A target parameter estimation method via atom-reconstruction in radar mainlobe jamming

Mainlobe jamming(MLJ)brings a big challenge for radar target detection,tracking,and identification.The suppression of MLJ is a hard task and an open problem in the electronic counter-counter measures(ECCM)field.Target parameters and target direction estimation is difficult in radar MLJ.A target parameter estimation method via atom-reconstruction in radar MLJ is proposed in this paper.The proposed method can suppress the MLJ and simultaneously provide high estimation accuracy of target range and angle.Precisely,the eigen-projection matrix processing(EMP)algorithm is adopted to suppress the MLJ,and the target range is estimated effectively through the beamforming and pulse compression.Then the target angle can be effectively estimated by the atom-reconstruction method.Without any prior knowledge,the MLJ can be canceled,and the angle estimation accuracy is well preserved.Furthermore,the proposed method does not have strict requirement for radar array construction,and it can be applied for linear array and planar array.Moreover,the proposed method can effectively estimate the target azimuth and elevation simultaneously when the target azimuth(or elevation)equals to the jamming azimuth(or elevation),because the MLJ is suppressed in spatial plane dimension.

Application of a Shape-Preserving Advection Scheme to the Moisture Equation in an E-grid Regional Forecast Model

This paper presents a methodology which is very useful to design shape-preserving advection finite difference scheme on general E-grid horizontal arrangement of variables through introducing a two-step shape-preserving positive definite advection scheme in the moisture equation of the LASG-REM (LASG regional E-grid eta-coordinate forecast model). By trial-forecasting six local heavy raincases, the efficiency of the shape-preserving advection scheme in practical application has been examined. The LASG-REM with the shape-preserving advection scheme has a good forecasting ability for local precipitation.

A Two-Step Shape-Preserving Advection Scheme

This paper proposes a new two-step non-oscillatory shape-preserving positive definite finite difference advection transport scheme, which merges the advantages of small dispersion error in the simple first-order upstream scheme and small dissipation error in the simple second-order Lax-Wendroff scheme and is completely different from most of present positive definite advection schemes which are based on revising the upstream scheme results. The proposed scheme is much less time consuming than present shape-preserving or non-oscillatory advection transport schemes and produces results which are comparable to the results obtained from the present more complicated schemes. Elementary tests are also presented to examine the behavior of the scheme.

SOME SHAPE-PRESERVING QUASI-INTERPOLANTS TO NON-UNIFORMLY DISTRIBUTED DATA BY MQ-B-SPLINES

Based on the definition of MQ-B-Splines,this article constructs five types of univariate quasi-interpolants to non-uniformly distributed data. The error estimates and the shape-preserving properties are shown in details.And examples are shown to demonstrate the capacity of the quasi-interpolants for curve representation.

Mainlobe jamming suppression via improved BSS method for rotated array radar

This study deals with the problem of mainlobe jamming suppression for rotated array radar.The interference becomes spatially nonstationary while the radar array rotates,which causes the mismatch between the weight and the snapshots and thus the loss of target signal to noise ratio(SNR)of pulse compression.In this paper,we explore the spatial divergence of interference sources and consider the rotated array radar anti-mainlobe jamming problem as a generalized rotated array mixed signal(RAMS)model firstly.Then the corresponding algorithm improved blind source separation(BSS)using the frequency domain of robust principal component analysis(FDRPCA-BSS)is proposed based on the established rotating model.It can eliminate the influence of the rotating parts and address the problem of loss of SNR.Finally,the measured peakto-average power ratio(PAPR)of each separated channel is performed to identify the target echo channel among the separated channels.Simulation results show that the proposed method is practically feasible and can suppress the mainlobe jamming with lower loss of SNR.

APPROXIMATION AND SHAPE-PRESERVING PROPERTIES OF Q-STANCU OPERATOR

We introduce the definition of q-Stancu operator and investigate its approximation and shape-preserving property. With the help of the sign changes of f（x） and Ln = f（f, q;x） the shape-preserving property of q-Stancu operator is obtained.

ON SHAPE-PRESERVING PROPERTIES AND SIMULTANEOUS APPROXIMATION OF STANCU OPERATOR

In the present paper, the shape-preserving properties and the monotonicity for convex functions of Stancu operator are given. Moreover, the simultaneous approximation problems of this operator are also considered.

