The traditional Range Doppler(RD)algorithm is unable to meet practical needs owing to the limit of resolution.The order of fractional Fourier Transform(FrFT)and the length of sampling signals affect SAR imaging perfor...The traditional Range Doppler(RD)algorithm is unable to meet practical needs owing to the limit of resolution.The order of fractional Fourier Transform(FrFT)and the length of sampling signals affect SAR imaging performance when FrFT is applied to RD algorithm.To overcome the above shortcomings,the purpose of this paper is to propose a high-resolution SAR image algorithm by using the optimal order of FrFT and the sample length constraints for the range direction.The expression of the optimal order of SAR range signals via FrFT is deduced in detail.The initial sample length and its constraints are proposed to obtain the best sample length of SAR range signals.Experimental results demonstrate that,when the range sampling-length changes in a certain interval,the best sampling-length will be obtained,which the best values of the range resolution,PSLR and ISLR,will be derived respectively.Compared with traditional RD algorithm,the main-lobe width of the peak-point target of the proposed algorithm is narrow in the range direction.While the peak amplitude of the first side-lobe is reduced significantly,those of other side-lobes also drop in various degrees.展开更多
在雷达目标跟踪领域,当目标与雷达传感器存在相对运动时,多普勒(Doppler)效应致使接收信号产生频率偏移。这种频率变化与目标距离测量存在耦合关系,即多普勒距离耦合问题。在相控阵雷达采用线性调频(Linear Frequency Modulation,LFM)...在雷达目标跟踪领域,当目标与雷达传感器存在相对运动时,多普勒(Doppler)效应致使接收信号产生频率偏移。这种频率变化与目标距离测量存在耦合关系,即多普勒距离耦合问题。在相控阵雷达采用线性调频(Linear Frequency Modulation,LFM)信号进行常规跟踪时,虽然能获取大时宽带宽积提升距离分辨率,但脉冲压缩后产生的强距离多普勒耦合效应使传统的距离速度测量算法出现收敛速度慢、精度低的问题,尤其在航迹起始阶段对高速目标的跟踪极为不利,严重影响了雷达系统对目标的实时、精准监测。提出一种多普勒距离耦合下的三帧快速收敛算法。该算法利用3帧具有不同耦合系数的波形,构建多元约束方程,通过联合解算实现多目标速度和位置参数的同步获取。在验证处理流程中,采用迭代优化机制,对测量结果进行动态校准,有效降低距离与速度参数间的相互干扰,逐步逼近最优的距离和速度测量结果,从而实现快速、精准的目标跟踪。通过理论分析、蒙特卡罗仿真和外场实测数据验证,该三帧快速收敛算法展现出优异性能。在航迹起始阶段,对目标距离和速度测量解算的收敛速度是传统算法的4倍以上。所提出的多普勒距离耦合下的三帧快速收敛算法成功地解决了传统算法在处理多普勒距离耦合问题时存在的收敛慢、精度低等难题。该算法具有创新的波形设计和迭代优化策略,显著提升了相控阵雷达在复杂条件下的目标跟踪性能,为雷达目标跟踪技术的发展提供了新的思路和方法,具有较高的理论价值和实际应用前景。展开更多
To address the low-resolution imaging problem in relation to traditional Range Doppler(RD)algorithm,this paper intends to propose a new algorithm based on Fractional Fourier Transform(FrFT),which proves highly advanta...To address the low-resolution imaging problem in relation to traditional Range Doppler(RD)algorithm,this paper intends to propose a new algorithm based on Fractional Fourier Transform(FrFT),which proves highly advantageous in the acquisition of high-resolution Synthetic Aperture Radar(SAR)images.The expression of the optimal order of SAR range signals using FrFT is deduced in detail,and the corresponding expression of the azimuth signal is also given.Theoretical analysis shows that,the optimal order in range(azimuth)direction,which turns out to be very unique,depends on the known imaging parameters of SAR,therefore the engineering practicability of FrFT-RD algorithm can be greatly improved without the need of order iteration.The FrFT-RD algorithm is established after an analysis of the optimal time-frequency transform.Experimental results demonstrate that,compared with traditional RD algorithm,the main-lobe width of the peak-point target of FrFT-RD algorithm is narrow in both range and azimuth directions.While the peak amplitude of the first side-lobe is reduced significantly,those of other side-lobes also drop in various degrees.In this way,the imaging resolution of range and azimuth can be increased considerably.展开更多
Instantaneous Doppler frequency for squint SAR imaging has been found with ChirpScaling Algorithm (CSA). Because the azimuth sample is not perpendicular to the range sample,the range signal must impact on the azimuth ...Instantaneous Doppler frequency for squint SAR imaging has been found with ChirpScaling Algorithm (CSA). Because the azimuth sample is not perpendicular to the range sample,the range signal must impact on the azimuth signal in the squint SAR data processing, andthe different slant range targets have different Doppler frequencies. From the mathematicalmodel of SAR echo signal, this paper carefully analyzes the instantaneous azimuth frequency, theinstantaneous Doppler frequency component of the azimuth frequency and the impact of rangechirp on azimuth frequency, which explains that Doppler frequency should be properly selected forcorrect SAR imaging in the squint SAR. The results of point target simulation experiments showthat the way is reasonable for the squint SAR and can effectively complete range compressionand azimuth focusing, and improve images' quality.展开更多
基金This work is supported by the 13th Five-Year Plan for Jiangsu Education Science(D/2020/01/22)JSPIGKZ and Natural Science Research Projects of Colleges and Universities in Jiangsu Province(19KJB510022)。
文摘The traditional Range Doppler(RD)algorithm is unable to meet practical needs owing to the limit of resolution.The order of fractional Fourier Transform(FrFT)and the length of sampling signals affect SAR imaging performance when FrFT is applied to RD algorithm.To overcome the above shortcomings,the purpose of this paper is to propose a high-resolution SAR image algorithm by using the optimal order of FrFT and the sample length constraints for the range direction.The expression of the optimal order of SAR range signals via FrFT is deduced in detail.The initial sample length and its constraints are proposed to obtain the best sample length of SAR range signals.Experimental results demonstrate that,when the range sampling-length changes in a certain interval,the best sampling-length will be obtained,which the best values of the range resolution,PSLR and ISLR,will be derived respectively.Compared with traditional RD algorithm,the main-lobe width of the peak-point target of the proposed algorithm is narrow in the range direction.While the peak amplitude of the first side-lobe is reduced significantly,those of other side-lobes also drop in various degrees.
