SPACE-TIME ADAPTIVE PROCESSING FOR AIRBORNE RADAR:A CONVENIENT IMPLEMENTATION APPROACH

A convenient implementation approach to space-time adaptive processing for airborne radar has been proposed, which is added by some auxiliary array elements in the area of main-lobe clutter on the basis of 2-D Capon approach . It is of practical use for its small computational load. This approach possesses the ideal performance in the area of main-lobe clutter . In addition, the approach which is added by some auxiliary beams in the area of main-lobe clutter has also been discussed.

A NEW METHOD TO COMPENSATE CLUTTER RANGE DEPENDENCE FOR FORWARD LOOKING AIRBORNE RADARS

The clutter direction-Doppler curves are not aligned on the near range bins for forward looking airborne radar. As a result, the performance of clutter suppression by Space-Time Adaptive Processing (STAP) degrades greatly because of the clutter range dependence. To deal with this problem, a new compensated method is proposed in this paper. The method rebuilds the clutter covariance matrix based on spatial high resolution Minimum Variance Distortionless Response (MVDR) spectrum, and then finds a matrix to transform the covariance matrix of short-range gate to the referred far-range gate. The method can compensate the clutter range dependence well. The simulation results show validity of the method.

AN APPROACH TO SUPPRESS SHORT-RANGE CLUTTER FOR NON-SIDE LOOKING AIRBORNE RADAR

When the Airborne Early Warning(AEW) radar transmits medial or high Pulse Repetitive Frequency(PRF) signal,the range ambiguity occurs.The clutter of short-range clutter has serious range dependence problem for non-Side Looking Airborne Radar(non-SLAR).As a result,the clutter plus noise covariance matrix can not be estimated correctly,and the performance of clutter suppression obtained by Space-Time Adaptive Processing(STAP) degrades greatly.The uniform linear array has not elevation degrees;therefore,the short-range clutter can not be suppressed directly.A short-range clutter suppression method is proposed.The method first estimate the elevation angles of the ambiguous short-range gate,then eliminates short-range clutter by space time interpolation and adds moving target protection in the procedure.This method can suppress the short-range clutter well.Simulation results show the validity of the method.

IMPROVED DOPPLER WARPING METHOD FOR AIRBORNE RADAR WITH NON-SIDELOOKING ARRAY

Traditional range-dependency compensation space time adaptive processing(STAP)methods usually involve aligning the clutter spectrums in a certain point to reduce the clutter non-homogeneity.A novel compensation STAP method is proposed as an improved Doppler warping(DW)method for airborne radar with non-sidelooking radar.This method facilitates DW method to bring clutter spectrum of different range gates together in the mainlobe and subsequently compensation to accomplish space angle of different range gates alignment at multiple Doppler bins.Simulation results show that the proposed method can further reduce the clutter non-homogeneity of non-sidelooking array and significantly outperform traditional algorithms with only a little increase of the computation load.

A framework of rank-reduced space-time adaptive processing for airborne radar and its applications

A new equivalent formulation of the joint domain space-time optimum processor for airborne phased array radar application is derived. Then a new framework of space-time adaptive processing (STAP) for airborne radar systems which includes most of suboptimum algorithms in the literature is proposed. The performance of two typical rank-reduced time-space joint-domain processors based on Doppler pre-filtering is analyzed in detail based on the proposed framework.

Range walk and array rotation in space-time adaptive processing:effects and compensations

This paper proposes a unified clutter model incorporating the effects of range walk and array rotation for space-time adaptive processing（STAP） in airborne multi-channel early-warning radar.Based on this clutter model,STAP performance is then analyzed from the perspective of covariance matrix tapering（CMT）.For STAP performance degradation due to array rotation,a determinate compensation method is proposed based on the CMT method.Numerical examples are provided to verify the analysis and the proposed compensation method.

ON CLUTTER DOF FOR PHASED ARRAY AIRBORNE EARLY ARNING RADARS

In recent years,considerable attention has been paid to adaptive clutter suppressionfor airborne early warning(AEW)radars.A necessary condition for efficient clutter suppressionis that the number of adaptive degrees of freedom(DOF)is no less than that of clutter DOF.This paper analyzes the DOF of clutter for phased array AEW radars.The new results obtainedhere are helpful to design an adaptive system for clutter suppression.

