摘要
星载合成孔径雷达(Synthetic Aperture Radar,SAR)在轨成像技术是灾害检测、军事侦察等高时效遥感应用场景的关键手段,以现场可编程门阵列(Field-Programmable Gate Array,FPGA)+数字信号处理器(Digital Signal Processing/Processor,DSP)为处理核心是一种搭建星载SAR在轨成像系统的典型方案,在异构算力、能效比、灵活度等方面综合评价良好。但现有的FPGA+DSP系统在算法支持、大粒度处理、片上并行加速、复杂矩阵转置方面仍研究不足,成像性能仍然有较大提升空间。本文对支持大斜视、高分辨成像的非线性调频变标算法(Nonlinear Chirp Scaling Algorithm,NCS)算法进行分析,根据运算复杂度和类型将算法划分为主流程和辅助路程,以此为依据提出NCS算法在FPGA+DSP系统中的异构映射方案;针对多通道快速傅里叶变换(Fast Fourier Transform,FFT)处理后数据存储形式发生变换、难以流水处理的问题,提出基于时频抽取切换的多通道FFT协同处理方法,保证多通道FFT处理高效进行;针对不同粒度、不同并行度场景下转置需求复杂多变的问题,提出基于X-直接存储器访问(X-Direct Memory Access,XDMA)+片上分割转置的通用交叉转置方案。本文采用2片VX690T FPGA和2片FT6678 DSP为核心处理器研制了星载SAR成像板卡,实现了提出的系统设计方案。同时,本文搭建了基于模拟源+地检的验证环境,对条带/扫描/聚束/滑聚/TOPS模式的仿真点阵数据和条带/滑聚模式的实测数据进行处理。点阵数据的二维峰值旁瓣比约为-13.2 dB,二维积分旁瓣比约为-10.1 dB,成像质量良好;以条带模式为例,图像尺寸为32K×16K,基于NCS算法的平均成像时间为7.81 s,成像速度较现有方案大幅提升。
On-board Synthetic Aperture Radar(SAR)imaging technology is a key tool for time-sensitive remote sensing applications such as disaster monitoring and military reconnaissance.The typical construction of an on-board SAR imaging system using a Field-Programmable Gate Array(FPGA)coupled with a Digital Signal Processor(DSP)as the processing core is well-regarded for its heterogeneous computing power,energy efficiency,and flexibility.However,current FPGA+DSP systems are still under-researched in terms of algorithm support,large-grain processing,on-chip parallel acceleration,and complex matrix transposition,with significant room for performance enhancement.This paper analyses the Nonlinear Chirp Scaling(NCS)algorithm,suitable for large squint,high-resolution imaging,and partitions the algorithm into main and auxiliary paths based on computational complexity and type.A heterogeneous mapping scheme for the NCS algorithm within the FPGA+DSP system is subsequently proposed.To address the transformation of data storage formats post multi-channel Fast Fourier Transform(FFT)processing,which complicates pipelined processing,this work introduces a multi-channel FFT collaborative method based on time-frequency extraction switching to ensure efficient parallel FFT operations.Additionally,to handle the complexity of transpose requirements across various granularities and parallelisms,a universal cross transpose solution using X-Direct Memory Access(XDMA)and onchip segmented transposition is developed.Employing two VX690T FPGAs and two FT 6678 DSPs as core processors,this paper presents the development of an on-board SAR imaging card that implements the proposed system design.Moreover,a validation environment using simulated sources plus ground testing is established,processing simulation array data for strip/scan/spotlight/sliding spotlight/TOPS modes and actual data for strip/sliding spotlight modes.The array data demonstrates a two-dimensional peak sidelobe ratio of about−13.2 dB and an integrated sidelobe ratio of around−10.
作者
陈亮
李涌睿
丁杰
徐明
张至涵
张傲
谢宜壮
CHEN Liang;LI Yongrui;DING Jie;XU Ming;ZHANG Zhihan;ZHANG Ao;XIE Yizhuang(Radar Technology Research Institute,Beijing Institute of Technology,Beijing 100081,China;Beijing Key Laboratory of Embedded Real-time Information Processing Technology,Beijing 100081,China;Beijing Racobit Electronic Information Technology Co.,Ltd.,Beijing 100097,China)
出处
《信号处理》
CSCD
北大核心
2024年第1期138-151,共14页
Journal of Signal Processing
基金
国家重点研发计划项目(2021YFA0715204)。
关键词
星载合成孔径雷达
在轨成像
快速傅里叶变换
转置
spaceborn synthetic aperture radar
on-board imaging
fast Fourier transform
transpose