Polarization-space joint mainlobe jamming countermeasure technique based on divided dimensions

In order to solve the problem that the traditional space jamming countermeasure cannot deal with the mainlobe self-protecting jammings,a polarization-space joint mainlobe jamming countermeasure technique based on divided dimensions is proposed.Specifically,the digital beam of each row and column is firstly formed by using dual polarization digital receiving in multi-channel.Then,the polarization-space joint cancellation in both azimuth and elevation dimensions is carried out based on the polarization-space joint difference between the target echo and the jamming,as well as the divided dimension feature of the row and column beams.Finally,the sum and difference beams of the full array in the elevation or azimuth dimension are formed by the beams after jamming cancelling,and the monopulse angle measurement is further employed to obtain target angles.The effectiveness of the proposed technique is verified by simulations,indicating that the self-protecting jamming and multiple mainlobe following jammings can be both cancelled simultaneously with the angle measurement unchanged.

SHAPE-PRESERVING BIVARIATE POLYNOMIAL APPROXIMATION IN C([-1,1]×[-1,1])

In this paper we construct bivariate polynomials attached to a bivariate function, that approximate with Jackson-type rate involving a bivariate Ditzian-Totik ωξ-modulus of smoothness and preserve some natural kinds of bivariate monotonicity and convexity of function.The result extends that in univariate case-of D. Leviatan in [5-6], improves that in bivariate case of the author in [3] and in some special cases, that in bivariate case of G. Anastassiou in [1].

单脉冲测角的二维分级主旁瓣干扰联合抑制方法

针对矩形平面阵列天线同时存在主、旁瓣干扰的单脉冲测角问题,该文设计了2维分级自适应单脉冲波束形成算法(TDHJ-ADBF)。TDHJ-ADBF算法将矩形平面阵分为方位维和俯仰维两个正交维度,采用2维分级处理架构:第1级处理在测角维进行,采用低运算量的压缩多重信号分类法对测角维主瓣干扰进行快速识别与方向估计,构造阻塞矩阵滤除主瓣干扰,获得仅含旁瓣干扰和噪声的协方差矩阵,进而对和、差波束方向图进行指向与鉴角曲线联合约束,完成测角维旁瓣干扰抑制与波束形成处理;第2级在非测角维对残留的测角维主瓣干扰进行抑制。通过2维分级处理实现主、旁瓣干扰联合对抗,并保持单脉冲测角的鉴角曲线线性度。仿真结果表明,TDHJ-ADBF算法实现了对主、旁瓣干扰联合抑制,具有高精度的单脉冲测角性能。

主瓣干扰下雷达组网主被动联合跟踪调度方法

主瓣干扰是雷达面临的重要威胁,通过多雷达组网协同发挥体系效能是对抗此类威胁的有效手段。文中针对主瓣干扰下雷达组网协同探测系统跟踪性能下降的问题,提出一种基于强化学习的多目标跟踪主被动联合的资源调度方法。首先,给出干扰条件下的雷达主动量测模型和被动定位模型;然后,利用雷达在主动和被动工作模式下精度随干扰强度的不同变化趋势,设计了以最小化跟踪误差为目标的评价函数;最后,使用近端策略优化算法的强化学习智能体进行雷达主被动工作模式选择,将剩余的多雷达驻留时间分配作为凸优化问题进行求解。仿真实验结果表明,该方法相比传统的雷达工作模式分配策略,能够提升雷达组网协同探测系统在强干扰环境下的跟踪性能,从而提高系统抗干扰能力。

一种分时双极化阵列ADBF处理方法

针对双极化阵列工程实现难度大、成本高的问题,提出一种基于分时双极化阵列自适应波束形成(ADBF)处理方法.首先完成阵面接收信号的子阵级合成,分别计算水平极化和垂直极化两类子阵的导向矢量,进行自适应处理;然后从两个极化处理通道中选取信干噪比(SINR)较大者输出.仿真结果表明,该方法能够在大多数场景下实现干扰的有效抑制,具有较强的适用性和稳健性.该方法处理简单、易于工程实现,有效解决了子阵合成前数据量大、目标极化参数无法实时获取等问题.

一种快速的雷达天线扫描周期估算方法

针对传统自相关方法计算量较大的问题,提出了一种快速的雷达天线扫描周期估算方法。首先,分析了接收脉冲幅度序列的离散化频谱特性。其次,通过检测频谱峰值构造频率索引集合。在此基础上,基于频谱峰值的频率索引差分估算雷达天线扫描周期,该方法具有较低的计算复杂度。最后,仿真实验验证了所提方法的有效性。

多模式低副瓣阵列方向图综合方法

本文面向阵列天线低副瓣的实际应用需求,利用空时编码的思路设计加权矢量,分别提出序贯快速傅里叶变换(fast Fourier transform,FFT)方法、约束方程计算方法和优化函数求解方法,对应多脉冲低副瓣方向图综合时加权矢量时变、不变和奇偶交替变的3种不同工作模式。理论分析和仿真实验表明,序贯FFT和约束方程计算方法均能实现超低副瓣方向图(优于-50 dB),而优化函数求解方法在实现低副瓣的同时仍能保持方向图主瓣的良好性能,避免了传统方向图综合方法无法同时兼顾主副瓣性能的缺点。另外,从计算复杂度、随机幅相误差、干扰抑制等各方面综合分析了不同方法的优缺点,可为实际阵列天线的工程应用提供理论指导和技术参考。