基于KA-SRCN-pSTAP的低空风切变风速估计方法

针对由于独立同分布(IID)样本严重不足,导致极化空时自适应(pSTAP)处理性能下降,进而导致低空风切变风速估计不准确的问题,本文提出了一种基于知识辅助的稀疏表示杂波零陷极化空时自适应(KA-SRCN-pSTAP)的低空风切变风速估计方法。该方法首先利用杂波脊的先验知识辅助构造极化空时稀疏字典,然后利用极化空时稀疏字典,通过SRCN算法挑选原子并对到杂波线性子空间补空间上的投影矩阵进行估计,从而得到pSTAP权矢量,最后构造pSTAP滤波器对地杂波进行抑制,准确估计低空风切变风速。该方法仅使用少量IID样本,将SRCN算法与极化-空时域相结合,完成对风切变风速的有效估计。仿真实验结果证明该方法可以有效实现少样本情况下的风速准确估计。

基于波束对消的车辆运动地物杂波抑制方法

针对在快速运动车辆载体上雷达目标检测中强地物杂波的抑制问题,借鉴机载雷达空时处理原理,分析了车辆运动地物杂波分布特性,探讨了运动车辆雷达差波束地物杂波对消和波束地物杂波的适用性。实测数据表明该方法可有效抑制主副瓣地物杂波,提高车辆运动中对慢速飞行目标的检测能力。

基于子阵波束设计的空时二维杂波抑制方法

机载雷达接收端采用子阵处理时面临栅瓣杂波导致的复杂空时耦合分布,使主瓣波束方向存在多个由栅瓣杂波导致的检测性能凹口,目标检测性能恶化严重。针对此问题,该文首先分析了子阵处理中栅瓣杂波空时谱分布特性,并在此基础上提出了基于接收子阵波束设计的空时二维杂波抑制方法。该方法采用重叠子阵构型方案,通过子阵方向图设计形成在子阵间栅瓣区域处的宽凹口,实现对子阵间栅瓣区域杂波的预滤波。进一步构建子阵级空时处理器,由于栅瓣杂波已经在子阵内完成预滤波,避免了栅瓣杂波在空时二维平面上的耦合扩散,从而提高了杂波抑制和动目标检测性能。仿真结果表明,所提方法显著改善了栅瓣杂波区的输出信杂噪比损失性能。

基于可解释深度卷积网络的空时自适应处理方法

在实际应用中,空时自适应处理(STAP)算法的性能受限于足够多独立同分布(IID)样本的获取。然而,目前可有效减少IID样本需求的算法仍面临一些问题。针对这些问题,该文融合数据驱动和模型驱动思想,构建了具有明确数学含义的多模块深度卷积神经网络(MDCNN),实现了小样本条件下对杂波协方差矩阵快速、准确、稳定估计。所构建MDCNN网络由映射模块、数据模块、先验模块和超参数模块组成。其中,前后端映射模块分别对应数据的预处理和后处理;单组数据模块和先验模块共同完成一次迭代优化,网络主体由多组数据模块和先验模块构成,可实现多次等效迭代优化;超参数模块则用来调整等效迭代中可训练参数。上述子模块均具有明确数学表述和物理含义,因此所构造网络具有良好的可解释性。实测数据处理结果表明,在实际非均匀杂波环境下该文所提方法杂波抑制性能优于现有典型小样本STAP方法,且运算时间较后者大幅降低。

基于空时极化处理的机载雷达非平稳杂波抑制方法

针对传统方位-多普勒域空时自适应处理(STAP)方法无法区分不同模糊距离单元的杂波,难以有效抑制近程非平稳杂波的问题,提出了基于空时极化处理的机载雷达非平稳杂波抑制方法.该方法在俯仰-方位-多普勒3D-STAP方法的基础上引入回波的极化维信息,然后对回波信号进行极化-俯仰-方位-多普勒四维联合空时极化自适应处理.仿真结果表明,相对于传统方位-多普勒域STAP方法和俯仰-方位-多普勒3D-STAP方法,本文所提方法可更有效地实现对非平稳杂波的抑制.

基于三维原子范数的机载MIMO雷达STAP算法

针对机载多输入多输出(MIMO)雷达空时自适应处理(STAP)使用稀疏恢复技术时存在的格点失配问题,提出了一种基于三维原子范数的机载MIMO雷达STAP算法。该方法利用杂波空时谱在角度-多普勒域上固有的稀疏性,根据低秩矩阵恢复理论构造了基于三维连续原子集的MIMO雷达杂波信号稀疏恢复模型,避免了稀疏恢复中的格点失配问题,实现了杂波空时谱的高分辨率估计,有效提高了机载MIMO雷达STAP杂波抑制性能。仿真实验表明,本文方法在存在格点失配情况下的MIMO雷达STAP处理性能优于已有的基于字典网格的稀疏恢复方法和二维原子范数方法。

NEW METHOD FOR REDUCED RANK STAP—NON CLUTTER CHANNEL METHOD

For reduced-rank space-time adaptive processing(STAP) in airborne radar, this paper presents a new method — non clutter channel(NCC） method which is easy to implement in real radar systems. The NCC method uses those “channels” located in the non-clutter domain to construct the reduce-rank transformation matrix. This method avoids eigen-decomposition and the computational cost is very low. The performance is compared with that of several other methods; the simulation demonstrates that the NCC method can well approach the optimum performance and even outperform some more complex methods in low rank.

