基于FPGA的船只目标ISAR实时重聚焦处理实现

Real-time realization of ISAR refocusing of ship target based on FPGA

针对合成孔径雷达在船只目标成像过程中所出现的散焦问题,文中对现有算法进行优化处理,给出一种可用于FPGA实时处理系统的ISAR重聚焦算法。该算法基于逆合成孔径雷达成像原理对散焦目标进行重聚焦处理,可以极大改善成像质量。算法包括两部分,采用积累互相关法进行距离向包络对齐,结合相位梯度自聚焦算法与秩一相位估计算法对方位向散焦误差进行补偿。该算法通过硬件描述语言在FPGA上实现,其中复杂度较高的算法模块采用HLS设计优化实现。系统在单片FPGA上实现,实际SAR图像数据测试结果表明,所提出的FPGA实时重聚焦处理算法结合实际硬件,可在满足给定实时性指标要求的条件下,对散焦船只目标进行实时重聚焦处理,得到良好的聚焦效果。

Aiming at the defocusing problem of synthetic aperture radar in the process of ship target imaging,this paper optimizes the existing algorithms and provides an ISAR refocusing algorithm that can be used in FPGA real-time processing systems.This algorithm refocuses defocused targets based on the principle of inverse synthetic aperture radar imaging,which can greatly improve the imaging quality.The algorithm consists of two parts.The cumulative cross-correlation method is used to align the range envelope,and the phase gradient autofocus algorithm and the rank one phase estimation algorithm are combined to compensate for the orientation defocus error.The algorithm is implemented on FPGA through a hardware description language,and the more complex algorithm modules are implemented by HLS design optimization.The system is implemented on a single FPGA,and the actual SAR image data test results show that the proposed FPGA real-time refocus processing algorithm combined with actual hardware can refocus defocused ship targets in real time under the condition of meeting the requirements of given real-time performance indicators.And the focusing effect is good.