基于多重分数阶傅里叶变换ISAR快速成像算法

关于机动目标的逆合成孔径雷达成像技术在诸多应用领域扮演着重要的角色,但其应用一直存在一个严重问题——时变多普勒频率,它会在信号回波中引入高阶相位项,如调频率项,如果不对其进行精确补偿,最终获得的ISAR图像质量会出现明显恶化.针对上述问题,大量算法相继被提出用以实现调频率的估计,但是这些算法往往存在运算量大以及传递误差...

A Fast ISAR Imaging Method Based on Mutiple Fractional Fourier Transform

The inverse synthetic aperture radar(ISAR)imaging of maneuvering rotating targets plays an important role in many applications,but it always faces a serious challenge:the time-varying Doppler frequency,which will induce high-order phase terms,especially chirp rate term,degrading the quality of ISAR images significantly if it cannot be compensated properly.Many algorithms have been proposed to estimate and compensate the chirp rate,however,these methods always suffer from heavy computation burden and considerable error propagation effect.To tackle this problem,we propose a novel ISAR imaging algorithm based on multiple FRFT.The received ISAR signal is modeled as quadratic frequency modulated(QFM)signal first,and the linear term and cubic term can be removed by using coherently integrated generalized cubic phase function(CIGCPF).Then we propose the joint least square fractional Fourier transform(LS-FRFT)method to estimate the chirp rate term independently,which eliminates the effect of propagation error and reduces the computation load.Considering that measurement error and low signal-to-noise ratio(SNR)may degrade the error estimation accuracy,a weighted least square FRFT(WLS-FRFT)method is developed to improve the estimation accuracy and robustness.At last,real test results are presented to validate the proposed method.