REVERSE-RANGE-DOPPLER METHOD FOR AUTOMATED GEOCODING SAR IMAGES

Range-Doppler (RD) method and Reverse-Range-Doppler (RRD) method are combined together to achieve automatic geocoding of Synthetic Aperture Radar (SAR) image quickly and accurately in the paper. The RD method is firstly used to locate the four corners of the image, then the other pixels of the image can be located by Reverse-Range-Doppler (RRD) method. Resampling is performed at last. The approach has an advantage over previous techniques in that it does not require ground control points and is independent of spacecraft attitude knowledge or control. It can compensate the shift due to the assumed Doppler frequency in SAR image preprocessing. RRD simplifies the process of RD, therefore speeds up the computation. The experimental results show that a SAR image can be automated geocoded in 30 s using the single CPU (3 GHz) with 1 G memory and an accuracy of 10 m is attainable with this method.

PRF-ambiguity resolution for SAR by contrast minimization in range-Doppler domain

An algorithm was developed to accurately estimate the Doppler centroid,which is needed for high-quality synthetic aperture radar(SAR)image formation by resolving the SAR pulse repetition frequency(PRF)ambiguity.The algorithm uses the SAR range migration to resolve the PRF-ambiguity by searching for a PRF-ambiguity number that minimizes the intensity contrast in the range-Doppler domain.Experimental results show that the approach,compared with traditional methods for resolving the SAR PRF ambiguity,is more suitable for both high contrast scenes such as urban areas and low contrast scenes such as mountains.Moreover,the approach is more computationally efficient for there are no time-consuming correlations or fast Fourier transform(FFT)operations needed in the range-Doppler domain and only part of the range cells are used in the calculation.

基于卷积调制的SAR有源欺骗干扰方法研究

针对Range-Doppler二维滤波失配导致SAR有源欺骗性假目标一致性差的问题,提出了一种基于卷积调制的SAR有源欺骗干扰新方法:在平台成像模型及其Range-Doppler失配模型的基础上,建立SAR有源欺骗干扰模型,估算失配成像结果对应的动态范围,在欲形成假目标位置的附近,进行失真接近的欺骗信号调制与发射。仿真表明,该方法使得欺骗干扰能量趋于集中,增强了干扰的一致性、欺骗性和可控性。

适于斜视FM-CW SAR系统改进的距离-多普勒算法

"停-走"模式是目前脉冲SAR信号处理和理论分析的基础,FM-CW SAR由于其大的脉冲重复周期和100%的占空比,恶化了接收脉冲的畸变。文中分析了当天线斜视角增大时,导致传统距离-多普勒算法性能下降的主要误差来源,对FM-CW SAR的信号处理问题进行深入研究,提出了改进的适合斜视FM-CW SAR大扫频周期的距离-多普勒算法。通过理论推导及仿真实验,验证了改进模型和算法的可行性与正确性。

Velocity compensation methods for LPRF modulated frequency stepped-frequency(MFSF) radar

In the high speed target environment,there exists serious Doppler effect in the low pulse repetition frequency（LPRF） modulated frequency stepped frequency（MFSF） radar signal.The velocity range of the target is large and the velocity is high ambiguous,so the single method is difficult to satisfy the velocity measurement requirement.For this problem,a novel method is presented,it is a combination of cross-correlation inner frame velocity measurement and range-Doppler coupling velocity measurement.The cross-correlation inner frame method,overcoming the low Doppler tolerance of the cross-correlation between frames,can obtain the coarse velocity of the high speed target,and then the precision velocity can be obtained with the range-Doppler coupling method.The simulation results confirm the method is effective,and also it is well real-time and easy to the project application.

STUDY ON RD ALGORITHM USED IN SQUINT MODE AIRBORNE SAR PROCESSING

This paper studies two range-Doppler (RD) algorithms for the azimuth correlation in the squint mode airborne synthetic aperture radar (SAR). The modeling of squint mode airborne SAR spatial geometry and echo response is given. The procedure for the squint mode airborne SAR processing using the two RD algorithms is outlined. The simulation demonstrates that these two RD algorithms are suitable for squint mode airborne SAR when the squint angle is not larger than 20(°).