文摘在雷达目标跟踪领域,当目标与雷达传感器存在相对运动时,多普勒(Doppler)效应致使接收信号产生频率偏移。这种频率变化与目标距离测量存在耦合关系,即多普勒距离耦合问题。在相控阵雷达采用线性调频(Linear Frequency Modulation,LFM)信号进行常规跟踪时,虽然能获取大时宽带宽积提升距离分辨率,但脉冲压缩后产生的强距离多普勒耦合效应使传统的距离速度测量算法出现收敛速度慢、精度低的问题,尤其在航迹起始阶段对高速目标的跟踪极为不利,严重影响了雷达系统对目标的实时、精准监测。提出一种多普勒距离耦合下的三帧快速收敛算法。该算法利用3帧具有不同耦合系数的波形,构建多元约束方程,通过联合解算实现多目标速度和位置参数的同步获取。在验证处理流程中,采用迭代优化机制,对测量结果进行动态校准,有效降低距离与速度参数间的相互干扰,逐步逼近最优的距离和速度测量结果,从而实现快速、精准的目标跟踪。通过理论分析、蒙特卡罗仿真和外场实测数据验证,该三帧快速收敛算法展现出优异性能。在航迹起始阶段,对目标距离和速度测量解算的收敛速度是传统算法的4倍以上。所提出的多普勒距离耦合下的三帧快速收敛算法成功地解决了传统算法在处理多普勒距离耦合问题时存在的收敛慢、精度低等难题。该算法具有创新的波形设计和迭代优化策略,显著提升了相控阵雷达在复杂条件下的目标跟踪性能,为雷达目标跟踪技术的发展提供了新的思路和方法,具有较高的理论价值和实际应用前景。
基金supported by the 13th Five-Year Plan for Jiangsu Education Science(D/2020/01/22)JSPIGKZ(JSPI19GKZL405)Natural Science Research Projects of Colleges and Universities in Jiangsu Province(19KJB510022).
文摘To address the low-resolution imaging problem in relation to traditional Range Doppler(RD)algorithm,this paper intends to propose a new algorithm based on Fractional Fourier Transform(FrFT),which proves highly advantageous in the acquisition of high-resolution Synthetic Aperture Radar(SAR)images.The expression of the optimal order of SAR range signals using FrFT is deduced in detail,and the corresponding expression of the azimuth signal is also given.Theoretical analysis shows that,the optimal order in range(azimuth)direction,which turns out to be very unique,depends on the known imaging parameters of SAR,therefore the engineering practicability of FrFT-RD algorithm can be greatly improved without the need of order iteration.The FrFT-RD algorithm is established after an analysis of the optimal time-frequency transform.Experimental results demonstrate that,compared with traditional RD algorithm,the main-lobe width of the peak-point target of FrFT-RD algorithm is narrow in both range and azimuth directions.While the peak amplitude of the first side-lobe is reduced significantly,those of other side-lobes also drop in various degrees.In this way,the imaging resolution of range and azimuth can be increased considerably.
文摘Instantaneous Doppler frequency for squint SAR imaging has been found with ChirpScaling Algorithm (CSA). Because the azimuth sample is not perpendicular to the range sample,the range signal must impact on the azimuth signal in the squint SAR data processing, andthe different slant range targets have different Doppler frequencies. From the mathematicalmodel of SAR echo signal, this paper carefully analyzes the instantaneous azimuth frequency, theinstantaneous Doppler frequency component of the azimuth frequency and the impact of rangechirp on azimuth frequency, which explains that Doppler frequency should be properly selected forcorrect SAR imaging in the squint SAR. The results of point target simulation experiments showthat the way is reasonable for the squint SAR and can effectively complete range compressionand azimuth focusing, and improve images' quality.