子阵级单脉冲四通道主瓣干扰对消角度分辨率分析

针对子阵级单脉冲雷达,研究了和差四通道主瓣干扰对消技术。为此,构建了二维子阵级单脉冲四通道干扰对消信号模型,并提出了以有用信号信噪比损失值为指标的定量方法来表征主瓣干扰对消角度分辨率。基于此,进一步推导了干扰对消角度分辨率的解析表达式,并明确了对消角度盲区的理论边界。仿真与暗室实验的结果验证了该解析式的正确性。研究可为四通道主瓣干扰对消技术的理论边界分析和工程实现提供参考。

太赫兹异物探测系统的一种硬件幅相失真补偿方法

太赫兹(THz)成像技术是一种新发展的高频段成像技术,在军事和安全领域具有重要的应用价值。文中的实波束THz异物探测(FOD)系统未进行宽带幅相失真补偿时,一维像主副瓣比较差,微小目标无法成二维像。考虑到该成像系统采用了高频段易于实现的调频连续波自混频去斜方法,传统的宽带成像系统在信号产生时所实施的宽带幅相预失真补偿方法无法起效,为此,文中给出了实波束THz FOD系统的一种硬件幅相失真补偿方法。该方法通过对接收机数字下变频的正交数据实施先相后幅的通带失真补偿,完成了THz FOD系统的幅相失真补偿。采用该补偿方法的THz FOD系统一维像加海明窗主副瓣比>40 dB,可实现对微小目标成二维像。

基于信干噪比最大化的盲提取抗主瓣干扰方法

针对雷达主瓣干扰抑制问题,提出一种基于信干噪比(signal to interference plus noise ratio,SINR)最大化的盲提取主瓣干扰抑制方法。与盲分离不同,盲提取能够从多路混合信号中提取出感兴趣的一路分量,这更适合在多信源多通道的复杂电磁环境下进行干扰抑制。该方法在混合信号距离域建立SINR最大化的优化模型,采用粒子群优化(particle swarm optimization,PSO)算法进行求解并提取出目标回波信号实现主瓣干扰抑制。经仿真测试,该方法相较于传统的盲分离干扰抑制方法,提升了干扰抑制效果;无需信源数目估计,对通道数目要求更低,在欠定场景中依然适用;减小了计算复杂度,更适用于复杂电磁环境。

SAR实时快速处理抗主瓣欺骗式干扰方法

主瓣欺骗干扰与真实目标场景具有相同的角度,二者在多个表征域具有高度相似性,严重降低了合成孔径雷达系统对真实目标的检测和判断能力。针对该问题,为保证有效抑制主瓣欺骗干扰,文中提出了一种实时快速处理抗主瓣欺骗干扰算法。首先,提出了一种基于方位相位编码的回波恢复框架,并且该框架能够对原始回波数据进行分组处理;其次,提出了一种模块化处理的快速算法来加快所提方法的处理效率;最后,通过点目标和分布式目标仿真实验验证了所提方法的有效性和可行性。通过与传统主瓣欺骗干扰方法进行对比,文中所提方法不仅能够降低计算复杂度,还能减少对系统资源的占用。

基于双差通道的近主瓣干扰抑制方法研究

电磁对抗在现代战争中发挥着越来越重要的作用,雷达对电磁干扰的抑制能力决定了雷达能否发挥作战能力。本文重点研究近主瓣干扰的识别与抑制,给出了一种雷达近主瓣干扰的识别方法,提出了一种基于双差通道的近主瓣干扰抑制方法,并分析了应用该方法进行干扰抑制后对雷达测角能力的影响。仿真结果表明,本文所提方法能够抑制来自波束近主瓣的干扰,并且具备一定的工程实用性。

基于分数域滤波处理的阵列雷达主瓣干扰抑制算法

为提升主瓣干扰下阵列雷达探测性能,提出了一种分数域滤波处理的阵列雷达抗主瓣干扰抑制算法,可有效抑制主瓣干扰。通过分数阶傅里叶变换在分数域搜索主瓣干扰,根据峰值确定干扰在分数域的位置,从而在分数域进行滤波处理,然后对回波信号再进行阻塞矩阵处理,从而更好地滤除主瓣干扰。仿真实验验证了所提算法的有效性。