像。提出了一种基于乘积型高阶相位函数(product high order phase function, PHPF)的瞬时成像方法。通过构造不同的乘积型高阶相位函数,并对其进行一维搜索即可得到调频率变化率和调频率值的估计,补偿高次相位后进行快速傅里叶变换(fast Fourier transform, FFT),根据幅度最大的位置估计中心频率和幅度信息,在距离〖CD*2〗频率平面和距离〖CD*2〗调频率平面对目标进行瞬时成像,可以获取更多的目标信息。最后,实测数据成像结果验证了该方法的有效性。

ISAR imaging of complexly moving targets based on product high-order phase function

In inverse synthetic aperture radar (ISAR) imaging, when targets have nonuniform rotation even three dimensional rotation, the high order phase term which influences azimuth focusing badly can not be neglected. In this condition, the range Doppler (RD) algorithm is not a very effective way for ISAR imaging. A new imaging method based on product high order phase function (PHPF) is presented. By searching the position of maximum magnitude of PHPF, the chirp rate and quadratic chip rate are gotten. Furthermore, fast Fourier transform (FFT) is performed after compensating the high order phase term to acquire the information about the center frequency and magnitude of these scatters according to the criterion of maximum magnitude. Thus the high quality range instantaneous Doppler (RID) and range instantaneous chirp rate (RIC) ISAR images of the target are obtained, so more information of targets can be gotten. Finally, the imaging results of real data prove the effectiveness of the proposed method.