Ballistic target recognition based on multiple data representations and deep-learning algorithms

Target recognition is a significant part of a Ballistic Missile Defense System(BMDS).However,most existing ballistic target recognition methods overlook the impact of data representation on recognition outcomes.This paper focuses on systematically investigating the influences of three novel data representations in the Range-Doppler(RD)domain.Initially,the Radar Cross Section(RCS)and micro-Doppler(m-D)characteristics of a cone-shaped ballistic target are analyzed.Then,three different data representations are proposed:RD data,RD sequence tensor data,and RD trajectory data.To accommodate various data inputs,deep-learning models are designed,including a two-Dimensional Residual Dense Network(2D RDN),a three-Dimensional Residual Dense Network-Gated Recurrent Unit(3D RDN-GRU),and a Dynamic Trajectory Recognition Network(DTRN).Finally,an Electromagnetic(EM)computation dataset is collected to verify the performances of the networks.A broad range of experimental results demonstrates the effectiveness of the proposed framework.Moreover,several key parameters of the proposed networks and datasets are extensively studied in this research.

Study of SAR imaging with COMPASS signal

A concept of space-surface bistatic synthetic aperture radar (SS-BSAR) passive imaging system is proposed,which is parasitic on the signal of COMPASS Navigation Satellite System (CNSS).The feasibility is demonstrated by analyzing the signal ambiguity function and the range resolution as well as the system topology.Due to the multiple peaks of signal in the auto-correlation function,a new correlation is used to remove the side-peaks.A double-channel receiver is employed to receive the direct satellite signal and the ground reflected signal.The direct signal is a reference signal in range compression,and may also be used for transmitter-receiver signal synchronization.The reflected signal is raw data collected for imaging.Then,a modified range-Doppler imaging algorithm is derived based on the system geometric models and BSAR imaging principle.The proposed algorithm is verified via signal simulation.The work in this paper is of great value to the further use of COMPASS signal,as well as other global navigation satellite signals in passive imaging.

Synthetic UWB Range Profile Using SFPTs and Class MUSIC for High-resolution Velocity Estimation

A method, called class multiple signal classification （CMUSIC）, is proposed to estimate high-resolution radial velocity in each pulse train （subband, i.e. narrowband） with M pulses based on stepped frequency pulse trains （SFPTs） signal. A synthetic ultra-wideband （UWB） high-resolution range profile （HRRP） is then obtained by fast Fourier transform （FFT） processing along the subbands after compensating the range-Doppler coupling and Doppler dispersion with the estimated velocity. Compared with the other methods, CMUSIC has fine performance of velocity estimation at low signal-to-noise ratio （SNR） level. This method also has excellent performance with small Mas long as the requirement, i.e. Mis large than Q, is able to be fulfilled, where Q is the number of targets with different radial velocities. In addition, through a radial velocity resolving, the method can be well suitable for targets moving at high radial velocities, which has significant practical value with considerable progress made in the national defence technology and the advanced vehicles moving at high speed springing up. Simulation results demonstrate the feasibility and effectiveness of the method.

Doppler ambiguity analysis and suppression for LTE-based passive bistatic radars

In this study,we provide a detailed analysis of the frequency division duplex long term evolution downlink(FDD LTE DL)signal for passive bistatic radars that use the signal as an illuminator of opportunity.In particular,we analyze the crossambiguity function and illustrate its undesired deterministic peaks in the Doppler dimension due to the specific structure of the FDD LTE DL signal.A new adaptive mismatched filtering method is proposed for pre-processing the original reference signal to suppress these undesired deterministic peaks in the range-Doppler processing.The effectiveness of our proposed method is demonstrated via simulations following robustness analysis,showing that all undesired peaks are suppressed below-40 dB,with only 1.7 dB reduction in the main peak.