Improved Multistage Wiener Filters in Nonhomogeneous Clutter Environments

A new method combining space-time preprocessing with multistage Wiener filters（STPMWF）is proposed to improve the performance of space-time adaptive processing（STAP）in nonhomogeneous clutter scenario.The new scheme only requires the data from the primary range bin,thus it can suppress discrete interferers efficiently,without calculating the inverse of covariance matrix.Comparing to the original MWF approach,the proposed scheme can be regarded as practical solutions for robust and effective STAP of nonhomogeneous radar data.The theoretical analysis shows that our STPMWF is simple in implementation and fast in convergence.The numeric results by using simulated data exhibit a good agreement with the proposed theory.

非均匀杂波背景下STAP降维算法研究

机载雷达对地观测时,面临由于平台运动引起杂波谱展宽,平台偏航引入垂直基线使杂波谱对高程敏感,导致方位与距离模糊。复杂地物场景局部杂波散射强度变化以及大量目标干扰等非理想因素,致使杂波分布非均匀,严重制约了杂波抑制性能与动目标检测性能。针对上述问题,本文所采用的空时自适应处理(STAP)降维算法可以有效解决慢速运动目标低检出问题,提高非均匀杂波背景下杂波的抑制能力,增强运动目标的检测性能。其特点在于:利用多维域数据实现在线地物区域划分,增大有效样本容量,样本充足条件下直接估计杂波加噪声协方差矩阵实现杂波抑制。针对孤立离散杂波、干扰,结合杂波谱重构解决单样本下的地形杂波抑制与干扰对消,通过实测数据分析证明了本文所提算法的有效性。

基于空时采样矩阵的机载MIMO雷达杂波抑制方法

相对于传统机载相控阵雷达单输入多输出(SIMO)体制,多输入多输出(MIMO)机载雷达中的空时自适应处理(STAP)技术可以获得杂波抑制和动目标检测性能的大幅提升。但是传统机载MIMO雷达空时自适应处理所需要的计算量和样本需求量巨大,无法满足非均匀杂波环境和实时性要求。为了解决这一问题,本文提出了一种机载MIMO雷达空时自适应杂波抑制方法(clutter suppression based on space time sampling matrix,CSBSM)。该方法利用了杂波协方差矩阵的低秩特性,基于空时采样矩阵构造杂波协方差矩阵,并通过空时滑窗处理对杂波功率进行估计,在非均匀杂波环境下CSBSM方法仅需要单个样本即可实现对杂波的有效抑制。同时,由于空时采样矩阵和独立采样点位置可离线计算,因此CSBSM方法的运算量较小,适用于极端非均匀杂波环境。计算机仿真结果验证了所提方法的有效性。

和差天线空时自适应测角方法及性能分析

雷达模拟和差天线技术通过射频功率合成器形成和差波束,在目标角度测量中应用广泛,然而运动平台雷达经过空时自适应处理(Space-Time Adaptive Processing,STAP)后难以还原鉴角曲线,即自适应处理后的等效鉴角曲线与静态鉴角曲线发生偏离.针对此问题,本文提出和差天线体制雷达空时自适应测角方法 .该方法通过和差STAP算法抑制杂波后实现角度估计,并且通过理论推导建立了角度估计与和通道输出信噪比、差通道剩余杂噪比之间的关系,重点分析了杂波剩余对角度估计的非一致性影响.仿真实验验证了本文方法的有效性.

机载非合作双基地雷达杂波仿真与分析

利用脉冲雷达信号作为辐射源的机载非合作双基地雷达系统相对于传统机载非合作双基地雷达系统更具优势,但同时也面临杂波对目标检测造成影响的问题。首先,针对固定雷达发射站作为辐射源的机载非合作双基地雷达杂波进行研究,建立杂波几何模型;然后,分析了正侧视阵、斜视阵、前视阵三种阵面构型条件下杂波的空时二维特性;最后,介绍空时自适应处理(STAP)算法,通过信杂噪比改善因子仿真验证了STAP方法抑制杂波的可行性,为之后的机载非合作双基地雷达目标检测提供了前提。

岸基多通道雷达仿机载海杂波测量与分析方法

为充分研究和认知海杂波空时二维特性,提出了基于岸基多通道雷达模拟实现机载平台运动功能的海杂波测量方法,并提出了相应场景下测量数据特性分析方法.通过逆相位中心偏置技术,实现岸基多通道雷达收发相位中心随脉冲重复周期移动,使得海杂波数据具备空时二维耦合特性,且利用测量数据中相参脉冲随雷达多通道数目周期变化特点,实现单距离单元对应海杂波空时特性表征量的精确估计.实测数据结果表明,基于提出的特性分析方法得到的海杂波抑制效果优于传统方法,在非主瓣杂波区域信杂噪比损失优于传统2 dB,抑制后剩余杂波的平均距离-多普勒改善1 dB.基于岸基多通道雷达开展模拟机载平台运动场景下的海杂波测量试验,具有测量简单、成本低、获取样本数据量大等优点,且利用多通道雷达海杂波特性分析方法开展海杂波空时特性研究,大大提高了特性分析精度.